Flame retardants and pesticides overtake heavy metals as biggest contributors to IQ loss
January 14, 2020
Science Daily/New York University
Adverse outcomes from childhood exposures to lead and mercury are on the decline in the United States, likely due to decades of restrictions on the use of heavy metals, a new study finds.
Despite decreasing levels, exposure to these and other toxic chemicals, especially flame retardants and pesticides, still resulted in more than a million cases of intellectual disability in the United States between 2001 and 2016. Furthermore, as the target of significantly fewer restrictions, experts say, flame retardants and pesticides now represent the bulk of that cognitive loss.
NYU Grossman School of Medicine researchers found that IQ loss from the toxic chemicals analyzed in their study dropped from 27 million IQ points in 2001 and 2002 to 9 million IQ points in 2015 and 2016.
While this overall decline is promising, the researchers say, their 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, called polybrominated diphenyl ethers (PDBEs), and organophosphate pesticides increased from 67 percent to 81 percent during the same study period.
"Our findings suggest that our efforts to reduce exposure to heavy metals are paying off, but that toxic exposures in general continue to represent a formidable risk to Americans' physical, mental, and economic health," says lead study investigator Abigail Gaylord, MPH, a doctoral candidate in the Department of Population Health at NYU Langone. "Unfortunately, the minimal policies in place to eliminate pesticides and flame retardants are clearly not enough."
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 say. Heavy metals, lead and mercury in particular, 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 their 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.
"Although people argue against costly regulations, unrestricted use of these chemicals is far more expensive in the long run, with American children bearing the largest burden," says senior study author Leonardo Trasande, MD, MPP, the Jim G. Hendrick, MD Professor at NYU Langone Health.
Publishing online Jan. 14 in the journal Molecular and Cellular Endocrinology, the new study is the only long-term neurological and economic investigation of its kind, the authors say. The investigators analyzed PBDE, 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 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.
While exposure to these chemicals persists despite tightened regulations, experts say Americans can help limit some of the effects by avoiding the use of household products or foods that contain them.
"Frequently opening windows to let persistent chemicals found in furniture, electronics, and carpeting escape, and eating certified organic produce can reduce exposure to these toxins," says Trasande, who also serves as chief of environmental pediatrics in the Department of Pediatrics at NYU Langone.
Trasande notes that the impact of these chemicals may be worse than their study can capture since there are far more hazards that affect brain development than the four highlighted in the investigation, and other potential consequences beyond IQ loss. "All the more reason we need closer federal monitoring of these substances," she says.
The study authors say they plan to explore the cost of exposure to endocrine-disrupting chemicals in other countries.
https://www.sciencedaily.com/releases/2020/01/200114101724.htm
Prenatal exposure to flame retardants linked to reading problems
January 10, 2020
Science Daily/Columbia University Irving Medical Center
A new study from researchers at Columbia University Vagelos College of Physicians and Surgeons suggests that prenatal exposure to flame retardants may increase the risk of reading problems.
The study was published in the January 2020 print edition of Environmental International.
An estimated 2 million children have learning disorders; of these, about 80% have a reading disorder. Genetics account for many, but not all, instances of reading disorders.
In the current study, the researchers hypothesized that in utero exposure to polybrominated diphenyl ethers (PBDEs) -- a type of flame retardant that is known to have adverse effects on brain development -- might alter the brain processes involved in reading. (While use of PBDEs has been banned, exposure to the compounds is still widespread because they do not degrade easily in the environment.)
The research team analyzed neuro-imaging data from 33 5-year-old children -- all novice readers -- who were first given a reading assessment to identify reading problems. They also used maternal blood samples, taken during pregnancy, to estimate prenatal exposure to PDBEs.
The researchers found that children with a better-functioning reading network had fewer reading problems. The also showed that children with greater exposure to PDBEs had a less efficient reading network.
However, greater exposure did not appear to affect the function of another brain network involved in social processing that has been associated with psychiatric disorders such as autism spectrum disorder.
"Since social processing problems are not a common aspect of reading disorders, our findings suggest that exposure to PDBEs doesn't affect the whole brain -- just the regions associated with reading," says Amy Margolis, PhD, assistant professor of medical psychology in the Department of Psychiatry at Columbia University Vagelos College of Physicians and Surgeons.
Although exposure to PDBEs affected reading network function in the 5-year-olds, it did not have an impact on word recognition in this group. The finding is consistent with a previous study, in which the effects of exposure to the compounds on reading were seen in older children but not in emergent readers. "Our findings suggest that the effects of exposure are present in the brain before we can detect changes in behavior," says Margolis. "Future studies should examine whether behavioral interventions at early ages can reduce the impact of these exposures on later emerging reading problems."
The paper is titled "Functional Connectivity of the Reading Network is Associated with Prenatal Polybrominated Diphenyl Ether Concentrations in a Community Sample of 5 Year-Old Children: A preliminary study."
https://www.sciencedaily.com/releases/2020/01/200110155258.htm