Monday, May 11, 2009

Human Health Effects of DDT

Several folks, after reading my last post on DDT, have asked me about DDT's health effects on people. Their point: while DDT may prevent some people from dying of malaria isn't there a cost to their long-term health?

Once again, context is key. The major negative effects of DDT have been on animals--particularly birds and fish. This is very important and not something the environment can sustain, especially since DDT accumulates in any animal's fat tissue (including people's).

As far as we know, DDT's health effects on people are minimal compared to that on fish and birds--something that was straightforwardly acknowledged last year on the website of the World Resources Institute, where Al Gore serves on the board of directors.

More recently there has been some research to indicate that DDT may act as a hormone disrupter and affect fertility as well as promote premature delivery. Animal studies have also suggested a possible cancer risk--but once again that would presumably be at very high dose.

So, if you are just going to look at health effects in people, the scales tip toward using DDT in those parts of sub-Saharan Africa in particular where it would be most helpful.

This is the same kind of cost-benefit ratio that is seen with giving polio vaccines that also sometimes cause the disease itself.

The cost to the environment is the more worrying issue--and something that needs to be addressed whenever DDT is used as part of an anti-malaria program. Fortunately, the amount of DDT that is needed for residential spraying is small. South Africa has shown the spraying can be done with minimal impact on the environment--by training sprayers and making sure no DDT is diverted to agricultural use.

It's a fascinating topic--and hard to find experts who are truly impartial. In my experience of reporting on the topic, people from both the left and right use DDT to score political points without regard to what facts are like on the ground.

Makes me think I should look more closely at the latest report that the World Health Organization has decided to work towards the total elimination of DDT, perhaps even in malarial zones.

Related posts:
Back and Forth on DDT Again
Can Malaria Be Eradicated?

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