Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and no longer represents OSHA Policy. It is presented here as historical content, for research and review purposes only.

Metalworking/Machining Fluids

Millions of workers engaged in the manufacture of automobiles, farm equipment, aircraft, heavy machinery, and other hardware are exposed to machining fluids. Occupational exposure to these fluids has resulted in various cancers, respiratory diseases, and skin problems. There is evidence of impaired health at levels well below the Permissible Exposure Limit (PEL) for oil mists (5 mg/m3 time weighted average (TWA)) and the "nuisance dust" exposure limits applicable to all other machining fluids (15 mg/m3 TWA for total particulate). In order to improve worker protection, OSHA is designating metalworking/machining fluid exposure as a priority for comprehensive rulemaking. OSHA intends to work together with business, labor and the professional community to develop this rule in a consensual manner.

Hazard Description

Machining or metalworking fluids are in widespread, high volume use throughout the manufacturing industries for their coolant, lubricant, and corrosion resistant properties during operations such as metal grinding, boring, drilling, and turning. These fluids are complex mixtures of oils, detergents, surfactants, biocides, lubricants, anti-corrosive agents, and other potentially toxic ingredients.

There is an extensive body of scientific literature which demonstrates that worker exposure to machining fluids of all types is strongly associated with cancer (several respiratory and digestive sites) and non-malignant respiratory effects (occupational asthma). Because the usage patterns, chemistry and toxicology of these materials is very complicated, it has been difficult to determine precise links between specific fluid formulations or specific ingredients with specific health effects in exposed workers. The risks for various cancers are dose-related to all major types of machining fluids, but the evidence about cancer excesses is based on information about past exposures which may differ qualitatively and quantitatively from current exposures. It is clear, however, that the risk of occupational asthma and related respiratory conditions is related to current exposure levels and current materials.


More than a dozen recent epidemiological studies have reported statistically significant increases in one or more cancer sites, such as esophagus (1), stomach (2-4), pancreas (4-8), larynx (9, 10), colon (1), rectum (8, 9) and other cancers (1-13). In these studies, for many groups of workers, the risk has been two to ten times the expected rate.

There is strong epidemiologic evidence that exposures to all types of machining fluids cause substantially elevated risk of cancer. The most comprehensive cohort mortality study published provides strong evidence that exposure to soluble or synthetic fluids in grinding operations is associated with esophageal and pancreatic cancer; that straight fluids are associated with rectal cancer; and that synthetic fluids are associated with pancreatic and possibly colon cancer. (5, 8) For each cancer site the risk increases as the duration of exposure increases. For example, the risk of esophageal cancer reaches 12-fold with more than one year exposure to grinding. The risk for colon and pancreatic cancer reach 2- to 3-fold after three years of exposure to synthetic machining fluids. The risk for rectal cancer is 3-fold after one year of exposure to straight machining fluids.

Respiratory Effects

Occupational respiratory illnesses due to exposure to machining fluids include respiratory irritation, bronchitis, lipoid pneumonia, hypersensitivity pneumonitis, and extrinsic asthma. (12, 13, 15, 16) In particular, evidence from clinical studies and medical surveillance in both the U.S. and U.K. document that occupational asthma is caused by exposure to several different types of machining fluids (17-20). Epidemiologic evidence also suggests that exposure to machining fluids is related to both asthma incidence (21, 22) and asthma mortality (6). Overall the evidence indicates that risk of asthma exists in several different settings with different types of fluids.

Acute loss of forced expiratory lung volume (FEV1) of greater than 5% across the workshift has been associated with exposure to each of the major types of machining fluids in three independent cross-sectional studies (15, 23, 24). These lung function changes are correlated with occupational asthma. Loss of lung function became worse as exposures increased, supporting the conclusion that exposures below 1.0 mg/m3 total particulate (and possibly below 0.5 mg/m3) cause increased risk.

Workers experience skin contact with machining fluids as a result of splashing, dripping or leaking. Skin problems include irritation and allergic contact dermatitis (16). They also inhale mists and aerosols of these fluids generated during high speed, high friction, metalworking operations. There are many well known effective techniques available to reduce worker exposure, including protective clothing, mechanical splash guards and enclosures, local exhaust ventilation, preventive maintenance programs, and others.

