Disclaimer: These guidelines were developed under contract using generally accepted secondary sources. The protocol used by the contractor for surveying these data sources was developed by the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA), and the Department of Energy (DOE). The information contained in these guidelines is intended for reference purposes only. None of the agencies have conducted a comprehensive check of the information and data contained in these sources. It provides a summary of information about chemicals that workers may be exposed to in their workplaces. The secondary sources used for supplements 111 and 1V were published before 1992 and 1993, respectively, and for the remainder of the guidelines the secondary sources used were published before September 1996. This information may be superseded by new developments in the field of industrial hygiene. Therefore readers are advised to determine whether new information is available.

OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR DICHLORVOS

INTRODUCTION

This guideline summarizes pertinent information about dichlorvos for workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new information is available.

SUBSTANCE IDENTIFICATION

* Formula

C(4)H(7)Cl(2)O(4)P

* Structure

(For Structure, see paper copy)

* Synonyms

2,2-dichlorovinyl dimethyl phosphate; DDVP; dichlorophos; dichlorovas;

vapona; dimethyl dichlorovinyl phosphate

* Identifiers

1. CAS No.: 62-73-7

2. RTECS No.: TC0350000

3. DOT NA: 2783 55 (dichlorvos); DOT UN: 3017 28 (organophosphorus pesticides, liquid, toxic, not otherwise stated)

4. DOT label: Poison (dichlorvos); Poison, flammable liquid (organophosphorus pesticides, liquid, toxic, not otherwise stated)

* Appearance and odor

Dichlorvos is a colorless to amber oily liquid with a mild aromatic odor.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 220.98

2. Boiling point (at 20 mm Hg): 140 degrees C (284 degrees F) (decomposes)

3. Specific gravity (water = 1): 1.42 at 25 degrees C (77 degrees F)

4. Vapor density: Not applicable.

5. Melting/Freezing point: Data not available.

6. Vapor pressure at 20 degrees C (68 degrees F): 0.012 mm Hg

7. Solubility: Slightly soluble in water and glycerol; soluble in kerosene, ethanol, chloroform, and acetone. Miscible with alcohol, aromatic and chlorinated hydrocarbon solvents, aerosol propellants, and most nonpolar solvents.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: Contact with water or an alkali causes rapid hydrolyzation.

2. Incompatibilities: None reported.

3. Hazardous decomposition products: Dichlorvos readily decomposes in strong acids or alkalies. Toxic gases and vapors such as phosphorus, chlorinated oxides, and carbon monoxide may be released in a fire involving dichlorvos.

4. Special precautions: Dichlorvos attacks some forms of plastic, rubber, and coatings. It is corrosive to iron and mild steel.

* Flammability

The National Fire Protection Association has not assigned a flammability rating to dichlorvos. Other sources rate dichlorvos as practically nonflammable when this substance is exposed to heat or open flame.

1. Flash point: Data not available.

2. Autoignition temperature: Data not available.

3. Flammable limits in air: Data not available.

4. Extinguishant: For small fires use dry chemical, water spray, or regular foam. Use water spray, fog, or regular foam to fight large fires involving dichlorvos.

Fires involving dichlorvos should be fought upwind from the maximum distance possible. Keep unnecessary people away; isolate the hazard area and deny entry. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Containers of dichlorvos may explode in the heat of the fire and should be moved from the fire area if it is possible to do so safely. If this is not possible, cool fire exposed containers from the sides with water until well after the fire is out. Stay away from the ends of containers. Dike fire control water for later disposal; do not scatter this material. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving dichlorvos.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for dichlorvos is 1 milligram per cubic meter (mg/m(3)) of air as an 8-hour time-weighted average (TWA) concentration. The OSHA PEL also bears a "Skin" notation, which indicates that the cutaneous route of exposure (including mucous membranes and eyes) contributes to overall exposure [29 CFR 1910.1000, Table Z-1].

* NIOSH REL

The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for dichlorvos of 1 mg/m(3) as a TWA for up to a 10-hour workday and a 40-hour workweek. NIOSH also assigns a skin notation to dichlorvos [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned dichlorvos a threshold limit value (TLV) of 0.1 ppm (0.90 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek. The ACGIH also assigns a "Skin" notation to dichlorvos [ACGIH 1994, p. 19].

* Rationale for Limits

The NIOSH limit is based on the risk of cholinesterase inhibition [NIOSH 1992].

