Exposure to DDT

There is some evidence for chemically mediated endocrine disruption in amphibians. The egg yolk protein, vitellogenin, is inducible in amphibians by exposure to DDT. " Males of the short clawed toad Xenopus laevis given 250 fig/g or 1 fig/g o,p -DDT for seven days have been shown to produce vitellogenin, although the induction was less than that achieved by treatment with 1 fig/g of either 17/1-oestradiol or diethylstilboestrol. Research has also shown that endocrine disrupting chemicals can alter sex ratios in wild populations of certain species PCB congeners and organochlorine compounds have been linked with male domination of sex ratios in polluted compared to unpolluted sites. ... 

Iwaniuk, A.N., Koperski, D.T., and Cheng, K.M. et al. (2006). The effects of enviromnental exposure to DDT on the brain of a songbird Changes in structures associated with mating and song. Behavioural Brain Research 173, 1-10. 

In mice, exposure to DDT during gestation and in the neonatal stage has also caused developmental neurotoxicity, in the form of behavioral deficits in the learning process, that persisted into adulthood. Human studies have suggested that alterations in functions that are hormonally controlled such as duration of lactation, maintenance of pregnancy, and fertility may occur from DDT exposure. ... 

Laws ER Jr, Curley A, Biros FJ Men with intensive occupational exposure to DDT—a clinical and chemical study. Arch Environ Health 15 766-755, 1967... 

Laws ER Jr, Maddrey WC, Curley A, Burse VW Long-term occupational exposure to DDT. Arch Environ Health 27 318-321, 1973... 

Siddiqui, M.K.J., Saxena, M.C., Misra, U.K., Krishna Murti, C.R., 1981b. Long-term occupational exposure to DDT. Arch. Environ. Hlth. 48, 301-308. 

Similar to those observed for environmental samples, human exposure to DDTs in Vietnam were very high and among the highest ranks for the developing countries and developed nations (Minh et al., 2004). As discussed earlier, high DDT contamination in Vietnam has been apparent in many environmental samples. This is also the case for humans and this fact raises concern over the possible toxic impacts on human health. This result suggests that Vietnam is a potential source of DDTs in the south Asian region. 

In addition to the studies on the trends of POP levels in the environmental samples, time trends of human exposure is also an important issue for understanding the long-term toxic impacts on general population. Minh et al. (2004) assessed the decline in the rate of human exposure to DDTs and PCBs over the 10 years period (1989 and 2001). A first-order kinetic approach was used to estimate the declining rate of DDTs and PCBs in human breast milk collected from Vietnam. The decrease in the POPs such as DDTs, PCBs, and HCHs in human breast milk was suggested to follow first-order kinetic (Noren Meironyte, 2000). Another important factor for the assessment is the half-life (Aieci, 2) defined as the duration in which initial concentrations decrease to a half. On the basis of the residue concentrations of OCs in 1989 reported by Schecter et al. (1989a) and the levels in 2001 obtained by Minh et al. (2004), the rate constant and tdeci/2 were estimated. 

Tissues such as fat, blood or liver can be examined for residues of the more stable chlorinated hydrocarbon pesticides. In most cases these tissues are available as a result of elective survery, autopsy or biopsy. Exposure to DDT results in some storage of the parent compound in body fat. A large portion, however, is metabolized and stored as DDE (jJ). Aldrin and hepta-chlor are similarly transformed and stored as dieldrin and hepta-chlor epoxide. Levels of the urinary metabolite DDA have been used to assess exposure or body burden of DDT (10, 11, 12). Hexachlorobenzene and the various isomers of hexachlorocyclo-hexane are stored in fat as the parent compound but a small... 

Herrera-Portugal C, Ochoa H, Franco-Sanchez G, Yanez L, Diaz-Barriga F (2005) Environmental pathways of exposure to DDT for children living in a malarious area of Chiapas, Mexico. Environ Res, 99(2) 158-163. 

Triana, with a population of 600, is located at the confluence of Indian Creek and the Tennessee River. From 1947 until 1971 DDT was manufactured in a plant 10 kilometers from Triana. Several thousand tons of DDT industrial waste accumulated in the sediments of a tributary of Indian Creek. Locally caught fish have had total DDT residual levels up to 100 times the tolerance of 5 parts per million (ppm) set by the Food and Drug Administration. The high levels of DDT residues in the 12 persons surveyed were suspected of resulting from their consuming fish which had accumulated DDT from sediments. The task at hand was to measure residents exposure to DDT and relate it, if possible, to health effects in the population—an example of a cross-sectional study. 

Smrek, A.L. Jones, B.T. Cross-sectional study of a community with exceptional exposure to DDT. JAMA, 1981, 245, 1926-1930. 

Isomers of hexachlorocyclohexane (HCH) are found in air, soil, water, food and even breast milk. Lindane is used in large quantities in agriculture and forestry as a wood preservative as well as in veterinary medicine. Provided that the required safety measures are adhered to, no liver damage occurs during the production of lindane. On the other hand, liver cell necrosis was observed in animal experiments after HCH isomers were added to the feed a carcinogenic effect was seen after long-term administration. An increased toxic potential is to be expected when there is simultaneous exposure to DDT, PCB, contraceptives, etc. 

Ortelee (12) studied a total of 40 men employed in the manufacture or formulation of DDT for up to 8 years and concluded that, with the exception of some minor skin and eye irritations, no illness was associated with exposure to DDT in this group of workers. 

Laws et al (1 ) studied a group of 35 men who had been employed in the production of DDT for more than five years. The authors concluded that they had found no ill effects, including cancer, attributable to exposure to DDT. 

In another example, this one from Borneo, the relationship between cats and DDT application takes an unusual turn that may or may not involve biomagnification. DDT had been sprayed on the longhouses of the natives for mosquito control. Domestic cats, reported to be at the top of a short terrestrial food pyramid, were supposedly dying from exposure to DDT through the consumption of geckos and roaches that lived in the thatched roofs of the long-houses. The death of the cats was reported to be associated with an explosion in the rodent population, which consumed stored crops. 

---