In 1986, it rained for three weeks straight in Midland, Mich., headquarters of Dow Chemical Corp. A wastewater containment facility at a Dow plant on the banks of the Tittabawassee River overflowed, and waste from the plant was carried downstream into the Saginaw flood plain. In 1995, Michigan began finding elevated levels of dioxins — chemicals that have been linked to cancer, birth defects, and disruption of hormone and immune systems — in area fields, playgrounds, and residential neighborhoods. In some cases, the levels were as high as 7,200 parts per trillion; the residential cleanup standard in Michigan is 90 ppt. Dow denies that the plant, which at various times has produced mustard gas, Agent Orange, napalm, and pesticides, is the source of the dioxins. Even more alarming, the state Department of Environmental Quality dragged its feet in releasing information about the testing, and only did so after a whistleblower provided information on contamination sites and levels to Michigan environmental groups.