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Preliminary risk characterisation for the pyrethroid insecticide lambda-cyhalothrin identifies potential concerns for fish and aquatic invertebrates. Here we describe additional ecotoxicological studies for lambda-cyhalothrin generated to refine the aquatic risk assessment. These include tests conducted under more realistic exposure conditions (i.e. accounting for the rapid adsorption of lambda-cyhalothrin to sediments), studies on sediment toxicity and bioavailability, tests on a range of fish and invertebrate species in order to characterise sensitivity distributions, and field studies which have examined effects on invertebrate communities and fish populations under semi-natural conditions. Fish are generally less sensitive to lambda-cyhalothrin than are aquatic invertebrates, and fish species tend to be similar to each other in their sensitivities. Adsorption of lambda-cyhalothrin reduces exposure and hence the apparent toxicity of the compound to fish, and under field conditions no adverse effects on fish have been observed even at concentrations approaching the water solubility. For aquatic invertebrates, there is a wider range of sensitivities, with the Crustacea and Insecta predictably being the more sensitive taxa. Again, adsorption reduces the exposure of the chemical, and under field conditions no ecologically adverse effects have been observed at concentrations of c.0·02 μg litre−1. © 1998 Society of Chemical Industry
Maund et al. (Tue,) studied this question.