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This document on best practices was developed using the recommendations set forth in the OSHA Metalworking Fluids Standards Advisory Committee Final Report (1999); the NIOSH Criteria Document on Occupational Exposure to Metalworking Fluids (1998); and the Organization Resources Counselors, "Management of the Metal Removal Fluid Environment: A Guide to the Safe and Efficient Use of Metal Removal Fluids" (1999).
Maura Sheehan, Sc. D.
Professor, Environmental Health
West Chester University
Department of Health
West Chester, PA 19383
Lee Newman, M.D.
Div. of Env. & Occup. Hlth. Sci.
Nat'l. Jewish Medical & Research Ctr.
1400 Jackson Street
Denver, CO 80206
Dennis O'Brien, Ph.D.
Director, Division of Physical Sciences and Engineering
National Institute for Occupational Safety and Health
4676 Columbia Parkway
Cincinnati, OH 45226
Daniel Teitelbaum, M.D.
Medical Tox. & Occup. Med. Corp.
155 North Madison
Denver, CO 80206
Int'l. Assoc. of Machinists & Aerospace Workers
9000 Machinists Place
Upper Marlboro, MD 20722
United Steel Workers of America
Five Gateway Center
Pittsburg, PA 15222
President, UAW Local Union 599
812 Leith Street
Flint, MI 48505
810-238-1616 x 414 work
Frank Mirer, Ph. D.
Director, Health & Safety Dept.
International Union, UAW
8000 East Jefferson Avenue
Detroit, MI 48214
David Wegman, M.D.
Univ. of Massachusetts Lowell
Department of Work Environment
Lowell, MA 01854
Director of Human Resources & Government Affairs
Precision Machined Products Assoc.
6700 West Snowville Road
Brecksvile, OH 44141- 3292
Manager, Bovernment Affairs
National Tooling & Machining Assoc.
9300 Livingston Road
Ft. Washington, MD 20744
John Howell, Ph. D.
Director, Safety, Health, & Environmental Affairs
Castrol Industrial North America
1001 West 31st Street
Downers Grove, IL 60515
630-241-4000 x 5235 work
Henry Lick, Ph. D., CIH, CSP, ROH
Manager, Industrial Hygiene
Ford Motor Company
104 Central Laboratory
15000 Century Drive
Dearborn, MI 48120
Organization Resources Counselors, Inc.
1910 Sunderland Place, NW
Washington, D.C. 20036
Henry Anderson, M.D.
Bureau of Public Health
State of Wisconsin,
1400 E. Washington Ave., Rm. 96
Madison, WI 53703
Kenneth Kushner, CIH, SCP
Principal - Occ. Safety & Industrial Hygiene
The Timkin Company
Mail Drop gne-13
1835 Dueber Avenue, SW
Canton, OH 44706
ConnectiCOSH & IAMAW Local 700
care of: 1510 Saybrook Road
Middletown, CT 06157
TABLE OF CONTENTS
Millions of workers engaged in manufacturing parts for products such as automobiles, farm equipment, aircraft, heavy machinery, and other hardware are exposed to metalworking fluids (MWFs). Metalworking fluids are in widespread, high volume use for their coolant, lubricant, and corrosion resistant properties during machining operations. These fluids are complex mixtures of oils, detergents, surfactants, biocides, lubricants, anti-corrosive agents, and other potentially toxic ingredients.
This document focuses on that group of metalworking fluids known as metal removal fluids. Metalworking fluids/metal removal fluids are also called machining fluids, cutting fluids, and cutting oils. These fluids are those used in grinding, cutting, boring, drilling, and turning metal. Although metal removal fluids is a more specific term, these fluids are most often referred to by the generic term metalworking fluids. It is believed that employers and employees are more likely to associate this document with their work environment if the term they commonly use is in the title and text. Consequently, OSHA will use the more common term, metalworking fluids, throughout the document. While the scope of this document is limited to metal removal operations and their fluids, the exclusion of other metalworking fluids or related processes or environments does not imply the lack of a potential problem in these related fluids, processes or environments. A glossary of metalworking fluid terms is included in Appendix 1.
In 1993, the International Union, United Automobile, Aerospace & Agricultural Implement Workers of America (UAW) petitioned OSHA for an emergency temporary standard. OSHA subsequently issued a Priority Planning report, which identified metalworking fluids as an issue worthy of Agency action. The Assistant Secretary then asked the National Advisory Committee on Occupational Safety and Health (NACOSH) for recommendations on how to proceed. NACOSH recommended that OSHA form a Standards Advisory Committee (SAC) to address the issues of occupational exposure to metal removal fluids. The Secretary of Labor signed the charter establishing the Metalworking Fluids SAC on August 28, 1997. The Standards Advisory Committee comprised of 15 representatives from unions, academia, affected industries that included large and small employers, and NIOSH and State public health professionals, issued a report in 1999. A summary of that report is available on OSHA's website.
What Does This Manual Address?
This document provides general information about the metalworking fluid environment and the health hazards of occupational exposure to MWFs. This Manual recommends occupational health guidelines to mitigate the adverse health effects associated with occupational exposure to MWFs. It covers major topics such as a systems management approach, exposure assessment, medical surveillance, and training. Systems management includes a comprehensive programmatic approach including such things as machine enclosure, ventilation, fluid management, and other actions to control exposure and minimize contact with the fluid. The material in this Manual will help safety and health professionals apply their resources to the industrial hygiene problems associated with the metalworking environment. Engineering, work practice, and administrative controls that help reduce workplace exposures are identified and appropriate methods are described that limit exposures.
Additional Health and Safety Hazards
Other potential safety and health hazards associated with the metalworking fluid environment but not addressed in this Manual include:
B. THE BASICS OF METALWORKING FLUIDS
Industrial operations requiring the grinding, cutting, or boring of metal parts also require the use of metalworking fluids to meet productivity and quality requirements. Metalworking fluids (MWFs) have two primary functions: to cool and to lubricate.
All metal removal processes generate a tremendous amount of heat. This heat must be reduced in order to achieve productivity and part quality. The cooling effect provided by a metalworking fluid gives the cutting tool or grinding wheel a longer life and helps to prevent burning and smoking. At the point where the tool is in contact with the part, lubrication is necessary to reduce friction between the tool and the part, resulting in improved tool life and better finishes on the metal cut.
Metalworking fluids also provide corrosion protection for the newly machined part and machine tool. Water-miscible metalworking fluid formulations (those fluids that are meant to be diluted with water) include components that slow or prevent such corrosion. MWFs also help remove chips or swarf (an accumulation of fine metal and abrasive particles) from the cutting zone.
What Are the Different Types of Metalworking Fluids?
There are four major classes of metal-working fluids widely available: straight oil, soluable oil, semisynthetic, and synthetic. Many metalworking fluids, except the straight oils, are mixed with water for use. Each has additives such as surfactants, biocides, extreme pressure agents, anti-oxidants, and corrosion inhibitors to improve performance and increase fluid life (refer to Appendix 2 for a listing of typical additives).
Straight Oil: This type of metalworking fluid is made up mostly of mineral (petroleum) or vegetable oils. Petroleum oils used for these fluids today tend to be "severely solvent refined" or "severely hydrotreated" (refining processes which reduce cancer-causing substances called polynuclear aromatic hydrocarbons [PAHs] present in crude oil). Other oils of animal, marine or synthetic origin can also be used singly or in combination with straight oils to increase the wetting action and lubricity.
Straight oils can be recognized by an oily appearance and viscous feel. These materials may contain chlorinated and sulfur additives. This product is not diluted with water before use.
Straight-oil metalworking fluids are generally used for processes that require lubrication rather than cooling. They perform best when used at slow cut speeds, high metal-to-metal contact or with older machines made specifically for use with straight oils. Straight-oil MWF systems may require fire protection.
Soluble Oil: Soluble oil is also called emulsifiable oil. It is made up of from 30 to 85 percent of severely refined lubricant base oil and emulsifiers to help disperse the oil in water. The fluid concentrate usually includes other additives to improve performance and lengthen the life of the fluid. Soluble oil products are supplied as concentrates that are diluted with water to obtain the working fluid. They may have colorants added.
Soluble oils in general provide good lubrication and are better at cooling than straight oils. Drawbacks in using soluble oils, however, are that they sometimes have poor corrosion control, are sometimes "dirty" (i.e., machine tool surfaces and nearby areas become covered with oil or difficult-to-remove product residues), may smoke (they may not cool as well as semisynthetics and synthetics), and may have poor mix stability or short sump life.
Semisynthetic: This type of metalworking fluid contains a lower amount of severely refined base oil, for example, 5-30 percent in the concentrate. Semisynthetics offer good lubrication, good heat reduction, good rust control, and have longer sump life and are cleaner than soluble oils. They are comprised of many of the same ingredients as soluble oils and contain a more complex emulsifier package.
Synthetic: These metalworking fluid formulations do not contain any petroleum oil. They contain detergent-like components to help "wet" the part and other additives to improve performance. Like the other classes of water-miscible fluids, synthetics are designed to be diluted with water.
Among the four types of fluids, synthetic metalworking fluids generally are the cleanest, offer the best heat reduction, have excellent rust control, and offer longer sump life. In addition, this type of metalworking fluid is transparent (allowing the operator to see the work) and are largely unaffected by hard water.
What Are the Signs That a Fluid May No Longer Be Safe to Use?
There are many signs that a fluid has undergone changes and is no longer safe to use because of emerging health hazards. If one or more of the following changes occur, the fluid should be evaluated to see if it is safe for continued use or if it should be replaced.
C. PRINCIPLES OF FLUID SELECTION
How Can You Obtain Safety and Health Information About a Fluid?
The fluid supplier will normally be your best source of information about a fluid. The supplier should be familiar with the health effects associated with the fluid to be used and can provide you with up to date material safety data sheets.
Some suppliers go a step further and provide additional assistance such as providing a chemical or fluid management program, a customer support program, and a product stewardship program which includes health, safety, and environmental support. These programs can be especially helpful since they usually include current and comprehensive health and safety information required by OSHA's hazard communication standard, recommendations for effective fluid management, and information on the proper use and disposal of their products.
The supplier may also be able to assure you that its products comply with applicable governmental safety and environmental regulatory considerations; provide analysis of in-use fluids, including characterization of microbial content; and provide air sampling to measure employee exposure.
What Are the Health, Safety, and Environmental Concerns That Should Be Considered When Selecting a Fluid?
When selecting a fluid, consider the following:
If soluble oils or synthetic fluids are used, ASTM Standard E 1497-00, Standard Practice for Safe Use of Water-Miscible Metalworking Fluids should be consulted for safe-use guidelines, including product selection, storage, dispensing, and maintenance.
Most water-miscible metalworking fluids contain a chemical biocide that kills various microscopic organisms and protects the fluids from microbial degradation. To protect workers, make sure that the biocides used in your fluids and as sump-side additives are registered by the U.S. Environmental Protection Agency (EPA) for use as additives to metalworking fluids and are used in accordance with the conditions of registration. Biocide concentration should not exceed that needed to meet fluid specifications, since an excessive amount may cause employees to experience skin or respiratory irritation or sensitization.
The National Center for Manufacturing Sciences' Metalworking Fluids Optimization Guide (NCMS Guide) describes the important factors to consider when selecting metal removal fluids. The NCMS Guide also includes an example of a MWF selection process to assist you in making an appropriate selection.
