Recalibration of the earthworm tier 1 risk assessment of plant protection products

ABSTRACT In the first step of earthworm risk assessment for plant protection products (PPPs), the risk is assessed by comparing the no‐observed effect levels (NOELs) from laboratory reproduction tests with the predicted exposure of the PPP in soil, while applying a trigger value (assessment factor [AF]) to cover uncertainties. If this step indicates a potential risk, field studies are conducted. However, the predicted environmental concentration in soil, which can be calculated, for example, for different soil layers (ranging from 0–1 cm to 0–20 cm), and the AF determine the conservatism that is applied in this first step. In this review paper, the tier 1 earthworm risk assessment for PPPs is calibrated by comparing the NOEL in earthworm reproduction tests with effect levels on earthworm populations under realistic field conditions. A data set of 54 pairs of studies conducted in the laboratory and in the field with the same PPP was compiled, allowing a direct comparison of relevant endpoints. The results indicate that a tier 1 AF of 5 combined with a regulatory relevant soil layer of 0 to 5 cm provides a conservative tier 1 risk assessment. A risk was identified by the tier 1 risk assessment in the majority of the cases at application rates that were of low risk for natural earthworm populations under field conditions. Increasing the conservatism in the tier 1 risk assessment by reducing the depth of the regulatory relevant soil layer or by increasing the tier 1 AF would increase the number of false positives and trigger a large number of additional field studies. This increased conservatism, however, would not increase the margin of safety for earthworm populations. The analysis revealed that the risk assessment is conservative if an AF of 5 and a regulatory relevant soil layer of 0 to 5 cm is used. Integr Environ Assess Manag 2016;12:643–650. © 2015 SETAC Key Points Earthworms are keystone species in soils and this is reflected in a risk assessment scheme for plant protection products (PPPs), which is at the EU‐Level. Calibration is possible by comparing conservative lab endpoints to reference tier (field effect studies). A comprehensive, representative dataset of 54 PPPs (i.e., earthworm studies relevant for the registration process, performed both in the laboratory and in the field under good laboratory practice) was used to calibrate the current risk assessment scheme. In the current paper, a realistically conservative trigger and a regulatory relevan