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 This information may be superseded by new developments in the field of industrial hygiene.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 CHROMIUM (III) COMPOUND (as Cr)

INTRODUCTION

This guideline summarizes pertinent information about chromium (III) compounds 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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.

APPLICABILITY

The general guidelines contained in this document apply to all of the chromium (III) compounds. Examples of such compounds include chromium (III) oxide, chromium (III) acetate, and chromium (III) nitrate. For illustrative purposes, the physical and chemical properties of several chromium (III) compounds are presented below.

SUBSTANCE IDENTIFICATION

Chromium (III) oxide

* Formula

Cr(2)O(3)

* Structure

(For Structure, see paper copy)

* Synonyms

Chromic oxide, chrome green, chrome oxide green, green cinnabar, dichromium trioxide

* Identifiers

1. CAS No.: 1308-38-9

2. RTECS No.: GB6475000

3. Specific DOT number: None

4. Specific DOT label: None

* Appearance and odor

Chromium (III) oxide is light to dark green or bright green, fine crystalline solid.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 152

2. Boiling point (at 760 mm Hg): 4000 degrees C (7232 degrees F)

3. Specific gravity (water = 1): 5.21

4. Vapor density: Not applicable.

5. Melting point: 2435 degrees C (4415 degrees F)

6. Vapor pressure: Not applicable.

7. Solubility: Insoluble in water, acids, alcohols, and alkalies.

8. Evaporation rate: Not applicable.

Chromium (III) acetate

* Formula

C(6)H(9)CrO(6)

* Structure

Cr(C(2)H(3)O(2))(3)þH(2)O

* Synonyms

Chromic acetate, chromium triacetate

* Identifiers

1. CAS No.: 1066-30-4

2. RTECS No.: AG2975000

3. Specific DOT number: None

4. Specific DOT label: None

* Appearance and odor

Chromium (III) acetate is a grayish to green or violet powder, crystalline or paste-like material. The commercial product is usually sold as a concentrated solution and may contain sodium acetate or other impurities.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 229.1

2. Boiling point: Data not available.

3. Specific gravity: Data not available.

4. Vapor density: Not applicable.

5. Melting point: Data not available.

6. Vapor pressure: Not applicable.

7. Solubility: Soluble in water; insoluble in alcohol.

8. Evaporation rate: Data not available.

Chromium (III) nitrate

* Formula

N(3)O(9)Cr

* Structure

Cr(NO(3))(3) (anhydrous); Cr(NO(3))(3)þ9H(2)O (nanohydrate)

* Synonyms

Chromic nitrate, chromium trinitrate, chromium nitrate

* Identifiers

1. CAS No.: 13548-38-4

2. RTECS No.: GB6280000

3. DOT UN: 2720 35

4. DOT label: Oxidizer

* Appearance and odor

Chromium (III) nitrate is a pale green, extremely deliquescent powder. The nanohydrate form is a purple to deep violet monoclinic crystalline solid.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 238

2. Boiling point: Decomposes above 60 degrees C (140 degrees F) (anhydrous); decomposes above 100 degrees C (212 degrees F) (nanohydrate)

3. Specific gravity: Data not available.

4. Vapor density: Not applicable.

5. Melting: 60 degrees C (140 degrees F)

6. Vapor pressure: Not applicable.

7. Solubility: Anhydrous chromium (III) nitrate is soluble in water, ethyl acetate, and DMSO. It is practically insoluble in benzene, carbon tetrachloride, and chloroform (may react violently with ether). Hydrated chromium (III) nitrate is soluble in water and alcohol.

8. Evaporation rate: Not applicable.

* Reactivity

1. Conditions contributing to instability: The conditions contributing to the instability of chromium (III) compounds may vary with each specific compound.

2. Incompatibilities: Contact between chromium (III) nitrate and strong reducing agents, fuels or ethers should be avoided. Contact between chromium (III) oxide and glycerol, oxygen difluoride, and strong oxidizers such as bromine, chlorine, and fluorine should be avoided. Other incompatibilities may exist for specific chromium (III) compounds and should be considered before handling or storage operations are performed.

