Dioxins/TCDD environmental fate

For risk assessment purposes, an important objective in evaluating the environmental fate of PCDD/Fs is predicting the major pathways of human exposure. It is well established that the food chain, especially meat and dairy products, accounts for more than 90% of human exposure to PCDD/Fs and perhaps as much as 99% of human exposure to 2,3,7,8-TCDD.34 In industrialized countries, the average daily intake via food (the major route of exposure to dioxins and furans) ranges from 1.5 to 2.5 pg TEQ kg-1 body weight. 

The environmental behavior of chemicals with a very low volatility, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), has been the subject of several studies over the last few years. The focus of these studies has varied from the development of physical property data ( 1,2) to lab and field tests of the mobility and/or fate of TCDD. 

The majority of available data on the fate of PCDD pertains only to 2,3,7,8-tretrachlorodibenzo-/7-dioxin (TCDD). Since the data are generally not quantitative, interpretation and extrapolation to natural environmental conditions has to be viewed with some caution. Hence, only a qualitative concept of the behavior of PCDD in the environment is presented. PCDDs tend to be rapidly and strongly sorbed by most soils (Firestone, 1977 Ward and Matsumura, 1978), suggesting relative immobility in most matrices. Using partition coefficient data for an octanol/water mixture and its relationship to the organic matter and its content in sediment and soils. 

Ward, C.T., and F. Matsumura. 1978. Fate of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in a model aquatic environment. Archives of Environmental Contamination and Toxicology 7 349-357. 

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