Chemical Safety Of Drinking Water

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 is the third edition of the WHO's guidelines which are used by countries worldwide to set standards for the regulation of drinking water quality and effective approaches to water safety management. This revised edition has been updated to take account of recent developments in risk assessment and management. Topics discussed include: a framework for drinking water safety and discussion of the roles and responsibilities of different stakeholders, such as national regulators, water suppliers and independent surveillance agencies; guidance on microbial safety of drinking water through safety plans; new scientific information on chemicals, waterborne pathogens and individual chemical hazards of actual or potential concern. It also considers the application of the guidelines in specific circumstances, such as in emergencies and disasters, and to specific applications, such as bottled water. It also contains information on over 130 documents which substantiate or explain the content of the Guidelines, and on good practice guidance in achieving drinking-water safety.

A review of the nation’s new coverages serves as a ready reminder that drinking water safety is more than regional of local concern. In recent times, the print media alone has drawn attention to barium, bacteria, heavy metals, and increasingly organic contaminants, in public water supplies located in Florida, Rhode Island, Texas, Oregon, Illinois, Minnesota, North Carolina, Michigan, and California, to name a few. In an effort to address one of the major issues confronting the future of the nation’s drinking water supplies, chemical contamination, the Drinking Water Research Foundation and the American Chemical Society presented the symposium, "Safe Drinking Water: the Impact of Chemicals on a Limited Resource." To add balance to the total presentation, two papers were included that were not part of the symposium. Many questions as to the public significance of hundreds of organic chemicals known to be present in the national drinking water supply are waiting to be answered. In some areas of the country, aid rain-induced alterations of the natural leaching process represent an unexplored potential source of toxic pollutants. Finding workable ways to clean up the water supply will be an ongoing task. Addressing these questions, as well as investigating how other countries are responding to these problems, the alternate sources available, such as bottled water, and point of use devices, the presenters in this symposium have attempted to explain the problems, situation, and alternatives. As progress is made in one area, setbacks will occur in another. As we eliminate problems thought chemical technology, we often create others, such as contamination of our waters. While all the situations, problems, and alternatives are not discussed in these proceedings, it is hoped that some attention will be brought to the public, government, and private sectors so that future work will be done to assure the nation of safe drinking water resources.

This publication provides a structured approach to analyzing hazards to groundwater quality, assessing the risk they may cause for a specific supply, setting priorities in addressing these, and developing management strategies for their control. This book summarizes which pathogens and chemicals are relevant to human health, how they are transported, reduced, removed or retarded; provides practical guidance on characterizing the drinking-water catchment area and assessing potential health hazards; provides guidance on prioritising both hazards and management responses; presents key information on potential management actions and explains their integration into a comprehensive Water Safety Plan from catchment to consumer; and describes policy, land-use planning and implementation of pollution prevention, groundwater, with overviews of specific management approaches applicable to agriculture, sanitation, industry, mining, military sites, waste disposal and traffic.--Publisher's description.

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.