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. This information may be superseded by new developments in the field of industrial hygiene.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 2,4-D (DICHLOROPHENOXYACETIC ACID)

INTRODUCTION

This guideline summarizes pertinent information about 2,4-D 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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(6)H(6)Cl(2)O(3)

* Structure

(For Structure, see paper copy)

* Synonyms

2,4-D Acid; 2,4-PA; hedonal; trinoxol

* Identifiers

1. CAS No.: 94-75-7

2. RTECS No.: AG6825000

3. DOT UN: 2765 55

4. DOT label: Poison, keep away from food (phenoxy pesticides, solid, toxic, n.o.s)

* Appearance and odor

2,4-D is an odorless, white to yellow crystalline powder. It is dispersable in water or oils and can be applied as a spray.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 221.04

2. Boiling point (at 0.4 mm Hg): 160 degrees C (320 degrees F)

3. Specific gravity: 1.56 to 1.57

4. Vapor density: 7.6

5. Melting point: 138 degrees C (280.4 degrees F)

6. Vapor pressure at 20 degrees C (68 degrees F): 0 mm Hg

7. Solubility: Slightly soluble in water; soluble in alcohol and in other organic solvents.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: None reported.

2. Incompatibilities: Contact between 2,4-D and strong oxidizers such as chlorine, bromine, and fluorine should be avoided.

3. Hazardous decomposition products: Toxic gases and vapors of chlorine (or the fumes of chlorides) may be released in a fire involving 2,4-D.

4. Special precautions: None reported.

* Flammability

2,4-D is not combustible

The National Fire Protection Association has not assigned a flammability rating to 2,4-D. Other sources rate 2,4-D as 1 (a slight fire hazard) 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 2,4-D.

Fires involving 2,4-D 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 2,4-D may explode in the heat of the fire and should be moved from the fire area if it is possible to do so safely. 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 chemical protective clothing and self-contained breathing apparatus when fighting fires involving 2,4-D.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for 2,4-D is 10 milligrams per cubic meter (mg/m(3)) of air as an 8-hour time-weighted average (TWA) concentration [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 2,4-D of 10 mg/m(3) as a TWA for up to a 10-hour workday and a 40-hour workweek [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned 2,4-D a threshold limit value (TLV) of 10 mg/m(3) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 17].

* Rationale for Limits

The NIOSH limit is based on the risk of skin irritation and central nervous system effects [NIOSH 1992].

The ACGIH limit is based on the toxicity noted in animal feeding studies [ACGIH 1991, p. 377].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to 2,4-D can occur through inhalation, ingestion, eye or skin contact, and absorption through the skin [Hathaway et al. 1991].

* Summary of toxicology

1. Effects on Animals: 2,4-D is both an excitant and a depressant of the central nervous system [Hathaway et al. 1991]. It is also a moderate skin irritant and a severe eye irritant [Parmeggiani 1983]. The acute oral LD(50) for 2,4-D ranges from 100 mg/kg in dogs to 1,000 mg/kg in guinea pigs [ACGIH 1991; Parmeggiani 1983]. The dermal LD(50) in rabbits is 1,400 mg/m(3) [Sax and Lewis 1989]. Acute overexposure of 2,4-D may cause sudden death due to ventricular fibrillation and cardiogenic shock. Animals exposed to large amounts of 2,4-D developed extreme stiffness of the extremities, incoordination, lethargy, stupor, and coma. Severe dilation and congestion of the blood vessels in the lungs, liver, and kidneys occurs; death is due to congestion of the liver and pneumonia [Hathaway et al. 1991; ACGIH 1991]. Moderate cumulative toxicity due to 2,4-D has been reported in animals by some authors [Parmeggiani 1983], but others report no pathological changes following low dose 2,4-D exposure in the diet [ACGIH 1991]. 2,4-D is mutagenic in a variety of animal test systems [NIOSH 1995]. It also has teratogenic and fetotoxic effects causing fetal growth retardation and skeletal abnormalities in rats [Rom 1992; Sax and Lewis 1989; NLM 1995]. IARC studies of the carcinogenicity of 2,4-D in animals have been inconclusive [NLM 1995].

2. Effects on Humans: Human exposure to 2,4-D has been associated with central and peripheral nervous system effects, liver and kidney damage, and death [NLM 1995; Hathaway et al. 1991; ACGIH 1991]. Several case control studies of soft-tissue sarcoma and lymphoma have suggested an increased risk among workers exposed to phenoxyacetic acid herbicides, including 2,4-D. However, IARC deems the evidence of 2,4-D's carcinogenicity in humans inadequate, and other studies have failed to confirm an increased incidence of malignancy in workers using such herbicides [Hathaway et al. 1991]. Workers employed in the manufacture of 2,4-D and 2,4,5,-T had a significantly increased frequency of slowed nerve conduction [Hathaway et al. 1991]. A farming student committed suicide by ingesting at least 6.5 grams of 2,4-D. Violent convulsions preceded death, but no significant autopsy findings were noted [Hathaway et al. 1991]. One terminal patient with disseminated coccidiomycosis was administered 2,4-D intravenously for 19 doses. Central nervous system depression and peripheral neuropathology followed this treatment. 2,4-D is mutagenic in human test systems [NIOSH 1995].