The ACGIH limit is based on the risk of plasma cholinesterase depression [ACGIH 1991, p. 447].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to dichlorvos can occur through inhalation, ingestion, eye or skin contact, and absorption through the skin [Sittig 1991].

* Summary of toxicology

1. Effects on Animals: Dichlorvos is an anticholinesterase agent and may cause excessive salivation, eye tearing, sweating, constricted pupils, respiratory distress, anorexia, vomiting, diarrhea, weakness, twitching, paralysis, a slow and irregular heartbeat, convulsions, coma, and death [Hathaway et al. 1991]. Dichlorvos also has reproductive effects and causes malformed offspring in rodents. The acute toxicity of dichlorvos for laboratory animals is significantly high; the dermal LD(50) for rabbits is 107 mg/kg and 80 mg/kg in rats; and the acute oral LD(50) in rats is 25 mg/kg [NIOSH 1995; ACGIH 1991; Sax and Lewis 1989]. The lowest single oral dose that causes observable behavioral changes is 10 mg/kg in calves [NLM 1995]. The neurotoxic effect of dichlorvos on the central and peripheral nervous system was investigated in acute and subchronic experiments using male rats. The acute group received a single oral dose of 88 mg/kg and the two subchronic groups received a daily oral dose of 1.6 mg/kg or 0.8 mg/kg for a period of 6 weeks. Both the acute and subchronic groups exhibited significant changes in the functions of the central nervous system, increase of EEG mean frequency, decrease of EEG amplitude, and peripheral nervous system decrease of conduction velocity, and increase of relative and absolute refractory periods. In one of two studies on the long-term effects of dichlorvos by oral exposure, an increased but not statistically significant number of squamous-cell tumors were found in mice [ACGIH 1991]. However, the International Agency for Research on Cancer (IARC) has concluded that the evidence for the carcinogenicity of dichlorvos in animals is inadequate [IARC 1987]. Administered intraperitoneally during pregnancy, dichlorvos produced developmental abnormalities in rat fetuses [NIOSH 1995]. Dichlorvos is mutagenic in bacterial and mammalian test systems [NIOSH 1995; NLM 1995].

2. Effects on Humans: Dichlorvos is an organophosphorus pesticide and is therefore a cholinesterase inhibitor. Overexposure to this substance causes symptoms that vary by route of exposure. Inhalation causes ocular and respiratory symptoms. Ingestion causes gastrointestinal effects, while skin absorption causes localized sweating and muscle twitching in the area where entry occurred. If exposure is severe, muscle weakness, twitching, fasciculation, and paralysis may occur. Paralysis of the respiratory muscles may cause death. Cardiac irregularities, including complete heart block, may also occur [Hathaway et al. 1991]. Dichlorvos is easily absorbed through the skin, gastrointestinal tract, and lungs because of its high volatility [Parmeggiani 1983]. It is rapidly inactivated by the liver, and persons with liver disease may be less tolerant of the toxic effects than normal persons [Gosselin 1984]. Human volunteers exposed for 30 minutes/hour each hour, 10 hours/day for 14 days at concentrations of 0.14 to 0.33 mg/m(3) had no changes in cholinesterase levels, airway resistance, or vision. At a concentration of 1 mg/m(3) for 7.5 to 8.5 hours, volunteers experienced a 20- to 25-percent reduction in cholinesterase levels [ACGIH 1991]. Thirteen workers exposed over a period of a year to an average concentration of 0.7 mg/m(3) showed decreases of 35 percent and 60 percent, respectively, in red blood cell and plasma cholinesterase levels [Hathaway et al. 1991]. At a level of 0.1 ppm, the plasma cholinesterase is reported to drop by 20 percent [ACGIH 1991]. Daily exposure to dichlorvos at levels insufficient to produce results on a single-dose basis may produce symptoms after several days exposure. Continuing exposure after symptoms appear can produce increasingly severe effects [Hathaway et al. 1991]. Dichlorvos has also been reported to cause allergic contact dermatitis [ACGIH 1991]. Dichlorvos causes methylation of DNA in vitro, but there is no evidence of mutagenicity in humans [Hathaway et al. 1991]. IARC has concluded that there is no adequate data for evaluating the carcinogenicity of dichlorvos in humans [IARC 1987].

