Client: University of Michigan, Ann Arbor
Elevated levels of dioxins have been found in the soil of the Tittabawassee River flood plain and nearby areas. Beginning in the fall of 2004, the University of Michigan was conducting a two-year study to find out whether the elevated levels of dioxins in the soil in the city of Midland, and in the Tittabawassee River flood plain between Midland and Saginaw, have also caused elevated levels of dioxins in residents' bodies.
The study area is the vicinity of the Dow Chemical Company facility in Midland, Michigan. Since the 1940s, areas North-East of the Dow facility have been exposed to the deposition of dioxins resulting from incinerator outfall. Two types of incinerator facilities were used to dispose of solid wastes contaminated with halogenated compounds, including dioxins. During high temperature incineration, so-called de novo chemical synthesis processes take place resulting in the formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) as by-products which are then dispersed from the smoke stack. Whereas prior to 1970 incineration was fairly inefficient resulting in the formation, dispersion and deposition of higher concentrations of these by-products, modernization of the facilities since 2000 to a high efficiency (99.9999% destruction of dioxins) incinerator resulted in significant source reduction of emissions. With a prevailing N.E. wind direction, the emission plume impacted the downwind communities. It is assumed that the measured elevated soil dioxin concentrations, ranging from 1-500 ppt (ng/g soil), are largely the result from emission plume deposition prior to the 1980s.
The objectives of this project were to: