How Dioxins and Furans are Formed, Destroyed and Prevented
Dioxins and furans are unwanted by-products of incineration, uncontrolled burning and certain industrial processes. Industrial sources of dioxin to the environment include incinerators, metal smelters, cement kilns, the manufacture of chlorinated organics, and coal burning power plants. Dioxin is also produced by non-industrial sources (now considered by the U.S. Environmental Protection Agency (EPA) to be the greatest source in the U.S.), like residential wood burning, backyard burning of household trash, oil heating, and emissions from diesel vehicles. According to the U.S. EPA, cigarette smoke also contains a small amount of dioxin. Of the 210 dioxin and furan compounds, 17 are generally the focus of regulatory action. In addition, 12 of the polychlorinated biphenyls (PCBs) display a similar chemical structure and mechanism of toxicity. PCBs were manufactured commercially until 1977. However, Dow did not commercially manufacture PCBs.
Just as combustion provides a means for dioxin formation, so too does it allow for its destruction, through careful controls. A high combustion temperature, adequate combustion time, and turbulence to distribute heat all contribute to maximize dioxin destruction. Dioxin formation following combustion is prevented by quickly cooling combustion gases, and minimizing the presence of certain metals known to promote dioxin formation. Dow has worked to prevent dioxin formation in its processes by shutting down older, less efficient units; adding new equipment to existing units; and employing advanced controls. Dow has also implemented new technology to recycle wastes as useful raw materials, thereby minimizing the need for incineration.