Multigeneration studies on DDT in mice

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.

Carcinomas of the Liver in Osborne-Mendel Rats Ingesting DDT

Osborne-Mendel male and female rats ingested 200, 400, 600, or 800 ppm DDT composed of 81.8% p,p isomer and 18.2% o,p isomer for periods up to 2 years. Male and female rats developed higly significant incidences of hepatocellular carcinomas. The carcinomas varied from well-differentiated to undifferentiated. There was a highly significant increase in carcinomas of the ovary in treated female rats. Lymphosarcomas were also increased in DDT-treated male rats.

Alterations in male reproductive hormones in relation to environmental DDT exposure

DDT [1, 1, 1-trichloro-2,2-bis (p-chlorophenyl)-ethane] compounds are used for indoor residual spraying (IRS) to control malaria mosquitoes. DDT is an endocrine disruptor chemical in experimental conditions, but little is known of adverse effects related to living conditions with continual uptake across a time span by all possible means of exposure. Based on estrogenic and/or anti-androgenic effects found in animal studies, we hypothesized that chronic DDT/DDE exposures in men may be associated with changes in male reproductive hormones. We tested this hypothesis by compared the magnitude and direction of associations between DDT and DDE (1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene) concentrations and male reproductive hormones in samples collected from IRS and non-IRS areas. We sampled a cross-section of 535 men (aged 18-40 years). Men living in IRS villages had significantly higher DDT and DDE concentrations compared with men from non-IRS villages. Men with DDT or DDE uptake (as reflected in detectable plasma concentrations) had significantly higher total-, free and bio-available testosterone (T), and lower follicle stimulating hormone (FSH) concentrations; lower luteinizing hormone (LH) concentrations were only evident with DDT uptake. To establish a dose-dependent effect, four sub-categories were defined. Men with the highest DDT (74-519 μg/g) and DDE (173-997 μg/g) concentrations had significantly higher total-, free and bio-available T, and lower FSH concentrations compared with subjects with non-detectable isomer concentrations. Estradiol concentrations were significantly higher in men with DDT and DDE concentrations in both the third (DDE: 27-172 μg/g; DDT: 5-73 μg/g) and fourth (DDE: 173-997 μg/g; DDT: 74-519 μg/g) categories. Men from IRS villages were significantly more likely to have higher total and bioavailable T as well as higher estradiol concentrations OR = 2.5 (95% CI 1.2, 3.2); OR 2.5 (95% CI 1.6, 4.0) and OR = 2.3 (95% CI 1.3, 4.1) compared to men from non-IRS villages, after controlling for age, BMI, personal use of pesticides, and smoking. Men living in IRS villages with life-long exposure (17.6 (±6) years) at the current residence with multiple exposure modalities incurred the highest degree of physiological imbalance over and above circulating isomer concentrations. Further studies are needed to elucidate the health implications of these findings.

Pesticide exposure: human cancers on the horizon

Dichlorodiphenyltrichlorethane, a halogenated hydrocarbon, was introduced as an insecticide in the 1940s. In her book "Silent Spring", Rachel Carson expressed her concern for the environment, plants, animals, and human health about the potential harmful effects of such chemicals. In 1972, the Environmental Protection Agency banned the chemical in the USA. DDT and its metabolite DDE are lipid soluble compounds that persist in the environment and bioaccumulate in the body in adipose tissue at levels far higher than those in blood and breast milk. This paper evaluates the possibility of cancer occurring in humans from DDT exposure. Some risk of lymphoma, leukemia, pancreatic cancer, and breast cancer was found in humans exposed to DDT. Animal studies showed a significant association between DDT administration and lymphoma, respiratory cancer, liver cancer, and estrogenic effects on mammary tissue. On the basis of on epidemiological principles, human studies were deficient in adequate sample sizes and were not exempt from such confounding factors as multiple chemical exposure, lifestyle factors, genetic, and other environmental influences. Extrapolation of data on DDT toxicity from animals to humans has limitations. With the persistence of DDT and DDE in the environment, the potential risk to the health of man, animals, and the environment remains.

