This article is more than 5 years old. Information may no longer be current.
Prenatal exposure to endocrine-disrupting chemicals tied to lower IQ in boys
Click Here to Manage Email Alerts
Early prenatal exposure to a mixture of endocrine-disrupting chemicals found in common consumer products is associated with lower intellectual functioning among boys at age 7 years, according to findings published in Environment International.
In an analysis of more than two dozen endocrine-disrupting chemicals (EDCs) measured in the urine or blood of more than 700 mothers, researchers identified bisphenol F (BPF) as the primary chemical of concern, suggesting that the bisphenol A (BPA) replacement compound may not be any safer for children.
“When mothers are exposed to chemicals found in everyday consumer products during early pregnancy, it can have a lasting impact on her child’s brain development,” Eva Tanner, PhD, MPH, a postdoctoral researcher in the department of environmental medicine and public health at the Icahn School of Medicine at Mount Sinai, told Endocrine Today. “Some newer chemicals we thought were safer may actually be just as harmful. Protecting child health over the long term will require a joint effort. We need consumers to demand products with fewer chemicals, industry to innovative, and our governments to invest more in biomonitoring and health research.”
Assessing exposure
Tanner and colleagues analyzed data from 718 mother-child pairs from the Swedish Environmental Longitudinal, Mother and Child, Asthma and Allergy (SELMA) study, a population-based study of pregnant women recruited during their first trimester between 2007 and 2010 (mean maternal age at recruitment, 31 years; baseline weight, 69 kg; 44% nulliparous; 6% smokers; mean maternal IQ, 115). Women provided first-morning urine and fasting blood samples during their first prenatal visit (median, 10 weeks). The urine samples were analyzed by liquid chromatography-tandem mass spectrometry to quantify 24 urinary analytes; plasma was analyzed for 22 persistent organic pollutants (chlorinated or brominated). Researchers used weighted quantile sum (WQS) regression to assess the association between levels of 26 EDCs measured during the first trimester with offspring IQ scores at age 7 years, measured via the Wechsler Intelligence Scale for Children. To evaluate generalizability, the researchers conducted repeated holdout validation, a machine learning technique.
Within the cohort, mean gestational age was 40 weeks and mean birth weight was 3,641 g, with 64% of children fully or partially breastfed until age 6 months. Mean child IQ score was 100.
Researchers observed a mean 2.2-point decline in full-scale IQ score for an interquartile range change in the WQS index (EDC mixture) among all children (95% CI, –3.4 to –1). Stratified by sex, researchers observed a mean 3.6-point decline in IQ among boys (95% CI, –5.3 to –2) and a 1.8-point decline among girls (95% CI, –3.5 to 0) for an interquartile range change in the WQS index. The findings were attenuated in analyses using repeated holdout validation, with researchers finding a 0.8-point decline in IQ for an interquartile range change in the WQS index among all children (95% CI, –2.1 to 0.5). In sex-stratified analyses, there was a 1.9-point decline in IQ for an interquartile range change in the WQS index (95% CI, –3.6 to –0.2) among boys; however, there was no decline observed among girls.
“Specifically, full-scale IQ scores were nearly 2 points lower among boys for an interquartile range change in the ‘deciled’ WQS index,” the researchers wrote. “This mixture effect encompassed all 26 compounds across several chemical classes. Further evaluation of chemical weights within the WQS index identified phenols, particularly BPF, short-lived pesticides, plasticizers, and perfluoroalkyl substances as chemicals of concern among boys, but persistent chlorinated compounds had consistently lower weights.”
Chemicals of concern
The researchers noted that BPF made the largest contribution to the index with a weight of 14%. Other chemicals of concern included 3-phenoxybenzoic acid (PBA; 9%), 3,5,6-trichloro-2-pyridinol (TCP; 9%), monoethyl phthalate (MEP; 6%), monobenzyl phthalate (MBzP; 4%), perfluorooctanoic acid (PFOA; 6%), perfluorooctane sulfonate (PFOS; 5%), perfluorohexane sulfonic acid (PFHxS; 4%), triclosan (5%) and BPA (4%).
“Many of the chemicals we identified as harmful only stay in the body a short amount of time,” Tanner said. “This means that if a someone takes steps to lower exposure now, the levels detected in their body will quickly decline. However, it can be difficult to know what chemicals are contained in many consumer products since they are not typically labeled. In general, women who are pregnant or trying to become pregnant can reduce exposure by avoiding canned foods, plastics and pesticides.”
Tanner said more research is needed on how specific chemicals influence different areas of a child’s cognitive ability, such as verbal comprehension and reasoning ability.
“We are currently doing further work to understand how BPA and its replacement compounds may impact these different areas,” Tanner said. “Our findings also show that current risk assessment for chemicals can be questioned. When regulators set safety guidelines, they only look at one chemical at a time. However, our results indicate that mixtures of chemicals can be harmful, even when individual chemical levels are low. We are developing ways to incorporate mixtures into risk assessment.” – by Regina Schaffer
For more information:
Eva Tanner, PhD, MPH, can be reached at the Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, New York, NY 10029; email: eva.tanner@mssm.edu.
Disclosures: The authors report no relevant financial disclosures.
Read more about
Click Here to Manage Email Alerts