The organochlorine insecticide content of human tissues

Storage Levels of Ddt Metabolites in Mouse Tissues following Long Term Exposure to Technical DDT

The storage levels of DDT and its metabolites, following the long term administration of technical DDT at the dose levels of 2, 20, 50 and 250 ppm to mice, were evaluated in the fat tissue, liver, kidney, brain and reproductive organs. In addition, storage levels were evaluated in foetuses and newborns of DDT-treated mothers. Apart from op'-DDT, there was a direct relationship between the concentration of each metabolite in each organ and the dose to which the animal was exposed. The highest concentration of DDT and metabolites was found in the fat tissue followed by reproductive organs, liver and kidney together, and lastly brain. The most prevalent metabolite was pp'-DDT, except in the liver, where pp'-DDD showed the highest concentration. Pregnant females had lower concentrations of all metabolites than non-pregnant females. The concentration of residues in samples of total foetal litters was directly related to the concentration of DDT fed to the mother. There was a strong negative correlation between the concentration of pp'-DDT and that of pp'-DDD in the foetuses and the placentas of the same litter. A significant increase in whole body DDT concentration was observed shortly after birth.

Relative lipid content as the sole mechanistic determinant of the adipose tissue:blood partition coefficients of highly lipophilic organic chemicals

The adipose tissue:blood partition coefficient (PCat:b) refers to the ratio of chemical concentration or solubility in adipose tissue and blood. The solubility of a chemical in adipose tissue or whole blood is equal to the sum total of its solubility in lipid and water fractions of these matrices. For highly lipophilic organic chemicals (HLOCs, i.e., chemicals with log n-octanol:water partition coefficients (PCo:w) greater than four), their solubility in the water fractions of both tissue and blood is negligible, and therefore their solubility in lipid fractions of tissue and blood alone determines PCat:b. Since the numerical value representing chemical solubility in lipids is likely to be the same for both blood lipids and adipose tissue lipids, the PCat:b values should be hypothetically, equal to the ratio of lipid content of adipose tissue and blood. The objective of the present study was therefore to verify whether the PCat:bs of HLOCs (volatile organics, dioxins, PCBs, PBBs, DDT) are equal to the ratio of adipose tissue and blood lipid levels. The data on lipid content of rat and human blood and adipose tissues were obtained from the literature. The calculated tissue:blood lipid ratios were comparable to the human and rat PCat:b of volatile organic chemicals, dioxins, PCBs, PBBs and/or DDT obtained from the literature. These results then suggest that, regardless of the identity and PCo:w of HLOCs, their PCat:b is equal to the ratio of lipid in adipose tissues and blood.

Monograph: reassessment of human cancer risk of aldrin/dieldrin

In 1987, the US Environmental Protection Agency (EPA) classified aldrin and dieldrin as category B2 carcinogens, i.e. probable human carcinogens, based largely on the increase in liver tumors in mice fed either organochlorine insecticide. At that date, the relevant epidemiology was deemed inadequate to influence the cancer risk assessment. More time has now elapsed since early exposures of manufacturing workers to aldrin/dieldrin; therefore, updated epidemiological data possess more power to detect exposure-related differences in cancer risk and mortality. Also, recent experimental studies provide a plausible mode of action to explain the mouse specificity of dieldrin-induced hepatocarcinogenesis and call into question the relevance of this activity to human cancer risk. This monograph places this new information within the historic and current perspectives of human cancer risk assessment, including EPA's 1996 Proposed Guidelines for Carcinogen Risk Assessment. Updated epidemiological studies of manufacturing workers in which lifetime exposures to aldrin/dieldrin have been quantified do not indicate increased mortality or cancer risk. In fact, at the middle range of exposures, there is evidence of a decrease in both mortality from all causes and cancer. Recent experimental studies indicate that dieldrin-induced hepatocarcinogenesis in mice occurs through a nongenotoxic mode of action, in which the slow oxidative metabolism of dieldrin is accompanied by an increased production of reactive oxygen species, depletion of hepatic antioxidant defenses (particularly alpha-tocopherol), and peroxidation of liver lipids. Dieldrin-induced oxidative stress or its sequelae apparently result in modulation of gene expression that favors expansion of initiated mouse, but not rat, liver cells; thus, dieldrin acts as a nongenotoxic promoter/accelerator of background liver tumorigenesis in the mouse. Within the framework of EPA's Proposed Guidelines for Carcinogen Risk Assessment, it is proposed that the most appropriate cancer risk descriptor for aldrin/dieldrin, relating to the mouse liver tumor response, is 'not likely a human carcinogen', a descriptor consistent with the example of phenobarbital cited by EPA.