D. REQUIRED AND RECOMMENDED EXPOSURE LIMITS
Currently two OSHA air contaminant permissible exposure limits apply to MWFs. They are 5 mg/m3 for an 8-hour time weighted average (TWA) for mineral oil mist, and 15 mg/m3 (8-hour TWA) for Particulates Not Otherwise Classified (PNOC) [applicable to all other metalworking fluids], 29 CFR 1910.1000. No other requirements exist.
In addition, there are other recommended exposure limits. In 1998, the National Institute for Occupational Safety and Health (NIOSH) published a criteria document which recommended an exposure limit (REL) for MWF aerosols of 0.4 mg/m3 for thoracic particulate mass as a time-weighted average (TWA) concentration for up to 10 hours per day during a 40-hour work week. Because of the limited availability of thoracic samplers, measurement of total particulate mass is an acceptable substitute. The 0.4 mg/m3 concentration of thoracic particulate mass approximately corresponds to 0.5 mg/m3 for total particulate mass. The NIOSH REL is intended to prevent or greatly reduce respiratory disorders causally associated with MWF exposure. It is NIOSH's belief, that in most metal removal operations, it is technologically feasible to limit MWF aerosol exposures to 0.4 mg/m3 or less (NIOSH 1998b).
The American Conference of Governmental Hygienists (ACGIH) threshold limit value (TLV) for mineral oils is 5 mg/m3 for an 8-hour TWA, and 10 mg/m3 for a 15-minute short-term exposure limit (STEL).
In 1999, the OSHA Metalworking Fluids Standards Advisory Committee also recommended a new 8-hour time-weighted average permissible exposure limit (PEL) of 0.4 mg/m3 thoracic particulate (0.5 mg/m3 total particulate). The committee based the recommended PEL on studies of asthma and diminished lung function.
E. HEALTH EFFECTS
Metalworking fluids (MWFs) can cause adverse health effects through skin contact with contaminated materials, spray, or mist and through inhalation from breathing MWF mist or aerosol.
Skin and airborne exposures to MWFs have been implicated in health problems including irritation of the skin, lungs, eyes, nose and throat. Conditions such as dermatitis, acne, asthma, hypersensitivity pneumonitis, irritation of the upper respiratory tract, and a variety of cancers have been associated with exposure to MWFs (NIOSH 1998a). The severity of health problems is dependent on a variety of factors such as the kind of fluid, the degree and type of contamination, and the level and duration of the exposure.
Skin contact occurs when the worker dips his/her hands into the fluid or handles parts, tools, and equipment covered with fluid without the use of personal protective equipment, such as gloves and aprons. Skin contact may also result from fluid splashing onto the employee from the machine if guarding is absent or inadequate.
Two types of skin disease associated with MWF exposure are contact dermatitis and acne.
Contact dermatitis is the most commonly reported skin disease associated with MWFs. People with contact dermatitis have itchy skin and a rash, often with cracks, redness, blisters, or raised bumps. The two kinds of contact dermatitis are irritant contact dermatitis and allergic contact dermatitis. In irritant contact dermatitis the rash is confined to the area in contact with the irritating substance. In allergic contact dermatitis the rash can spread beyond the area directly in contact with the irritant. Fourteen to 67 percent of workers exposed to MWFs are at risk for developing dermatitis (NIOSH 1998a). This high rate of dermatitis indicates susceptibility of many employees to the irritating or sensitizing nature of MWFs and their contaminants or additives. Once the skin is compromised, very small exposures, which previously did not have any effect, can cause an episode of dermatitis. It is important to try to prevent skin disease from developing and to treat it early because untreated dermatitis can lead to more serious complications (NIOSH 1998a).
In metalworking operations contact dermatitis may be caused by any of the following factors: clothing contaminated with MWF; poor personal hygiene (e.g., allowing MWF to remain in contact with skin by not washing after exposure); poor housekeeping practices; higher than recommended metalworking fluid concentrations; high alkalinity of in-use fluid which can remove natural skin oils; metal processing aids such as degreasers, cleaners, or rust inhibitors; metal shavings contained in the fluid which may abrade the skin; prolonged contact with the MWF; tramp oils (e.g., hydraulic fluids, gear or spindle oils, way lubes, grease); hand washing with abrasive soaps or with water that is excessively hot or cold; seasonal conditions (e.g., winter dryness); other contaminants (e.g., water in an oil based system).
People working with water based, synthetic, and semi synthetic MWFs are most at risk for developing contact dermatitis.
Straight oils are often associated with acne-like disorders characterized by pimples in areas of contact with the MWFs. Red bumps with yellow pustules may develop on the face, forearms, thighs, legs, and other body parts contacting oil-soaked clothing.
Inhalation of MWF mist or aerosol may cause irritation of the lungs, throat, and nose. In general, respiratory irritation involves some type of chemical interaction between the MWF and the human respiratory system. Irritation may affect one or more the following areas: nose, throat (pharynx, larynx), the various conducting airways or tubes of the lungs (trachea, bronchi, bronchioles), and the lung air sacks (alveoli) where the air passes from the lungs into the body. Exposure to MWF mist or aerosol may also aggravate the effects of existing lung disease.
Some of the symptoms reported include sore throat, red, watery, itchy eyes, runny nose, nosebleeds, cough, wheezing, increased phlegm production, shortness of breath, and other cold like symptoms. These symptoms may indicate a variety of respiratory conditions, including acute airway irritation, asthma (reversible airway obstruction), chronic bronchitis, chronically impaired lung function, and hypersensitivity pneumonitis (HP). When symptoms of respiratory irritation occur, in many cases it is unclear whether the disease was caused by specific fluid components, contamination of the in-use fluid, products of microbial growth or degradation, or a combination of factors.
Exposure to MWFs has been associated with asthma. In asthma, airways of the lung become inflamed, causing a reduction of the flow of air into and out of the lungs. During an asthmatic attack, the airways become swollen, go into spasms and fill with mucous, reducing airflow and producing shortness of breath and a wheezing sound. A variety of components, additives, and contaminants of MWFs can induce new-onset asthma, aggravate pre-existing asthma, and irritate the airways of non-asthmatic employees.
Chronic bronchitis is a condition involving inflammation of the main airways of the lungs that occurs over a long period of time. Chronic bronchitis is characterized by a chronic cough and by coughing up phlegm. The phlegm can interfere with air passage into and out of the lungs. This condition may also cause accelerated decline in lung function, which can ultimately result in heart and lung function damage.
Hypersensitivity pneumonitis (HP) is a serious lung disease. Recent outbreaks of HP have been associated with exposure to aerosols of synthetic, semi synthetic, and soluble oil MWFs. In particular, contaminants and additives in MWFs have been associated with outbreaks of HP (NIOSH 1998a). In the short term, HP is characterized by coughing, shortness of breath, and flu-like symptoms (fevers, chills, muscle aches, and fatigue). The chronic phase (following repeated exposures) is characterized by lung scarring associated with permanent lung disease.
Other factors, such as smoking, increase the possibility of respiratory diseases. Cigarette smoke may worsen the respiratory effects of MWF aerosols for all employees.
A number of studies have found an association between working with MWF and a variety of cancers, including cancer of the rectum, pancreas, larynx, skin, scrotum, and bladder (NIOSH 1998a). Studies of MWF and cancer have relied on the health experiences of workers exposed decades earlier. This is because the effects of cancers associated with MWF may not become evident until many years after the exposure. Airborne concentrations of MWF were known to be much higher in the 1970s - 80s than those today. The composition of MWFs has also changed dramatically over the years. The fluids in use prior to 1985 may have contained nitrite, mildly refined petroleum oils, and other chemicals that were removed after 1985 for health concerns. Based on the substantial changes that have been made in the metalworking industry over the last decades, the cancer risks have likely been reduced, but there is not enough data to prove this.
F. ENGINEERING AND WORK PRACTICE CONTROLS
How Can Occupational Exposures Be Controlled?
Occupational exposures can be controlled by the application of a number of well-known principles including engineering and work practice controls, administrative controls, and use of personal protective equipment. These principles may be applied at or near the hazard source, to the general workplace environment, or at the point of occupational exposure to individuals. Engineering and work practice controls, applied at the source of the hazard, are generally the preferred and most effective means of control. In machine shops where workers are at risk of exposure to metalworking fluids, exposure may be controlled by some or all of the following: (1) proper design and operation of the MWF delivery system; (2) isolation; (3) effective local exhaust ventilation (see Appendices 3 and 4); (4) effective general or dilution ventilation; (5) good work practices on the part of the machinists, including the proper use of controls; and (6) proper maintenance of equipment;
What Design Considerations and Operational Procedures Can Be Used to Control Misting?
Many factors influence the generation of MWF mists, which can be minimized through the proper design and operation of the MWF delivery system (Figure 1). ANSI Technical Report B11 TR 2-1997 (Mist Control Considerations for the Design, Installation and Use of Machine Tools Using Metalworking Fluids) [ANSI 1997] provides guidelines for minimizing mist and vapor generation. Another useful document is ASTM E 1972-98, Standard Practice for Minimizing Effects of Aerosols in the Wet Metal Removal Environment.
Fine mists are produced when MWF streams break up during use. This occurs when the fluid is applied and interacts with the spinning tools or parts, and when fluid is moved at high velocity in open conduits. Small mist droplets are easily suspended in air and can escape containment or collection.
The MWF delivery system should be designed to generate a minimum amount of fluid mist. Factors that can reduce misting include low-pressure delivery of MWF, matching the fluid to the application, using MWF formulations with low oil concentrations, using mist suppressants, avoiding contamination with tramp oils, minimizing the MWF flow rate, covering fluid reservoirs and return systems where possible, maintaining control of MWF chemistry, and proper machine maintenance.
An adequate, low-pressure flow of MWF delivered directly to the cutting zone, where it floods and cools the workpiece and cutting tool, is usually most effective in reducing misting. A high-pressure delivery of MWF, on the other hand, may create mists, may not supply adequate cooling or lubrication, and may not have sufficient flow to properly remove swarf or chips from the cutting area.
The use of mist suppressants should also be considered. Mist suppressants work at the source, enlarging the size of the mist droplets so that they don't stay suspended in air as long. The use of mist suppressants may also reduce fluid loss and vapor generation.
Another basic step that can be taken to reduce employee exposure to mist is to interrupt or reduce the flow of MWF when practical. As an example, the flow of MWF should be interrupted when machining is not occurring. This not only reduces mechanically generated mist, it also reduces degradation of the MWF and oxidation of the biocides. Quiet time also allows tramp oil to float and solids to settle so that they can be removed more easily. An intermittent flow (or change in pressure) of the MWF (e.g., 30 seconds on, then 2 minutes off) may often be more effective at moving chips than a continuous flow. Extended periods of fluid inactivity (more than 8-10 hours) should be avoided as this promotes the growth of anaerobic bacteria in those fluids that are heavily contaminated and/or do not contain the correct concentration of the right biocide.
Proper equipment maintenance is also important. Leaking seal packing, leaking mechanical seals, and leaking ports in delivery pumps allow air into the metalworking fluid, increasing the amount of mist produced. Filtration and delivery systems that are properly maintained also reduce misting and minimize splashing.
Metalworking fluids should not be allowed to flow over the unprotected hands of employees loading or unloading parts. Use of compressed air blow-offs to dry parts of excess fluid should be avoided, unless adequate ventilation controls are provided to capture the airborne mist created by the compressed air.
How Can Isolation Be Used to Control Exposures?
