(Beyond Pesticides, February 27, 2012) For the first time since its initial evaluation almost 30 years ago, the U.S. Environmental Protection Agency (EPA) has revised, despite objections from the chemical industry, its dioxin exposure assessment for acute human health risks –setting an “acceptable” level of 0.7 picograms per kilogram per day. Environmentalists said EPA’s estimated average exposure, currently at 0.5—3 picograms per kilogram per day, puts a portion of the population above the EPA danger threshold.
Work on updating the health assessment began in 1991 and was partially completed with the February 12 release of the Final Non-Cancer Dioxin Science Assessment. While EPA characterized the findings as showing that “generally, over a person’s lifetime, current exposure to dioxins does not pose a significant health risk,” the Assessment establishes a daily “acceptable” exposure threshold, or reference dose, which the agency says is comparable to levels which people routinely experience. Beyond Pesticides reviewed the underlying chemistry and historical exposure patterns, including diet and human health effects of dioxins, in a recent Daily New blog entry leading up to the Assessment’s release.
EPA’s decision to adopt its recommended reference dose of 0.7 picograms of dioxins per kilogram of body weight per day that it originally proposed in a 2010 draft version is one the Assessment’s significant outcomes. A picogram is one-trillionth of a gram. The reference dose does not contribute to enforceable standards, but is crucial for setting many guidelines, including cleanup of Superfund and other hazardous waste sites, industrial emission controls, drinking water standards and dietary guidelines for fish. The newly-confirmed EPA reference dose is lower than the World Health Organization’s daily limit of roughly 2.3 picograms.
Arnold Schecter, Ph.D., of the University of Texas School of Public Health, an experienced dioxins researcher and author, said EPA’s statement about people in general not being at risk could be misleading. “I am puzzled regarding the statement about the health risk over a lifetime. As phrased it seems correct, for the average person, but we vary in sensitivity and time of exposure and there are some instances of higher exposure. Why not mention these as well?” Dr. Schecter commented. Stephen Lester, Ph.D., Science Director of the Center for Health, Environment & Justice, which has worked on dioxin issues for several decades, said data in the new report show “that the average background exposure of the American public to dioxin in food is very close to or above the EPA new reference dose.”
While EPA states that air emissions of dioxin chemicals have decreased 90% in recent years, the total disposal or other releases of such compounds actually increased 18% from 2009 to 2010. Air releases of dioxins also increased by 10% during that time period. Chemical manufacturers accounted for almost 64% of total disposal or other releases of dioxins in 2010 with electric utilities accounting for an additional 35%. Manufacturing processes for polyvinyl chloride plastics, the bleaching of pulp at paper mills and the incineration of municipal solid waste are significant contributors to the formation and release of dioxin chemicals. Total disposal or other releases of dioxins for 2010 were 54,426 grams per kilogram of body weight per day, including 1,234 grams of air releases. Dioxins are contaminants in numerous pesticides, including the widely herbicide 2,4-D, the wood preservative pentachlorophenol, and the disinfectant triclosan.
EPA stated that it is working as expeditiously as possible to complete the second component of the Science Assessment on the carcinogenicity of dioxin chemicals.
Source: Environmental Health News
All unattributed positions and opinions in this piece are those of Beyond Pesticides.