Chromium trichloride

Short-term toxicity to fish

Description of key information

The acute LD50 towards freshwater fish (96h, rainbow trouts) was found being 57.4 mg/L whereas the acute toxicity to saltwater fish appears to be lower (LD50 (96h, mummichog) of 161 mg/L as chromium trichloride hexahydrate).

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

57.4 mg/L

Marine water fish

Marine water fish

Effect concentration:

161 mg/L

Additional information

Freshwater

In the key study Bills et al. (1977) found the LC50 (96h, rainbow trout) being 11.2 mg Cr/L or 57.4 mg/L as chromium trichloride hexahydrate. In this study the effects of pre-treatment of rainbow trouts by different concentrations of polychlorinated biphenyls on the acute toxicity to six different contaminants (mercury(II), chromium(III), cyanides, nitrates, nitrites, and chlorides) was investigated. Acute toxicity to these contaminants was tested using a control group of rainbow trouts (no pre-treatment towards PCBs) a low level group (PCB concentration of 0.46 µg/g tissue) and a high level group (PCB concentration of 3.40 µg/g tissue). The results found for the control groups exposed to chromium(III) was a LC50 (96h) of 11.2 mg Cr/L. Results with animals from the low level and high level group were 9.0 and 7.05 mg Cr/L respectively. The result for the control group is considered representative for acute toxicity towards chromium trichloride and can be converted to LC50 (96h) of 57.4 mg/L as chromium trichloride hexahydrate.

Tis finding is supported by a publication of Stevens et al. (1984), using chromium trinitrate nonahydrate as chromium(III) source, which is also very well water soluble. A 96-h LC50 of 4400 µg/L chromium (equimolar to 22.6 mg/L as chromium trichloride hexahydrate) was obtained with two-month-old juvenile fish. This study was conducted to determine the acute effects of the test substance on the early life stages of steelhead trout (Salmo gairdneri). Eight concentrations of 1100, 1933, 1966, 2900, 3100, 3966, 5650, 5825 µg Cr/L and a control were administrated to the test fish. After 96 hours exposure, the 96-h LC50 of 4400 µg/L as chromium was obtained with two-month-old juvenile fish.

Another supporting study using chromium trinitrate nonahydrate was published by Hale et al. (1977). The 96-h LC50 of the test substance to (2-month-old) rainbow trout was 24.09 mg Cr/L (equivalent to 123.5 mg/L as chromium trichloride hexahydrate). The 96-hour toxicity bioassays was conducted in a mobile bioassay laboratory and conducted according to standard method using a continuous flow proportional diluter to evaluate the short-term toxicity of the test substance to 2-month-old rainbow trout. 4.02 - 64.25 mg Cr/L were applied to the test fish. After 96 hours exposure, the 96-h LC50 of the test substance to (2-month-old) rainbow trout was 24.09 mg Cr/L.

In conclusion, the LC50 to fish of 57.4 mg/L as chromium trichloride hexahydrate, reported by Bills et al. is used for hazard and risk assessment, supported by data on acute fish toxicity determined using chromium trinitrate as chromium(III) source.

Saltwater

In the key-study Dorfman et al. (1977) assessed 20 metals in 30 compounds for toxicity towards mummichog fish. For chromium(III) chloride he showed in this assay a LD50 (96h, mummichog) of 31.5 mg Cr/L (equivalent to 96 mg CrCl3/L or 161 mg CrCl3.6H2O/L). The TL50 values found in this assay varied from greater than 1000 mg/L to 0.2 mg/L. Metals with the greatest toxicity were mercury and copper.

In some tests the reduced pH was probably the immediate cause of death. For example, aluminum ammonium sulfate, aluminum chloride, beryllium sulfate, chromium chloride, ferric ammonium sulfate, ferric chloride, molybdenum oxide and zirconyl chloride in higher concentrations (1000, 100 and 10 mg/L, and occasionally 1 mg/L of the metal ion) resulted in pH readings of 4 or less.

In conclusion, chromium chloride was of low toxicity in this assay to saltwater fish (mummichog - Fundulus heteroclitus) and the LC50 found was 31.5 mg Cr/L (equivalent to 96 mg CrCl3/L or 161 mg CrCl3.6H2O/L). The toxicity was apparently due to the reduction of pH in the test system caused by chromium trichloride addition as equivalent values were found following 24, 48, 72 and 96 hours of exposure.

In a supporting study Negilski et al. (1976) investigated the toxicity of chromium(III) towards juvenile mullet in a static test design using chromium trinitrate as chromium(III) source. The 96-h LC50 value for chromium(III) was 53 mg Cr/L (equimolar to 272 mg/L as chromium trichloride hexahydrate). This finding does support the lower toxicity to saltwater fish compared to freshwater species.