Rhodium chloride (RhCl3), hydrate

Short-term toxicity to aquatic invertebrates

Description of key information

The 48-hour EC50 for Daphnia magna is 290 µg Rh L-1.

Additional information

Okamoto et al. (2014) assessed the toxicity of 50 metals, including rhodium (as rhodium trichloride hydrate) to Daphnia magna. The study followed OECD guideline 202, with 5 test concentrations included and a spacing factor of 2. pH of the test solutions was adjusted using sodium hydroxide. Test concentrations were analysed using ICP-MS and results reported based on measured values. The study is assigned a Klimisch score of 2 (reliable with restrictions) as it followed a standard test guideline, but is not GLP compliant and as a number of metals were tested in the same study some of the methodological details and the individual data for each metal are not reported. The 48-hour EC50 for Daphnia magna is 290 µg Rh L-1.

The acute toxicity of rhodium to the freshwater amphipod Hyalella azteca was assessed in the publication by Borgmann et al. (2005) and this is included as a supporting study. The study is reliable with acceptable restrictions; it is non-GLP and has some limitations in study design or reporting, but is otherwise adequate for assessment. A static test of 7 days was carried out. Rhodium was tested in solution with 10% HCl, which was used as preservant. Two test series were conducted using tap water and soft water. Multiple tests were conducted, but only one or a few concentrations of Rh were included in each test. The data were then pooled and analyzed as if they had all been obtained from a single test. Metal concentrations were analysed in the soft water series only.

Based on nominal concentrations, the 7-day LC50 of rhodium (with 10% HCl) to Hyalella azteca in soft water and tap water were determined to be 980 μg Rh L-1, and >3150 μg Rh L-1, respectively. Based on measured concentrations, the 7-day LC50 of rhodium (with 10% HCl) to Hyalella azteca in soft water was determined to be 804 μg Rh L-1.