* Signs and symptoms of exposure

1. Acute exposure: Symptoms and signs usually appear within minutes of exposure but they may be delayed for as long as 12 hours. After inhalation, the initial symptoms and signs are a feeling of tightness in the chest, wheezing due to bronchospasm, blurring of vision, tearing, runny nose, and frontal headache. Ingestion causes sweating, nausea, vomiting, diarrhea, cramps, urination and defecation, and anorexia within 15 minutes to 2 hours of exposure. Skin absorption can produce local sweating and muscle fasciculations within 15 minutes to 2 hours after exposure. Death is usually caused by respiratory muscle paralysis and consequent asphyxiation.

2. Chronic exposure: Continued exposure to dichlorvos may cause headache, weakness, decreased memory, easy fatigability, disturbed sleep, loss of sensation in the skin, and paralysis. Delayed neurological symptoms are reversible after exposure ceases, but recovery is low and may not be complete.

EMERGENCY MEDICAL PROCEDURES

* Emergency medical procedures: [NIOSH to supply]

5. Rescue: Remove an incapacitated worker from further exposure and implement appropriate emergency procedures (e.g., those listed on the Material Safety Data Sheet required by OSHA's Hazard Communication Standard [29 CFR 1910.1200]). All workers should be familiar with emergency procedures, the location and proper use of emergency equipment, and methods of protecting themselves during rescue operations.

EXPOSURE SOURCES AND CONTROL METHODS

The following operations may involve dichlorvos and lead to worker exposures to this substance:

* The manufacture and transportation of dichlorvos

* Liberated during formulation and mixing for insecticidal application; used as a fumigant and as an anthelmintic in animals

* Liberated during application on vegetables, animals, agricultural premises, and for outdoor fogging; used as an insecticide in tablets, rubbing devices, resin strips, animals collars (e.g., pest or flea collars); used in powder form on animals and in animal buildings; used in insect baits; used as an insecticide in restaurants, hospitals, and aircraft

* Incorporated into plastic strips that slowly release vapor for use in disinfection of homes and aircraft

Methods that are effective in controlling worker exposures to dichlorvos, depending on the feasibility of implementation, are as follows:

* Process enclosure

* Local exhaust ventilation

* General dilution ventilation

* Personal protective equipment

Workers responding to a release or potential release of a hazardous substance must be protected as required by paragraph (q) of OSHA's Hazardous Waste Operations and Emergency Response Standard [29 CFR 1910.120].

Good sources of information about control methods are as follows:

1. ACGIH [1992]. Industrial ventilation--a manual of recommended practice. 21st ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

2. Burton DJ [1986]. Industrial ventilation--a self study companion. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

3. Alden JL, Kane JM [1982]. Design of industrial ventilation systems. New York, NY: Industrial Press, Inc.

4. Wadden RA, Scheff PA [1987]. Engineering design for control of workplace hazards. New York, NY: McGraw-Hill.

5. Plog BA [1988]. Fundamentals of industrial hygiene. Chicago, IL: National Safety Council.

MEDICAL SURVEILLANCE

OSHA is currently developing requirements for medical surveillance. When these requirements are promulgated, readers should refer to them for additional information and to determine whether employers whose employees are exposed to dichlorvos are required to implement medical surveillance procedures.

* Medical Screening

Workers who may be exposed to chemical hazards should be monitored in a systematic program of medical surveillance that is intended to prevent occupational injury and disease. The program should include education of employers and workers about work-related hazards, early detection of adverse health effects, and referral of workers for diagnosis and treatment. The occurrence of disease or other work-related adverse health effects should prompt immediate evaluation of primary preventive measures (e.g., industrial hygiene monitoring, engineering controls, and personal protective equipment). A medical surveillance program is intended to supplement, not replace, such measures. To detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodically during the term of employment, and (3) at the time of job transfer or termination.

* Preplacement medical evaluation

Before a worker is placed in a job with a potential for exposure to dichlorvos, a licensed health care professional should evaluate and document the worker's baseline health status with thorough medical, environmental, and occupational histories, a physical examination, and physiologic and laboratory tests appropriate for the anticipated occupational risks. These should concentrate on the function and integrity of the central nervous system, respiratory system, and blood. Medical surveillance for respiratory disease should be conducted using the principles and methods recommended by the American Thoracic Society.

A preplacement medical evaluation is recommended to assess medical conditions that may be aggravated or may result in increased risk when a worker is exposed to dichlorvos at or below the prescribed exposure limit. The health care professional should consider the probable frequency, intensity, and duration of exposure as well as the nature and degree of any applicable medical condition. Such conditions (which should not be regarded as absolute contraindications to job placement) include a history and other findings consistent with diseases of the central nervous system, respiratory system, or blood.