Organochlorine compounds in relation to breast cancer, endometrial cancer, and endometriosis: an assessment of the biological and epidemiological evidence

There is an increasing public and scientific concern that certain chlorinated compounds, recognized as environmental pollutants, may cause estrogen-related neoplastic disease in humans. The main hypothesis has been that certain organochlorines, through their estrogenic actions, might cause breast cancer. From experimental studies, both in vitro and in vivo, there is evidence that certain organochlorine compounds may cause estrogenic effects, whereas others may cause antiestrogenic effects. In limited studies, some of these compounds in high doses have also been shown to increase and reduce the frequency of estrogen-related tumors in animals. The epidemiological findings regarding the association between organochlorines and breast cancer are inconclusive. However, the largest and best designed study has been interpreted as negative with respect to DDT and polychlorinated biphenyls (PCB) in relation to breast cancer. Associations between organochlorine exposure and endometrial cancer or endometriosis have even more limited empirical basis. The hypothesis that human exposure to environmental levels or organochlorines would favor an estrogenic overactivity leading to an increase in estrogen-dependent formation of mammary or endometrial tumors is not supported by the existing in vitro, animal and epidemiological evidence. It can, however, not be conclusively rejected on the basis of available data.

Endpoints of spermatotoxicity in the rat after short duration exposures to fourteen reproductive toxicants

Multiple endpoints of spermatotoxicity in short duration tests (1-5 days exposure; 2.5-week assay interval) were investigated in a number of chemicals reported to produce minimal to severe reproductive effects when administered subchronically. Six of these chemicals (boric acid, dinoseb, 2,5-hexanedione, methoxychlor, metronidazole, ornidazole) produced substantial spermatotoxicity after 1 to 5 doses. Spermatotoxic effects of chlordimeform were equivocal while p,p'-DDT, n-hexane, and sodium chlorite were judged negative. Four chemicals with known acute effects (benomyl, busulfan, ethylene glycol monomethyl ether, nitrobenzene) elicited expected histopathologic responses after a single dose. Testicular histology, testicular sperm head counts, cauda sperm counts, sperm morphology, and sperm velocity proved to be the most toxicologically sensitive endpoints in one or more of the studies, but histopathology of the testis and epididymis was the most consistent indicator of reproductive damage. The percentage of motile sperm and sperm concentration in the epididymal fluid were the least sensitive measurements. The data suggested that most chemicals with the potential to produce moderate to severe sperm damage are detectable with a short duration test. Complementary multiple endpoints enhanced the interpretation of results, often identified cellular targets, and provided insight on possible mechanisms. Specific responses were often similar to specific effects reported for subchronic exposures. A short duration test could be of value as a screen in structure-activity studies or to set priorities for chemicals requiring further evaluation. As a supplement to breeding studies, the data generated in the short test could also be used to enhance the design and interpretation of the longer tests.

Histopathology of Carcinomas of the Liver in Mice FED Perthane

B6C3F1 female mice fed an average dose of 3,000 ppm of perthane for 2 years developed a highly significant incidence of hepatocellular carcinomas of the liver. Male mice fed 2,500 ppm perthane had a slight increase of carcinoma of the liver. Some of the carcinomas were well-differentiated; however, most were poorly differentiated or undifferentiated. Perthane-treated mice also had well and poorly differentiated cholangiocarcinomas and carcinosarcomas, neoplasms not seen in control mice.

Commercial laboratory animal diets: toxicant and nutrient variability

A commercial rodent feed was analyzed for a series of nutrients and potential contaminants during a 5-yr period. Annual average Cu and vitamin A concentrations were generally at least 12% lower than the approximate concentrations listed by the manufacturer, whereas Ca, protein, and vitamin B1 were within +/- 5% and fat and Zn within +/- 8% of the manufacturer's specifications. Frequently, Se was found at concentrations at which it has been shown to interact with the process of chemical carcinogenesis. DDT, dieldrin, Cd, and Pb were occasionally close to concentrations known to have biological effects.

