Is it time to bring back JunkScience.com’s DDTees?
Today’s New York Times article “As an Insecticide Makes a Comeback, Uganda Must Weigh Its Costs” states:
But the United States banned the use of DDT in 1972 over the chemical’s hazardous environmental impact. Studies have also linked DDT to diabetes and breast cancer. One examination of the consequences of using DDT to fight malaria in sub-Saharan Africa, conducted by the National Institute of Environmental Health Sciences, said the chemical might have increased infant deaths. [Emphasis added]
I traced the diabetes claim to a study published in the July 2009 Environmental Health Perspectives. Aside from the usual fatal flaws of weak association epidemiology, this study’s assertion that DDT metabolite DDE was associated with incident diabetes is laughable since the average body mass index (BMI) of the study subjects was 33.2 — e.g., meaning that the average study subject was likely to be obese (check out this chart to see what height/weight combos make for a BMI of 33+).
Moreover, no significant associations were reported for study subjects with a BMI less than 29.
I don’t know whether obesity leads to diabetes or diabetes leads to obesity, but there’s no evidence that DDT is involved.
What about infant deaths?
The National Institute of Environmental Health Sciences study referred to by the New York Times doesn’t even try to associate DDT with nonmalarial infant death. It instead only estimates nonmalarial deaths that may be associated with DDT spraying, the alleged “association” being based on three studies “suggesting” that DDT exposure may increase pre-term delivery and small-for-gestational-age births, and shorten the duration of lactation.
Here’s my quick take on those three studies:
- Association between maternal serum concentration of the DDT metabolite DDE and preterm and small-for-gestational-age babies at birth is an effort to retrospectively blame DDT for premies and underweight births 35 years after the births. But this can’t be credibly done with biased data and weak/inconsistent statistical associations.
- DDE and Shortened Duration of Lactation in a Northern Mexican Town reports statistically insignificant results.
- Polychlorinated Biphenyls (PCBs) and Dichlorodiphenyl Dichloroethene (DDE) in Human Milk: Effects on Growth, Morbidity,and Duration of Lactation confounding risk factors were not considered in a multivariate regression model (i.e., all at the same time), so its hard to blame DDT on even a statistical basis.
So contrary to the New York Times‘ assertion, there is no credible evidence that DDT has anything to do with diabetes, heart disease or infant deaths. Moreover, given that one million children under the age of five die every year from malaria, even if DDT did increase the risk of diabetes, breast cancer and infant death, those risks would be better than the alternative. While the Times misinforms millions are dying needlessly.