Isolation of the employee through mechanical parts handling equipment and machine enclosures can minimize skin and inhalation exposure. Simple splash guarding may suffice for low production machines, while high production machines generally require complete enclosure with ventilation. In addition, transfer machines should be located away from other operations and workers should be protected with isolation booths or air curtain-exhaust ventilation (NIOSH 1998b).
Should an Exhaust Ventilation System Be Installed to Control Mist?
One way to reduce employee exposure to MWF aerosols is to install an exhaust ventilation system to prevent the accumulation or recirculation of airborne contaminants in the workplace. A local exhaust ventilation system is the primary means for controlling employee exposure to air contaminants. This exhaust system is termed "local" because the source of exhaust or suction is located adjacent to the source of contamination. If properly designed, such an arrangement removes a contaminant directly from its source before it has an opportunity to escape into the workplace environment where it could be inhaled by an employee. Capturing and removing a contaminant at its source is the principle objective of local exhaust ventilation.
You are much more likely to successfully ventilate operations that produce MWF aerosols if the machine tool and machining operations are enclosed as much as possible. Where an exhaust hood (i.e., enclosing hood) is used that completely or partially encloses the process or contaminant generation point, it essentially surrounds the contaminant source, thereby isolating the process from the employee and the workplace. Thus, when the MWF aerosol is emitted from the machining operation, it is already either totally or at least partially inside the hood. The aerosol is contained inside the enclosure by an inward flow of air through the hood opening(s) and is prevented from escaping into the workplace air.
Also effective is locating an exhaust hood (i.e., an exterior hood) in close proximity to an emission source without enclosing it. Then, the movement of air flowing into the hood captures contaminants at their source and induces the contaminants to flow into the hood along with the moving air. Since this hood does not completely or partially enclose the process, the MWF aerosol is released outside rather than inside the physical confines of the hood. The capture velocity for this type of hood should be designed to overcome the velocity with which the generated aerosol is released from the process, and the motion of the air (in front of the hood) into which the aerosol is released.
Local exhaust ventilation of machining operations is not the only strategy for reducing employee exposures to aerosols, vapors, mists, and dust. General or dilution ventilation systems rely on the supply and exhaust of air with respect to an area, room, or building rather than on a localized exhaust source to control airborne contaminant concentrations.
Dilution ventilation is different from local exhaust ventilation because, instead of capturing emissions at their source and removing them from the air, dilution ventilation allows the contaminant to be emitted into the general workplace air and then dilutes the concentration of the contaminant by circulating large quantities of air into and out of the work area(s). Generally speaking, local exhaust ventilation is more effective than dilution ventilation in achieving contaminant control and employee protection.
What Are the Types of Exhaust Hoods?
Many types of exhaust hoods are available. Some designs are more effective than others. ANSI Technical Report B11 TR 2-1997 contains guidelines for exhaust ventilation of machining and grinding operations and recommends only enclosure type exhaust hoods for MWF mist control. Enclosures are classified by ANSI according to the extent of enclosure: close capture (partial enclosure at the point of operation), total enclosure (enclosure of the entire machine), or tunnel enclosure (continuous enclosure over several machines).
Types of exhaust hoods:
A close capture enclosure (Figure 2) is a contaminant-capturing hood that is mounted very close to the point of mist generation. By nature, it has a high entrainment velocity and lower air volume requirements. The problem with this device, though, is there may be significant loss of the MWF into the exhaust system, requiring excessive make-up fluid to be added.
Total or complete enclosure (Figures 3 and 4) is defined as a box or housing around the machine or process. The housing is not intended to be airtight. The openings are normally limited to the minimum required to allow for part entry/egress, maintenance, or utility access. The enclosure is provided with exhaust ventilation with the replacement air entering through the openings designed into the enclosure. Total enclosures will have low air volume requirements.
A tunnel enclosure encompasses two or more connected workstations or machining processes.
Push-pull ventilation consists of a jet of air blown across the process emission source (i.e., work piece/cutting tool) toward an exhaust hood. The push-pull hood is generally used on open surface tanks and is not recommended for effective capture of contaminants generated by machine tools. Generally, it is not used unless close capture or total enclosure is not possible.
The side-draft hood (capture exhaust hood) is located behind or to the side of the worker and tends to pull the contaminants away from the breathing zone of the operator. Large volumes of air are usually required for this type of hood design.
The canopy hood (receiving hood) is located above the machine operator's breathing zone. Large volumes of air are required for this type of hood design. In addition, if the hood is not properly designed, contaminated air can pass through the employee's breathing zone.
The downdraft hood is a device located in the floor or at the base of the machine. It pulls contaminants vertically down below the breathing zone of the operator. It requires large volumes of exhaust air.
Why Are Machine Tool Enclosures Necessary?
Studies show that aerosol mists may have an adverse effect on exposed workers. That's why mist generating operations should be enclosed and ventilated. Enclosures and appropriate exhaust ventilation minimize the release of MWF aerosols into the workplace. When you put in place well-designed enclosures and splashguards you prevent metalworking fluids from spilling on the ground and improve the general cleanliness of the operation. Consequently, existing enclosures and splashguards should be maintained. Missing equipment and enclosures should be restored. If guarding has been removed or the enclosure not maintained, MWF may escape through openings in the enclosure.
What If Existing Equipment Lacks an Enclosure?
Retrofitting existing equipment should be considered if other control measures (previously mentioned) have been tried and were unsuccessful in reducing airborne mist concentrations to acceptable levels. ANSI Technical Report B11 TR 2-1997 should be used as a guide. However, unless exhaust hood retrofits are properly designed and constructed, retrofits may not effectively capture metalworking fluid aerosols. With some equipment, retrofitting may not be possible or even economically feasible (ORC 1999), in which case modifying MWF handling to reduce or eliminate mist generation is crucial. When ever possible, ventilated enclosures should be phased in with new machinery or machinery rebuilds.
Is it Necessary to Provide Make-Up Air?
Exhaust ventilation systems (whether they are local or dilution) require the replacement of exhausted air to ensure that they operate properly. Replacement air, also called make-up air, can be supplied naturally by atmospheric pressure through open doors, windows, wall louvers, and adjacent spaces as well as through cracks in walls and windows, and beneath doors; or by mechanical means such as a dedicated replacement air system.
Ideally, the make-up air should be provided, controlled, and conditioned by a mechanical system rather than relying on random infiltration. Mechanical air handling systems, which can range from simple to complex, all distribute air in a manner designed to meet the ventilation, temperature, humidity, and air quality requirements established by the user. Individual units may be installed in the space they serve, or central units can be installed to serve multiple areas.
A good make-up air system would have the following characteristics:
Air exhausted from machine tool enclosures and hoods is often cleaned and recirculated in the workplace (NIOSH 1998a). In a recirculation system, exhaust air that is removed from the process is cleaned and recycled back to the facility (the objective of recirculation of exhaust air is to return cleaned air to the facility in order to reduce the amount of energy required to heat or cool make-up air). Criteria to ensure the safe recirculation of exhaust air are discussed in, The Recirculation of Industrial Exhaust Air (NIOSH 1978), and general guidelines for recirculating exhaust air are presented in Industrial Ventilation: A Manual of Recommended Practice (ACGIH 1998).
Though the benefits obtained by recirculating exhaust air can be great, the method is not a simple one, and it is not without problems. The air quality of the recirculated air should be such that the employee is not exposed to a potential health hazard. Before returning this air to the workplace, all contaminants should be removed. The ventilation system should be maintained and cleaned so that it does not itself become a source of air contamination.
The efficiency of any air cleaner in a recirculation system should be such that respirable particles or harmful gases and vapors are removed before the air re-enters the workroom. Commercially available mist collectors are typically multi-stage and should use a high-efficiency particulate air (HEPA) filter as a final stage. Air cleaners without a HEPA filter typically spew small particles out into the workplace.
In addition, air monitoring equipment should be installed and air sampling should occur on a real-time basis to ensure that the recirculated air is clean, since to determine that a harmful exposure has occurred after the fact does not provide adequate protection to the employee. Other adequate safety precautions should also be considered. These may include multiple air cleaning systems installed in series or automatic sensing devices to warn of air cleaner failure along with a means of diverting the recirculated air outdoors if the air cleaner fails. If unfiltered exhaust air is vented outside the work environment, local air pollution authorities should be contacted regarding the relevant regulations.
What Is the Function of a Mist Collector and How Should It Be Maintained?
A mist collector is an air cleaning device used for removing MWF aerosol from an exhaust airstream before discharge into the ambient air. Guidance for design and maintenance is contained in ANSI Technical Report B11 TR 2-1997. Factors which should be considered in the design and selection of a mist collector are collector efficiency, filter life, collector maintenance, and pressure drop.
Many commercial mist collection systems are available. In general, commercial collectors have multiple stages utilized in series. The purpose of the first stage(s) in a multi-stage collector is to remove swarf and to reduce the mist loading to the final stage, which is typically a 95% DOP filter or HEPA (high efficiency particulate air) filter. Often a three-stage collector, which includes a 95% DOP or HEPA filter is used for MWF operations:
Where Can the Exhaust Air of the Mist Collector Be Discharged?
The discharged exhaust air of the mist collector can be directed back into the shop or it can be directed outdoors through the roof or wall of the building (ORC 1999). A disadvantage of discharging the cleaned air back into the shop is that if the mist collector is operating improperly, mist will go back into the workplace. In addition, vapors or bioaerosols that may contribute to respiratory problems and to odor problems are not removed by the filters.
Discharging the mist collector exhaust from the building eliminates the possibility of increasing the indoor mist level and gets rid of the moisture and vapors in the building. However, it can increase the need for building supply air. You may also need to get a permit from EPA, State or local authorities for venting the process air from the building.
In cases where exhaust air is discharged into the shop:
Work practices, as distinct from engineering controls, involve the way in which a task is performed. OSHA has found that appropriate work practices lower employee exposures to hazardous substances and reduce safety hazards. Some fundamental and easily implemented work practices are: (1) use of appropriate personal hygiene practices, (2) use of barrier and moisturizing creams, (3) good housekeeping, (4) periodic inspection and maintenance of process and control equipment, (5) use of proper procedures to perform a task, and (6) provision of supervision to ensure that proper procedures are followed.
Good personal hygiene is an important control measure in preventing occupational skin disorders. Employees should be encouraged to maintain good personal hygiene by cleaning MWF-contaminated skin periodically (especially before breaks and meals) with gentle soaps, clean water, and clean towels; and to minimize personal contact with MWF, metal debris, and other potentially harmful chemicals in the workplace. Employees should not place their unprotected hands and arms repeatedly into MWFs. Unwashed skin covered with unwashed and unchanged clothes prolongs contact with MWFs and other chemicals. In addition, rapid evaporation of water from the fabric leaves behind MWF at much higher than intended concentrations, which is a major cause of dermatitis.
Employees should change work clothing that becomes soaked with metalworking fluids and contaminants during the work shift, and should change from contaminated work clothes into street clothes before leaving work. Employees should wear clean work clothing at each shift.
Easy access to hand washing facilities must be provided if employees are to minimize contact with harmful chemical agents. Inconveniently located washing facilities invite undesirable practices such as washing at workstations with solvents, mineral oils, or industrial detergents, none of which is appropriate or intended for skin cleansing. Excessive skin cleansing with harsh agents can produce an irritant contact dermatitis or aggravate preexisting dermatitis.
In addition, employees should keep personal items such as food, drink, cosmetics, and tobacco separate from the work environment to prevent any unnecessary additional exposure to MWFs.