3. Hazardous decomposition products: Toxic gases may be released in a fire involving chromium (III) compounds. Specific thermal degradation products are dependant on which compound is involved in the fire, but the following substances could be expected; nitrogen oxides, carbon oxides, and chromium oxides.

4. Special precautions: None reported.

* Flammability

The National Fire Protection Association has not assigned flammability ratings to the example chromium (III) compounds described in this guideline.

1. Flash point: Data not available.

2. Autoignition temperature: Data not available.

3. Flammable limits in air: Data not available.

4. Extinguishant: Use an extinguishant that is suitable for the materials involved in the surrounding fire.

Fires involving chromium (III) compounds should be fought upwind from the maximum distance possible. Isolate the hazard area and deny access to unnecessary personnel. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving chromium (III) compounds.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for chromium (III) compounds (as Cr) is 0.5 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 chromium (III) compounds of 0.5 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 chromium (III) compounds a threshold limit value (TLV) of 0.5 mg/m(3) as a TWA for a normal 8-hour workday and a 40-hour workweek. The ACGIH also gives the chromium (III) compounds an A4 designation, not classifiable as a human carcinogen [ACGIH 1994, p. 16].

* Rationale for Limits

The NIOSH limit is based on the low-order of toxicity associated with these compounds [NIOSH 1992].

The ACGIH limit is based on the low-order of toxicity associated with these compounds [ACGIH 1991, p. 313].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to chromium (III) compounds can occur through inhalation, ingestion, and eye or skin contact.

* Summary of toxicology

1. Effects on Animals: The trivalent chromium (III) compounds have a relatively low-order of toxicity in experimental animals as compared to hexavalent chromium compounds. The oral LD(50) chromium (III) nitrate in rats is 3,250 mg/kg [NIOSH 1995]. The inhalation LC(50) for chromium trichloride in mice is 31.5 mg/m(3) for 2 hours [Sax and Lewis 1989]. Chromium (III) oxide administered to rats at a concentration of 2 or 5 percent of the diet had no effect on reproductive capacity [NLM 1995]. Although trivalent chromium has the capacity to damage DNA, it is not thought to be an effective mutagen due to its poor cellular uptake [Rom 1992]. There is no evidence that chromium (III) compounds are carcinogenic in experimental animals [Hathaway et al. 1991].

2. Effects on Humans: Chromium (III) compounds can effect the skin, liver, and kidneys in humans. Dermal contact with trivalent chromium compounds has resulted in contact dermatitis [ACGIH 1991; Rom 1992]. Chromium (III) compounds can also affect the kidneys and liver (no further information on exposure given) [Rom 1992]. No adverse effects were observed in workers exposed to chromium (III) oxide and chromic sulfide for 20 to 25 years [NLM 1995]. There is no evidence that chromium (III) compounds are carcinogenic in humans [Hathaway et al. 1991].

* Signs and symptoms of exposure

1. Acute exposure: No signs or symptoms of acute exposure to chromium (III) compounds have been reported in humans.

2. Chronic exposure: Chronic exposure to chromium (III) compounds may result in dermatitis, liver damage, or kidney damage in humans.

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 chromium (III) compounds and lead to worker exposures to these substances:

* The manufacture and transportation of chromium (III) compounds

* Use of chromium (III) compounds as catalysts, corrosion inhibitors, mordants in dyeing processes, pigments, abrasives, refractory materials, in electric semiconductors, and as photographic chemicals

Methods that are effective in controlling worker exposures to chromium (III) compounds, 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 chromium (III) compounds 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 chromium (III) compounds, 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, and kidneys.

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 chromium (III) compounds 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, or kidneys.

* 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 exposure to chromium (III) compounds. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of chromium (III) compounds on the skin, liver, or kidneys. 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. No biological monitoring test acceptable for routine use has yet been developed for chromium (III) compounds.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne chromium (III) compounds (as Cr) is made using a mixed cellulose ester filter (MCEF), 0.8 microns. Samples are collected at a maximum flow rate of 2.0 liter/minute until a minimum collection volume of 480 liters (or a maximum collection volume of 960 liters) is reached. The sample is then treated with deionized water. Analysis is conducted by atomic absorption spectroscopy (AAS). This method (OSHA ID-121) is described in the OSHA Computerized Information System [OSHA 1994] and is fully validated. NIOSH has also published a similar method (Method No. 7204) in the NIOSH Manual of Analytical Methods [NIOSH 1994].

