George F. Fries

Health implications of 2,3,7,8-tetrachlorodibenzodioxin (TCDD) contamination of residential soil.

Extrapolations from animal toxicity experiments (including carcinogenicity and reproductive effects) to possible human heath effects can be used to estimate a reasonable level of risk for 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD). Extrapolations are derived from: (1) review of published studies, (2) a complex set of assumptions related to human exposure to contaminated soil, and (3) estimates of (a) a dose response curve, (b) appropriate margins of safety, and/or (c) applicable mechanisms of action. One ppb of 2,3,7,8-TCDD in soil is a reasonable level at which to begin consideration of action to limit human exposure for contaminated soil.

DDT induces a decrease in eggshell calcium.

Japanese quail fed o,p′, and p,p′-DDT produced eggs with thinner shells and lower calcium content than usual.

The Pbb Episode in Michigan: An Overall Appraisal

Polybrominated biphenyls (PBB) were used as a fire retardant. In common with other halogenated hydrocarbons, PBBs are lipophilic and resistant to chemical and metabolic degradation. Cattle on about 25 Michigan farms were exposed to as much as 250 g per head of PBB when it was accidentally mixed in cattle feed in 1973 to 1974. Livestock exposures several orders of magnitude lower occurred on several hundred other farms because of carryover and equipment contamination in feed mills. Approximately 85% of the Michigan population received some exposure to PBB because dairy product marketing involves mixing milk from many farms. A few cases of high human exposure, which may have been as great as 10 g, occurred when residents of the more highly exposed farms consumed their own products. Although numerous clinical signs and pathological changes were reported in exposed cattle, only anorexia, lacrimation, emaciation, hyperkeratosis, and kidney damage were confirmed in controlled studies. The acute toxicity of PBB in laboratory animals is low, but a variety of subacute effects have been reported. Induction of microsomal enzymes, enlargement and histopathological changes of the liver, fetotoxicity, and immunosuppression are among the more significant. Epidemiological studies of exposed humans have revealed no pattern of clinical signs or symptoms that were related to PBB exposure. A complete evaluation of the human consequences of exposure to PBB await the conclusion of long-term epidemiological studies.

Evaluation of potential transmission of 2,3,7,8-tetrachlorodibenzo-p-dioxin-contaminated incinerator emissions to humans via foods

Interest in the potential sources of human exposure to TCDD (dioxins, TCDD and equivalents, or 2,3,7,8-tetrachlorodibenzo-p-dioxin) via foods has recently shifted from phenoxy herbicides to products of combustion and waste disposal. Proposals to locate municipal waste combustors in rural areas have raised concerns that emissions, which could contain TCDD, could contaminate animal feeds and such human foods as milk, meat, and vegetables. Important factors that can affect the results of an assessment of incinerator emissions include (1) the emission and deposition rates of TCDD from the source, (2) the fractional retention and half-life of fly ash on plants, (3) the environmental half-life of TCDD, (4) the animal feeding and management systems, (5) the bioavailability of TCDD and related compounds, (6) the metabolism and pharmacokinetics of TCDD in farm animals, (7) food consumption levels, (8) the half-life of TCDD in humans, and (9) the model selected to estimate cancer risk. For persons living in the area of highest deposition near an incinerator, a possible uptake of TCDD from foods of animal origin was estimated to be about 10-40 fg/kg.d, which was much greater than the 1-5 fg/kg.d uptake estimated for foods of plant origin. The total uptake of TCDD from foods by the maximally exposed population will usually be about 500- to 1000-fold greater than that due to inhalation. Although milk was assumed to be the most important food pathway in several previous assessments that evaluated the hazards of airborne emissions, we determined that the deposition-forage-cattle-beef pathway was the more important route of exposure. The previous assessments appear to have used inappropriate pharmacokinetic models for TCDD and to have overestimated pasture use for dairy cows. The amount of TCDD accumulated in soil from airborne emissions was found to be less important than the amount deposited in forage, a finding that is the opposite of the usual conclusions drawn for other routes of TCDD introduction into agricultural environments. Based on the assumption and parameters used in this assessment, the potential human health risks due to TCDD emissions from incinerators are insignificant compared to other background sources of TCDD. It would be desirable to measure TCDD in soil and crops around existing facilities to better evaluate this assessment, but it is likely that concentrations would be too low to reliably quantitate.

Embryotoxic and teratogenic effects in unhatched fertile eggs from hens fed polychlorinated biphenyls (PCBs).

