(Beyond Pesticides, July 25, 2011) Exposure to certain pesticides and polycyclic aromatic hydrocarbons (PAHs) in the womb has been linked to neural tube defects, which lead to conditions such as spina bifida, according to researchers at Peking University in China. The study finds elevated levels of the organochlorine pesticides DDT, alpha-hexachlorocyclohexane (a lindane contaminant) and endosulfan, as well as PAHs in the placentas of women who had babies or aborted fetuses with such birth defects. The study, “Association of selected persistent organic pollutants in the placenta with the risk of neural tube defects,” was published July 8, 2011 in the online edition of the Proceedings of the National Academy of Sciences.
While most organochlorine pesticides are banned or restricted, they still continue to cause problems decades after their widespread use has ended. This study reinforces the need for a more precautionary approach to regulating pesticides and industrial chemicals. Once released into the environment, many chemicals can affect health for generations, either through persistence or genetic means.
PAHs are a group of over 100 different chemicals that are formed during the incomplete burning of coal, oil and gas, garbage, or other organic substances like tobacco or charbroiled meat. PAHs are usually found as a mixture containing two or more of these compounds, such as soot. The Agency for Toxic Substances and Disease Registry (ATSDR) says exposure to PAHs usually occurs by breathing air contaminated by wild fires or coal tar, or by eating foods that have been grilled.
According to the National Institute of Child Health and Human Development, part of the National Institutes of Health (NIH), neural tube defects are birth defects of the brain and spinal cord. The two most common neural tube defects are spina bifida and anencephaly. In spina bifida, the fetal spinal column doesn’t close completely during the first month of pregnancy. There is usually nerve damage that causes at least some paralysis of the legs. In anencephaly, much of the brain does not develop. Babies with anencephaly are either stillborn or die shortly after birth. They are one of the most common birth defects, occurring in approximately one in 1,000 live births in the U.S.
While insufficient levels of folic acid, a type of B vitamin, before and during pregnancy are solidly linked to neural tube defects, environmental pollutants have also been suspected. Previous studies have linked PAHs to this type of birth defect, but only relying on questionnaires or blood tests alone. By examining the placenta, the researchers were able to see what was actually reaching the fetus.
The researchers told Reuters that they recruited pregnant women in four rural counties in northern Shanxi province where neural tube defects occur in 14 out of every 1,000 babies, far higher than the national average. Women whose placentas had higher than average levels of the PAH chemicals from burning coal were 4.5 times more likely to have babies with defects, while those with higher than average levels of pesticides were around 3 times more likely to have babies with defects.
For more information on diseases linked to pesticide exposure, see Beyond Pesticides’ Pesticide-Induced Diseases Database.