Barrier and Moisturizing Creams
Barrier creams may be useful for some employees (NIOSH 1998a). They may be applied to exposed skin areas to prevent contact with harmful agents. There are two main types of barrier creams: water-repellant and solvent-repellant. The primary application of water-repellant creams is in machine shop operations, where gloves cannot always be worn safely, and where water-based cutting fluids are used (SACMA 1990).
The use of good quality barrier creams on exposed skin areas can offer protection against the development of dermatitis if used consistently and re-applied as necessary throughout the shift. The use of moisturizing creams may also be protective. Although barrier creams and moisturizing creams protect the skin, they must be viewed as supplements only. They do not replace good personal hygiene or the use of chemical-protective gloves.
Moisturizing creams replenish the moisture in the hands; barrier creams prevent moisture in the hands from escaping and keep mild irritants from penetrating to the skin. Creams should be selected based on the characteristics of the fluids being used. Creams must also be used with care, as some operations may be contaminated by them. Barrier creams should be applied only to healthy skin and should not be used if the employee has dermatitis.
Good housekeeping is an important control measure to prevent operator contact with MWFs and other potential hazards, and to prevent contamination of the MWFs by dirt and debris. Cleaning of floors, equipment, and the general work environment should be done by properly trained and equipped personnel working on a planned schedule. People assigned to cleaning should be supplied with proper equipment, materials, and protective clothing, and be trained in safe procedures.
On a day-to-day basis, spills should be cleaned up immediately. Wastes (including floor wash water) should not be dumped or swept into MWF sumps or coolant return trenches. Solvent-soaked rags should be deposited in airtight metal receptacles. All machines should be cleaned and have the MWF changed periodically.
Periodic Inspection and Maintenance
Periodic inspection and maintenance of process equipment (e.g., fluid filtration and delivery systems) and control equipment, such as ventilation systems, is another important work practice control. Equipment that is in disrepair will not perform as intended. The failure of the ventilation system, for example, can result in elevated exposures of MWF to machine workers. Maintenance of the fluid chemistry as well as properly maintained filtration and delivery systems provide cleaner MWFs, reduce mist, and minimize splashing and emissions.
Regular inspections can detect abnormal conditions so that timely maintenance can be performed. If process and control equipment is routinely inspected, maintained, and repaired, or is replaced before failure occurs, there is less chance that hazardous employee exposures will occur.
Use of Proper Procedures
One important element of this program is training employees to follow the proper work practices and operational procedures for their jobs. Employees must know the proper way to perform job tasks to minimize their exposure to MWF and other hazardous chemicals. For example, machine operators should thoroughly understand the proper addition and dilution of fluids and components. How to recognize if a ventilation system is not working properly is important. Procedures for getting something fixed should be known by machine operators. Employees can be informed of proper operating procedures through fact sheets, discussions at safety meetings, and other educational means.
Good supervision is another important work practice. It provides needed support for ensuring that proper work practices are followed by employees. By stressing proper work procedures and ensuring that employees wear the necessary protective clothing and equipment, a supervisor can do much to minimize unnecessary employee exposure to safety hazards and airborne contaminants.
G. PERSONAL PROTECTIVE EQUIPMENT
When Should Employees Use Personal Protective Equipment (PPE)?
Engineering controls, work practice controls, and a MWF management program are the preferred methods for reducing employee exposure to metalworking fluid. However, in some situations, personal protective clothing and/or respirators should be used to prevent dermal contact with the MWFs or unhealthy airborne exposures.
What OSHA Standards Govern the Use of Personal Protective Equipment?
OSHA's Personal Protective Equipment Standard (29 CFR 1910.132) requires employers to evaluate the need for personal protective equipment in their workplaces, to provide the proper equipment, and ensure it is properly used and maintained (even when it is employee owned). The standard has an employee training provision that requires that each affected employee demonstrate an understanding of the training before being allowed to use PPE.
Other standards, 29 CFR 1910.133 through 1910.138, clarify and expand the requirements for specific areas such as hand protection, eye and face protection, and protective footwear. These standards are intended to make sure that the employee is protected and that PPE doesn't create any new hazards of itself.
What Are Some of the Specific Requirements of the Personal Protective Equipment Standard (29 CFR 1910.132)?
The standard requires that the employer conduct a workplace review for hazards that require PPE to be used. This can be done by surveying each work task, looking for potential injury and illness sources, and then organizing and analyzing the resulting data. An assessment may then be made of the potential for injuries and illnesses, the type and level of risk, and the seriousness of the hazard. Material safety data sheets, operating manuals for machines, and any warnings of the companies that made the machines, tools, and chemicals used in the shop should all be considered in the final assessment. From this survey, PPE can be selected.
Training is necessary for each employee who is required to use PPE. Each employee must be trained to know when PPE is necessary; what PPE is necessary; how to properly put on, take off, adjust, and wear it; the limitations of the PPE; and the proper care, maintenance, useful life, and disposal of the PPE. For example, for chemical splash goggles the employer should point out to the employees what the goggles protect against, how to wear them, how to adjust them, what they won't protect against (UV radiation, welding arcs, intense light, etc.), how to clean and store them safely, and finally how to know when its time to get a new pair. This can be done easily and effectively with short commercially produced training videos. Some makers of equipment have inexpensive (or even free) videos that are adequate.
In addition, each affected employee must demonstrate an understanding of the training, and be able to use PPE properly, before being allowed to do work requiring the use of PPE. If the employer has reason to believe that an employee does not have the understanding and skill required to safely use the assigned PPE, then the employer must retrain that employee. It may also be necessary for the employer to re-evaluate the training program.
How Can the Employer Tell If MWF Hazards Warrant Employees Wearing Personal Protective Equipment?
The employer should conduct a survey to identify all potential safety and health hazards from machining operations using MWF. They may include:
Protective equipment for employees exposed to metalworking fluids should protect wearers from chemicals as well as punctures, cuts and abrasions. Employees should wear gloves, protective sleeves, aprons, trousers, and caps as needed and appropriate to protect their skin from contact with MWFs. Eye protection such as goggles and face shields should be worn to guard against chemical splash when handling the neat chemicals, and safety glasses with side shields can be worn for most other machining operations to prevent eye contact with MWFs.
Since excellent manual dexterity is often required of machine operators, some personal protective equipment, such as gloves, may not be appropriate for some operations and may even be a serious safety hazard from possible entanglement in moving tools or workpiece parts. Consequently, if gloves are required, special attention should be given to guarding the equipment. In any event, the employer should specify the operations for which gloves are permitted. Gloves and other protective equipment, where used to prevent dermatitis, must be chemical-resistant or impervious to the chemicals contacted.
Eye and face protection must also be worn to protect employees from hazards of flying particles. Such protection may be required for employees working at or near operating metalworking processes or transferring as-received MWFs and other materials, such as additives, to the machine tool or fluid sump or reservoir. Foot protection is needed against hazards such as falling objects, and objects that may penetrate the feet. When floors of the work area are oily, safety shoes with slip-resistant soles should be provided.
When Should Respirators Be Worn?
Before requiring the use of respiratory protection, the employer must institute effective engineering controls (such as machine enclosures and/or local exhaust ventilation), work practice controls, and/or administrative controls, as necessary, to reduce employee exposure to at or below the OSHA PELs of 5 mg/m3 for mineral oil mist and 15 mg/m3 for Particulates Not Otherwise Classified (PNOC) (applicable to all other metalworking fluids), expressed as 8-hour time-weighted averages. If these controls fail to reduce and maintain employee exposures, to or below the applicable PEL, then the employer must provide respiratory protection.
When respirators are required, a comprehensive respiratory protection program as outlined in the OSHA respiratory protection standard (29 CFR 1910.134) must be established. Important elements of the OSHA respiratory protection standard include:
When respirators other than filtering facepieces are being voluntarily worn by employees, the employer must:
Respirators must be selected by correctly matching the respirator with the hazard, the degree of the hazard (airborne concentrations in the employee's breathing zone), and the user. Respirators should be selected by the person who is in charge of the program and knowledgeable about the workplace and the limitations associated with each type of respirator.
Particulate respirator filters are classified into three filter series, depending on the resistance of the filters to oil:
The NIOSH recommended respiratory protection for employees exposed to metalworking fluid aerosol appears in Appendix 5 (NIOSH 1998a). The NIOSH REL is directed at reducing exposure to MWF aerosols - not to vapors from MWFs and its aerosols. Guidance on the selection of appropriate respirator filters is presented in the NIOSH Guide to the Selection and Use of Particulate Respirators Certified Under 42 CFR 84 (NIOSH 1996).
H. ESTABLISHING A METALWORKING FLUID MANAGEMENT PROGRAM
Why Is Establishing a Metalworking Fluid Management Program Important?
There are many factors that affect the generation of MWF mist, all interacting with each other, so an approach that takes the entire system into account will be the most effective. Addressing only one or a few of the issues will probably be ineffective, while dealing with all the issues in a systematic way will be beneficial.
MWF systems are complex, biologically active, and constantly changing in response to conditions of use. However, MWF systems can be maintained in a stable condition over relatively long periods of time. For that to happen, there should be a well thought-out and consistently enforced fluid management plan. The plan should identify key elements of the program and the individual(s) responsible for their implementation.
What Elements Should a Fluid Management Program Include?
The main elements of the fluid management program include the following:
Designation of overall responsibility for performance of the system The designated person(s) coordinating the fluid management program should receive input from all available sources along with information on finished part quality, production quantity, and production cost data. Whoever is selected to track the system's performance should understand the chemistry involved in the metalworking processes.
Designation of responsibility for adding materials All system additions should be controlled and recorded by a designated person(s). Chemicals to be added may include fresh biocides, MWF fluid additives or concentrates, and waters or oils used to make up for fluid loss in the metalworking process.
A written standard operating procedure (SOP) for testing the fluid A procedure should be in place to test the fluids periodically to keep their performance in optimal shape. Such an SOP should include:
The metalworking fluid manager should decide which factors need to be recorded and tracked. These factors should be prioritized and customized for specific facility situations. For instance, in a facility using water-miscible MWFs with good microbiological control in a soft-water area, a manager's list of priorities may look like this:
Training programs - Managers and employees should have training to understand the basic functioning of the fluid management system, including what can affect the proper functioning of a particular metalworking fluid system and prolong or shorten its useful life, and the warning signs of impending problems. Employees who work in the metalworking fluid environment should also receive training about the safety and health hazards of the chemicals to which they are exposed.
What Are Some of the Ways to Minimize and Control Bacterial and/or Fungi Growth?
Clean System Before Introducing Fresh Metalworking Fluid - It is important to clean the machine tool's MWF delivery system; otherwise, you are exposing the new fluid to the same conditions that forced you to change the fluid in the first place. This is particularly true in the case of bacteria and/or fungi contamination. By draining the sump only, you are disposing of the majority of the bacteria/fungi, but as long as there is some residual MWF in the system, there will be some residual bacteria/fungi. These bacteria/fungi consume the organic components (oil and other additives) present in the metalworking fluid. By allowing them to come into contact with fresh fluid, you are providing them a free food supply. Due to the abundance of food, they will rapidly multiply and within a short period of time, you will find yourself pumping out the machine tool sump again.
Existing bacteria and fungi should be killed by the proper addition of biocide, and then the coolant pumped out and discarded. Any accessible colonies should be physically removed, a suitable cleaner circulated through the system, the cleaner removed, and the system well rinsed before refilling with fresh MWF.
