The volume of freshwater on the Earth is theoretically enough to serve the needs of human population, but the distribution of water resources worldwide aren’t equal, and practical approaches to water quality management are highly diverse. How can the safety of water throughout the world be best ensured? Additionally, how safe should drinking water be?
Enter the WHO
In 2000, an estimated 2,213,000 people died from exposures to poor sanitation and contaminated water. The majority of those sickened and killed by water-related diseases were children less than 5 years of age. Most disconcerting is the fact these afflictions are preventable, given the availability of appropriate resources. Currently, 1.1 billion people--primarily in the developing world--lack access to an improved water supply. Point-of-use (POU) disinfection and basic education on hygiene, hand washing and sanitation appear to be the most affordable and effective control measures in developing nations. For some, the provision of safe water isn’t just a health benefit to consumers but a key to achieving critical economic gains. The reduction of medical costs and improvement in economic well-being of a population greatly exceed the potential costs of the initial investment in water treatment.
One goal of the World Health Organization (WHO) is to promote the availability of safe water supplies to all people regardless of their social, economical or geographical challenges. The organization states that safe water is a right for all people. To meet this end, the WHO has compiled guidelines to assist governments in the development of policies and programs aimed at the provision of safe drinking water.
A long history
First published in 1958, the WHO “International Standards for Drinking Water” has been continuously modified as new research findings and risk assessment information becomes available regarding a variety of chemical and microbial water contaminants. Revisions were released in 1963 and 1971. In 1984, the name was changed to the “Guidelines for Drinking Water Quality” to reflect an advisory rather than regulatory intention. Within four years after the 1984-1985 three-volume edition was published, a new version was in the works that contained more up-to-date information on the health risks of chemical contaminants and a major emphasis on microbial water quality. These three volumes emerged during 1992-1997, and involved the participation of over 200 experts from 40 different developing and developed countries who attended a total of 18 planning and review meetings.
Based predominately on the 1984 format, the three-volume edition is divided as follows:
• Volume 1, Recommendations--provides essential information on guideline values for various drinking water contaminants and the criterion used to evaluate the various microbiological, chemical and radiological contaminants considered.
• Volume 2, Health Criteria and Other Supporting Information--focuses on health criteria for specific contaminants, listing guideline values and going into greater depth on the health risks of the contaminants listed in volume 1.
• Volume 3, Surveillance and Control of Community Water Supplies--deals greatly with small communities such as those in rural areas of developing countries and how to control contaminants and minimize potential risks.
The third, and most recent, edition of the “Guidelines for Drinking Water Quality” was prepared over a period of six years and remained open for public comment and review until February 2003. This edition represents a major revision over previous guidelines, promoting a trend toward preventive management and a more holistic approach toward the supply of safe water. This proactive approach utilizes risk assessment and risk management principles aimed at source water protection. The latest edition further suggests scaling back current end-use monitoring approaches and implementing online monitoring for key pollution indicators, i.e., turbidity and pH.
In the current guidelines, additional emphasis is placed on waterborne microbial risks compared to risks of chemical exposures in water because waterborne chemical exposures are less likely to be the cause of acute health effects. In addition, many chemical contaminants are detectable by the consumer because of an unacceptable taste, odor or appearance whereas the presence of harmful or even deadly microbial agents can easily go unnoticed.
A universal standard?
The guidelines recognize that different regions and suppliers, i.e., a large utility vs. a small community or individual supply, have dramatically different needs and resources available. While control of microbial contaminants continues to be a major concern across the board, certain chemical contaminants are added while others are ranked lower on the priority list. Particular concerns with a given contaminant are often site specific. Therefore, the guidelines don’t promote the implementation of an international, or universal, standard for drinking water but rather endorse a risk management principle applicable to a variety of water sources.
Risk management involves the assessment of the entire water supply and potential treatment needs or failures associated with that supply. A risk management plan also includes action strategies for dealing with expected and unexpected water contamination events.
Some water sources are more difficult to protect. Additionally, even the highest quality of water is subject to contamination when passing through the channels of distribution. Thus, the concept of a multiple barrier principle in addition to source protection is further developed in the third edition of the guidelines.
Contamination of water supplies often occurs as a peak event, episodic fluctuations in treatment efficacy and source water quality. These events result in substantial outbreaks as well as endemic (increased baseline) levels of disease but aren’t likely identified during routine sample collection and direct pathogen monitoring. If detected, the peak event would likely be over by the time a responsive action was implemented. Therefore, the WHO guidelines recommend a comprehensive water plan intended to identify potential treatment failures or vulnerabilities to the system. The plan is proactive and includes inline monitoring targets, rather than direct end-use monitoring that’s more time consuming and may not provide information of contamination event until long after it has occurred.
While a case is easily made for the need to implement preventive management approaches to assure safe water, it may be difficult to identify sources of water contamination. Source water protection is the first barrier in drinking water treatment and an integral aspect of preventive management of water quality, but it’s only one step in a multi-barrier approach. Generally, the more barriers in place, the less your risk of exposure. The WHO guidelines recognize that POU devices at the consumer’s tap provide a final barrier for drinking water treatment and can increase consumer confidence in the safety of their water, especially given the likelihood of contamination in the distribution system. For some, POU treatment systems provide the only barrier of protection, i.e., populations served by private wells or rainwater collection devices.
The WHO “Guidelines for Drinking Water Quality” are aimed primarily at health regulators and policy makers as a tool to develop national standards for water quality. A variety of other stakeholders, key to the assurance of safe drinking water supplies, will also find the guidelines to be a valuable reference. As new information arises, the guidelines continually evolve through a process of rolling revision. Addenda are routinely published and made available as supplemental information to the current guidelines edition, keeping up to date with the ever-changing database. With all of these complex issues and uncertain variables that water quality regulators face, it remains prudent for the individual to examine all options of water treatment including the use of POU devices that enable one to accept responsibility for the quality of water they consume.
1. Guidelines for Drinking Water Quality, Third edition, World Health Organization, Geneva, Switzerland, 2003: www.who.int/water_sanitation_health/GDWQ/Updating/3rdedition.htm
2. WHO, “Assessing Microbial Safety of Drinking Water: Improving Approaches and Methods,” March 2003.
About the author
Dr. Kelly A. Reynolds is a research scientist at the University of Arizona with a focus on development of rapid methods for detecting human pathogenic viruses in drinking water. She holds a master of science degree in public health (MSPH) from the University of South Florida and doctorate in microbiology from the University of Arizona. Reynolds has also been a member of the WC&P Technical Review Committee since 1997.