Implementing atmospheric fate in regulatory risk assessment of pesticides:(How) can it be done?

Atmospheric fate of pesticides and their possible effects in ecosystems bey ond the immediate surrounding of the application site are not actively cons idered in currently used regulatory risk assessment schemes. Concern with r espect to atmospheric transport and subsequent deposition of pesticides in non-target areas is however growing. In this article the results of discuss ions on the possibilities of implementing atmospheric fate in regulatory ri sk assessment are presented. It is concluded that implementing atmospheric fate in regulatory risk assessment schemes is possible and that, from a sci entific point of view, these schemes should distinguish between pesticides on the basis of both their possibility/probability to reach non-target area s and on their toxicity. This implies that application of the precautionary principle or use of intrinsic pesticide properties alone is not considered justifiable. It is recommended that the risk assessment scheme should foll ow a tiered approach. The first tier should be entered only if the existing regulatory risk assessment procedure, including a local PEC:PNEC calculati on, has been passed and involves a test for the pesticide's total atmospher ic emission potential, i.e. its potential for becoming airborne during and after application. The second tier, which is only entered if the total emis sion potential is higher than a certain trigger value, should consist of a PEC:PNEC calculation for regional off-site areas (10-50 km) (tier 2A). If t he pesticide's atmospheric transport potential is expected to exceed a cert ain value, the PEC:PNEC ratio should also be calculated for more remote are as (> 1000 km) (tier 2B).