The weighty problem of POPs.
Valvi, D, MA Mendez, D Martinez, JO Grimalt, M Torrent, J Sunyer and M Vrijheid. 2011. Prenatal concentrations of PCBs, DDE, DDT and overweight in children: A prospective birth cohort study. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.1103862.
Children exposed to certain persistent chemicals in the womb have a higher risk of being overweight, according to research published in the journal Environmental Health Perspectives.
The findings provide new evidence of the negative health effects of exposure to contaminants known as POPs – shorthand for persistent organic pollutants. The results add to growing evidence that suggests POPs – by acting as endocrine disruptors – can influence weight gain.
POPs include a wide variety of long-lasting chemicals that collect in fat and accumulate in wildlife and people. A variety of industrial processes either use or unintentionally produce and release POPS. Some were made as pesticides – such as DDT – and others as electrical insulators – namely, polychlorinated byphenyls (PCBs). Decades ago, countries worldwide have banned the use of many of the POPs – including PCBs.
Yet they still occur in wildlife and humans at levels that can cause health concerns. Exposure can lead to a wide range of health consequences, including effects on the nervous and reproductive systems. POPs can also act as endocrine disruptors and disrupt hormone function.
The developing fetus is exposed to POPs passed from the mother through the placenta. In general, young children are particularly susceptible to POPs' toxicity because they have yet to develop ways to detoxify chemicals in the body.
To explore the link between POPs and obesity, the scientists followed 344 children on the Spanish Island of Menorca – which has no industrial sources of POPS – from birth to 6.5-years-old. They measured concentrations of PCBs, DDT and DDE in cord blood at birth. They measured each child’s body mass index (BMI) at age 6.5 and administered a questionnaire about their diets. Children with a high BMI – in the heaviest 15 percent as defined by the World Health Organization – were considered overweight. They accounted for other factors that can influence body weight, such as birth weight and whether or not the mother smoked.
They found that both PCB and DDE exposure led to an increased risk of weight gain in children as assessed by BMI scores. The link between being overweight and PCB and DDE levels in chord blood was stronger in girls than boys. DDT was only associated with weight gain in boys, especially in children with average or above average fat intakes. In some cases, children with higher POPs exposures were almost twice as likely to be overweight compared to children with lower exposures, depending on the pollutant and gender.
The study suggests that POPs exposure in the womb may be linked to obesity risks as the children grow but the risks vary between boys and girls.
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