* Signs and symptoms of exposure

1. Acute exposure: Acute exposure to 2,4-D has caused irritation of the skin, eyes, throat, and chest; nausea, vomiting, and diarrhea; muscle twitching and weakness; swelling or aching of the extremities; numbness; flaccid paralysis; hyporeflexia and hyperflexia; malaise, headache, and dizziness; low blood pressure; increased body temperature; loss of appetite and weight; malaise; stupor, convulsions, and death [Hathaway et al. 1991; Parmeggiani 1983]. Protein in the urine has also been reported following acute exposure [ACGIH 1991].

2. Chronic exposure: Chronic exposure to 2,4-D may cause contact dermatitis, weakness, rapid fatigability, headache, dizziness, sensation of drunkenness, gastrointestinal and cardiovascular disturbances, impairment of liver function, pain in the region of the stomach and liver, increased salivation, a sweet taste in the mouth, and increased hearing sensitivity [Parmeggiani 1983].

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 2,4-D and lead to worker exposures to this substance:

• The manufacture, formulation, and transportation of 2,4-D
• Use as a herbicide, a military defoliant (a component in agent orange), and fungicide
• Use as a plant growth regulator, and in fruit drop control
• Use to increase latex output of old rubber.

Methods that are effective in controlling worker exposures to 2,4-D, 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 2,4-D 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 2,4-D, 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 skin, liver, kidneys, and central nervous system.

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 2,4-D 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 skin, liver, kidneys, or central nervous system.

* 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 2,4-D exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of 2,4-D on the skin, liver, kidneys, or central nervous system. 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. A biological monitoring method for 2,4-D involves the measurement of 2,4-D concentrations in either plasma or urine by means of flame-ionization gas chromatography using on-column methylation. The urinary or plasma concentrations that correspond to an airborne concentration of 10 mg/m(3) have not been established; however, no adverse effects have been noted in workers who ingested 2,4-D at a dose of 5 mg/kg with plasma and urine levels of up to 40 and 100 mg/L, respectively.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne 2,4-D is made using a glass fiber filter (Gelman type or equivalent). Samples are collected at a recommended flow rate of 3.0 liters/minute until a recommended collection volume of 200 liters is reached. Analysis is conducted by high performance liquid chromatography using an ultraviolet detector (HPLC/UV). This method is described in the OSHA Computerized Information System [OSHA 1994] and is fully validated. NIOSH Method No. 5001 for 2,4-D is the same as the method described above [NIOSH 1994b].

PERSONAL HYGIENE PROCEDURES

If 2,4-D contacts the skin, workers should immediately wash the affected areas with soap and water.

Clothing contaminated with 2,4-D 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 2,4-D, particularly its potential for causing irritation and central nervous system effects.

A worker who handles 2,4-D 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 2,4-D or a solution containing 2,4-D is handled, processed, or stored.

STORAGE

2,4-D 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 2,4-D should be protected from physical damage and should be stored separately from strong oxidizers such as chlorine, bromine, and fluorine.

SPILLS AND LEAKS

In the event of a spill or leak involving 2,4-D, 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. Do not touch the spilled material; stop the leak if it is possible to do so without risk.

2. Notify safety personnel.

3. Use water spray to reduce vapors.

4. For small dry spills, use a clean shovel and place the material into a clean, dry container; cover and remove the container from the spill area.

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

6. For large liquid spills, build dikes far ahead of the spill to contain the 2,4-D for later reclamation or disposal.

The 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

2,4-D is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (SARA) (Title III) in 42 USC 11022.

* 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 2,4-D is 100 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].

* Community right-to-know requirements

BULLET TEXT = 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 2,4-D per calendar year or otherwise use 10,000 pounds or more of 2,4-D 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 2,4-D 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. 2,4-D is listed as a hazardous waste under RCRA and has been assigned EPA Hazardous Waste No. U240. This substance has been banned from land disposal until treated by incineration.

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 2,4-D 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 2,4-D. 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 2,4-D. The resistance of various materials to permeation by 2,4-D (dimethylamine ammonium salt) is shown below:

Material	Breakthrough time (hr)
natural rubber	>8
neoprene	>8
nitrile rubber	>8
polyvinyl chloride	>8

To evaluate the use of these PPE materials with 2,4-D, 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 2,4-D.

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

ACGIH [1991]. Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ACGIH [1994]. 1994-1995 Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

Baselt RC [1980]. Biological monitoring methods for industrial chemicals. Davis, CA: Biomedical Publications.

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Forsberg K, Mansdorf SZ [1993]. Quick selection guide to chemical protective clothing. New York, NY: Van Nostrand Reinhold.

Hathaway GJ, Proctor NH, Hughes JP, and Fischman ML [1991]. Proctor and Hughes' chemical hazards of the workplace. 3rd ed. New York, NY: Van Nostrand Reinhold.

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Mickelsen RL, Hall RC, Chern RT, Myers JR [1991]. Evaluation of a simple weight-loss method for determining the permeation of organic liquids through rubber films. Am Ind Hyg Assoc J 52(10): 445-447.

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NIOSH [1987b]. NIOSH respirator decision logic. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-108.

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NIOSH [1994b]. NIOSH manual of analytical methods. 4th ed. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113.

NIOSH [1995]. Registry of toxic effects of chemical substances: 2,4-D. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Standards Development and Technology Transfer, Technical Information Branch.

NJDH [1989]. Hazardous substance fact sheet: 2,4-D. Trenton, NJ: New Jersey Department of Health.

NLM [1995]. Hazardous substances data bank: 2,4-D. Bethesda, MD: National Library of Medicine.

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