Operate System at Correct Concentration All water based metalworking fluids are designed to be operated at a given concentration dissolved or emulsified with water. The correct concentration is important to provide the cutting operation with optimal lubricity and cooling, corrosion protection, and resistance to bacteria and fungus. Operating a system at a low concentration may result in decreased tool life, bacteria and/or fungus problems, possible corrosion and eventual downtime. Operating a system at too high a concentration may result in dermatitis, foaming, and heavy residues.
Proper mixing procedures are critical to the attainment of long metal removal fluid life and economical use of metalworking fluid concentrate, as well as to the elimination of metalworking fluid concentration related problems. Premixing the MWF concentrate with pure water at the MWF manufacturer's recommended concentration is important for initial charge. Actual concentration in machines must be checked frequently and adjusted as needed with pure water, concentrate, or premixed fluid as appropriate to maintain the recommended range.
Ensure Makeup Water Is of Adequate Quality The quality of makeup water is very important. Water used for making MWF mixtures should be as pure as possible for the most economical and trouble-free use. Minerals in metal working fluid water can corrode machine tools and machined parts, can aggravate deposition of residues on machine tools, and can increase the rate at which bacteria and fungi grow in the metalworking fluid. It is also essential that the proper water miscible MWF be selected.
Water that contains certain dissolved ions such as calcium and magnesium is termed "hard" because they will form scale upon evaporation and will form insoluble soap scum when mixed with many MWFs. Other minerals such as sulfates are detrimental because they promote the growth of sulfate-reducing bacteria that produce a "rotten egg" odor. Some, including sulfates and chlorides, are corrosive to metal and contribute to rust. Minerals are thus very detrimental to the performance of MWF mixtures. The more concentrated these minerals are, the faster they build-up and cause adverse effects to appear. Therefore, the purer the water for making MWF mixtures is initially, the longer the fluid can be used before problems occur. One method of removing minerals is to run it through a zeolite softener followed by a reverse osmosis filter. Purified water can also be produced by deionization, which removes most of the dissolved minerals thus producing a high quality process water.
Incorporate Biocides The incorporation of effective biocides is also helpful in preventing or retarding degradation caused by bacterial action. These compounds may be incorporated as components in formulated MWFs or may be added to MWFs before and during use. Biocidal activity should be broad enough to suppress the growth of a highly diverse contaminant population. Over time, chemical and biological demands may consume the biocides and cause the concentrations to fall below those needed to inhibit microbial growth. Biocides should be added judiciously to prevent microbial growth or to arrest modest growth. Some biocides that function very well in clean products can actually serve as food for the various types of bacteria found in water miscible fluids that are so easily contaminated. Grossly contaminated fluids should be treated if necessary with biocide just prior to pumpout as part of the overall cleaning procedure, but this should be done after operators have ceased working with the fluid (i.e., offshift). Conscientious monitoring and prevention of microbial growth is the best approach for preventing the buildup of endotoxins and other hazardous biological substances and for preserving fluid quality and function.
Miscellaneous Factors To avoid problems related to bacteria and/or fungi growth a good filtration system should be in place. A metalworking fluid is subjected to the metal chips and fines of the process, airborne contamination from cascading fluid over a part and the machine, machine leakages, residues left on the part from previous operations, water, operators, and other factors. Whenever possible, these contaminants need to be removed (IAMS 1996).
The build-up of chips and metal fines in the metalworking delivery system provide an excellent "nesting" area for bacteria. In large systems, these chip beds many extend for many yards in sluices and pipes. The associated biomass will be too large for simple treatment with biocides to be effective. The periodic removal of this debris minimizes the potential for bacteria growth and extends MWF life.
Tramp oil is non-emulsified oil that is mechanically entrained in a MWF in large droplets. Tramp oil often results from machine tool hydraulic or way lube systems leaking oil into metalworking fluids. Tramp oil damages MWFs by extracting key components, by providing food for microbes, and by providing an area of reduced oxygen which promotes the growth of anaerobic bacteria. Consequently, all possible steps should be taken to reduce oil leakage.
In some cases it is not possible to avoid tramp oil. Oil is applied to the ways of machine tools to insure proper movement of the workpiece during the machining operation. As the MWF comes into contact with the ways or the oil drips off the way, tramp oil is introduced into the MWF. This should be minimized by applying the required amount of way lube and no more, and by making sure that way lubricators run only when the machine tool runs.
The amount of tramp oil in the system should be minimized through hand skimming or by the use of skimmers, separators, or other devices. Since tramp oil separates and floats when agitation ceases these devices are particularly effective when the system pumps are not running, as on weekends and off-shift. Using system quiet time to facilitate skimming will help prevent problems. In addition, finding a MWF and way oil that are compatible will also help.
It is important to maintain good housekeeping by teaching your company's employees not to use machine tool sumps as trash receptacles. Paper cups, uneaten food, cigarette butts, and other trash should not be seen floating in the MWF. These not only introduce bacteria into the sump but provide nutrients for bacteria. Trash should go in trash containers even if it means the employee has to walk away from the machine tool.
What Should Be Done After MWFs Reach the End of Their Service Life?
All fluids, even those used with well-managed systems, eventually reach the end of their useful life. When testing shows that the fluid in a system has reached the point where making additions to the fluid is no longer effective, or when the level of bacteria or mold has become unmanageable, the system must be properly drained, cleaned and recharged (see Appendix 6). Periodic checks of the system on a regular basis are strongly recommended. The size of the system will indicate the frequency and type of testing.
How Does a Facility Determine If It Has Good MWF Management?
A self-assessment should be done to determine good MWF management. The procedure outlined in Appendix 7 (developed by the Organization Resources Counselors) is recommended. It involves the use of a checklist and covers the features of the management plan that are common to all shop MWF systems. It also covers individual processes, locations, or MWF systems within the shop. The purpose of the self-assessment metric is not to grade a shop's performance, but rather to provide information for improvements in the MWF management program. Regardless of the outcome, the assessment information should be used to improve the MWF management program. Other checklists may also be effective in evaluating the fluid management program.
I. INSTITUTING AN EXPOSURE MONITORING PROGRAM
Why Should Exposure Monitoring (Air Sampling) Be Conducted?
Good management of the MWF environment includes assessing the level of employees' exposure to MWF. Exposure monitoring provides a means of determining the effectiveness of engineering controls and work practices, the overall performance of the metalworking system management program, and assists in the proper selection of personal protective equipment. Air sampling helps identify the high exposure jobs or tasks so that the employer can determine ways to reduce these exposures, for example, by improved ventilation to control MWF mist, and may also indicate the level of exposure associated with the presence or absence of health complaints.
How Is Employees' Exposure to MWFs and Fluid Contaminants Assessed?
There are two kinds of exposure assessment: qualitative and quantitative.
A qualitative assessment identifies the shop areas where exposure to MWFs is possible and estimates the level of airborne exposure and the extent of mist or dermal exposure hazards. Qualitative assessments are often performed to rule out the need for quantitative assessments. Such estimates may be based on expert industrial hygiene opinion, the presence of MWF-related adverse health effects, any past exposure measurements, and possibly the results of a direct-reading aerosol instrument. Objective data, discussed below, is also a good qualitative assessment tool. An employer should first conduct a qualitative assessment to characterize generally what the upper limits of exposure may be for each operation in the MWF environment. For example, in some MWF operations, such as automated transfer lines where machining takes place, operators do not routinely come into contact with MWF. In contrast, maintenance employees on such transfer lines may be required to change or adjust tools and be exposed to MWF for extended periods. Area and source sampling, discussed below, is considered a qualitative tool for estimating the airborne exposure of workers.
Quantitative assessment measures the amount of exposure to MWFs. Exposure monitoring is generally performed in response to employee concerns, complaints, symptoms or irritation or health effects, or where experience indicates that exposure to MWF aerosol may be relatively high. Exposure monitoring is generally not needed if the employer can show that a process, operation, or activity has low exposures If the qualitative assessment indicates that the exposure levels of MWF may exceed either of the current OSHA PELs you should conduct quantitative air monitoring (breathing zone air samples) for those employees whose exposure is at issue.
What Is Objective Data and How Can It Be Used in Qualitative Assessments?
Objective data is used in qualitative assessments to show that a process, operation, or activity is highly unlikely to result in significant exposures under all foreseeable conditions. For example, many small, low volume, or ventilated machining operations just do not create exposures above an appropriate exposure limit. The kind of objective data that employers would use to demonstrate this may include information from industry studies, laboratory product test results, insurance companies, or trade associations. You should make sure that the data are obtained under workplace conditions closely resembling the processes, types of materials, control methods, work practices and environmental conditions in your current operations or under conditions that would results in even higher exposures that the conditions in your workplace.
How Is Air Sampling to Be Conducted?
If a qualitative assessment shows that air sampling should be done, a strategy for sampling should be developed.
Personal samples give the best estimate of an employee's exposure level since they represent the actual airborne contaminant concentration in the employee's breathing zone during the sampling period, and is the preferred method for determining a employee's time-weighted average (TWA) exposure. Where several employees perform the same job, on the same shift, and in the same work area, and the length, duration, and the level of MWF aerosol are similar, an employer may sample a representative fraction of the employees instead of all employees. Personal sampling can also be used to assess work practice controls.
Source and area samples are useful supplements to personal monitoring. However they cannot substitute for taking personal breathing zone samples. Area sampling is useful for evaluating overall air contaminant levels in a work area and for investigating cross-contamination with other areas in the facility. Area sampling may help to determine the source of MWF aerosol exposures. Source sampling can be used to assess the effectiveness of engineering controls. It is also useful to take a sample when the target equipment is not running. Exposure at a work station when the target equipment is not running will tell how much of the exposure is due to adjacent sources, and how much comes from the target machine.
What Are the Sampling and Analytical Methods That Can Be Used?
The OSHA Chemical Sampling Information file contains current sampling technology for mineral oil mist and other metalworking fluids (Particulates Not Otherwise Classified). The OSHA sampling procedure for mineral oil mist is listed under IMIS: 5010; and for other metalworking fluids, under IMIS: 9135 (Appendix 8).
The current OSHA recommended media sampling for mineral oil mist requires a pre-weighed, 5-micron low-ash polyvinyl chloride (LAPVC) filter. The sample can be taken at a flow rate of 2.0 L/min. Total sample volumes not exceeding 960 liters are recommended. The current recommended media sampling for all other metalworking fluids also requires a pre-weighed, 5-micron low-ash polyvinyl chloride filter. The recommended sampling flow rate and total sample volume is also the same as for mineral oil mist. The filter media captures total aerosol, and the gross weight measured does not require laboratory analysis. A cyclone should not be used with this method.
NIOSH recommends thoracic sampling and gravimetric measurement of MWF aerosol using NIOSH Method 0500 (see Appendix 9) with a sampling device that collects the thoracic fraction. If a thoracic sampling device is not available, a total dust sampler can be used and the result can be divided by 1.25 to estimate the thoracic fraction. NIOSH Method 0500 can be used to measure the total material collected.
When there are simultaneous exposures to nontoxic particulate materials, ASTM PS 42-97 Provisional Standard Test Method for Metal Removal Fluid Aerosol in Workplace Atmospheres (American Society for Testing and Materials (ASTM)), may be useful to estimate the soluble component of the workplace aerosol. This method improves the specificity (ability to measure only MWF) of the analytical method by removing non-MWF materials from the analysis. In ASTM PS 42-97, a sample of MWF mist is collected on a PTFE membrane filter and then a combination of standardized gravimetric and solvent extraction techniques are used. The extraction solvent removes the fluid components and leaves the insoluble particulate on the filter, regardless of MWF formulation. The resulting extract can be subjected to various analytical techniques to determine the total or specific components of the extracted MWF. In this method, both total particulate matter and extractible mass MWF aerosol concentrations in a range of 0.05 to 5 mg/m3 in workplace atmospheres can be quantified.
