More neurodevelopmental disability caused by flame retardants, pesticides than heavy metals

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Though adverse outcomes from childhood exposures to lead and mercury are on the decline in the United States, like due to restrictions on the use of heavy metals, exposure to toxic chemicals including flame retardants and pesticides still resulted in more than a million cases of intellectual disability between 2001 and 2016, according to a new study published in the journal Molecular and Cellular Endocrinology.

New York University Grossman School of Medicine researchers analyzed polybrominated diphenyl ethers (PDBEs), organophosphate, lead, and methylmercury exposures in blood samples from women of childbearing age and 5-year-olds. Data on women and children was obtained from the National Health and Nutrition Examination Survey.

The researchers used results from several previous environmental health studies to estimate the annual number of intelligence quotient (IQ) points lost per unit of exposure to each of the four main chemicals in the study. Then, they estimated the lost productivity and medical costs over the course of the children's lives linked to long-term intellectual disability using a second algorithm, which valued each lost IQ point at $22,268 and each case of intellectual disability at $1,272,470.

The scientists found that IQ loss from the toxic chemicals analyzed dropped from 27 million IQ points in 2001 and 2002 to 9 million IQ points in 2015 and 2016. While the overall decline is promising, the researchers said, the findings also identify a concerning shift in which chemicals represent the greatest risk.

 Among toxin-exposed children, the researchers found that the proportion of cognitive loss that results from exposure to chemicals used in flame retardants, PDBEs, and organophosphate pesticides increased from 67 percent to 81 percent during the same study period. As the target of significantly fewer restrictions, flame retardants and pesticides now represent the bulk of that cognitive loss, the researchers said.

The substances analyzed are found in household products from furniture upholstery to tuna fish and can build up in the body to damage organs, researchers said. Heavy metals, lead, and mercury are known to disrupt brain and kidney function. In addition, they, along with flame retardants and pesticides, can interfere with the thyroid, which secretes brain-developing hormones. Experts say exposure at a young age to any of these toxins can cause learning disabilities, autism, and behavioral issues.

In the investigation, the researchers found that everyday contact with these substances during the 16-year study period resulted in roughly 1,190,230 children affected with some form of intellectual disability. Overall childhood exposures cost the nation $7.5 trillion in lost economic productivity and other societal costs.

While exposure to these chemicals persists despite tightened regulations, Americans can help limit some of the effects by avoiding the use of household products or foods that contain them, according to Leonardo Trasande, MD, MPP, senior study author.

"Frequently opening windows to let persistent chemicals found in furniture, electronics, and carpeting escape,” said Trasande, “and eating certified organic produce can reduce exposure to these toxins.”