WHO drinking water quality guidelines for selected herbicides

Following the successful introduction of its Guidelines for Drinking-Water Quality in 1984, the WHO Regional Office for Europe was approached by the Government of Italy to develop, as a matter of urgency, recommendations for guidelines levels of certain herbicides found in drinking water supplies. Realizing the extent of the problem, the Regional Office for Europe organized two consultations to develop drinking water quality guidelines for the following 11 herbicides most commonly used in Italy: alachlor, metolachlor, pyridate, atrazine, molinate, simazine, bentazon, pendimethalin, trifluralin, MCPA and propanil. The presence of these and other herbicides in ground and surface water has been reported in several countries. Although the main purpose of these guidelines is to provide guidance to the Government of Italy in making risk management decisions, the information given was also intended to assist the other countries of the European Region in setting standards or in developing alternative control procedures where the implementation of standards is not feasible. The purpose of this paper is to review the process of health risk assessment used in the development of the WHO drinking water quality guidelines for selected herbicides. It will also reveal the major dilemmas and concerns expressed by the participating experts during the process of scientific deliberations, in the interests of understanding the complex issues involved in reaching the bare figures of the recommended guidelines.