Ideally, chemicals that are toxic to human health are identified and removed from use. Many such chemicals, known as persistent organic pollutants (POPs), have been studied individually for their ill effects in humans. DDT, for instance, once a widely used insecticide, is now classified as a probable human carcinogen and has not been used in the United States since the early 1970s.1 Other insecticides have similarly been banned but have long half-lives and can persist in the environment for decades. Humans are exposed to POPs mainly through diet, say Ouidir and colleagues, with exposure “nearly ubiquitous.”2
The association between POP exposure during pregnancy and birth weight has not been established, as results from previous studies have been inconsistent, according to researchers.2 In addition, birth weight does not distinguish growth-restricted fetuses from those that are constitutionally small. Therefore, Ouidir and colleagues analyzed maternal plasma levels of POPs and measures of fetal growth. Their research was published in JAMA Pediatrics.2
The investigators examined chemical class mixtures of organochlorine pesticides (OCPs), dioxin-like polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), among other groups of POPs, as well as individual chemicals, in 2,284 nonobese low-risk pregnant women before 14 weeks of gestation. They measured 14 fetal growth biometrics using ultrasonography throughout the women’s pregnancies, with researchers focusing their main findings on head and abdominal circumference and femur length measurements.
The researchers found that the OCP mixture was negatively associated with most fetal growth measures, with a reduction of 4.7 mm (95% confidence interval [CI], -6.7 to -2.8 mm) in head circumference, 3.5 mm (95% CI, -4.7 to -2.2) in abdominal circumference, and 0.6 mm (95% CI, -1.1 to -0.2 mm) in femur length. In addition, exposure to the PCB and PBDE mixtures were associated with reduced abdominal circumference.
OCPs have been associated with adverse effects on the endocrine system, lipid metabolism, and embryonic development. They also can result in hematologic and hepatic alterations.3
The JAMA Pediatrics study authors point out that their findings may not take into account the risk pregnant women with occupational exposure to POPs, or other higher exposure situations, may have, as the POP concentrations in their sample were low compared with levels in a nationally representative sample of pregnant women. They say that their findings provide insight into the “implications of POPs for fetal growth when exposures are low and suggest that, even if exposures could be successfully minimized, these associations may persist.”2