* Periodic medical evaluations

Occupational health interviews and physical examinations should be performed at regular intervals during the employment period, as mandated by any applicable Federal, State, or local standard. Where no standard exists and the hazard is minimal, evaluations should be conducted every 3 to 5 years or as frequently as recommended by an experienced occupational health physician. Additional examinations may be necessary if a worker develops symptoms attributable to dichlorvos exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of dichlorvos on the central nervous system, respiratory system, or blood. Current health status should be compared with the baseline health status of the individual worker or with expected values for a suitable reference population.

* Termination medical evaluations

The medical, environmental, and occupational history interviews, the physical examination, and selected physiologic or laboratory tests that were conducted at the time of placement should be repeated at the time of job transfer or termination to determine the worker's medical status at the end of his or her employment. Any changes in the worker's health status should be compared with those expected for a suitable reference population.

* Biological monitoring

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. The measurement of red blood cell cholinesterase is a nonspecific, qualitative indicator of acute or chronic exposure to dichlorvos. Workers should be removed from further exposure if their red blood cell cholinesterase activity falls below 70 percent of their baseline level.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne dichlorvos is made using an OSHA Versatile Sampler (OVS-2), 13 mm XAD-2 tube (270/140 mg sections, 20/60 mesh) with a glass fiber filter enclosed. Samples are collected at a maximum flow rate of 1 liter/minute until a maximum collection volume of 480 liters is reached. The sample is then treated with toluene. Analysis is conducted by gas chromatography using a flame photometric detector (GC/FPD). This method (OSHA #62) is fully validated and is described in the OSHA Computerized Information System [OSHA 1994]. NIOSH has published a similar method (Method No. 5600) for the determination of a worker's exposure to organophosphorus pesticides [NIOSH 1994b].

PERSONAL HYGIENE PROCEDURES

If dichlorvos contacts the skin, workers should immediately wash the affected areas with large amounts of soap and water.

Clothing contaminated with dichlorvos should be removed immediately, and provisions should be made for the safe removal of the chemical from the clothing. Persons laundering the clothes should be informed of the hazardous properties of dichlorvos, particularly its potential for causing systemic toxicity (including cholinesterase inhibition) through dermal absorption.

A worker who handles dichlorvos should thoroughly wash hands, forearms, and face with soap and water before eating, using tobacco products, using toilet facilities, applying cosmetics, or taking medication.

Workers should not eat, drink, use tobacco products, apply cosmetics, or take medication in areas where dichlorvos or a solution containing dichlorvos is handled, processed, or stored.

STORAGE

Dichlorvos should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's Hazard Communication Standard [29 CFR 1910.1200]. Containers of dichlorvos should be protected from physical damage and heat sources, and should be stored separately from strong alkalies or strong acids. Empty containers of dichlorvos should be handled appropriately.

SPILLS AND LEAKS

In the event of a spill or leak involving dichlorvos, persons not wearing protective equipment and fully-encapsulating, vapor-protective clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:

1. Notify safety personnel.

2. Remove all sources of heat and ignition.

3. Ventilate potentially explosive atmospheres.

4. Do not touch the spilled material; stop the leak if it is possible to do so without risk.

5. Use non-sparking tools.

6. Water spray may be used to reduce vapors, but the spray may not prevent ignition in closed spaces.

7. For small liquid spills, take up with sand or other noncombustible absorbent material and place into closed containers for later disposal.

8. For large liquid spills, build dikes far ahead of the spill to contain the dichlorvos for later reclamation or disposal.

SPECIAL REQUIREMENTS

U.S. Environmental Protection Agency (EPA) requirements for emergency planning, reportable quantities of hazardous releases, community right-to-know, and hazardous waste management may change over time. Users are therefore advised to determine periodically whether new information is available.

* Emergency planning requirements

Employers owning or operating a facility at which there are 1,000 pounds or more of dichlorvos must comply with EPA's emergency planning requirements [40 CFR Part 355.30].

* Reportable quantity requirements for hazardous releases

A hazardous substance release is defined by EPA as any spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment (including the abandonment or discarding of contaminated containers) of hazardous substances. In the event of a release that is above the reportable quantity for that chemical, employers are required to notify the proper Federal, State, and local authorities [40 CFR 355.40].

