In July of 2011, Community Correspondent Rachelle Parker wrote about Butte Environmental Council's (BEC) fascinating study assessing dioxin levels in backyard chicken eggs around Oroville. She outlined the history of the Koppers fire which caused dioxin contamination in surrounding soil and the original study by the former California Department of Health Services (CDHS). Dioxin is known for its toxicity and persistence in the environment. BEC recently held a workshop in Oroville about dioxin to educate community members about this issue.
The intention of BEC's study was to gain a better understanding of the public's exposure to dioxin by eating backyard chicken eggs. Julia Murphy, Education and Outreach Assistant at BEC, explained that dioxin is linked to a myriad of negative health effects, "from hormone disruption and immune system dysfunction, to birth defects and cancer." But because we are exposed to dioxin from a variety of sources, it is difficult to draw a straight cause-and-effect line from the source to adverse health effects.
BEC also wanted to assess how long dioxin remains in soil, as there is a great lack of data on this subject. What is known about dioxin? It has a half-life of seven to 11 years in the human body, and it is passed from mothers to babies via breast milk. Dioxin binds to organic material in soil, which is scratched and consumed by chickens. Because dioxin is fat-soluble, it becomes concentrated in chicken eggs and other animal products. Fruit and vegetables, on the contrary, do not store dioxin.
The FDA has set 1 part per trillion (ppt) as the "level of concern." The results of testing 18 eggs in different areas of Oroville yielded an average dioxin level of 2.32 ppt. However, several outliers of 14.7 ppt, 7.25 ppt and 4.55 ppt increased this average. The CDHS study which sampled eggs in 1988 and 1994 yeilded an average dioxin level of 4.2 ppt. "It appears that over 25 years since the original study, dioxin levels have slightly decreased; however we are working with a very small sample size," said BEC's Education and Outreach Coordinator, Mary Muchowski. Julia Murphy added, "It's unclear whether we're looking at the Koppers' legacy of dioxin contamination or more recent sources of exposure." Other local sources of dioxin include cogeneration plants and rendering plants, incineration of industrial and medical wastes, backyard barrel burning and chemical manufacturing.
Muchowski and Murphy believe that free-range and backyard chicken eggs are still healthier than store bought eggs. They cited a study by Mother Earth News showing that eggs from chickens raised on open pasture have lower saturated fat and cholesterol, and more vitamin E, vitamin A, omega 3's and beta carotene than store bought eggs. They suggested that homeowners who have high levels of dioxin in their tested eggs remove treated wood from their yard, refrain from putting ash in chicken pasture, keep chickens in a coop to limit their exposure to soil, or just eat egg whites, which contain substantially less fat, and therefore minimal dioxin.
Nancy Kerns was one of the Oroville residents who participated in the study. "I was eager to participate and happy that BEC offered the testing," she said. However, she was "surprised and dismayed to see that our eggs contained dioxin at a level of 1.3 ppt." The previous study of dioxin in backyard chicken eggs of Oroville performed by CDHS led to a public advisory urging people not to eat eggs with dioxin levels of 2 ppt or higher. Therefore, there is inconsistent information from governmental regulatory agencies about the level of dioxin that can be safely consumed. Some studies even suggest that there is no safe threshold dose, said Murphy.
Kerns and her husband still eat their backyard eggs, but with more caution. "We are now conscious of the amount of eggs we eat every week, and we would never offer them to pregnant women or children," Kerns said. The Butte Environmental Council will continue their public education workshops at various locations around Oroville. "We plan to work with the Department of Public Health to explore the need for a second advisory as well," said Murphy.
BEC's study is unique in that they work with individual participants to provide education and tools to minimize their exposure. The data is also significant because it contributes to establishing regional patterns of dioxin contamination. BEC hopes to replicate this study in 10-15 years to further the body of knowledge about how this potent chemical behaves in the environment and how to best protect the public's health.