Zinc selenite

Short-term toxicity to fish

Description of key information

The most critical LC50 for freshwater fish was a 96-h LC50 for SeO2 for fathead minnow (Pimephales promelas) of 2060 µg Se/L. The most critical LC50 for marine fish was a 96-h LC50 of 3300 µg Se/L for the anadromous fish species Morone saxatilis (striped bass) obtained from a test in brackish water with Na2SeO3.

Key value for chemical safety assessment

LC50 for freshwater fish:

2 060 µg/L

LC50 for marine water fish:

3 300 µg/L

Additional information

For acute toxicity to fish, a total of 56 sources were identified as possibly relevant. After review, 54 studies were retained as relevant (including 4 reviews). Only 6 studies were assigned a Klimisch 1 (reliable) or Klimisch 2 score (reliable with restrictions). Reliable data were available for SeO₂, Na₂SeO₃ and Na₂SeO₄ and for 8 freshwater species from 6 different families (Pimephales promelas, Carassius auratus and Notemigonus crysoleucas (Cyprinidae), Jordanella floridae (Cyprinodontidae), Lepomis macrochirus (Centrarchidae), Ictalurus punctatus (Ictaluridae), Salvelinus fontinalis (Salmonidae), Stizostedion vitreum (Percidae)) and 2 marine species (from 2 families: Pargus major (Sparidae), and Morone saxatilis (Moronidae)). All results are based on added dissolved elemental Se concentrations.

For freshwater species, the LC50 values ranged from 2060 to 28460 µg Se/L. The lowest LC50 represented a 96-h LC50 for SeO₂ for fathead minnow, Pimephales promelas (Cardwell et al., 1976). The highest LC50 was a 96-h LC50 for bluegill (Lepomis macrochirus) from a toxicity test from the same study with the same test substance.

For brackish/saltwater species, reliable LC50 values were found between 3300 and 76000 µg Se/L. The lowest LC50 was a 96-h LC50 for the anadromous fish species Morone saxatilis (striped bass) resulting from a toxicity test in brackish water with Na₂SeO₃ as test substance (Chapman, 1992). The highest LC50 represented a 96-h LC50 for red seabream (Pargus major) obtained from a toxicity test in natural filtered uncontaminated seawater with Na₂SeO₄ as test substance (Takayanagi, 2001).

For freshwater fish, the data are inconclusive with regard to the question whether selenite compounds are more toxic than selenate compounds. This is mainly due to the low number of available effect concentrations for both selenium forms. Even when the data for SeO₂ (which forms H₂SeO₃ upon dissolution in water) are considered as selenite data, still no conclusion can be made. For marine fish however, data are available from two different studies in which a single fish species was exposed to either selenite or selenate. From these data it can be concluded that selenite is more toxic than selenate to the two fish species under consideration.