Application of biological data in cancer risk estimations of chlordane and heptachlor

Regulatory agencies traditionally use doses associated with ambient concentrations of contaminants in environmental media to estimate lifetime excess cancer risks. This approach is, however, limited by the errors inherent in making several default assumptions such as daily water and food intakes and organ absorption factors. A methodology was developed in this study to estimate daily human doses of chlordane and heptachlor from measured metabolites in adipose tissue. Human biomonitoring data, pharmacodynamic and pharmacokinetic parameters in humans and animals, and selected dose-response data from animal carcinogenicity studies were utilized in this procedure for cancer risk assessment in man. Conversion factors, based on body surface area, were used for animal-to-man extrapolation. Conservative estimates from the Global 82 linearized multistage mathematical model (95% upper confidence limit) associate a 1 x 10(-5) risk probability level to chlordane and heptachlor doses of 1.1 x 10(-4) and 4.0 x 10(-5) mg/kg-day, respectively, via all potential routes of exposure. The unit cancer risks associated with "internal" dose estimates from human adipose tissue concentrations were calculated and compared with U.S. Environmental Protection Agency (1986a, Carcinogenicity Assessment of Chlordane and Heptachlor/Heptachlor Epoxide, EPA-600/6-87-004) unit risks in air and water. The implications and uncertainties associated with the risk estimates were also discussed.

Organochlorine pesticides and polychlorinated biphenyls in human adipose tissue

Halogenated organic compounds are highly lipophilic chemicals that are persistent in the environment as a result of their use and chemical stability. Some of these compounds are also present in the environment as metabolites or oxidation products of a parent compound or as by-products formed in the production of chlorinated compounds. Chronic exposure to the general population results mainly through the food chain. Because they are lipophilic, and because many are metabolized slowly, these chemicals tend to concentrate in body fat tissue. This contribution has described these halogenated organic compounds, discussed their use, regulation and prohibition throughout the world, and reviewed published studies on the levels of these chemicals found in the adipose tissue of humans and animals. For many years, residues of halogenated organic compounds have been detected in the human adipose tissue of individuals in a number of countries, including those in Europe, Asia, and Africa, as well as in the U.S. The levels detected have been used as an index of the level of general population exposure of these compounds over time. Over the past two decades, most countries have observed a steady decline of this level of exposure, reflecting a reduction in the use of these compounds, restrictions on or banning of their use, and a corresponding decrease in their environmental levels. The levels of concentrations vary from chemical to chemical as well as from isomer to isomer. Since the use of aldrin and dieldrin has now been banned or restricted in the U.S. and a number of other countries, residue levels have slowly decreased. Mean values in human adipose tissue in the U.S. and some foreign countries ranged from 0.04 to 0.40 ppm for dieldrin. Aldrin was detected only in Argentina and Poland in the 1970s and endrin was not detected anywhere at anytime. By 1978, all products containing BHC registered in the U.S. has been either discontinued or reformulated to incorporate lindane rather than BHC. The potential for exposure to BHC is virtually nonexistent in the U.S.; however, exposure to lindane is possible since products containing this chemical are still marketed, and used particularly in the manufacture of human medicine. DDT was banned for agricultural purposes in the U.S. in 1972, although it is still used elsewhere for public health vector control. Since the decline in use of DDT, however, the average levels of concentration have also declined. Heptachlor, chlordane, and trans-nonachlor (a component of both heptachlor and chlordane) are chlorinated cyclodienes.(ABSTRACT TRUNCATED AT 400 WORDS)

Organochlorine pesticide concentrations in perinatal samples from mothers and babies

Samples were obtained from Dutch mothers and their babies throughout the perinatal period and analyzed by gas-liquid chromatography with electron-capture detection for a range of organochlorine pesticides. Organochlorine concentrations in the blood of breast or bottle-fed babies were not significantly different. Differences in organochlorine concentrations in blood between mothers who had "slimmed" and those who had not were small, but it must be noted that there were few slimming mothers in our sample. Twelve to 21% and 36-61% of the estimated daily intake of dieldrin and DDT, respectively, by mothers may be eliminated by lactation. The placenta restricts the transmission of organochlorine pesticides to the fetus to some extent. The very low concentrations of organochlorine in fetal blood prevented a study of the comparative metabolism in mothers and babies.