The reportable quantity of dichlorvos is 10 pounds. If an amount equal to or greater than this quantity is released within a 24-hour period in a manner that will expose persons outside the facility, employers are required to do the following:

- Notify the National Response Center immediately at (800) 424-8802 or at (202) 426-2675 in Washington, D.C. [40 CFR 302.6].

- Notify the emergency response commission of the State likely to be affected by the release [40 CFR 355.40].

- Notify the community emergency coordinator to the local emergency planning committee (or relevant local emergency response personnel) of any area likely to be affected by the release [40 CFR 355.40].

* Community right-to-know requirements

Employers who own or operate facilities in SIC codes 20 to 39 that employ 10 or more workers and that manufacture 25,000 pounds or more of dichlorvos per calendar year or otherwise use 10,000 pounds or more of dichlorvos per calendar year are required by EPA [40 CFR Part 372.30] to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of dichlorvos emitted or released from their facility annually.

* Hazardous waste management requirements

EPA considers a waste to be hazardous if it exhibits any of the following characteristics: ignitability, corrosivity, reactivity, or toxicity as defined in 40 CFR 261.21-261.24. Under the Resource Conservation and Recovery Act (RCRA) [40 USC 6901 et seq.], EPA has specifically listed many chemical wastes as hazardous. Although dichlorvos is not specifically listed as a hazardous waste under RCRA, EPA requires employers to treat waste as hazardous if it exhibits any of the characteristics discussed above.

Providing detailed information about the removal and disposal of specific chemicals is beyond the scope of this guideline. The U.S. Department of Transportation, EPA, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (703) 412-9810 (in the Washington, D.C. area) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance.

RESPIRATORY PROTECTION

* Conditions for respirator use

Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Respirators must be worn if the ambient concentration of dichlorvos exceeds prescribed exposure limits. Respirators may be used (1) before engineering controls have been installed, (2) during work operations such as maintenance or repair activities that involve unknown exposures, (3) during operations that require entry into tanks or closed vessels, and (4) during emergencies. Workers should only use respirators that have been approved by NIOSH and the Mine Safety and Health Administration (MSHA).

* Respiratory protection program

Employers should institute a complete respiratory protection program that, at a minimum, complies with the requirements of OSHA's Respiratory Protection Standard [29 CFR 1910.134]. Such a program must include respirator selection, an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, respirator fit testing, periodic workplace monitoring, and regular respirator maintenance, inspection, and cleaning. The implementation of an adequate respiratory protection program (including selection of the correct respirator) requires that a knowledgeable person be in charge of the program and that the program be evaluated regularly. For additional information on the selection and use of respirators and on the medical screening of respirator users, consult the latest edition of the NIOSH Respirator Decision Logic [NIOSH 1987b] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a].

PERSONAL PROTECTIVE EQUIPMENT

Workers should use appropriate personal protective clothing and equipment that must be carefully selected, used, and maintained to be effective in preventing skin contact with dichlorvos. The selection of the appropriate personal protective equipment (PPE) (e.g., gloves, sleeves, encapsulating suits) should be based on the extent of the worker's potential exposure to dichlorvos. There are no published reports on the resistance of various materials to permeation by dichlorvos.

To evaluate the use of PPE materials with dichlorvos, users should consult the best available performance data and manufacturers' recommendations. Significant differences have been demonstrated in the chemical resistance of generically similar PPE materials (e.g., butyl) produced by different manufacturers. In addition, the chemical resistance of a mixture may be significantly different from that of any of its neat components.

Any chemical-resistant clothing that is used should be periodically evaluated to determine its effectiveness in preventing dermal contact. Safety showers and eye wash stations should be located close to operations that involve dichlorvos.

Splash-proof chemical safety goggles or face shields (20 to 30 cm long, minimum) should be worn during any operation in which a solvent, caustic, or other toxic substance may be splashed into the eyes.

In addition to the possible need for wearing protective outer apparel (e.g., aprons, encapsulating suits), workers should wear work uniforms, coveralls, or similar full-body coverings that are laundered each day. Employers should provide lockers or other closed areas to store work and street clothing separately. Employers should collect work clothing at the end of each work shift and provide for its laundering. Laundry personnel should be informed about the potential hazards of handling contaminated clothing and instructed about measures to minimize their health risk.

Protective clothing should be kept free of oil and grease and should be inspected and maintained regularly to preserve its effectiveness.

Protective clothing may interfere with the body's heat dissipation, especially during hot weather or during work in hot or poorly ventilated work environments.

REFERENCES

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