EPA Steps Up PRGs for Dioxin in Soil

The U.S. Environmental Protection Agency is seeking public comment on draft interim preliminary remediation goals (PRGs) for cleanup of dioxins in soil.

The announcement, which was made Dec. 31, fulfills a commitment by EPA Administrator Lisa P. Jackson to propose interim cleanup goals by the end of 2009.

"While EPA works to complete the dioxin reassessment, this interim guidance will help us make better informed decisions on cleanup alternatives at contaminated sites," said Mathy Stanislaus, assistant administrator for EPA’s Office of Solid Waste and Emergency Response. “We are following through on our commitment to use the best available science to help protect human health and the environment.”

Dioxins may cause a large number of different health effects, like cancer and reproductive effects. Dioxins are of concern because they are the result of combustion and are absorbed from the air into the food chain where they can stay for many years.

Currently, EPA’s recommended dioxin PRGs are 1,000 part per trillion (ppt) for dioxin in residential soil and a level within the range of 5,000-20,000 ppt in commercial/industrial soil. The new draft interim PRGs are 72 ppt for residential land uses and 950 ppt for commercial/industrial land uses, thus lowering the amount of dioxins levels for these land uses.

The draft interim PRGs also include consideration of the potential absorption of dioxin through skin exposure. This will provide a tool for site evaluation that was not available when EPA last recommended PRGs for dioxins in soil in 1998.

In 1991, in light of significant new data on the potential human health effects of dioxins, EPA began the development of a comprehensive evaluation of exposure and human health effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most toxic of the group of chemicals known as dioxins, and other dioxin-like compounds. This draft dioxins assessment has been through several independent external peer reviews, the latest a 2004 review by a scientific panel convened by the National Academy of Sciences. When the EPA dioxin risk assessment is complete, it will be the agency's scientific foundation for future decision-making about dioxins in the environment.

EPA will be taking public comment on the draft interim PRGs for 50 days following publication in the Federal Register, and anticipates issuing the final interim PRGs in June 2010. Upon completion of the dioxins reassessment, currently expected by the end of 2010, EPA will consider the need to update the interim PRGs.