Chromium trichloride

Long-term toxicity to aquatic invertebrates

Description of key information

From daphnia reproduction studies a NOEC of 3.4 mg/L (as chromium trichloride hexahydrate) is derived for daphnia magna (freshwater species) whereas for saltwater species in a 293 days exposure study to Polychaete (Neanthes arenaceodentata) a NOEC of 258 mg/L as chromium trichloride hexahydrate was derived.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

3.4 mg/L

Marine water invertebrates

Marine water invertebrates

Effect concentration:

258 mg/L

Additional information

Freshwater

In a key study by Kühn et al. (1989), performed by the German BGA in total 73 investigations were carried out in order to determine the "no observed effect concentration" (NOEC) of 73 environmentally relevant substances in the 21 d Daphnia reproduction test. The test was conducted in line with the provisional procedure proposed by the Federal Environmental Agency (Umweltbundesamt) (as of 1 January 1984). Daphnia magna Straus was used as the test organism. Evaluation parameters for fixing the NOEC were the mortality of the parent animals, the reproduction rate and the appearance of the first offspring during the test period. The concentrations of substances in the test preparations were chemically quantified. The NOEC values obtained for ethyl parathion, and the active ion Cd (II) were in the concentration range 1 ng /L to 1 µg/L, for 13 tested substances in the range 1 µg /L to- < 0.1 mg/L and for 23 substances in the range 0.1 to < 1 mg/L.

For chromium(III), tested as chromium trichloride hexahydrate, the most sensitive parameter in the daphnia reproduction test was reproduction and the NOEC was set to 0.7 mg Cr/L and 3.4 mg CrCl3.6H2O/L respectively.

In a supportive study published by Biesinger et al. (1972) effects of various metals on daphnia reproduction was investigated, amongst other of chromium(III) compounds. Chromium(III) chloride hexahydrate was used in the experiments, which investigated reproductive performance of daphnia magna over 21 days exposure. The survival rate during experiment was reported as LC50 being 2000 µg/L, whereas 50% reproductive impairment was observed at 600 µg Cr/L and 16% impairment at 330 µg Cr/L. The concentration of 330 µg Cr/L (equivalent to 1005 µg/L chromium trichloride, anhydrous or 1.69 mg/L as chromium trichloride hexahydrate) was referred to as safe concentration in this study.

Boutet et al. (1973) In this study in total 14 different metal ions were tested for acute and chronic toxicity on freshwater crayfish (2 species: Austropotamobius p.p. and Orconestus limosus) at 16 °C. The chronic study was performed with 30 days exposure period in two independent experiments, one with feeding and one without. Although EC50 values found were lower when feed was provided, the difference was rather slight and all EC50 values with both species were in the range of 1.2 - 3.1 mg Cr/L, equivalent to 6.2 – 15.9 mg/L as chromium trichloride hexahydrate.

Saltwater

Oshida et al. (1981) reported a 293-day NOEC of chromium chloride to Polychaete (Neanthes arenaceodentata) being 50.4 mg Cr/L. Thus, the 293-day NOEC of the chromium trichloride can be estimated to be 153.5 mg/L based on equimolar adjustment to molecular weight of chromium trichloride anhydrous or 258 mg/L as chromium trichloride hexahydrate.

In contrast to the effects of Cr VI, no abnormal biological effects were observed in polychaetes exposed to Cr III. The Cr III precipitate in the long-term experiment did not affect the mortality rate, maturation time required for spawning, or number of young per brood. This finding seemed paradoxical since it is the Cr III that is more active in biochemical cycles (Mertz, 1969), although it does lend support to the premise that Cr III is much less toxic to marine invertebrates than Cr VI (Chipman, 1966).

This finding also supports observations in other species that saltwater species do tolerate chromium(III) better then freshwater species.