A direct reading instrument (real-time aerosol monitor) can be used in some cases as an alternative to conventional sampling and analysis that uses pumps and filters with subsequent gravimetric analysis. Aerosol monitors (photometers) can be used for screening operations for further evaluation or determining locally high concentrations of aerosol. Aerosol monitors are also useful in identifying mist or particulate sources and can be useful in determining time-dependent fluctuations in mist or particulate levels. They sample the workplace air and instantaneously measure the concentration of airborne dusts and mists by measuring the amount of light scattered by these materials.
Because these monitors cannot differentiate between MWF mist and dust, care must be used when evaluating areas near dry machining operations or other sources of particulate. Although the results of these measurements are typically displayed with the units mg/m3, these numbers should be considered as estimates of the true concentration, since the amount of light scattered depends on the characteristics of the aerosol in addition to its concentration. Consequently, these instruments should be calibrated by comparing them with gravimetric techniques for each combination of aerosol size and fluid type.
How Often Should Monitoring Be Done?
NIOSH recommends that surveys be repeated at least annually. For employees exposed to concentrations at or above one-half the NIOSH REL, NIOSH recommends that monitoring be undertaken at least every six months. If results show that aerosol levels are below the REL, you can just keep tabs on your system by completing the self-assessment metalworking fluid management checklist to ensure that the MWF is properly managed and aerosol mists controlled through the use of equipment.
In addition, employee exposures should be reevaluated whenever a significant change in production, equipment, process, product formulation, personnel, or control measures takes place, that might cause new or additional exposure to MWFs. If you get reports from employees complaining of conditions related to exposure to MWFs, (see discussion on medical monitoring in this guide), you should monitor workplace exposures of those employees as soon as possible.
Employers should notify the affected employee(s) of the results of the monitoring of metalworking fluid exposure. Notification should be in writing, either by distributing copies of the results to the employees or by posting the results.
How Can a Small Company Get Industrial Hygiene Assistance in Obtaining Monitoring Services?
Some of the ways to reduce sampling costs for small business can be achieved through the use of insurance carriers, fluid supplier product stewardship, the OSHA Consultation Program (Appendix 10), NIOSH Health Hazard Evaluations, and through union and association efforts.
Data may be available to you from previous exposure measurements. For example, studies may have been conducted in your industry. Your trade association may have data, or manufacturers of the MWF fluids used in your workplace may have conducted laboratory tests that provide employee exposure data. To generalize from data obtained from these sources or an industry-wide survey, however, you must show that the conditions that existed in the survey, such as the operations, MWF fluids, control methods, work practices, and environmental conditions, are similar to those in your own workplace.
J. MEDICAL MONITORING OF EXPOSED EMPLOYEES
What Is Medical Monitoring?
Medical monitoring is a process of periodic medical screenings aimed at early diagnosis and treatment of disease in employees exposed to a hazardous substance.
Why Is Medical Monitoring Important?
Whatever the exposure in a shop, control of MWF exposures by engineering and work practice controls and implementation of a MWF management program may not eliminate all possibility of illness or injury due to exposure to MWFs. Medical monitoring of employees will help identify those experiencing early evidence of respiratory impairment or skin disease due to failure of control systems or inadequate hygiene and respirator programs.
Taking corrective action will reduce the incidence and severity of lung and skin disease in people working with MWFs.
What Is the Medical Monitoring Process?
Medical monitoring should be directed and supervised by a qualified and licensed physician or health care professional who periodically reviews an employee's health status by collecting health information from the employee and/or conducting a physical examination and appropriate medical tests. An adequate program includes:
Who Should Be Included in the Medical Monitoring Program?
All exposed employees will benefit from participating in a medical monitoring program. Newly hired or transferred employees should undergo a pre-placement evaluation to determine a baseline status. All employees should have periodic exams following job placement. People working in high exposure areas or working in areas where one or more co-workers have developed lung disease (asthma, bronchitis, HP, etc.) or skin disease should be evaluated more frequently.
What Does Medical Monitoring Consist Of?
At a minimum, medical examinations should consist of an examination of the lungs and a standardized respiratory symptom questionnaire that addresses all of the potential respiratory conditions that have been associated with MWF exposure. OSHA has a respiratory symptom questionnaire associated with the Respiratory Protection Standard, Appendix C to 29 CFR 1910.134. The respiratory protection questionnaire contains appropriate questions about respiratory conditions. However, questions about other conditions relating to MWF exposure should be added when questionnaires are used for medical monitoring for MWFs.
NIOSH recommends that if an employer's resources permit, routine periodic examinations should include baseline spirometric (lung function) testing for comparison with future tests. NIOSH recommends that anyone who administers a spirometric test as part of an occupational medical monitoring program should have completed a NIOSH-approved training course in spirometry. Spirometry equipment and procedures should comply with American Thoracic Society guidelines.
The initial medical examination should also consist of a skin examination and history of skin problems.
What Symptoms or Conditions Are Considered Most Important in the Medical Monitoring of MWF Employees?
Symptoms or conditions important in the medical monitoring process can be identified by the use of OSHA's Respirator Medical Evaluation Questionnaire, or a comparable questionnaire, and a skin history. A few examples include:
All employees included in the medical monitoring program should be provided with periodic health exams. Medical monitoring and follow-up medical evaluations should be provided at a reasonable time and place and without cost to the participating employees.
Periodic health evaluations should include a medical exam of the lungs and the skin, spirometric testing, as well as a brief questionnaire to determine if the person is experiencing any respiratory symptoms (such as shortness of breath, wheezing, chest tightness, or cough) and/or skin disorders. The questionnaire should also include a question on whether the person is taking any medications for these conditions.
The frequency of periodic exams depends on the frequency or severity of health effects in the employee population for a given worksite. If there is no evidence of any person contracting a disease associated with metal working fluids or MWF aerosols at a particular facility, then testing once a year would be reasonable. Employees in facilities where there has been an increase in the frequency and severity of MWF health related illnesses or symptoms should be tested more frequently, such as twice a year.
What If the Questionnaire, the Skin Examination, Pulmonary Function (Spirometric) Testing or Other Medical Tests Reveal Problems That Might Arise from Working with MWF?
Employees who develop new abnormal respiratory or skin symptoms or signs and workers with worsening pre-existing disease should be referred to a health practitioner for evaluation.
What Is Medical Management?
Medical management is the process of using medical information to help reduce health risks in the workplace. Management decisions may address broad issues, such as selecting a less irritating MWF or hand cleaner, or the decisions may apply only to specific employees. Job reassignment to an area where no skin exposure to MWF exists coupled with proper medical treatment for an individual who has a serious case of dermatitis is an example of a medical management decision that addresses a specific individual and enhances that person's recovery by eliminating subsequent occupational exposure.
What About Employee Self-reporting of Symptoms or Medical Problems?
Employees should be strongly encouraged to report any medical condition that they feel may be related to their work with MWFs to the appropriate plant personnel. It is important for employers to recognize that workers may put off self-referral or even deny exposure-related symptoms on periodic questionnaires for fear that reporting of symptoms will lead to involuntary transfers or loss of income. That's why it's crucial for employers to encourage employees to promptly report any exposure-related symptoms and to let employees know that accurate reporting of symptoms is important to the program's success. The necessity of reporting medical symptoms should be part of the employee's training and should be reemphasized during periodic retraining.
The relationship between the employee and the health practitioner must remain confidential. The physician's report to the employer should only reveal specific findings or diagnoses related to occupational exposure to MWFs.
What Training Is Necessary?
Training of managers and employees in general is crucial to the proper management of metalworking fluids. Everyone in the workplace must understand why it is so important that certain procedures be followed. Then the likelihood increases that good practices will be carried out and health and safety risks will be greatly reduced (ORC 1999).
The employer must provide information and training to employees working in the metalworking fluid environment so that they can perform their job safely. Managers should receive training as appropriate, including training in the employer's health and safety program for metalworking fluid processes and metalworking fluid management. Training should be well organized, integrated into the existing requirements of the OSHA Hazard Communication Standard, and be specific to the individual circumstances of each facility.
What Are Some of the Requirements Under OSHA's Hazard Communication Standard?
Under OSHA's Hazard Communication Standard (29 CFR 1910.1200), employers must train employees about the hazards of materials to which they are exposed. This standard requires employers to develop, implement and maintain at the workplace a written, comprehensive hazard communication program that includes provisions for labeling containers, collecting and making available MSDSs, and having in place an employee training and information program. The standard also requires employers to make a list of all the hazardous chemicals in the workplace as part of the written hazard communication program.
The following are a few of the major requirements of the hazard communication standard:
Training should be conducted:
Employees should be informed about metalworking fluids and other hazardous chemicals in their work areas and the availability of information from MSDSs or other sources. Employees should be instructed about the adverse health effects associated with exposure to these chemicals. In addition, employees should be trained to detect and report hazardous situations (e.g., the appearance of bacterial overgrowth and degradation of MWFs).
Employees should be informed that exposures to MWFs during metalworking operations can occur through inhalation of MWF aerosols and through contamination of the skin by settled mists, splashes, dipping of hands and arms into MWFs, or handling of parts coated with MWF. Instruction should include information about how exposures can be controlled by a combination of proper MWF use and application, MWF system maintenance, isolation of the operation(s), ventilation, and other operational procedures.
Employees should be aware that dermal exposures may be reduced by the use of machine guarding and protective clothing and equipment such as gloves, face guards, aprons, or other protective work clothes. Employees should be encouraged to maintain good personal hygiene and housekeeping practices to prevent MWFs from contaminating the workplace.
The training program should be conducted in such a way that the employee is able to understand the information. The training program should provide answers to the following questions:
Each program should be custom designed to consider the individual circumstances of each facility, and it has to be geared to a specific audience. In particular, the name and title of the person(s) responsible for aspects of the MWF management program should be included in the training. For guidance in developing a training program, one can refer to the outline (Appendix 11) developed by the OSHA Metalworking Fluids Standards Advisory Committee.
American Automobile Manufacturers Association (AAMA), 1996. Symposium Proceedings: The Industrial Metalworking Environment Assessment and Control. Detroit, Michigan: AAMA.
American Conference of Governmental Industrial Hygienists (ACGIH). 2000. Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati, OH: ACGIH.
American Conference of Governmental Industrial Hygienists (ACGIH). 1998. Industrial Ventilation: A Manual of Recommended Practice, 23rd edition, Cincinnati, OH: ACGIH,
American National Standard Institute (ANSI) Z9.2- 1979 (1991), Fundamentals Governing the Design and Operation of Local Exhaust Systems, New York, NY: ANSI.
American National Standards Institute (ANSI). 1997. Mist Control Considerations for the Design, Installation and Use of Machine Tools Using Metalworking Fluids, ANSI B11 TR 2-1997, New York, NY: ANSI.
American National Standards Institute (ANSI). 1998. American National Standard for the Recirculation of Air from Industrial Process Exhaust Systems, ANSI/AIHA Z9.7-1998. Amer Ind Hyg Assoc, publisher. Fairfax, VA.
American Society for Testing and Materials (ASTM). 1994. Standard Practice for Safe Use of Water-Miscible Metalworking Fluids, E 1497-94. West Conshohocken, PA: ASTM.
