Last year the USEPA completed and published the non-cancer portion of its health assessment for dioxin, one of the most toxic substances ever tested.This event passed without much fan-fare and little coverage by the media. With exception to CHEJ, even the environmental and health advocacy community paid it little attention. This is remarkable because the EPA’s health assessment on dioxin adds an important piece of new information that answers the question about the levels of dioxin in the American food supply. Until publishing this report, EPA had sidestepped the question of setting a reference dose for dioxin because they knew if they did this, they could no longer deny the obvious – the average daily intake of dioxin in food exceeds our best measure of what’s safe, EPA’s reference dose.
A reference dose is generally defined as “a level below which exposures are generally considered to be safe.” EPA’s Reference Dose for dioxin is 0.7 picograms TEQ per kilogram per day (pg/kg/d). According to EPA data, the adult daily intake of dioxin is 66 pg/day. Dividing this value by the average weight of an adult (70 kilograms), you get an average daily intake of dioxin of 0.94 TEQ pg/kg/d, 34% higher than the safe level. For children the numbers are even higher because of their smaller body size.
For example, a 2003 study by the National Academy of Sciences Committee on Dioxin in Food found that children ages 1 to 5 were exposed to 1.09 pg TEQ/kg/day and children ages 6-11 years old were exposed to 0.69 pg TEQ/kg/day. According to this analysis, dioxin exposure in children 1 to 5 years old exceeds EPA’s reference dose and that children 6 to 11 years old have dioxin exposure that is virtually identical to the reference dose. A recent research paper found that the average daily intake of dioxin in 207 pre-school aged children was 1.01 pg TEQ/kg/day, well above the EPA reference dose of 0.7 pg /kg day.
EPA has argued for some time that dioxin exposures are going down and in 2009 EPA published a paper that estimated the daily average intake of dioxin to be only 0.54 pg TEQ/kg/day. This estimate was based on an EPA estimate of dioxin levels in food. Unfortunately, there is no consensus of how much dioxin exists in the food we eat. We know that over 95% of our daily exposure results from ingestion of animal fat, primarily meat and dairy and that people who live near specific dioxin sources are exposed to even higher concentrations.
It is clear however that large numbers of the U.S. population, especially children, are being exposed to dioxin in food at levels that exceed EPA’s reference dose. We need to stop pretending that dioxin levels in food are not a problem and take this issue on. We need better data on dioxin levels in food and how it gets there, and for EPA, FDA, and USDA to engage in this issue. This is not likely however, until the public begins to demand it.