The U.S Environmental Protection Agency (EPA) on March 31 announced that it will not regulate the chemical called perchlorate in drinking water. Perchlorate is widely used in rocket fuel and munitions, fertilizers, and is also a component of fireworks and airbag initiators for vehicles, among other things. While it can occur naturally, high concentrations have been found in at least 26 states, typically near military bases and defense contractors in the U.S. West, particularly around Las Vegas and in Southern California. Human exposure to high levels of the chemical has been linked to a deficiency of iodide in the thyroid...