Pesticides, including herbicides, insecticides, fungicides, fumigants and rodenticides, provide important benefits in public health, food production and aesthetics (http://www.epa.gov/agriculture/ag101/pestbenefits.html). Unlike most other important chemicals, pesticides are designed to impact living systems (http://www.cdc.gov/niosh/docs/81-123/). Consequently there has long been a concern about environmental and human consequences of widespread pesticide use. Carson1 effectively voiced this concern and documented some problems in her 1962 book, Silent Spring. Global pesticide use increased dramatically between the 1960s and 1990s, and more slowly thereafter, but large increases continue to occur in many developing countries.2 The estimated worldwide use in 2007 was 5211 million pounds of active ingredients, with herbicides accounting for the major use in agriculture, and about 40% of the use overall.3 To place this figure in context, it is close to one pound for each of the 6.6 billion people then inhabiting the globe, albeit with unequal distribution.

Human occupational exposure is expected during pesticide production and application, but the general population can also be exposed through drift, contamination of water and food supplies, and biological concentration through the food chain.4 In addition, pesticide use for vector control and elimination of nuisance pests is an important exposure source for a considerable portion of the world population, and is an especially important source of exposure indoors.5 These varied pathways have resulted in such ubiquitous exposure that persistent pesticides or their metabolites can be found at low levels in biological tissues of much of the world's population. This includes many who may be …