Chronic aquatic effect assessment for the fungicide azoxystrobin.

The present study examined the ecological effects of a range of chronic exposure concentrations of the fungicide azoxystrobin in freshwater experimental systems (1270-L outdoor microcosms). Intended and environmentally relevant test concentrations of azoxystrobin were 0 µg active ingredient (a.i.)/L, 0.33 µg a.i./L, 1 µg a.i./L, 3.3 µg a.i./L, 10 µg a.i./L, and 33 µg a.i./L, kept at constant values. Responses of freshwater populations and community parameters were studied. During the 42-d experimental period, the time-weighted average concentrations of azoxystrobin ranged from 93.5% to 99.3% of intended values. Zooplankton, especially copepods and the Daphnia longispina group, were the most sensitive groups. At the population level, a consistent no-observed-effect concentration (NOEC) of 1 µg a.i./L was calculated for Copepoda. The NOEC at the zooplankton community level was 10 µg azoxystrobin/L. The principle of the European Union pesticide directive is that lower-tier regulatory acceptable concentrations (RACs) are protective of higher-tier RACs. This was tested for chronic risks from azoxystrobin. With the exception of the microcosm community chronic RAC (highest tier), all other chronic RAC values were similar to each other (0.5-1 µg a.i./L). The new and stricter first-tier species requirements of the European Union pesticide regulation (1107/2009/EC) are not protective for the most sensitive populations in the microcosm study, when based on the higher tier population RAC. In comparison, the Water Framework Directive generates environmental quality standards that are 5 to 10 times lower than the derived chronic RACs.