Chemical Contaminants in Drinking Water: Where Do We Go from Here?

Where Do We Go from Here? Given the number of chemicals in the environment and people's variability in exposure and susceptibility to harm, it's a daunting challenge to catalog all possible drinking water contaminants and assess their associated health risks. But after reviewing the state of the science and the data gaps surrounding drinking water contaminants , a team of authors presents in this issue of EHP an ambitious roadmap to help future studies identify and elucidate risks presented by specific contaminants. Although microbial agents are the largest cause of waterborne diseases worldwide, 1 chemical contaminants in drinking water have been associated with a broad array of adverse health effects, including cancer, cardiovascular disease, neurological disease, and miscarriage. 2 Some contaminants enter water through leaching, accidental spills, runoff, and atmospheric deposition. Others, such as disinfec-tion by-products and lead, are introduced during treatment or even at the tap. 3 Contaminants may occur naturally, or they may derive from human-related activities, such as industry, agriculture, and mining. Not only have the prevalence and uses of chemicals escalated in the last century, but the analytical techniques to detect them have become exquisitely sensitive. Consequently, it is possible to define vanishingly small levels of both well-studied and emerging contaminants in drinking water. The presence of a contaminant does not necessarily translate to an adverse impact on human health; the levels may be unimportant , exposure is not a given, and toxicity may depend on individual susceptibility. Assessing the human health effect of any given chemical requires careful epidemiological and toxicological study, which has not been conducted for most drinking water contaminants. 1 " The amount that we know about chemicals is really very little, " says Herman Gibb, president of research consultancy Tetra Tech Sciences, who was not involved with the review. " We keep hammering on the same chemicals like arsenic, cadmium, and so forth, but there are so many chemicals that we don't know much about. And even for the chemicals for which we have relatively good information , we still don't know enough. " To address the knowledge gaps, the Centre for Research in Environmental Epidemiology (CREAL) in Barcelona organized a workshop in 2012 to discuss the state of the science vis-à-vis chemical contaminants in drinking water and make recommendations for future research. " Having the workshop and writing [this review] has led to some ideas for future collaborations, " says …