ZnCrO(4)

(For Structure, see paper copy)

Basic zinc chromate, zinc yellow, zinc chrome yellow, zinc chromate (VI) hydroxide, citron yellow, primrose yellow, C.I. pigment yellow 36, chromium zinc oxide

1. CAS No.: 13530-65-9

2. RTECS No.: GB3290000

3. Specific DOT number: None

4. Specific DOT label: None

Zinc chromate is a yellow, crystalline, odorless powder. It is a hexavalent chromium compound.

1. Molecular weight: 181.36

2. Boiling point: Data not available.

3. Specific gravity: 3.4 at 20 degrees C (68 degrees F)

4. Vapor density: Data not available.

5. Melting point: Data not available.

6. Vapor pressure: Data not available.

7. Solubility: Insoluble in cold water and acetone; decomposes in hot water; soluble in acids and liquid ammonia.

8. Evaporation rate: Data not available.

1. Conditions contributing to instability: None reported.

2. Incompatibilities: Contact between zinc chromate and hydrazine results in explosive decomposition. Contact between zinc chromate and combustible, organic, or other oxidizable materials (such as paper, wood, sulfur, aluminum, and plastics), or strong oxidizers should be avoided.

3. Hazardous decomposition products: None reported.

4. Special precautions: None reported.

Zinc chromate is not combustible.

The National Fire Protection Association has not assigned a flammability rating to zinc chromate.

Fires involving zinc chromate 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 zinc chromate.

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for zinc chromate (as chromic acid and chromates) is 0.1 milligram per cubic meter (mg/m(3)) of air as a ceiling limit. A worker's exposure to zinc chromate shall at no time exceed this ceiling level [29 CFR 1910.1000, Table Z-2].

The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for zinc chromate of 0.001 mg/m(3) as a TWA for up to a 10-hour workday and a 40-hour workweek. NIOSH considers zinc chromate a potential human carcinogen [NIOSH 1992].

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned zinc chromate a threshold limit value (TLV) of 0.01 mg/m(3) as a TWA for a normal 8-hour workday and a 40-hour workweek. The ACGIH considers zinc chromate a confirmed human carcinogen (A1-substance) [ACGIH 1994, p. 36].

The NIOSH limit is based on the risk of lung cancer, skin ulcers, and lung irritation [NIOSH 1992].

The ACGIH limit is based on the risk of lung cancer [ACGIH 1991, p. 1752].

Exposure to zinc chromate can occur through inhalation, ingestion, and eye or skin contact.

1. Effects on Animals: Zinc chromate has produced cancer in experimental animals following intrapleural and intrabronchial implantation [ACGIH 1991]. Bronchial carcinomas in rats were produced by intrabronchial implantation of zinc chromate [IARC 1987]. Injection-site sarcomas were produced in both rats and mice following intramuscular, intrapleural, and subcutaneous injections of zinc chromate [IARC 1987]. Zinc chromate is mutagenic in in vitro test systems [NIOSH 1989]. The International Agency for Research on Cancer (IARC) has concluded that there is sufficient evidence for the carcinogenicity of zinc chromate in experimental animals [IARC 1990].

2. Effects on Humans: Exposure to zinc chromate can cause irritation, tissue ulceration, and cancer in humans. Inhalation of dusts containing chromates causes irritation of the mucous membranes [Rom 1992]. Gastric distress, olfactory sense impairment, and the yellowing of teeth and tongue may also result from excessive exposures to chromates. If exposures are prolonged, ulcerations of the nasal mucosae may occur as well as possible septal perforations. Prolonged dermal contact may produce ulceration of the skin. The increased exposure that results from an ulcer may result in renal chromate toxicosis, liver failure or death [Rom 1992]. Ocular effects including eye lesions, conjunctivitis, and keratitis have been associated with exposures to chromates [Rom 1992]. Prolonged exposure to chromates can cause chronic bronchitis, rhinitis, or the growth of nasal mucosal polyps [Rom 1992]. Exposures may also lead to chemical pneumonitis. Chronic exposures to hexavalent chromium compounds can cause lung and gastrointestinal tract cancer including cancer of the esophagus, stomach, intestines, and pancreas [Rom 1992]. Of six studies that examined the association between exposure to zinc chromate and lung cancer, five were cohort studies and one was a proportionate mortality study [ACGIH 1991]. In four of the five cohort studies there were also exposures to lead chromates. All of the cohort studies demonstrated an association between exposure to chromates and lung cancer. It was noted that because of the compounded exposures with lead chromate it was not possible to separate out the effects caused by each individual chromate compound [ACGIH 1991]. IARC has concluded that there is sufficient evidence for the carcinogenicity of hexavalent chromium compounds to humans [IARC 1990].

1. Acute exposure: Acute exposure to zinc chromate can cause irritation of the eyes and mucous membranes and also skin rash, ulceration, and allergy.

2. Chronic exposure: Chronic exposure by direct contact with zinc chromate can cause lesions of the eyes, skin, and mucous membranes, nasal septal perforations, olfactory sense impairment, and yellowing of the teeth and tongue. Prolonged inhalation exposure can cause chronic bronchitis, rhinitis, and nasal mucosal polyps, and also lead to chemical pneumonitis. Symptoms include wheezing, pain during inspiration, and coughing. Additionally, chronic exposures to hexavalent chromium compounds have been reported to be associated with fever, gastric distress, and weight loss, and such exposures may also result in lung and gastrointestinal tract cancer including cancer of the esophagus, stomach, intestines, and pancreas.

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.

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.

Before a worker is placed in a job with a potential for exposure to zinc chromate, 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 and respiratory system. 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 zinc chromate 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 or respiratory system.

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 zinc chromate exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of zinc chromate on the skin or respiratory 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.

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. Because occupational exposure to zinc chromate may cause diseases with prolonged latent periods, the need for medical surveillance may extend well beyond the termination of employment.

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. Urine tests for chromium performed shortly after exposure can help indicate the level of exposure to zinc chromate. However, no biological monitoring test acceptable for routine use has yet been developed for zinc chromate.

Zinc chromate is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (SARA) (Title III) in 42 USC 11022.

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].

Employers are not required by the emergency release notification provisions in 40 CFR Part 355.40 to notify the National Response Center of an accidental release of zinc chromate; there is no reportable quantity for this substance.

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 zinc chromate emitted or released from their facility annually.

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 zinc chromate 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.

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 zinc chromate 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).

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 and the NIOSH Guide to Industrial Respiratory Protection.