Maximum permissible and negligible concentrations for some organic substances and pesticides

The aim of the paper is to provide interested parties the methods that were used for generic hazard assessment in The Netherlands, and the resulting s o-called maximum permissible concentrations (MPCs) and the negligible conce ntrations (NCs) for approximately 150 organic substances and pesticides. Th e MPCs and NCs were derived for water, sediment, and soil. The concentratio n in the environment above which the risk of adverse effects was considered unacceptable to ecosystems is called the MPC. The MPCs take into account t hat the substances are distributed among the different environmental compar tments, and are harmonized accordingly. The MPCs served as a basis for the Dutch government to set generic environmental quality standards (EQS) in Th e Netherlands (IWINS, 1997). EQS in turn are used by the Dutch Government t o assess the environmental quality and for other environmental policy purpo ses. Concentrations in the environment below which the occurrence of advers e effects is considered to be negligible are called NCs. Hazards must be re duced when the environmental concentration of a substance exceeds its MPC. In-between this limits reduction of hazards is preferable. The MPC is a sci entifically derived hazard limit. The NC is simply defined as 1% of the MPC . In general, there is a great demand for ecotoxicological data that curren tly limits a more reliable estimate of many MPCs. For water, approximately half of the MPCs are derived on the basis of four or more NOECs (no observe d effect concentrations). For the other half, MPCs are based on only a few chronic or acute tests. For soil and sediment, however, almost no ecotoxico logical data are available, and MPCs for those compartments have, in many c ases, been derived from MPCs in water applying the equilibrium partitioning method (EqP-method), resulting in MPCs with greater uncertainty. Some of t he methods and underlying assumptions that have been used may need improvem ent. For example, the factor between MPC and NC, the statistical extrapolat ion method, the method that is used for secondary poisoning, the role of th e background concentrations of 'naturally' occurring substances, and the bi oavailability and the EqP-method. There is a great need for hazard limits, and the present compilation tries to provide those as well as identifying r esearch gaps. (C) 2000 Academic Press.