Dichromium tris(chromate)

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72 hour ErC50 of chromium (III) hydroxide sulphate was > 848.6 µg/L, the corresponding no-observed effect concentration (NOEC) was 4.01 µg/L. The 72 hour EyC50 of chromium (III) hydroxide sulphate was 76.1 µg/L, the corresponding NOEC was 4.01 µg/L

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

0.7 µg/L

Additional information

No studies with dichromium tris(chromate) are available. A read across is proposed to chromium (III) hydroxide sulphate, because the only source of significant environmental exposure will be to the trivalent form of chromium.

Exponentially growing algal cells (Desmodesmus subspicatus) were exposed for a period of 72 hours to a range of chromium (III) hydroxide sulphate concentrations, nominally 0.0032, 0.01, 0.032, 0.1, 0.32, 1.0, 3.2, 32 and 100 mg/L. Initial measured concentrations were 1.28, 4.01, 8.89, 15.47, 52.49, 173.33, 327.53, 313.72, 637.73 and 848.61 µg/L. Measured values in the test media declined at subsequent analytical sampling intervals.  The results of the study are based on the initial measured concentrations; this is recommended in the guideline in those cases, where there is a decrease in concentration of test item over time, which is not accompanied by a decrease in toxicity over time.

The 72 hour E_rC₅₀of chromium (III) hydroxide sulphate was > 848.6 µg/L, the corresponding no-observed effect concentration (NOEC) was 4.01 µg/L. The 72 hour E_yC₅₀of chromium (III) hydroxide sulphate was 76.1 µg/L, the corresponding NOEC was 4.01 µg/L.