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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

The most critical EC50 was a 48-h EC50 value for Daphnia magna from an acute toxicity test with sodium selenite. No reliable data were identified for marine invertebrates.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
550 µg/L

Additional information

In total, 59 studies were allocated to this endpoint; 58 studies were considered relevant (including 5 review publications); 9 studies were considered reliable (Klimisch 1 or 2). Reliable data were available for H2SeO3, Na2SeO3, Na2SeO4 and selenomethionine (both seleno-L- and seleno-DL-methionine). No reliable data were available for brackish or marine organisms. All reliable data were for freshwater organisms: 6 Crustacea (Daphnia magna, Daphnia pulex, Ceriodaphnia dubia, Hyalella azteca, Gammarus pseudolimnaeus, and Gammarus lacustris), and 2 insects (Diptera: Chironomus riparius and Chironomus decorus). All results are based on added dissolved Se concentrations.

The data for Se-(D)L-methionine were not taken into account for the assessment of direct effects of selenite to aquatic organisms because there is some concern on different biochemical behaviour of this selenium containing amino acid compared to inorganic Se compounds. The short-term L(E)C50 values for inorganic Se substances varied between 550 and 48200 µg Se/L. The highest value represents a 48-h LC50 for larvae of the dipteran species Chironomus decorus obtained in a test with sodium selenite (Maier and Knight, 1993). The lowest value is a 48-h EC50 value for Daphnia magna reported by Maier et al. (1993) for the same substance. L(E)C50 values for selenate compounds ranged from 580 to 23700 µg Se/L. Selenium toxicity appears to differ strongly among the invertebrate species. Although it is generally assumed that organo-selenium forms are the most toxic and that Se as selenite is more toxic than Se as selenate, no consistent differences in toxicity are found across Se substances for all aquatic invertebrate species tested (L(E)C50 values for Se-(D)L-methionine vary between 310 and 194000 µg Se/L).

For Chironomus decorus, a short-term dietary toxicity study was also considered reliable (although usually not considered under REACH). The dietary toxicity study observed significant growth reduction at 2.84 mg Se/kg dw in food for Na2SeO3 and at 2.11 mg Se/kg dw in food for Na2SeO4 (corresponding with 4.05 and 2.55 mg Se/kg dw whole body, respectively).