Moorland grouse - Flubendazole use for parasitic worm control: preliminary environmental assessment

5. Preliminary Risk Assessment

As Predicted No Effect Concentrations (PNECs) have not been derived (see section 4 and appendix B) for soil and water compartments, this section presents the predicted environmental concentrations alongside thresholds of toxic effect to give some context to the sections above. In order to develop risk quotients (ie PEC/PNEC) for the compartments to conclude on levels of risk, as well as more certain PECs additional ecotoxicity data would be needed to derive PNECs.

5.1. Surface waters

Comparing the PECs derived in section 3.3 with levels of effect in aquatic organisms may underestimate the level of risk for the water compartment because two potentially significant exposure routes are not included in the PEC calculation. Based on the release of the substance in its dissolved form to a watercourse alone the measured no observed effect threshold in the water flea is about 5000 times higher than the water concentration. For sediment, with the same caveats as for the watercolumn plus uncertainty in the effects threshold, the estimated no observed effect threshold is about 2000 times higher than the sediment concentration.

5.2. Soil

The estimated threshold for effects in soil dwelling organisms that is derived from aquatic data (see section 4.2) is around 500 times higher than the PEC_soil (see section 3.2 and appendix C). Whilst there is uncertainty in the values, the PEC_soil is based on birds excreting all of the flubendazole they consume unmetabolised and accounts for year on year use and release. So this comparison can be considered to represent a reasonable worst case.