PERSONAL HYGIENE PROCEDURES

If chromium (III) compounds contact the skin, workers should immediately wash the affected areas with soap and water.

Clothing contaminated with chromium (III) compounds 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 chromium (III) compounds.

A worker who handles chromium (III) compounds 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 chromium (III) compounds or a solution containing chromium (III) compounds is handled, processed, or stored.

STORAGE

Chromium (III) compounds 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 chromium (III) compounds should be protected from physical damage and should be stored separately from strong reducing agents, fuels, ethers, glycerol, oxygen difluoride, and strong oxidizers such as bromine, chlorine, and fluorine. Other incompatibilities may exist for specific chromium (III) compounds and should be considered before storage operations are performed.

SPILLS AND LEAKS

In the event of a spill or leak involving chromium (III) compounds, persons not wearing protective equipment and 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. Collect the spilled material in the most safe and convenient manner possible for later disposal or reclamation.

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. The EPA requirements may differ for specific chromium (III) compounds, therefore, for illustrative purposes an example compound (chromium (III) acetate) is used in the following section.

* Emergency planning requirements

Chromium (III) acetate 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 chromium (III) acetate is 1,000 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

Employers are not required by EPA in 40 CFR Part 372.30 to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of chromium (III) acetate 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 chromium (III) acetate 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 chromium (III) compounds 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 chromium (III) compounds. 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 chromium (III) compounds.

There are no published reports on the resistance of various materials to permeation by chromium (III) compounds.

To evaluate the use of PPE materials with chromium (III) compounds, 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 chromium (III) compounds.

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.

CFR. Code of Federal regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.

DOT [1993]. 1993 Emergency response guidebook, guide 32. Washington, DC: U.S. Department of Transportation, Office of Hazardous Materials Transportation, Research and Special Programs Administration.

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.

Lewis RJ, ed. [1993]. Hawley's condensed chemical dictionary. 12th ed. New York, NY: Van Nostrand Reinhold Company.

Lide DR [1993]. CRC handbook of chemistry and physics. 73rd ed. Boca Raton, FL: CRC Press, Inc.

Mickelsen RL, Hall RC [1987]. A breakthrough time comparison of nitrile and neoprene glove materials produced by different glove manufacturers. Am Ind Hyg Assoc J 48(11): 941-947.

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.

NIOSH [1987a]. NIOSH guide to industrial respiratory protection. 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. 87-116.

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.

NIOSH [1992]. Recommendations for occupational safety and health: Compendium of policy documents and statements. 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. 92-100.

NIOSH [1994]. 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: Chromium (III) acetate, Chromium (III) nitrate, chromium (III) oxide. 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 [1987]. Hazardous substance fact sheet: Chromium (III) nitrate. Trenton, NJ: New Jersey Department of Health.

NJDH [1992]. Hazardous substance fact sheet: Chromium (III) oxide. Trenton, NJ: New Jersey Department of Health.

NLM [1995]. Hazardous substances data bank: Chromium (III) acetate, chromium (III) oxide. Bethesda, MD: National Library of Medicine.

OSHA [1994]. Computerized information system. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration.

Rom WN [1992]. Environmental and occupational medicine. 2nd ed. Boston, MA: Little, Brown and Company.

Sax NI, Lewis RJ [1989]. Dangerous properties of industrial materials. 7th ed. New York, NY: Van Nostrand Reinhold Company.

Sittig M [1991]. Handbook of toxic and hazardous chemicals. 3rd ed. Park Ridge, NJ: Noyes Publications.

USC. United States code. Washington. DC: U.S. Government Printing Office.

Windholz M, ed. [1983]. Merck Index 10th ed. Rahway, NJ: Merck & Company.