Nowadays, dichlorodiphenyl-dichloroethylene (DDE), the main degradation product of the pesticide dichlorodiphenyl trichloroethane (DDT), is detected in all adults and in nearly all newborns in most countries worldwide.1^–4 Thus, even a small increase in the risk of obesity that DDE might confer on offspring would have important implications.5 6 This is the main finding that Karmaus et al (see page 143) report in this issue: the weight and BMI of offspring in adulthood were significantly related to the extrapolated prenatal DDE levels of their mothers.7 Specifically, compared to maternal DDE levels below 1.5 μg/l, the authors observed an increase in offspring BMI of 1.65 when prenatal DDE was 1.5–2.9 μg/l, and an increase of 2.88 if DDE was greater than 2.9 μg/l. These concentrations of DDE are common worldwide; in cord blood, amniotic fluid and serum of pregnant women, DDE is often in the range 0.6–1.9 μg/l or 15–500 ng/g.1 4 8 9

It is often overlooked that human concentrations of DDE can vary more than a 1000-fold within the same population1; in the United States, for example, concentrations range from less …