Chromium trichloride

Endpoint summary

Additional information

Chromium trichloride in its anhydrous form is barely soluble in water but slowly transforms to chromium trichloride hexahydrate in an aqueous environment. Thus, the hexahydrate form is the predominant species found in aqueous systems.

Chromium trichloride hexahydrate is a fully soluble inorganic salt and thus is not subject to hydrolysis other than ionic dissociation. In the aquatic environment and biotic systems it is present in dissociated form and not subject to phototransformation, which is not applicable to inorganic salts.

The concept of biodegradation is not applicable to inorganic substances such as chromium trichloride. Thus, testing for biodegradation in water, sediment and soil is waived.

Chromium is an essential element to most species and ubiquitous in the environment. To assess bioconcentration in aqueous environment some data were identified in the public literature. In a 20-week study that was conducted early in 1968 with chromium trinitrate as chromium(III) source to corroborate an earlier experiment on uptake by Crassostrea virginica. About 200 November-harvested oysters were placed in each of eight 120-liter tanks making use of a flow-through sewer water system. During the acclimatisation and experimental periods the sea water was maintained at a flow rate of 2.5 l/min and a 20 ±1 degree C temperature with salinity variable but usually 31 ± 2 ppt. The test animals were subjected to continuous levels of the test substance at 0.05 ppm and 0.1 ppm. Each week the test animals were removed for analysis.

The test result indicated the metal in the tissues of the test animals ranged from less than 0.21 ppm to 6.28 ppm at 0.05 ppm concentration group and ranged from less than 0.21 ppm to 11.49 ppm at 0.1 ppm concentration group.

The BCF for chromium(III) was not specified in this study. However, it was recalculated and indicated to be 116 as reported in the AMBIENT WATER QUALITY CRITERIA FOR CHROMIUM published by U.S. ENVIRONMENTAL PROTECTION AGENCY.

Accumulation and elimination of chromium(III) of the earthworm Eisenia andrei was determined in an artificial soil through exposure to chromium trinitrate. Five concentration groups of 10, 32, 100, 320 and 1000 mg/kg dw soil and control group were administrated to the test earth worms. Chromium was significantly accumulated and earthworm reproduction significantly reduced at soil concentrations of 100 mg/kg and higher. However, chromium(III) was completely eliminated and reproduction no longer affected at the end of a 3-week recovery period. BCF values for the accumulation of chromium in the worms were 0.031-0.047 at the three lowest and 0.016-0.019 at the two highest dose levels. Control soil contained 6.3 mg Cr/kg dry weight; the BCF value for worms kept in this soil therefore is 0.048.

In summary it can be stated that chromium (III) does not significantly bioaccumulate in American oysters and does not bioaccumulate in earthworms.

Chromium trichloride is expected to have a low potential for adsorption, as it is an inorganic salt, fully dissociated in aqueous media and thus having virtually no potential for adsorption to soil or sediment. Thus, this endpoint is waived. For the purpose of risk assessment a KOC value of 1 (as worst case) is used.

As chromium trichloride is very soluble, it is mobile in the aqueous environment. However, exposure to air is considered negligible as inorganic salts do have virtually no vapour pressure.