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PCDD and PCDF measurements were made on selected retail milk products, including paper packaged milk samples, covering all known paper carton suppliers in the state of California during 1989. Significant levels of 2,3,7,8 tetrachlorodibenzofuran (TCDF) and 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) were found in the paper packaged milk in all brands investigated except one. All other 2,3,7,8 substituted PCDFs and PCDDs were either not detected or detected at very low levels. Two non 2,3,7,8 substituted TCDFs were consistently detected in the contaminated milk samples. Using the mean concentration of 2,3,7,8 TCDF and TCDD detected and assuming a 480 ml daily consumption of milk for an adult, we estimated that the milk represented an additional 2.3 pg/kg/day of TCDD equivalent exposure based on the California toxic equivalence (CA TE), but only a 0.56 pg/kg/day increase using the International TE (ITE). The lifetime cancer risk was calculated to be 470 10 6 (CA TE) and 80 10 6 (ITE). Monitoring of retail milk products continued during 1990 but 2,3,7,8 TCDD and 2,3,7,8 TCDF were either not detected or detected at very low levels in all products investigated.

Controlled exposure studies under laboratory and field conditions have been initiated to investigate the biotransfer and bioaccumulation of PCDD/Fs in soil, at low concentrations, to animals which have contact with soil. The chicken was chosen as a model for grazing animals. The accumulation over time of specific isomers is being tracked in eggs, blood, feces, liver, adipose, and edible flesh. Measurable increases of PCDD/F concentration in eggs of exposed chickens, as compared to controls, were seen after 30 days of exposure. The exposure characterization, as well as data on isomer specific biotransfer and bioaccumulation rates in eggs are discussed.

Additional data have been obtained which relate the bioaccumulation of polychlorodibenzodioxins and polychlorodibenzofurans (PCDDs and PCDFs) in foraging chickens to the ingestion of soil contaminated at the low part per trillion (ppt) level. These new data indicate that both the concentration and congener profiles of PCDDs and PCDFs in eggs and body tissues, are correlated with the PCDD and PCDF concentration and congener profile seen in soil on which these chickens were grazing. Additionally, a cow grazing in these areas of low soil PCDD/PCDF contamination showed characteristic PCDD and PCDF profiles in milk. Breast milk from women living in the area did not show the characteristic PCDD/PCDF contamination. Controlled feeding studies of chickens have been initiated which are designed to demonstrate the transfer of PCDDs and PCDFs from soil to tissue and eggs and to establish the kinetics and equilibrium concentrations of the bioaccumulation. Levels and patterns of PCDDs and PCDFs in tissues and eggs from foraging animals appear to be closely related to the levels and patterns in the soils to which they are exposed. This suggests the possibility of animals functioning as sensitive biomonitors for low level soil contamination. In addition, if such animals are used for food, the possibility of human exposure to PCDDs and PCDFs must be considered.

We studied dioxin levels in residents of two California households where dioxin contaminated homegrown eggs and beef were found, in order to determine the level of exposure to dioxins. Risk assessments for carcinogenicity and reproductive toxicity showed that theoretical risks exceeded proscribed regulatory levels. Advisory guidelines were issued about consumption of eggs, chicken and beef. Serum samples from exposed and matched rural comparison subjects were analyzed and preliminary dioxin data show statistically significant elevations of 2,3,7,8-penta and hexa dioxin isomers for both homes. Comparison subjects from rural California had lower serum dioxin levels than those previously reported for Missouri and Sweden. Adipose tissue from a resident of one of the homes was tested for dioxins. The resident died six months later and a post mortem retesting of adipose and testing of liver and lung tissues for dioxins was done. No unusual dioxin levels were found; levels of dioxin in adipose remained stable despite six months of not eating contaminated produce. Dioxins were not a contributing cause of death. In this study, dioxin contaminated eggs and beef have elevated 2,3,7,8-tetra, penta and hexa dioxin levels in serum. The ongoing investigation will seek to delineate the source and extent of contamination, and to determine the extent of the exposed population and potential health impacts.

Studies carried out in California, following a fire which involved a pentachlorophenol wood treatment plant have indicated that low concentrations of dioxins and furans in soil can lead to bioaccumulation in chickens and cattle which are in contact with the soil. These compounds were found to distribute into various tissues of the animals and into the eggs of the chickens. A significant change in congener profile and isomer pattern was seen when comparing soils to tissues. Source tests of local incinerators showed quite different congener profile than was seen in soils. Concentrations found in animal products used as food suggest the possibility of excessive human exposure based on modest consumption assumptions.