SummaryThe PCBs tested with caged White Leghorn hens were ‘Aroclors 1221, 1232, 1242, 1248, 1254, 1268, 5442 and BP-6’, fed at the 20 ppm level. In addition, 1242, 1248 and 1254 were also fed at the 2 ppm level. Feeding 20 ppm ‘Aroclors 1232, 1242, 1248 and 1254’ reduced hatchability and caused teratogenic effects in the embryos. The most common abnormalities found in the unhatched embryos were edema and unabsorbed yolk. Since ‘Aroclors 1221 and 1268’ did not adversely affect embryonic development, adverse effects of the PCBs were not directly related to the degree of chlorination of the biphenyls, or to the amount of total residue.

Polychlorinated Biphenyl-induced Decrease in Liver Vitamin A in Japanese Quail and Rats

Summary‘Aroclor 1242’ (PCB) or DDT increased liver weight and lipids and decreased liver vitamin A of male and female rats or male Japanese quail. Laying female quail did not show consistent changes, presumably due to mobilization of lipid and vitamin A for egg yolk. When egg laying was inhibited, PCB reduced liver vitamin A 50%. ‘Aroclor 1242’ reduced egg production, but had no effect on egg weight or eggshell thickness.

Herd health status of animals exposed to polybrominated biphenyls (PBB).

The health status of 16 herds of dairly cattle exposed to low levels of polybrominated bipenyl (PBB) was compared with that of 15 control herds. Milk production of the contaminated herds was not significantly changed in 1972, 1973, and 1974 and was not significantly different from that of control herds in the same years. Mortality of adult cows and calves, the percentages of cows culled from the herds because of old age and low production, disease, or sterility, and the general health conditions were similar in the two groups. Serum concentrations of calcium, glucose, and cholesterol in contaminated herds were significantly different from those of the control herds, but the relationship to PBB exposure needs further investigation.

Oral bioavailability of aged polychlorinated biphenyl residues contained in soil

Bioavailability of toxic chemicals is a potentially important factor in determining the risk associated with soil contamination. Interest in bioavailability of chemicals recently increased because of such incidents as the Missouri and Seveso TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) episodes and the polybrominated biphenyl (PBB) episode in Michigan, which involved human and/or food animal exposure to accidentally contaminated soil. An inherent difficulty in interpreting bioavailability data obtained with environmental samples is that it is not possible to be certain of the extraction efficiency of the system used in the soil analyses. In this study, it was possible to utilize archival soil samples that had been treated with {sup 14}C-labelled polychlorobiphenyls (PCB) eight years previously. The primary purpose of this study was to compare the bioavailability of PCB in these soils with the bioavailability of PCB added to normal rat diets or corn oil. The secondary purpose was to compare dietary inclusion with gavage as a method of administration because gavage frequently was used in the previous studies.

Retention and excretion of polybrominated biphenyls by hens

ConclusionsThe retention and elimination of PBB by hens are qualitatively similar to those of PCBs and chlorinated hydrocarbon pesticides. Steady-state level in eggs was about the same as the level in the diet, and after 63 days the level in body fat was about 4 times the level in diet.The FDA action levels for PBB are 0.05 ppm in eggs and 0.3 ppm in fat. Residues in meat and eggs should not exceed the action levels if the diet level is below 0.05 ppm. Feed consumption and egg production decrease slightly when we fed 20 ppm (LILLieet al., 1974), but effects would not likely be detectable if the diet contained only 0.05 ppm.

Bioavailability of soil‐borne polybrominated biphenyls ingested by farm animals

Concentrations of polybrominated biphenyl (PBB) were measured in the fat of livestock on several farms on which soil-borne PBB in confinement areas was the only source of residue. Ratios of concentrations in fat to concentrations in soil were 0.37 for dairy heifers, 0.27 for primaparous dairy cows, 0.10 for multiparous dairy cows, 0.27 for beef cows, 0.39 for beef calves, 0.37 for ewes, and 1.86 for swine. Multiparous dairy cows had lower ratios because of the excretion of PBB in milk during long-term lactation, and swine had higher ratios because they ingest greater amounts of soil than other species. Diets containing 5% PBB-contaminated soil, or 5% contaminated soil amended with activated carbon, were fed to lambs for 56 d. Accumulation of soil-borne PBB in fat, when adjusted for intake, did not differ significantly from accumulation of PBB from a diet in which PBB was added to cornmeal. Amending soil with activated carbon had no effect on residue accumulation. About 70% of PBB in a control diet with PBB added to cornmeal was absorbed, as measured by using titanium as an unabsorbed marker. Absorption of soil-borne PBB was 65% from unamended soil, 57% from soil amended with 0.3% activated carbon, and 56% from soil amended with 0.6% activated carbon. The differences were not great enough to be of practical importance. These results with PBB may be useful in assessing and managing risks of other soil-borne contaminants that have chemical characteristics similar to those of PBB.