"Despite growing health concerns about atrazine, an agricultural weedkiller sprayed on farm fields across the Midwest, most drinking water is tested for the chemical only four times a year -- so rarely that worrisome spikes of the chemical likely go undetected.
High levels of the herbicide can linger in tap water during the growing season, according to more frequent tests in some agricultural communities.
Spread heaviest on cornfields, atrazine is one of the most commonly detected contaminants in drinking water. Studies have found that exposure to small amounts of the chemical can turn male frogs into females and might be more harmful to humans than once thought.
Manufacturers say their own research proves the chemical is safe. But alarmed by other studies, the Obama administration is conducting a broad review that could lead to tighter restrictions. It is also mulling changes in laws that require water utilities to test for atrazine just once a quarter or, in some cases, once a year."