Friday, January 22, 2010

DDT in Africa

Back when it was released in 1962, Rachael Carson’s Silent Spring was a major jolt to the public consciousness towards pesticides and the environment. The outcry helped found the environmental movement and pushed towards banning the use of DDT in the US in 1972. Unfortunately back then, we didn’t realize to what extent chemicals can remain persistent in the environment long after their discontinuation. And in areas where use was once heavy or heavily contaminated, like a Superfund site, the land remained noxious.

In the early 90s, DDT became a major issue again because it was found that DDT degradation products were toxic to wildlife, particularly alligators. So what kind of group breaking finding could suddenly get the public into a furor and into action once again?

“Abnormally small phalli.”

Aaah, one of my favorite bits of information. Nothing grabs the public’s attention more than a couple of small dicks. Much like BPA, which I talked about earlier this week; DDT and its metabolites are endocrine disrupting chemicals. They act as estrogen mimics leading to feminizing effects in male populations.

This isn’t so much a problem in US but in other parts of the world, DDT use remains high. DDT is so far, the most effective and inexpensive methods for controlling malaria in Africa, where more than 700,000 children die each year (though efficacy is decreasing as mosquitoes are developing resistance). Because of the high exposure to DDT, such as through household spraying, the incidence of urogential defects is incredibly high. Out of more than 3300 African boys studied, 11% were found to have at least one such urogenital defect (which I’ll spare you the details of) compared to the world average which is around 2%. The study found mothers exposed to household spraying were 33% more likely to have a son with such a defect compared to mother unexposed to DDT.

But, mother from villages that do not spray were found to have sons with similar morbidity being at 10%. One explanation is this may be due to DDT residue on food consumed by both villages. It also suggests DDT having generational effects. Most of the villages studied were sprayed between 1945 and 1979, meaning intergenerational impacts may be significant. DDT and its metabolites are known to be passed through breast milk and can remain persistent once in the body. The mother’s body burden, whether exposed directly through spraying or from breast milk, may be leading to the deformities in their sons.

DDT use in Africa remains highly controversial. Persistent organic pollutants such as DDT and PBDE are known to cause chronic toxicity. But how do you weigh out these negatives against the lives saved each year by their use?

No comments:

Post a Comment