Another piece of the puzzle’s in place as investigators work to find how wells near several Iowa towns got contaminated. The EPA’s Martin Kessler says the federal agency was testing sites where farmers stored grain, and treated it for pests. EPA Region 7 did a study of USDA grain bin sites used in 2000 and 2001, and chemicals that were used as grain fumigants. One common fumigant is a toxic chemical called perchlorate which is measured in parts per Billion for its potential hazard to human health. Perchlorate was found in a few private wells, within a 1-mile radius of former USDA grain storage bins. One EPA Region 7 is conducting an investigation in HIlls, one of the locations where perchlorate was found, and more sampling will be conducted in Napier and Ewart. The next round of inspections begin in December. Since the areas are largely rural, it’s not clear whether the chemical will pose a threat to human health.