DDT and DDT Metabolites
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Structure of DDT (di-chlorodiphenyltrichloroethane) |
| DDT was responsible for helping to stop malaria, typhus and other insect-borne illnesses. It also helped provide food for the world's exploding population, control body lice on World War II soldiers, and it's inventor even won the noble prize for it (O'Shea, 1999). Despite these positive accomplishments, DDT has also done a great deal of damage to the environment, especially aquatic species. |
| DDT and its metabolites are the best known and most widely reported organochlorines found in marine mammal tissue (O'Shea, 1999). DDT breaks down gradually into toxic metabolites. The metabolites of DDT that are commonly found in marine mammal tissue include DDE and DDD (O'Shea, 1999). DDE (dichlorodiphenylethylene) is the most stable and toxic of the DDT metabolites (USGS). Unfortunately, it is also the most widespread and abundant metabolite found in marine mammal blubber (O'Shea, 1999). |
| DDT is not only harmful to marine mammals, it also has high carcinogenic potential for humans. Due to this, it has been banned in many developed countries. DDT has been banned for the past 20 years in the U.S. but it is still found concentrated in soils, freshwater sediments, and aquatic vertebrates (GPA). |
| Worldwide, the use of DDT has been greatly reduced and concentrations in fish and wildlife have declined (USGS). A recent study showed that sea lions off the California coast carried one hundred times less DDT than they did two decades earlier (UCSU). |
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However, a study done in on the St. Lawrence River in Canada shows that there are still continuous inputs of DDT into the St. Lawrence River Basin and that DDT is making its way into the marine mammals of the region (Pham, 1996). This study also showed that release of DDT to the marine environment is often higher in the spring when the snow pack is melting (Pham, 1996).
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Diagram of Build up of DDT and Other Contaminants
in Marine Mammals
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This diagram shows the buildup of contaminants in male and non-reproducing female marine mammals. The contaminants are passed from mother to offspring during nursing. Contaminant levels drop as weaning occurs and the body begins to dispose of some of the contaminants. Levels then begin to rise and continue to do so for the rest of the animal's life. |
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This diagram shows the buildup of contaminants in female marine mammals. In the early years the same explanation as above applies. Then, as these females reproduce, they pass on the contaminants in their bodies to their nursing young. The small oscillations in this graph represent the births and nursing of young (approximately 2 years between each birth). |
| Source: Contaminant Anyalysis of Organochlorines in Blubber Biopsies from Blue Whales in the St. Lawrence |
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Blue Whale |
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