Organochlorine pesticide residues in human adipose tissue in Mexico: results of a preliminary study in three Mexican cities

The results of a preliminary search to determine the levels of organochlorine pesticide residues in the adipose tissue of the inhabitants of three Mexican cities of different socioeconomic characteristics are described herein. The concentrations and percent occurrence of nine compounds found are reported. In general, the samples analyzed had a large number of different organochlorine residues per sample. The results indicate that the inhabitants have been heavily exposed to 1,1,1-trichloro-2,2-bis (p-chloro-phenyl) ethane (DDT), and to a lesser degree, to 1,2,3,4,5,6,-hexachlorocyclohexane (BHC). The mean concentration of 1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene (DDE) in one of the groups (18.36 ppm lipid basis) was one of the highest reported in the literature. It is also noteworthy that DDT was found in only 63, 89, and 55% of the samples from the three cities.

Organochlorine compounds in adipose tissue of Greenlanders and southern Danes

Abdominal fat tissue samples from the general population of Greenland and from southern Denmark were analyzed for o,p'-DDE and p,p'-DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], p,p,-DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane], o,p'-DDT and p,p'-DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane], lindane (1,2,3,4,5,6-hexachlorocyclohexane), aldrin (1,2,3,4,10,10-hexachloro-1,4,4a,5,8,8a-hexahydro-endo-exo-1,4:5,8-dimethanonaphthalene), dieldrin (1,2,3,4,10,10-hexachloro-6,7-epoxy-1,4,4a,5,6,7,8,8a-octahydro-endo-exo-1,4:5,8-dimethanonaphthalene), heptachlor (1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methanoindene), heptachlor epoxide, and polychlorinated biphenyls (PCBs). Fat tissue from Greenlanders contained significantly higher amounts of p,p'-DDE (p less than or equal to 0.05), p,p'-DDT (p less than or equal to 0.01), and total DDT (SIGMA DDT, the sum of DDT and its metabolites) (p less than or equal to 0.01) than southern Danes. Lindane, aldrin-like residue, dieldrin heptachlor-like residue, heptachlor epoxide, and PCBs were present in adipose tissue of both groups and there were no significant differences between the groups. The p,p'-DDE level in Greenland was lower than that in the United States, eastern Europe, and India. Among Greenlanders of different ages the highest sigma DDT was found in the age group of 22-45 yr; the content of PCBs increased with age. Among southern Danes the highest sigma DDT was found in a higher age group than in Greenlanders. Among Greenlanders the content of aldrin-like residue decreased with age and that of dieldrin increased with age. A significant correlation was found (on the basis of wet weight) between p,p'-DDE and PCB content in southern Danes (p less than or equal to 0.02). The correlation between sigma DDT and PCB content was also significant in this population (p less than or equal to 0.01). These two relationships were not significantly correlated for the Greenlanders. The DDE/PCB and sigma DDT/PCB ratios were higher in Greenlanders than in southern Danes. These ratios are age-dependent and are highest in the age group 22-45 yr among the Greenlanders. A low DDE/PCB ratio and a low sigma DDT/PCB ratio have been proposed as markers for industrialization. In Greenlanders p,p'-DDE represented about 70% of sigma DDT. For southern Danes this level was about 90%. The data obtained are presented and discussed on the basis of both lipid and wet weight levels.

Organochlorine pesticide residues in human fat in the United Kingdom 1969-71

During the period 1969-71 samples of human body fat were taken during routine necropsies on 201 subjects over 5 years old and 20 stillborn babies and infants under 5 years old, and analysis was carried out for organochlorine pesticide residues. By comparing the results from this period with those from similar studies undertaken in 1963-4 and 1965-7, it is clear that a downward trend continues.

Heptachlor induced changes in fenitrothion metabolism

Pretreatment of rats with heptachlor administered in the food for 3 months increases the metabolism of fenitrothion. Comparison of oxon analogue levels in the blood and livers of pretreated and control animals suggests that the conversion of fenitrothion to its oxon analogue is enhanced and accelerated. This was studied by tracer methods, using P-fenitrothion.