Setting Priorities For Drinking Water Contaminants

The provision of safe drinking water has been an important factor in the improvement of the health status of U.S. communities since the turn of the last century. Nonetheless, outbreaks of waterborne disease and incidences of chemical contamination of drinking water continue to occur. Setting Priorities for Drinking Water Contaminants recommends a new process for the U.S. Environmental Protection Agency to use in deciding which potential drinking water contaminants should be regulated in public water supplies to provide the greatest protection against waterborne illnesses. The book covers chemical and microbiological contaminants and includes a historical review of past approaches to setting priorities for drinking water contaminants and other environmental pollutants. It emphasizes the need for expert judgment in this process and for a conservative approach that considers public health protection as the first priority.

Americans drink many gallons of tap water every day, but many of them question the safety of tap water every day as well. In fact, devices have been created to filter tap water directly before reaching cups. It's true; however, that the provision and management of safe drinking water throughout the United States have seen triumphs in public health since the beginning of the 20th century. Although, advances in water treatment, source water protection efforts, and the presence of local, state, and federal regulatory protection have developed over the years, water in the United States still contain chemical, microbiological, and other types of contaminants at detectable and at times harmful levels. This in addition to the growth of microbial pathogens that can resist traditional water treatment practices have led to the question: Where and how should the U.S. government focus its attention and limited resources to ensure safe drinking water supplies for the future? To deal with these issues the Safe Drinking Water Act (SDWA) Amendments of 1996 Safe included a request that the U.S. Environmental Protection Agency (EPA) publish a list of unregulated chemical and microbial contaminants and contaminant groups every five years that are or could pose risks in the drinking water of public water systems. The first list, called the Drinking Water Contaminant Candidate List (CCL), was published in March 1998. The main function of the CCL is to provide the basis for deciding whether to regulate at least five new contaminants from the CCL every five years. However, since additional research and monitoring need to be conducted for most of the contaminants on the 1998 CCL, the list is also used to prioritize these related activities. Classifying Drinking Water Contaminants for Regulatory Consideration is the third report by the Committee on Dinking Water Contaminants with the purpose of providing advice regarding the setting of priorities among drinking water contaminants in order to identify those contaminants that pose the greatest threats to public health. The committee is comprised of 14 volunteer experts in water treatment engineering, toxicology, public health, epidemiology, water and analytical chemistry, risk assessment, risk communication, public water system operations, and microbiology and is jointly overseen by the National Research Council's (NRC'S) Water Science and Technology Board and Board on Environmental Studies and Toxicology. In this report the committee needed to readdress its second report as well as explore the feasibility of developing and using mechanisms for identifying emerging microbial pathogens for research and regulatory activities. The promotion of public health remains the guiding principle of the committee's recommendations and conclusions in this report.

Contamination of drinking-water is a significant concern for public health throughout the world. Microbial hazards make the largest contribution to waterborne disease in developed and developing countries. Nevertheless, chemicals in water supplies can cause serious health problems--whether the chemicals are naturally occurring or derive from sources of pollution. At a global scale, fluoride and arsenic are the most significant chemicals, each affecting perhaps millions of people. However, many other chemicals can be important contaminants of drinking-water under specific local conditions. Often, identification and assessment of risks to health from drinking-water relies excessively on analysis of water samples. The limitations of this approach are well recognized, and contributed to the delay in recognizing arsenic in drinking-water as a significant health concern in Bangladesh and elsewhere. To overcome such limitations, the latest edition of the World Health Organization (WHO) Guidelines for Drinking-water Quality (WHO, 2004; WHO,2006) emphasizes effective preventive management through a 'framework for drinking-water safety' that incorporates 'water safety plans.' Effective preventive management of chemicals in drinking-water requires simple tools for distinguishing the few chemicals of potential local or national concern from the unmanageably long list of chemicals of possible significance. The aim is to identify and prioritize the chemicals of concern, to overcome the limitations of direct analysis of water quality, and ensure that limited resources are allocated towards the monitoring, assessment and control of the chemicals that pose the greatest health risks. Identifying and prioritizing chemical risks presents a challenge, especially in developing countries, because information on the presence of chemicals in water supplies is often lacking. This document provides guidance to help readers to meet that challenge. It shows how information on aspects such as geology and industrial and agricultural development, which is often readily available, can be used to identify potential chemical contaminants (and potential sources of chemicals), from catchment to consumer, and thus prioritize risks. As a supporting document to the Guidelines for Drinking-water Quality (WHO, 2004; WHO, 2006), this publication is aimed at policy-makers, regulators, managers and public health practitioners at national and local level. It is divided into three parts: Part A provides general guidance on using limited information in prioritizing chemicals in drinking-water for risk management. The need for such guidance is outlined in Chapter 1,which also describes the administrative and policy context. Chapter 2 describes the principles applied in prioritizing chemicals, provides information on some factors that affect chemical concentrations along pathways, and highlights several specific chemicals that are frequently considered priorities because of their widespread occurrence or significant health effects. Chapter 3 discusses the role of drinking-water standards and guidelines, and provides an overview of contemporary water quality management procedures. Part B provides practical guidance on identifying specific chemicals that are likely to be of concern in individual water supply systems. It groups chemical contaminants into five categories on the basis of their potential sources: naturally occurring, from agriculture activities, from human settlements, from industrial activities, and from water treatment and distribution processes themselves. Part C comprises the appendices. It includes guidance on the most likely sources of potential contaminants and on identifying chemicals that could be of concern in particular circumstances. The appendices address potential sources of chemicals considered in the WHO drinking-water guidelines (WHO, 2004; WHO, 2006), chemicals potentially discharged in effluents from industrial sources, and the association of pesticides with crops and crop types. This information is presented in an accessible format that will help users to determine the chemical hazards that can arise in the catchment, in treatment and in distribution, in large, medium and small water supplies. Many experts worldwide contributed to this work over a period of several years, beginning with the 1st Meeting of Experts on Monitoring Chemicals in Drinking Water, held in Bangkok, Thailand, in January 2001. This was followed by the 2nd Meeting of Experts on Monitoring Chemicals in Drinking Water, also held in Bangkok, in December 2001. Both meetings were sponsored by WHO and hosted by the Department of Health, Ministry of Public Health, Thailand. The draft guidance document was subsequently tested in a series of field trials in 2002-2003 in Indonesia, Fiji, Nepal, Mongolia, the Philippines and Thailand. Lessons learnt through the field trials provided feedback that was valuable in revising and finalizing the document. Readers should note that while this publication has been developed as a supporting document for, and with reference to, the Guidelines for Drinking-water Quality, the guidelines themselves are frequently updated and the latest information should always be sought by reference to relevant World Health Organization publications and web site. (http://www.who.int/water_sanitation_health/dwq/guidelines/en/index.html).

This volume describes the methods used in the surveillance of drinking water quality in the light of the special problems of small-community supplies, particularly in developing countries, and outlines the strategies necessary to ensure that surveillance is effective.