Preparation of the Guidelines:

At the time the Guidelines were published in 1984, it was recognized that, as new information became available on the potential health risks of contaminants in drinking water, the basis of the recommended GVs would require review and possible revision. New or changed guideline values would therefore have to be recommended.

In 1988, the decision was made within WHO to initiate revision of the Guidelines. Responsibility for carrying out this revision was shared by WHO headquarters and the Regional Office for Europe. Within WHO headquarters, both the Urban Environmental Health Unit and the International Programme on Chemical Safety (IPCS) participated; IPCS provided a major input to the health risk assessment of chemicals in drinking water. From the onset, it was agreed that the general philosophy of the 1984 Guidelines remained valid and should therefore not be changed.

Monograph format for chemical substances: (Table 1)

1.   General description

   • Identity
   • Physical and chemical properties
   • Organoleptic properties
   • Major uses
   • Environmental fate

2. Analytical methods
3. Environmental levels and human exposure

   • Air
   • Water
   • Food
   • Estimated total exposure, relative contribution of drinking water

4. Kinetics and metabolism in laboratory animals and humans
5. Effects on laboratory animals and in vitro test systems
6. Effects on humans
7. Guideline value

Note: Each monograph in Volume 2, Health Criteria and Other Supporting. Information, follows the general format presented and includes a list of scientific. All monographs may not, however, use each heading.

A series of planning and coordination meetings took place lo establish the scientific approach and mechanism for preparing evaluation documents for each constituent. This was followed by a series of review group meetings dealing with specific subject areas. Nineteen meetings were held over a period of four years; they involved participation of numerous institutions and over 200 experts from some 40 different countries.

Preparation of the Guidelines required intensive human and financial resources. They could not have been developed without the scientific and/or financial support of the following organizations and countries: the Danish International Development Agency (DANIDA), the Norwegian Agency for Development Cooperation (NORAD), the Swedish International Development Authority (SIDA), the United Kingdom Overseas Development Administration (ODA), Belgium, Canada, Denmark, Finland, France, Germany, Italy, Japan, the Netherlands, Norway, Poland, Sweden, the United Kingdom, and the United States.

For each selected chemical, a country was assigned to prepare a draft evaluation document examining its occurrence in drinking water, exposure from food and air, and effects on laboratory animals and humans. Based on evaluation of these data, a GV was al so proposed. The outline of an evaluation document is given in Table 1.

The draft evaluation document was then circulated for review by each of six coordinators to the "support countries" and selected experts. The coordinator prepared overviews of scientific issues lo be resolved and worked with the assigned countries to incorporate the comments received. This document was then submitted for evaluation to a review group meeting, which evaluated the health risk assessment data and recommended a GV. The role of the six coordinators was crucial in the revision process. All of the draft evaluation documents for disinfectants and DBPs were prepared by the U.S. Environmental Protection Agency (EPA); Bruce Mintz of ÉPA was the coordinator.

Previous evaluations carried out by national and internacional bodies such as the WHO/Intemational Labour Organisation/United Nations Environment Programme International Programme on Chemical Safety; the International Agency for Research on Cancer (IARC); the Joint Food and agriculture Organization of the United Nations (FAO)/WHO Meeting on Pesticide Residues (JMPR); and the Joint FAO/WHO Expert Committee on Food Additives (JECFA), which evaluates food contaminants as well as additives, provided a major input to the health risk assessment carried out in the Guidelines.