Chromic acid and chromates

CAS number: 1333–82–0 (CrO₃)

NIOSH REL: 0.001 mg Cr(VI)/m³ TWA; NIOSH considers chromic acid and chromates to be potential occupational carcinogens as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 0.1 mg CrO₃/m³ CEILING

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: Water soluble: 0.05 mg CrO₃/m³ TWA;

Certain water insoluble: 0.05 mg CrO₃/m³ TWA, A1

Description of Substance: Varies

Original (SCP) IDLH: 30 mg/m³ (as CrO₃)

Basis for original (SCP) IDLH: Very little quantitative data are available concerning the acute toxicity produced by the inhalation of chromic acid and chromates. AIHA [1956] reported that both the short exposure tolerance to chromic acid and the atmospheric concentration immediately dangerous to life are unknown. The chosen IDLH is based on the statements by ILO [1971] that "a man exposed for several days to concentrations of chromic acid mist of about 20 to 30 mg/m³ experienced cough, headache, dyspnea, and substernal pain; the signs persisted for 2 weeks. Another man working on the same process was similarly but less severely affected." No other useful data are available on which to base the IDLH.

Short-term exposure guidelines: None developed

ACUTE TOXICITY DATA

Lethal dose data:

Species	Reference	Route	LD50 (mg/kg)	LDLo (mg/kg)	Adjusted LD	Derived value
H2CrO4·2Na Rat	Gad et al. 1986	oral	51.9	-----	113 mg Cr(VI)/m3	11 mg Cr(VI)/m3
CrO3 Mouse Rat	Chi J Prev Med 1980 Kobayashi et al. 1976	oral oral	127 80	----- -----	462 mg Cr(VI)/m3 291 mg Cr(VI)/m3	46 mg Cr(VI)/m3 29 mg Cr(VI)/m3

Human data: A worker exposed for several days to concentrations of chromic acid mist of about 20 to 30 mg/m³ (equivalent to about 10 to 15 mg Cr(VI)/m³) experienced cough, headache, dyspnea, and substernal pain; the signs persisted for 2 weeks [ILO 1971]. Another man working on the same process was similarly but less severely affected [ILO 1971]. The fatal oral dose of chromium has been reported to be 1 to 3 grams [Seiler et al. 1988]. [Note: An oral dose of 1 to 3 grams is equivalent to a 70-kg worker being exposed to 667 to 2,000 mg Cr(VI)/m³ for 30 minutes, assuming a breathing rate of 50 liters per minute and 100% absorption.]

Revised IDLH: 15 mg Cr(VI)/m3 [Unchanged] Basis for revised IDLH: Based on toxicity data in humans [ILO 1971; Seiler et al. 1988], the original IDLH for chromic acid and chromates is not being revised at this time. However, instead of 30 mg/m3 (as CrO3), the IDLH is being expressed as its equivalent, 15 mg Cr(VI)/m3. [Note: NIOSH recommends as part of its carcinogen policy that the "most protective" respirators be worn for chromic acid and chromates at concentrations above 0.001 mg Cr(IV)/m3.]

REFERENCES:

1. AIHA [1956]. Chromic acid. In: Hygienic guide series. Am Ind Hyg Assoc Q 17:233-234.

2. Chi J Prev Med [1980]; 14:86-88 (in Chinese).

3. Gad SC, et al. [1986]. Acute toxicity of four chromate salts, Proceedings of the Chromium Symposium, pp. 43-58. In: DHHS/ATSDR Toxicological Profile for Chromium (Draft), p. 51.

4. ILO [1971]. Chromium, alloys, compounds. In: Encyclopaedia of occupational health and safety. 2nd ed. Vol. I (A-K). Geneva, Switzerland: International Labour Office, pp. 295-297.

5. Kobayashi H, Kamiya N, Hiraga K [1976]. Toxicological studies on chromium: acute toxicities of chromium trioxide. Annual Report of Tokyo Metropolitan Research Laboratory of Public Health 27:119-123 (in Japanese).

6. Seiler HG, Sigel H, Sigel A, eds. [1988]. Handbook on the toxicity of inorganic compounds. New York, NY: Marcel Dekker, Inc., p. 247.