Current Status

OSHA has permissible exposure limits (PEL) of 5 mg/m3 as an 8-hour TWA for mineral oil mists, and 15 mg/m3 TWA (total particulate) and 5 mg/m3 TWA (respirable fraction) for "nuisance dusts" (also called "particulates not otherwise regulated"), but there are no specific standards for machining fluids and most of their ingredients. Toxic effects have been reported among workers exposed to mineral oil mists below the current PELs, as noted above. The OSHA inspection data system (IMIS) contains more than 1,400 samples for airborne oil mist collected over the past two decades. In over 500 samples collected from 1990-1994 approximately 60% were below or equal to 0.5 mg/m3 and approximately 25% were greater than 1.0 mg/m3. The trend has been downward. For example, from 1980-1984 more than 50% of the samples were greater than 1.0 mg/m3.

The International Union, United Automobile, Aerospace and Agricultural Implement Workers of America (UAW) petitioned OSHA in December 1993 for an Emergency Temporary Standard (ETS) to lower the PEL for oil mists to 0.5 mg/m3 of total particulate. The UAW also petitioned the Environmental Protection Agency (EPA) for a S4 Test Rule under the Toxic Substances Control Act (TSCA). OSHA denied the UAW's request for an emergency standard but indicated that it would continue to consider a permanent standard.

There have been private sector recommendations, as well, to lower the permissible exposure limits. For example, the authors of the largest ongoing epidemiologic study of workers exposed to machining fluids, recommended to the UAW/General Motors Occupational Health Advisory Board that machining fluid exposures be kept below 0.5 mg/m3 total particulate: "Results from both the respiratory morbidity study and the mortality study suggest associations between machining fluid exposure and respiratory disease or cancer that are consistent with an interpretation of causality. Our initial dose-response analyses suggest that an exposure level of 0.5 mg/m3 would minimize any adverse health effect of worker exposure to machining fluids." (1)

The National Institute for Occupational Safety and Health (NIOSH) issued a draft NIOSH Special Hazard Review of the Metalworking Industry in May 1994; work is currently underway to complete the document. OSHA, NIOSH, and EPA are working on a joint Hazard Alert on machining fluids, planned for completion after the NIOSH Special Hazard Review.

In November 1994, NIOSH sponsored a 2-day information gathering meeting with representatives of government, labor, fluid manufacturers, and fluid users. In November 1995 over 700 representatives of business, labor and academia participated in a four day symposium on The Industrial Metalworking Environment: Assessment and Control, sponsored by the American Automobile Manufacturers Association (AAMA) in cooperation with the Independent Lubricant Manufacturers Association, the United Automobile Workers, OSHA, NIOSH and EPA. There was substantial evidence and viewpoints presented which supported the conclusion that existing standards are inadequate to protect worker health, that substantially lower exposures are feasible, and that the private sector is interested in working cooperatively with government on strategies to achieve lower exposures.

EPA is screening 95 metalworking fluid chemicals referred to EPA by NIOSH for the selection of possible testing candidates under Section 4 of TSCA.


Machining fluids meet the criteria for designation as an OSHA priority. There is a very large number of workers exposed to machining fluids; the health effects are serious; there is extensive scientific evidence of risk; and there are available control methods for reducing exposure. There is substantial evidence of serious health effects at exposure levels below existing relevant standards. There is also considerable interest within both business and labor in working with government agencies to find ways to reduce worker exposure. OSHA is designating metalworking/machining fluid exposure as a priority for comprehensive rulemaking. OSHA intends to work together with business, labor and the professional community to develop this rule in a consensual manner.

