Dioxins are a group of 210 chemicals with similar properties and structures that are usually found as a "mixture" in the environment. Dioxins are found at low levels in air, soil, water, and sediment as well in foods such meat, dairy, fish, and shellfish. The highest levels are usually found in sediments soil and animal fats. The most toxic chemical in the group is 2,3,7,8-tetrachlorodibenzo-para-dioxin, which is the "standard" to which other dioxins are compared. This paper examines the Michigan Department of Environmental Quality (MDEQ) assessment and remediation efforts in the Tittabawassee River (Michigan, USA) flood plain. Soil and sediment samples indicate higher than "normal" (background) levels of dioxins for soil and sediment, which exceed the Center for Disease Control (CDC) and U.S. Agency for Toxic Substances and Diseases Registry (ATSDR) action level of 1000 parts per trillion. Data presented indicates the difficulties associated with assessing historical dioxin levels in environments such as soil and sediments. Activities associated with these efforts such as dioxin and furan exposure studies, animal toxicology assessments, U.S. Environmental Protection Agency (EPA) enforcement, MDEQ efforts to expedite remediation, as well as future directions for this on-going project are discussed.

Although the U.S. Environmental Protection Agency presented a comprehensive review of the scientific literature in its 2003 draft reassessment of the risks of dioxin, the agency did not sufficiently quantify the uncertainties and variabilities associated with the risks, nor did it adequately justify the assumptions used to estimate them, according to this new report from the National Academies' National Research Council. The committee that wrote the report recommended that EPA re-estimate the risks using several different assumptions and better communicate the uncertainties in those estimates. The agency also should explain more clearly how it selects both the data upon which the reassessment is based and the methods used to analyze them.