Species differences in the acute toxicity and tissue distribution of DDT in mice and hamsters

Effects of Long-Term Intake of DDT on Rats

DDT is a pesticide used in malaria-control programmes throughout the world. Its potential carcinogenicity was studied in MRC Porton rats (Wistar-derived) which received dietary concentrations of 0, 125, 250 and 500 parts per million DDT (technical-grade) for life. The treatment had no adverse effects on body growth or survival rate. Various types of tumours were observed in animals in all groups: exposure to DDT resulted in statistically significant increased incidence of liver-cell tumours only in female treated rats; one such tumour was observed in control rats. No metastases of these tumours were found.

Lack of Carcinogenicity of DDT in Hamsters

Syrian golden hamsters were fed for their lifespan a diet containing 0, 125, 250 and 500 parts per million (ppm) of DDT. The incidence of tumour bearing animals was 13 % among control females and ranged between 11-20 % in treated females. In control males 8 % had tumours. The incidence of tumour bearing animals among treated males ranged between 17-28 %. The incidence of adrenal cortex tumours showed a dose-related increase among the DDT-treated males. A liver-cell tumour and 2 liver hemangioendotheliomas were observed in 3 males treated with 250 ppm DDT. No liver-cell tumours were observed in the controls. No significant difference in tumour incidence was observed in treated versus control Syrian golden hamsters.

Organochlorine and metal contaminants in baleen whales: a review and evaluation of conservation implications

The literature on organochlorine and metal contaminants in tissues of baleen whales includes data for approximately 1000 individuals in 10 species from various oceans of the world. Concentrations of these contaminants in tissues of baleen whales are low. Sources of variation in organochlorine concentrations in whales include age, sex, region of exposure, and feeding habits. Concentrations of sigma DDT and PCBs in baleen whales appear higher in the northern hemisphere than in the southern oceans, perhaps due to greater contamination of northern ecosystems and a higher incidence of fish in the diet. However, maximum concentrations are generally lower in tissues of baleen whales than in other marine mammal species, both on global and local scales. This is predictable based on the general distribution, habitats and trophic levels of baleen whales. We reviewed laboratory studies on the effects of selected organochlorine contaminants on direct mortality and impaired reproduction in other mammals, and critically examined observations attempting to link organochlorines to reproductive and population effects in marine mammals. There is no firm basis to conclude that the contaminants reviewed herein have affected baleen whale populations. Although more information on contaminants in baleen whales would be of value, as a matter of priority, research and management actions should focus on reducing human-caused mortality and increasing habitat carrying capacity for these species.

Metabolism of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane in the mouse

The metabolites of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD) found in the urine of female Swiss mice are reported. The metabolites of DDT are DDD, 1-chloro-2,2-bis(p-chlorophenyl)ethene (DDMU), 1,1-dichloro-2-bis(p-chlorophenyl)ethene (DDE), 2,2-bis(p-chlorophenyl)acetic acid (DDA), 2-hydroxy-2,2-bis(p-chlorophenyl)acetic acid (alpha OH-DDA) and 2,2-bis(p-chlorophenyl)ethanol (DDOH), while DDD afforded DDMU, DDE, DDA, alpha OH-DDA and DDOH. The relative excreted levels of DDA and DDOH and the absence of 2,2-bis(p-chlorophenyl)acetaldehyde (DDCHO) are not consistent with the generally accepted pathway for DDA formation, which involves sequential metabolism of DDT and DDD via DDOH to afford DDA. The quantitative results are interpreted to mean that DDA is formed by hydroxylation at the chlorinated sp3-side chain carbon of DDD to give 2,2-bis(p-chlorophenyl)acetyl chloride (DDA-Cl), which in turn is hydrolyzed to DDA. The excretion of alpha OH-DDA from both DDT- and DDD-treated mice has never been previously observed. It is suggested that this metabolite arises from the initial epoxidation of DDMU, a metabolite of DDT and DDD, to yield 1,2-epoxy-1-chloro-2,2-bis(p-chlorophenyl)ethane (DDMU-epoxide). This chloroepoxide is then hydrolyzed and oxidized to produce the alpha OH-DDA.

Metabolism of a DDT metabolite via a chloroepoxide

The 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethene (DDT) metabolic intermediate 1-chloro-2,2-bis(p-chlorophenyl)ethene (DDMU) is partially metabolized in vivo by mice to 2-hydroxy-2,2-bis(p-chlorophenyl)acetic acid (alpha OH-DDA) and other metabolites which are excreted in urine. The subsequent DDT metabolic intermediates 1-chloro-2,2-bis(p-chlorophenyl)ethane (DDMS) and 1,1-bis(p-chlorophenyl)ethene (DDNU) are metabolized to alpha OH-DDA to a much lesser extent. These results imply that DDMU may be metabolized via an alpha-chloroepoxide. The authentic DDMU-epoxide, which after oral administration is excreted as alpha OH-DDA, is mutagenic in the Ames assay, and thermally rearranges rapidly to the corresponding alpha-chloroaldehyde, 2,2-bis(p-chlorophenyl)-2-chloroacetaldehyde (alpha Cl-DDCHO). As expected alpha Cl-DDCHO yielded the same urinary metabolites as DDMU-epoxide. This suggested metabolic pathway for DDMU via a chloroepoxide intermediate may account for the tumorigenicity of DDT in mice.

Metabolism of 14C-DDT in the mouse and hamster

1. When 1,1-bis(p-chloro(14C)phenyl)-2,2,2,-trichloroethane (DDT) was fed to CF-1 mice and Syrian golden hamsters, conjugates of bis(p-chlorophenyl)-acetic acid (DDA) were the major urinary metabolites. As well as DDA-glycine, DDA-alanine and DDA-glucuronic acid previously identified, a new conjugate with serine is reported. 2. Small amounts of non-polar metabolites were detected in urine. Mouse urine contained DDE, whereas this was never detected in hamster urine. The relevance of this finding to the tumorigenicity of DDT in mice, compared with its inactivity in this respect in hamsters, is discussed.