农药

Hundreds of different pesticides are used throughout the United States, and in vast quantities – in 2007 alone, over 430,000 tons of pesticides, herbicides, insecticides, and fungicides were used by homes and businesses. Each year, about 2 million tons of pesticides are used globally to confront weeds, insects, and other pests. Pesticides are accepted for use in protecting crops against harmful pests and in protecting people against disease-carrying insects and other animals. Although useful for curtailing the presence and spread of harmful or unwanted animal or plant life, pesticides can spread throughout the environment and contaminate both surface and groundwater, which means that their widespread usage may cause the presence of pesticides in drinking water.

Modern, synthetic pesticides have been in use for almost 100 years, with earlier versions relying on the use of toxic heavy metals such as copper, lead, mercury, and arsenic. This progressed to the use of dichlorodiphenyl trichloroethane (DDT), discovered during World War II and gaining enormous popularity due to it effectiveness at low dosages. This lasted until the 1970s, when DDT was banned due to its damage to the environment and its toxicity to humans and impact as a carcinogen. A wide variety of synthetic pesticides have been developed since then – and many by necessity, as pests eventually develop resistances to pesticides, and many pesticides pass out of usage due to harmful side effects or environmental damage.

尽管农药提供了切实的好处 - 尤其是在农业领域的使用导致粮食生产的质量和数量增加，但几乎所有农药都存在危险，因为许多农药都可以在土壤中积累并进入供水。大多数进入供水的农药都是从农田或通过工业废水的径流来做到的。溪流，湖泊和地下水特别容易受到农药污染，因为它们与周围土壤的紧密相互联系。

当生物摄入农药时，即使是水中的农药浓度低，也可以通过食物链，然后又被其他生物体食用，并可能最终被人类食用。尽管特定农药在特定农药之间导致的人类毒性各不相同，但所有农药都旨在造成人身伤害。尽管EPA调节并监视许多潜在的饮用水污染物，但水中的许多农药并不受调节污染物。