Zinc selenite

Long-term toxicity to aquatic invertebrates

Description of key information

Reliable chronic NOEC values were available for freshwater invertebrates (range: 70 to 2953 µg Se/L) and marine invertebrates (44 to 74000 µg Se/L). The most critical NOEC for freshwater organisms was a 28-d NOEC for reproduction of Daphnia magna from a study with H2SeO3. For marine invertebrates, the most critical NOEC was a 28-d NOEC of 44 µg/L for survival and growth of Allorchestes compressa obtained in a study using Na2SeO3 as test substance. All reliable chronic NOEC values were used for the derivation of a PNECwater based on the statistical extrapolation approach.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:

70 µg/L

EC10, LC10 or NOEC for marine water invertebrates:

44 µg/L

Additional information

For this endpoint, 29 studies were identified as possibly relevant. After review, 25 studies were retained (including 5 reviews). Reliable results were obtained from 7 different studies. These results include data from toxicity tests with H₂SeO₃, Na₂SeO₃ and Na₂SeO₄. Reliable data were available for three freshwater and two marine invertebrates. The freshwater invertebrates represented were Daphnia magna and Hyalella azteca (Crustacea), and Chironomus riparius (Insecta, Diptera). The marine invertebrates represented were Allorchestes compressa and Artemia franciscana (Crustacea). All results are based on added dissolved Se concentrations.

For freshwater invertebrates, reliable NOEC values ranged from 70 to 2953 µg Se/L. The lowest NOEC resulted from a 28-d toxicity study on reproduction of Daphnia magna, in which H₂SeO₃ was used as test substance (Kimball, 1978). The highest NOEC value represented a 30-d NOEC for % emergence of the dipteran Chironomus riparius (Ingersoll et al., 1990). In this study, a mixture of Na₂SeO₄ and Na₂SeO₃ was added in a 5.7:1 ratio (Se-based) to the exposure media.

Two studies were identified reporting reliable data for saltwater species. Ahsanullah and Brand (1985) reported a 28-d NOEC of 44 µg Se/L for both survival and growth of the marine amphipod Allorchestes compressa obtained in a study using Na₂SeO₃ as test substance. The other reliable study reported 28-d NOEC values of 15000 and 74000 µg Se/L for reproduction and mortality of brine shrimp (Artemia franciscana) (Brix et al., 2004). In this study, Na₂SeO₄ was used as test substance.

One study was identified reporting reliable effect concentrations expressed as internal Se concentrations. Ingersoll et al. (1990) exposed D. magna for 21 days to a series of waterborne Se concentrations using a 6.6:1 mixture (Se-based) of Na₂SeO₄ and Na₂SeO₃. The 21-d NOEC for the endpoint reproduction was 156 µg Se/L or – when expressed as internal Se concentration – 14.7 mg Se/kg dw (whole body).

Although there are a lot of inter-species differences in sensitivity, selenite compounds seem to be about one order of magnitude more toxic than selenate compounds. However, there are not enough reliable data available to define the significance of this finding. Overall the order of sensitivity of the endpoints seems to be growth > reproduction > survival.