American Society for Testing and Materials (ASTM). 1997. Provisional Standard Test Method for Metal Removal Fluid Aerosol in Workplace Atmospheres, PS 42-97. West Conshohocken, PA: ASTM.
Boundy, M., Leith, D., Hands, D., Gressel, M., and Burroughs, G.E. 2000. Performance of Industrial Mist Collectors Over Time. Appl Occup Env Hyg 15: 928-935.
Code of Federal Regulations. 2000. Title 29, Part 1910 (1910.1000 to End). Washington, DC: U. S. Government Printing Office.
Institute of Advanced Manufacturing Sciences Incorporated (IAMS). 1996. Pollution Prevention Guide to Using Metal Removal Fluids in Machining Operations. Cincinnati, Ohio: IAMS.
Leith, D., Raynor, P.C., Boundy, M.G., Cooper, S.J. 1996. Performance of Industrial Equipment to Collect Coolant Mist. Am Indus Hyg Assoc J 57:1142-1148.
National Institute for Occupational Safety and Health (NIOSH). 1998a. Criteria for a Recommended Standard: Occupational Exposure to Metalworking Fluids. DHEW (NIOSH) Publication No. 98-102, NIOSH, Cincinnati, OH.
National Institute for Occupational Safety and Health (NIOSH). 1998b. What you need to know about Occupational Exposure to Metalworking Fluids. DHEW (NIOSH) Publication No. 98-116, NIOSH, Cincinnati, OH.
National Institute for Occupational Safety and Health (NIOSH). 1996. NIOSH Guide to the Selection and Use of Particulate Respirators Certified Under 42 CFR 84. DHEW (NIOSH) Publication No. 96-101, NIOSH, Cincinnati, OH.
OSHA MWF Standard Advisory Committee. 1999. Final Report of the OSHA Metalworking Fluids Standards Advisory Committee. Sheehan, M.J., chairperson and editor, West Chester University, PA.
Organization Resources Counselors (ORC), Inc. 1999. Management of the Metal Removal Fluid Environment. Washington, DC: ORC.
Suppliers of Advanced Composite Materials Association (SACMA), 1990. A Guide to the Prevention of Dermatitis. Arlington, VA: SACMA.
UAW-Chrysler National Training Center, 1998. Metalworking Fluids Safety Training Course, Student Manual. Detroit, MI: Author.
Woskie, S.R., Smith, T.J., Hammond, S.K., and Hallock, M.H. 1994. Factors Affecting Worker Exposures to Metal-Working Fluids During Automotive Component Manufacturing. Appl Occup Environ Hyg 9:612-621.
American Society for Testing and Materials (ASTM). 1994. Safe Use of Water-Miscible Metalworking Fluids, E 1497-94. West Conshohocken, PA: ASTM.
American Society for Testing and Materials (ASTM). 1995. Determining Carcinogenic Potential of Virgin Base Oils in Metalworking Fluids, D 1687-95. West Conshohocken, PA: ASTM.
Hagopian, J.H., and Bastress, E.K. 1976. Recommended Industrial Ventilation Guidelines. DHEW (NIOSH) Publication No. 76-162, NIOSH, Cincinnati, OH.
National Center for Manufacturing Sciences (NCMS). NCMS Report 0274RE95, 1997. Metalworking Fluids Optimization Guide. Ann Arbor, MI: NCMS.
National Institute for Occupational Safety and Health (NIOSH). 1978. The Recirculation of Industrial Exhaust Air. DHEW (NIOSH) Publication No. 78-141, NIOSH, Cincinnati, OH.
Appendix 1. Glossary
Bag Filter - a pressure filter where fabric bags are installed inside a cylindrical housing (pressure vessel) and the filtered liquid is pumped through the bag walls. Liquid flow is from the inside to the outside of the bag - dirt is trapped inside the bag.
Biocide - a chemical agent used to kill microbiological organisms (bacteria or fungi) in MWFs. Biocides are registered by the EPA under Federal Insecticide Fungicide and Rodenticide Act (FIFRA) and are known officially as antimicrobial pesticides.
Boring - an operation designed to machine internal work such as cylinders, holes in castings, and dies.
Cartridge Filter - a pressure filter where paper or fabric cartridges are installed inside a cylindrical housing (pressure vessel) and the filtered liquid is pumped through the cartridge walls. Liquid flow is usually from the outside of the cartridge wall through to the inside core. Dirt is deposited on the OD of the cartridge.
Clarifier - equipment used to remove contaminant from MWFs.
Close Capture Enclosure - a device mounted near a contaminant source for the purpose of containing or removing air contaminants. By design it will have a high entrainment velocity and lower air volume requirement.
Compatibility - "compatibility" of MWF means that the fluid does not chemically or physically react with other materials in the metalworking process.
Contaminants - substances contained in in-use metalworking fluids that are not part of the original fluid formulation. These can include abrasive particles, tramp oils, cleaners, dirt, metal particles, dissolved metals, hard water salts, bacteria, fungi, and microbiological byproducts.
Cutting - a machining operation that removes material from the workpiece by the use of a cutting medium (e.g., saw blade).
Decant System - system to separate light floating liquid (tramp oil) from a heavier liquid (water-soluble MWF).
DOP Filter - a high efficiency air filter that has been tested using the dioctylphthalate (DOP) challenge test.
Drilling - a machining operation where short holes can be made using a radial drill and the tool rotates in the operation. Drilling deep holes may require a gun drill and the workpiece may rotate in this operation.
Electrostatic Separator - an air cleaner that charges aerosol particles and then removes them from the airstream by passing the charged particles between high voltage plates to cause electrical migration to the surface.
Emulsion - a mixture of liquids that do not dissolve in each other to form a true solution, by have droplets of one liquid dispersed throughout the other. For MWF it is generally an oil and water mix.
Emulsifier - a substance added to soluble oil MWF to aid in forming an emulsion in the fluid (see above.)
Enclosure - a mechanical device that creates a separation or barrier between the process and the worker's environment. Enclosures may be designed as close capture, total enclosure or tunnel enclosures.
Endotoxin - a component of the cell wall of gram-negative bacteria.
Filter - a porous medium (disposable media, wedge-wire or mesh screen) through which liquid is passed to separate and trap particles held in suspension.
Grinding - a machining operation that is done with an abrasive wheel. The workpiece may be stationary, may rotate or move in a plane.
HEPA Filter - High efficiency particulate air filter. Available in different performance classifications ranging from 95 to 99.99% efficiency for 0.3 um DOP aerosol.
Hood - a hood is a generic term for a device designed to capture contaminated air and conduct it into an exhaust duct system. The term may include enclosures, canopy hoods, push-pull hoods, down draft hoods, side draft hoods or others.
In-Use MWF - metalworking fluid that is being used and continually recycled for lubrication, cooling, chip transport, and corrosion protection of a metal removal operation. These fluids are distinguished from "as received" metalworking fluids by the presence of contaminants from the metal removal process, the machine tool, and biological growth in water based fluids.
Media (Filter) - that part of the filter upon which the contaminant is actually trapped as the fluid passes through. Usually disposable media, permanent belt, and wedge-wire are used.
Medical Management - the use of medical information to help control the health risk posed by a contaminant in the workplace. The risk management decisions may be directed toward the entire workforce or they may be made for a single worker who is not able to safely work in an area due to a temporary or permanent medical condition.
Medical Monitoring - the collection of medical information to screen for health problems that may be related to work in a specific work environment. The focus is on early detection of health problems for the individual employee.
Medical Surveillance - is the systematic examination of medical monitoring data to determine if there are unusual patterns of health problems in the workplace. Statistical techniques may be used in larger workplaces to improve this analysis.
Metal Removal Process - a manufacturing process that removes metal to produce a finished part.
Metal Working Fluids - a generic term to describe four categories of fluids (straight oils, soluble oils, semi-synthetic and synthetic) that facilitate a wide variety of operations involving the working or modification of metals. Metal removal fluids are used in machining, grinding, and honing operations. Metal forming fluids are used in stamping, forging, drawing, coining, rolling, piercing, cold heading and wire/bar/rod drawing operations. Metal protecting fluids are used primarily for fingerprint displacing and indoor/outdoor storage. Metal treating fluids are used primarily for metal quenching operations. Drawing and forming fluids are similar or identical in composition to MRF's but are used in an entirely different way.
Mist - fine liquid droplets suspended in or falling through a moving or stationary gas atmosphere.
MWF System - removes particles from the fluid. The system must deal with the chips and swarf generated by the metal working process as well. It usually includes a clarifier, electrical controls, pumps and a trench return for chips and spent MWF. May also include water make-up, chiller for temperature control, tramp oil skimmer, variable speed pump control, etc.
Neat Oil - as it comes from the drum; not diluted. Usually refers to soluble oil before mixing with water to form soluble oil and water MWF mixtures. Sometimes used to describe straight mineral oil.
Occupational Exposure Guideline - a guide for use in evaluating worker exposures to particular workplace contaminants, especially where there is a lack of definitive data to establish a safe exposure level.
Particulate Matter - small dirt particles suspended in MWF or microscopic particles suspended in air.
Pressure Filter - a filter where the filtered liquid is pumped under pressure through the media. Examples are automatic flat bed filters, cartridge and bag filters.
Semi-Synthetic MWF - a water-based (reducible) MWF composed of both water-soluble components and emulsifiable components. It may or may not include performance-enhancing additives, and generally contains 5 to 30% (by volume) of oil. In mixed form semi-synthetic MWF may contain 5% or less of oil.
Soluble Oil MWF - a water-based (reducible) MWF composed of an emulsion of oil (or oil-like material) in water. It may or may not include performance-enhancing additives.
Straight Oil - usually refers to oil used as an MWF. Could be a mineral seal oil (40 to 50 SSU) used for honing, a light oil (90 to 100 SSU) used for aluminum machining (valve bodies) or a heavy oil with high-pressure additives used for broaching (250-450 SSU). Contains no water and is not mixed with water in normal conditions.
Surfactant - surface-active agent such as an emulsifier or detergent that lowers the surface tension of water.
Swarf - fine particles of metal, graphite and carbide that result from grinding operations.
Synthetic MWF - a water-based (reducible) MWF composed of a true solution of water-soluble organic and/or inorganic components. It may or may not include performance-enhancing additives.
Thoracic Particulate Mass - the portion of the MWF aerosol that penetrates beyond the larynx in the respiratory system.
Total Enclosure - a box or housing around the machine or process. The housing is not intended to be air tight. Openings are limited to the minimum required to allow for part entry/egress, maintenance or utility access.
Total Particulate Mass - the portion of the aerosol spectrum that would be sampled by a 37-mm, closed-face filter cassette that is worn by a worker and connected to a portable sampling pump operated at 2.0 liters/min.
Tramp Oil - petroleum contaminants of metalworking fluid that come from hydraulic oil, gear oil, way oil, and other lubricants.
Tramp Oil Skimmer - device for removing floating tramp oil. Common types are endless tube, disc, belt, and decant systems, All tramp oil removal systems require regular maintenance-systems remove fines as well as floating tramp oil and tend to plug up. Must be installed in a still or quiescent part of the filter dirty tank.
Tunnel Enclosure - a continuous total enclosure over two or more connected work stations or machining processes. The design principles are similar to those applied for total enclosure.
Turning - a machining operation that uses a single point tool that is fed into a rotating workpiece.
