Global variations in pesticide regulations and health risk assessment of maximum concentration levels in drinking water.

Pesticides are used worldwide in agricultural, residential garden, and commercial applications. The control of pesticide exposure is a worldwide problem since pesticide can enter human body via ingestion, inhalation, and dermal contact. For drinking water, many regulatory jurisdictions respond by specifying the maximum concentration level (MCL) of a pesticide that may occur. At least 145 regulatory jurisdictions in 103 nations have specified at least 5474 pesticide MCLs in drinking water. Unfortunately, regulatory agencies often disagree on the magnitude of MCLs. For individual pesticides, MCLs often vary five, six, or even seven orders of magnitude. An analysis of the drinking water MCL distributions of the 25 most commonly regulated pesticides (N > 100 MCLs each) is presented in this study. Health risk uncertainty models are applied to compute uncertainty bounds around realistic MCL values for each pesticide and to help examine whether these MCLs can protect human health or not. Results indicated that at least 162 MCLs for 23 of the 25 pesticides considered were found to exceed upper human health risk uncertainty bounds indicating that these MCLs may not be adequate to protect human health. Also, health risk characterization factors were computed based on the estimation of maximum legal exposures to quantify human health damage caused by drinking water pesticide MCLs, and results indicated that some pesticide MCLs could cause over 19,000 Disability-Adjusted Life Years (DALYs) per million population. These MCLs distributions are highly influenced by several value clusters dominated by U.S., World Health Organization, and European Union (EU) indicating that consensus MCLs may be emerging for these most commonly regulated pesticides.