Mutagenic and carcinogenic effects of pesticides

A discussion of the mutagenic and carcinogenic effects of various classes of commonly used pesticides. Classes discussed include halogenated hydrocarbons organophosphorus insecticides, and certain herbicides and fungicides. Halogenated hydrocarbons were found generally hazardous, causing sterility and displaying marginal or definite carcinogenic activity. Several organophosphorus insecticides have been shown to be mutagens; some have been shown to be carcinogens. Both the herbicide impurity tetrachlorodibenzodioxin, TCDD, and maleic hydrazide have been shown to be carcinogenic in mice and rats. The role of DNA as a critical target for carcinogenic activity is also discussed.

Interstitial cell carcinomas of the testis in Balb/C male mice ingesting methoxychlor

Balb/c and C3H strains male and female mice ingested 750 ppm methoxychlor or 100 ppm DDT in the diet for 2 years. Balb/c strain male mice ingesting methoxychlor developed a highly significant incidence of interstitial cell carcinomas of the testis. Balb/c strain male mice ingesting DDT and C3H strain male mice receiving methoxychlor or DDT did not have testicular tumors. The carcinomas of the testis varied from well-differentiated to poorly differentiated and undifferentiated and were capable of metastasis. Carcinomas of the testis have been described in Balb/c strain male mice, but not C3H, given estrogens. The carcinogenicity for testis of Balb/c strain male mice is most likely related to the estrogenic activity of methoxychlor.

Statistical design of toxicity assays: role of genetic structure of test animal population

This paper concerns certain statistical aspects of the problem of among-strain differences in cancer susceptibility and how these differences may affect the design of toxicity assays. First, the data of Innes et al. (1969) were examined to investigate the magnitude of within-study, between-strain differences in tumor induction. Although there was a very high overall association between mouse strains with respect to the induction of hepatomas, evidence of strain-to-strain variability was found for several compounds. Next, a number of long-term carcinogenicity studies with DDT were considered, and among-strain differences in cancer susceptibility for this compound were noted. Finally, it was shown that if susceptible subgroups do exist, and certain simplifying assumptions are made, then in many cases tumor increases can be detected more readily by studying several inbred mouse strains rather than a single outbred stock.

Effects of DDT on stable laboratory mouse populations

Four stable laboratory mouse populations were established; each contained approximately 400 mice of both sexes and all ages postweaning living in a single cage, as well as neonates caged in separate nesting boxes with their dams. Two were used to determine the effects of continuous exposure to a dietary level of 100 ppm DDT while the other two served as controls. The results indicated a significant decrease (p less than or equal to 0.05) in neonatal survival (lactation index) within 20 wk after the beginning of exposure to the toxicant in one of the exposed populations and by 30 wk in the other. This deleterious effect of the DDT continued through each succeeding generation. On the other hand, improved postweaning survival in DDT-fed mice was noted. Histological examination showed no tumors in test or control animals; other pathology was seen more frequently in control than in test animals.

Carcinogenicity of DDT (dichlorodiphenyl trichloroethane) in pure inbred Swiss mice

Inbred Swiss mice were treated with technical DDT (1) orally with the diet or by intubation; (2) subcutaneously and (3) by skin painting. The total duration of the experiment was 80 weeks. There was no difference in body growth and mortality between the experimental and control groups. Toxic manifestations of DDT were observed in treated mice in the form of tremor, convulsions and corneal opacity usually after 40 weeks. Oral and subcutaneous DDT treatment resulted in a significant increase in the incidence of tumours mainly of lymphoid tissues, lung and liver. The highest tumour incidence was recorded in the group of mice receiving DDT by subcutaneous injections. Males and females were equally susceptible. No evidence of carcinogenicity was observed in the painted group.

Pesticide induced DNA damage and its repair in cultured human cells

The effects of pesticides on the induction of unscheduled DNA synthesis in SV-40 transformed human cells (VA-4) in culture with and without metabolic activation by liver microsomes was studied. Results showed that ten of the thirteen compounds examined either directly or upon metabolic activation induced unscheduled DNA synthesis in the human cell system used. The DNA repair kinetics and size of the repaired regions resulting from treatment with four of the chemicals (Carbaryl, Chlordane, Dieldrin and 2.4-D Fluid) were studied by 313 nm photolysis of repaired regions containing bromodeoxyuridine (BUdR). The size of the repaired regions differed between compounds but could generally be classified as either of the X-ray (short) or UV-type (long).