Vacuum Filter - a filter where a vacuum is created on one side of the media, usually by means of the pump suction. Atmosphere pressure then pushes the dirty liquid through the media.
Water-miscible - designed to be diluted with water.
Wet Metalworking Fluid Environment - the workplace environment in which wet metalworking operations occur.
Worker Exposure - the exposure of a worker to metalworking fluids and contaminants that would occur without regard to the use of respirators.
Appendix 2. Typical Additives Included in MWFs - The following tables show possible additives included in the various metal removal fluids.
Table 1: Straight Oil Additives
Table 2: Soluble Oil Additives
Table 3: Semisynthetic Additives
Table 4: Synthetic Fluid Additives
Appendix 3. References for the Proper Design and Operation of Ventilation Systems Principles for the proper design and operation of ventilation systems can be found in the following publications:
Appendix 4. General Considerations for Enclosure/Exhaust Hood Design
Enclosures/exhaust hoods should be designed for efficiency, safety, accessibility, and compatibility with the metalworking fluid being used. Some general considerations, which are taken from ORC's Document Management of the Metal Removal Fluid Environment, include:
For a more comprehensive listing of exhaust ventilation system design specifications, refer to American National Standard Institute Technical Report: Fundamentals Governing the Design and Operation of Local Exhaust Systems, ANSI B11 TR2-1997.
Appendix 5. NIOSH-Recommended Respiratory Protection For Workers Exposed to Metalworking Fluid Aerosols*
Concentration of MWF aerosol (mg/m3) Minimum respiratory protection+
Appendix 6. Procedures for Draining, Cleaning, and Recharging Metalworking Fluid Delivery Systems
When DCR (Drain, Clean, and Recharge) is required, the following procedure, as recommended by the Organization Resources Counselors (ORC 1999), should be followed:
Consult your metalworking fluid supplier for specific information on dump, clean, and recharge procedures for your fluids.
Appendix 7. Self-Assessment Procedure How do I determine if my shop has good metal removal fluid (MRF) management?
We have put together a checklist to help you determine if your shop has good MRF management. It has three parts:
Part I asks questions in 6 different sections and covers the features of the management plan that are common to all shop MRF systems.
Part II also with 6 sections, covers individual processes, departments, or MRF systems within the shop. Copies of Part II can be distributed and completed for each department or system.
Part III is a summary that, when completed, will give you the overall rating for your shop.
The importance of individual checklist questions is rated using the following scale:
"C" _ Critical, e.g., has responsibility for MRF management been assigned?
"I" _ Important, e.g., are machine enclosures maintained in operating condition?
"G" _ Good Practice, e.g., are machines maintained in clean condition?
Only questions that apply to your facility are used to determine the rating. Please see Your Rating for instructions on figuring out your overall rating.
Regardless of the outcome, the assessment information should be used for improving the MRF management program. Copies of the checklist should be kept available for use in the improvement process.
A downloadable file of the entire self-assessment procedure is available in "rich text formatting" (ORC Self-Assessment Procedure.rtf). This file is usable with most word processing programs. Using this file reduces printing problems that may be encountered when printing directly from
Instructions: Circle the appropriate answer for the questions below (Y=Yes, N=No, NA=Not Applicable). If "No" is circled, make comments and recommend actions to correct the problem, if possible. Note that NA is not available for some questions. Calculate the scores for the categories as indicated. Transfer the information from this checklist to the summary sheet.
Type: C = Critical, I = Important, G = Good Practice
Instructions: Circle the appropriate answer for the questions below (Y = Yes, N = No, NA = Not Applicable). If "No" is circled, make comments and recommend corrective actions if possible. Note that NA is not available for some questions. Calculate scores for each of the six categories as well as for the overall checklist. Transfer results to the Summary Sheet.
Type: C = Critical, I = Important, G = Good Practice
Instructions: Complete Part I and as many copies of Part II as necessary to evaluate your shop. Transfer the information from the checklists to the sections below and make the calculations indicated. See the page Your Rating to figure out your score and interpret the overall rating.
Your rating is calculated as follows:
Appendix 8. OSHA Air Sampling Methods
OSHA Occupational Safety & Health Administration/
U.S. Department of Labor
Chemical Sampling Information Oil Mist, Mineral
General Description NAME: Oil Mist, Mineral
SYNONYM(s): Mist of white mineral petroleum oil; Petroleum-base cutting oil; Heat-treating oil; Hydraulic oil; Cable oil; Lubricating oil.
NIOSH: RTECS PY8030000
DOT: 1270 27
DESCRIPTION: Mist with an odor like burned lube oil.
INCOM: None hazardous
Exposure Limits OSHA GENERAL INDUSTRY PEL: 5 mg/m3 TWA
OSHA CONTRUCTION INDUSTRY PEL: 5 mg/m3 TWA
ACGIH TLV: 5 mg/m3 TWA; 10 mg/m3 STEL; As sampled by method that does not collect vapor.
NIOSH REL: 5 mg/m3 TWA; 10 mg/m3 STEL
Health Factors IARC: Mineral Oils, untreated and mildly-treated oils - Group 1, carcinogenic to humans
SYMPTOM(s): None reported
HEALTH EFFECTS: Explosive, Flammable (No adverse effects when Good Housekeeping Practices are used) (HE18) Accumulation in lungs (Pneumonitis) (HE10).
ORGAN: Respiratory system, skin
Monitoring PRIMARY SAMPLING/ANALYTICAL METHOD (SLC1):
MEDIA: Tared Low Ash Polyvinyl. Chloride (LAPVC) filter 5 microns
MAX V: 960 Liters MAX F: 2.0 L/min
ANL 1: Gravimetric
REF: 11, 12
CLASS: Fully validated
ANL A: Fluorometric
REF: 2 (OSHA ID-128)
CLASS: Partially validated
ANL A: Infrared; IR (Analysis is for oils which do not fluoresce)
REF: 2 (OSHA I-178SG)
CLASS: Partially validated
NOTE: Submit as a separate sample. Submit to laboratory only if sample weight is greater than the PEL. If the filter is not overloaded, samples may be collected up to an 8-hour period. Collect a sample of the bulk substance and send to the lab in a separate mailing container at the time the air samples are submitted. + Indicate on the sample sheet that a bulk sample has been submitted. Cutting oils may contain nitrosamines.
SECONDARY SAMPLING/ANALYTICAL METHOD (SAM2):
DEVICE: Detector Tube COMPANY: Draeger
PART #: 67 28371 RANGE: 2.5-10 mg/m3
DEVICE: Dector Tube COMPANY: Draeger
PART #: 67 33031 RANGE: 1-10 mg/m3
Revision Date: 01/12/99
* All Trademarks are the property of their respective owners.
OSHA Occupational Safety & Health Administration/
U.S. Department of Labor
NAME: Particulates not otherwise regulated (Total Dust).
SYNONYM(s): Dust, (Total) prior to 9/1/89; PNO
DESCRIPTION: Nuisance dust includes, but is not limited to; inert particulates, glass fibers or dust, mineral wool fiber, inert organic dust, inert mineral dust, provided that these inert particulates contain less than 1% free silica.
OSHA GENERAL INDUSTRY PEL: 15 mg/m3 (Z-3)
ACGIH TLV: 10 mg/m3 TWA Inhalable (total) dust containing no Asbestos and less than 1% crystalline Silica.
NIOSH REL: 10 mg/m3
PRIMARY SAMPLING/ANALYTICAL METHOD (SLC1):
MEDIA: Tared Low Ash Polyvinyl Chloride (LAPVC) filter 5 microns
MAX V: 960 Liters MAX F: 2.0 L/min -- DO NOT USE A CYCLONE --
ANL 1: Gravimetric
REF: 11, 12
CLASS: Fully validated
NOTE: Field method, do not submit to SLTC. Standard is for inert dust; noncompliance can be based on gross weight without analysis. If the filter is not overloaded, samples may be collected up to an 8-hour period.
Revision Date: 08/28/1995
* All Trademarks are the property of their respective owners.
Appendix 9. NIOSH Analytical Method 0500
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
DEFINITION: total aerosol mass CAS: NONE RETCS: NONE
METHOD: 0500, Issue 2
Issue 1: 15 February, 1984 Issue 2: 15 August, 1994
OSHA: 15 mg/m3
NIOSH: no REL less than 1%
ACGIH: 10 mg/m3, total dust less than 1% quartz
PROPERTIES: contains no asbestos and quartz
SYNONYMS: nuisance dust; particulates not otherwise classified
SAMPLER: filter (tared 37-mm, 5-um PVC filter)
FLOW RATE: 1 to 2 L/min
VOL-MIN: 7 L@15 mg/m3
- MAX: 133 L@15 mg/m3
SAMPLE STABILITY: Indefinitely
BLANKS: 2 to 10 field blanks per set
BULK SAMPLE: None required
TECHNIQUE: gravimetric (filter weight)
ANALYTE: airborne particulate material
BALANCE: 0.001 mg sensitivity: use same balance before and after sample collection
CALIBRATION: National Institute of Standards and Technology Class S-1.1 weights or ASTM Class 1 weights
RANGE: 0.1 to 2 mg per sample
ESTIMATED LOD: 0.03 mg per sample
RANGE STUDIED: 8 to 28 mg/m3
OVERALL PRECISION (srr): 0.056
ACCURACY: +/- 11.04%
APPLICABILITY: The working range is 1 to 20 mg/m3 for a 100-L air sample. This method is non-specific and determines the total dust concentration to which a worker is exposed. It may be applied, e.g., to gravimetric determination of fibrous glass in addition to the other ACGIH particulates not otherwise regulated .
INTERFERENCES: Organic and volitile particulate matter maybe removed by dry ashing 
OTHER METHODS: This method is similar to the criteria document method for fibrous glass  and Method 5000 for carbon black. This mehod replaces Method S349 . Impingers and direct-reading instruments may be used to collect total dust samples, but these have limitations for personal sampling.
SPECIAL PRECAUTIONS: None
PREPARATION OF FILTERS BEFORE SAMPLING:
Lab testing with blank filters and generated atmospheres of carbon black was done at 8 to 28 mg/m3 [2,6]. Precision and accuracy data are given on page 0500-1.
 NIOSH Manual of Analyical Methods, 3rd ed., NMAM 5000, DHHS (NIOSH) Publication No. 84-100 (1984).
 Unpublished data from Non-textile Cotton Study, NIOSH/DRDS/EIB.
 NIOSH Criteria for a Recommended Standard...Occupational Exposure to Fibrous Glass, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-152, 119-142 (1977).
 1993-1994 Threshold Limit Values and Biological Exposures indices, Appendix D, ACGIH, Cincinnati, OH (1993).
 NIOSH Manual of Analytical Methods, 2nd ed., V.3. S349. U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-C (1977).
 Documentation of the NIOSH Validation Tests, S262 and S349, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-185 (1977).
 Bowman, J.D., D.L. Bartley, G.M. Breuer, L. J. Doemeny, and D.J. Murdock. Accuracy Criteria Recommended or the Certification of Gravimetric Coal Mine Dust Personal Samplers. NTIS Pub. No
PB 85- 222446 (1984)
 Breslin, J.A., S.J. Page, and R.A. Jankowski. Precision of Personal Sampling of Respirable Dust in Coal Mines, U.S. Bureau of Mines Report of Investigaions # 8740 (1983).
METHOD REVISED BY: Jerry Clere and Frank Hearl, P.E., NIOSH/DRDS
Appendix 10. OSHA Consultation Directory
Appendix 11. Best Practices for Training