  1. Monson R, et al. (1992). Final Report to GM-UAW Occupational Health Advisory Board on Health Effects of Exposure to Machining Fluids. Harvard School of Public Health, unpublished report. October 30, 1992 (OSHA Docket No. 372, Ex. No. 2-7A).
  2. Park R, et al. (1994). Mortality at an Automobile Stamping and Assembly Complex. Am J Ind Med. 26:449-463.
  3. Park RM et al. (1988). Causes of Death Among Workers in a Bearing Manufacturing Plant. Am J Ind Med. 13:569-580.
  4. Silverstein M et al. (1988). Mortality Among Bearing Plant Workers Exposed to Metalworking Fluids and Abrasives. J. Occup Med. 30(9):706-714.
  5. Rotimi C, et al. (1993). Retrospective Follow-up Study of Foundry and Engine Plant Workers. Am J Ind Med. 24:485-498.
  6. Eisen EA, et al. (1992). Mortality Studies of Machining Fluid Exposure in the Automobile Industry I: A Standardized Mortality Ratio Analysis. Am J Ind Med. 22:809-824.
  7. Mallin K, et al. (1986). A Proportional Mortality Ratio Study of Workers in a Construction Equipment and Diesel Engine Manufacturing Plant. Am J Ind Med. 10:127-141.
  8. Vena JE, et al. (1985). Mortality of Workers in an Automobile Engine and Parts Manufacturing Complex. Br J Ind Med. 42:85-93.
  9. Tolbert PE, et al. (1992). Mortality Studies of Machining-Fluid Exposure in the Automobile Industry II: Risks Associated With Specific Fluid Types. Scand J Work Environ Health 18:351-360.
  10. Eisen EA, et al. (1994). Mortality Studies of Machining Fluid Exposure in the Automobile Industry III: A Case-control Study of Larynx Cancer. Am J Ind Med. 26:185-202.
  11. Acquavella JF, Leet TL. (1991). A Cohort Study Among Workers at a Metal Components Manufacturing Facility. J Occup Med. 33(8):896- 900.
  12. Ameille J, et al. (1995). Respiratory Symptoms, Ventilatory Impairment, and Bronchial Reactivity in Oil Mist-Exposed Automobile Workers. Am J Ind Med 27:247-256.
  13. International Agency for Research on Cancer (1984). IARC Monographs on the Evaluation of the Carcinogenic Risks of Chemicals to Humans: Mineral Oils (Lubricant Based oils and Derived Products), Vol. 33, Lyon, France: IARC, pp. 87-168.
  14. Eisen EA, et. al. (1992). Mortality Studies of Machining Fluids; An Exposure-Response Analysis of Respiratory and Digestive Cancers. Proceedings of the Ninth International Symposium on Epidemiology in Occupational Health, Cincinnati, OH. NIOSH Publication No. 94-112 (pp. 113-116).
  15. Kennedy SM et al. (1989). Acute pulmonary responses among automobile workers exposed to aerosols of machining fluids. Am J Ind Med 15:627-641.
  16. Sprince N, et al. (1994) Chapter 34, Oils and Related Petroleum Derivatives, in Textbook of Clinical Occupational and Environmental Medicine, Rosenstock L and Cullen MR, eds., Saunders, 1994.
  17. Hendy MS, Beattie BE, Burge PS (1985). Occupational Asthma Due to an Emulsified oil mist. Br J Ind Med 42: 51-54.
  18. Robertson AS, Weir DC, Burge PS (1988). Occupational Asthma Due to Oil Mists. Thorax 43: 200-205.
  19. Gannon PFG, Burge PS (1991). A Preliminary Report of a Surveillance Scheme of Occupational Asthma in the West Midlands. Br J Ind Med 48(9): 579-582.
  20. Rosenman KD, Reilly MJ (1993) Annual Report on Occupational Asthma in Michigan. Michigan Department of Public Health, Bureau of Occupational Health, Lansing, Michigan.
  21. Eisen EA (1995). Healthy Worker Effect in Morbidity Studies. Medicina del Lavoro, in press.
  22. Greaves IA, Eisen EA, Smith TJ, et. al. (1995). Respiratory Health of Automobile Workers Exposed to Metal Working Fluid Aerosols. II: Respiratory Symptoms. Amer J Indust Med (submitted).
  23. Kreibel D et. al. (June 1, 1994). Field Investigations of Acute Respiratory Effects of Machining Fluids. Final Report submitted to UAW/GM National Joint Committee on Occupational Health and Safety.
  24. Robins T et. al. (December 9, 1994). Respiratory Effects of Machining Fluid Aerosols. Final Report to the UAW/GM Occupational Health Advisory Board.