Safe drinking water: the toxicologist's approach

The production of adequate and safe drinking water is a high priority issue for safeguarding the health and well-being of humans all over the world. T raditionally, microbiological quality of drinking water has been the main c oncern, but over the last decades the attention of the general public and h ealth officials on the importance of chemical quality and the threat of che mical pollutants have increased with the increase of our knowledge on the h azards of chemical substances. There are many sources of contamination of d rinking water. Broadly they can be divided into two categories: contaminant s originating from surface and groundwater, and contaminants used or formed during the treatment and distribution of drinking water. Contaminants in s urface and groundwater can range from natural substances such as arsenic an d manganese leaching from soil, to contaminants introduced by human activit ies, such as run-off from agricultural activities, controlled discharge fro m sewage treatment works and industrial plants, and uncontrolled discharges or leakage from landfill sites and from chemical accidents. Disinfectants and disinfectant by-products are well known contaminants resulting from the processes used by the drinking water industry for the treatment and distri bution of water. The basic question in the production of drinking water is how to rid drinking water of potentially dangerous microorganisms and chemi cals without introducing new hazards that might pose new and different thre ats to human health. It is the responsibility of toxicologists to provide r isk assessments for chemical pollutants and to derive guidelines or standar ds for drinking water quality below which no significant health risk is enc ountered, to assure consumers that drinking water is safe and can be consum ed without any risk. This paper will focus on the toxicological procedures used by the World Health Organization to derive guideline values for chemic al compounds in drinking water, and will touch upon some critical differenc es in the nature of guidelines and legally binding standards. (C) 2000 Else vier Science Ltd. All rights reserved.