Moms' exposure to PAHs at work raises risk of rare birth defect.
Lupo, PJ, PH Langlois, J Reefhuis,CC Lawson, E Symanski, TA Desrosiers, ZG Khodr, AJ Agopian, MA Waters, KN Duwe, RH Finnell, LE Mitchell, CA Moore, PA Romitti, GM Shaw and the National Birth Defects Prevention Study. 2012. Maternal occupational exposure to polycyclic aromatic hydrocarbons and gastroschisis among offspring in the National Birth Defects Prevention Study. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.1104305.
For the first time, researchers have established a link between a women's workplace exposure to chemicals known as PAHs during early pregnancy and a higher risk of delivering a baby with a rare birth defect called gastroschisis.
Gastroschisis is a type of hernia. Babies with this condition are born with their intestines – and sometimes other organs – protruding through a hole next to their belly button.
Surgery is needed to place the organs back inside the body and repair the rupture. The babies may have trouble feeding, digesting food and absorbing nutrients.
In animal studies, polycyclic aromatic hydrocarbons, or PAHs, have been linked to multiple birth defects, including gastroschisis. In humans, cigarette smoke – which contains PAHs – also has been linked to this birth defect.
However, no previous human studies had looked at the association between workplace exposure to PAHs and gastroschisis. According to the authors, assessing workplace exposure to PAHs is important because “more than 95 percent of employed women in the United States remain employed during pregnancy” and “an increasing number of women are being exposed in their jobs to chemicals that can harm the fetus.”
PAHs are a group of more than 100 different chemicals naturally found in coal, coal tars, oil, wood, tobacco and other organic materials. They enter the environment when these materials aren't burned completely. Exposure occurs in many workplaces, including oil and gas production facilities and coal-fired power plants. Because PAHs are formed when meat is cooked at high temperatures, restaurants also can be a source of exposure.
In the study, mothers were asked about the jobs they held during the critical window of development for this birth defect – the month before getting pregnant through the third month of pregnancy. Based on their responses, trained staff determined whether the mother was potentially exposed to PAHs in her job. Researchers then compared potential workplace exposure to PAHs in mothers whose babies were born with this birth defect with those whose babies were born without any major birth defects.
Researchers found that mothers who were exposed to PAHs had 1.5 times the risk of having a baby with gastroschisis compared to women who were not exposed to PAHs at work. This was only found in women older than 19 years of age, which is notable because young maternal age is a known risk factor for this birth defect.
The authors suggest that the underlying mechanism for this birth defect may differ between mothers who are older than 19 years and those who are younger. The authors also do not discard the possibility that babies of older women may be predisposed to gastroschisis because these mothers have been exposed to PAHs for a longer time in their jobs.
The researchers did not assess PAH exposures in biological or environmental samples, which would have more accurately ascertained and characterized PAH exposure. Further research measuring exposures in urine or blood samples and monitoring air is needed to verify exposures and the increased risk.
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