A few decades back one of the commonest environmental causes of intellectual disabilities among babies was exposure to lead and mercury. A new study reveals that while exposure to these heavy metals is on the decline, there is risk of other toxic chemicals. Researchers have found that chemicals present in pesticides and flame retardants could be causing over a million cases of intellectual disabilities among babies between 2001 and 2016.
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The study titled, “Trends in neurodevelopmental disability burden due to early life chemical exposure in the USA from 2001 to 2016: A population-based disease burden and cost analysis,” was published in the latest issue of Molecular and Cellular Endocrinology this week.
Researchers from NYU Grossman School of Medicine specifically noted and many cases of low IQ and cognitivie disabilities among children were linked to these toxic chemicals. They wrote that as many as 27 million IQ points were lost in 2001 and 2002 and now in 2015 and 2016, there has been a 9 million loss of IQ points due to exposure to these toxic chemicals. Despite the drop in the number of cases with intellectual disabilities due to environmental toxin exposure, the researchers warn that too many children are still being affected.
The team of researchers explain that there has been a shift in the culprit chemicals that may be harming the babies. They noted that flame retardants called polybrominated diphenyl ethers (PDBEs), and organophosphate pesticides have become one of the biggest threats to cognitivie development in children. Their extensive analysis showed that there was an increase from 67 percent to 81 percent of cognitive loss between 2001 and 2016 due to organophosphate pesticides and PDBE exposure among the study population.
Lead researcher Abigail Gaylord, MPH, a doctoral candidate in the Department of Population Health at NYU Langone explained, “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. Unfortunately, the minimal policies in place to eliminate pesticides and flame retardants are clearly not enough.”
She and her colleagues explained that most of the toxic chemicals they analyzed in their study were found at home. They added that while some are part of the furniture and upholstery, others are part of the canned foods including tuna fish etc. These toxic chemicals, they added, could damage not only the brain and its development but also damage hormone secreting endocrine organs such as the thyroid. If the hormonal balance of these organs is affected, there is also a risk of impaired brain development explain the researchers. These may lead to behavioural problems and also learning difficulties and autism.
For this study the team looked at every day exposure of 1,190,230 children to everyday use substances containing any of these toxic chemicals including PDBE, organophosphates, lead and methyl mercury. These children were found to have some form or other of an intellectual disability and they were followed up for 16 years during the study. Samples of blood from women of reproductive age and children aged five were analyzed for these toxic chemicals. The cost burden of the intellectual disabilities of these kids was also estimated. An estimated loss of IQ points after exposure to each of the chemicals was also analyzed and estimated. This study is the largest of its kind and has been conducted for the longest duration. This makes the findings robust and reliable say experts. The data came from the National Health and Nutrition Examination Survey.
Results revealed that exposure to these chemicals led to disabilities that cost the nation $7.5 trillion in direct or indirect expenditures. These costs included the loss of productivity as well as other costs to the society. Senior author of the study, Leonardo Trasande, MD, MPP, the Jim G. Hendrick, MD Professor at NYU Langone Health, added, “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.” Trasande is also the chief of environmental pediatrics in the Department of Pediatrics at NYU Langone. The results also showed that each IQ point lost due to exposure to these toxic chemicals was linked to a cost burden of $22,268. For every child with an intellectual disability, the cost to the nation was estimated at $1,272,470.
Researchers advise that choice of household products and foods with these pesticides and chemicals should be avoided. Trasande said, “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.” She added that this could be the proverbial tip of the iceberg and the actual effects of the chemicals on the brain may be far more than what was estimated. She said, “All the more reason we need closer federal monitoring of these substances.” As a next step the team would study the effects of exposure to these chemicals on populations from other nations as well.
Abigail Gaylord, Gwendolyn Osborne, Akhgar Ghassabian, Julia Malits, Teresa Attina, Leonardo Trasande, Trends in neurodevelopmental disability burden due to early life chemical exposure in the USA from 2001 to 2016: A population-based disease burden and cost analysis, Molecular and Cellular Endocrinology, 2020, 110666, ISSN 0303-7207, https://doi.org/10.1016/j.mce.2019.110666.