By Lynda Huckestein, Project Chemist, Kelso, WA
Aquatic Humic Substances (AHS) result from the decomposition of plant and animal residues and are found in soil, sediment, and water. They are widespread in nature and are mostly comprised from naturally occurring dissolved organic matter in water.
The United States Environmental Protection Agency (EPA) will soon release its response to a 2006 National Academy of Sciences (NAS) report recommending changes to the EPA’s 2000 draft assessment of the risks posed by 2,3,7,8 Tetrachlorodibenzo-p-Dioxin.
Dioxins are environmental contaminants according to the Food and Drug Administration’s (FDA) website (September 2009). Most human dioxin exposure, however, occurs through the diet, with more than 95% coming through dietary intake of animal fats. Dioxins enter the food chain primarily in an air-to-leaf/soil-to-animal route.
In anticipation of the upcoming release, the EPA has established a special communication committee to address concerns about the safety of the food supply and other public health issues.
The EPA’s Waste Office, in response to this reassessment, is proposing lowering soil screening levels in residential areas from 1000 parts per trillion (ppt) to 72 ppt. However, given reported health risks, there are some that have been urging the EPA to adopt an even stricter 3.7 ppt-level.
