Vol. 38, No. 18

2-4-2009
By:

Ask the Expert, 2/5/09

Is the insecticide DDT (Dichloro-Diphenyl-Trichloroethane) still considered a danger?
Yes, for several reasons. While the product itself is not terribly dangerous, it breaks down into a byproduct called DDE. While DDE is not insecticidal, it is much more persistent in the environment than DDT. DDE has the capacity to do various nefarious things. It can bioconcentrate from water into aquatic organisms. It also can get passed up the food chain. Because DDE is very soluble in fat tissues and because there’s more fat in organisms as you move up the food chain, the concentration increases as you ascend. By the time you hit the upper reaches of the food chain, which includes humans, it can reach hazardous levels. That doesn’t mean instant death, but it includes negative impacts such as learning disabilities on the low end and organ toxicity of various kinds on the high end. But it’s rare to get that these days since we stopped using DDT in this country in 1972.

What spurred the DDT investigation?
In 1962, there were two factors that made a huge difference. Biologist Rachel Carson published a book called Silent Spring, and in it she showed for the first time that when you apply insecticides in the environment, they don’t just do their jobs and go away. They stick around and do things we didn’t intend them to do. Also, a new technology called gas-liquid chromatography (GLC) came into being. It was possible to analyze environmental samples for minute quantities of DDT. All of a sudden, when collecting the samples, it became clear DDT was everywhere, including the polar ice caps, where it had never been used. Like every insecticide, it hitches a ride on prevailing weather patterns. We had a new picture of insecticides and it turns out it was causing major environmental and health problems. We still have DDT in our tissues, but it’s not a health hazard. Recently someone decided if we had DDT around again, we could get rid of malaria, and it just makes me want to cry. We might be able to use it for a year, but we’ll have resistant insects again as well as a huge environmental problem. In specific cases we might be able to use it, but not as liberally as we did in the past.  

Is it still illegal to produce in the US?
The EPA set standards of what can and can’t be used, and the EPA said DDT does not meet those standards. Other places in the world have not done that. The risk assessment equation changes, so it might make sense for them to control malaria with DDT, and I respect that, but DDT is not a panacea even for those problems. It is surprising that DDT still shows up in environmental samples in this country and that’s because of the weather patterns. The levels aren’t high, but they’re there. We still don’t know if low levels have any consequences. There haven’t been any studies. We banned it originally because we thought it caused cancer, but we could never prove it.

onCampus Home