Over a million children have developed some form of intellectual disability over the past two decades after being exposed to chemicals including flame retardants, pesticides, lead, and mercury, a study has revealed.
In recent years, pesticides and flame retardants have overtaken lead and mercury as the chemicals responsible for the biggest loss of IQ among children, according to the paper published in the journal Molecular and Cellular Endocrinology.
The researchers believe this is due to regulations cracking down on the use of chemicals known to effect the parts of the body in charge of producing hormones, called endocrine disruptors. For instance, lead has been banned from gasoline, paint and drinking water systems in the U.S.
The researchers looked at data from past studies, including blood samples taken from women of childbearing age and 5-year-olds for the National Health and Nutrition Examination Surveys between 1999 and 2014. The team estimated the loss of IQ points linked to exposure to endocrine disrupting chemicals in the womb and in early life.
The study focused on four chemicals known to cross from a mother to her fetus through the placenta and cause neurodevelopmental damage. These were polybrominated diphenyl ethers (PBDEs) or flame retardants, pesticides known as organophosphates (OPs), a type of mercury called methylmercury, and lead.
Over the period the team examined, flame retardants, or PBDEs, resulted in 738,860 cases of intellectual disability and an estimated 162 million lost IQ points.
A decline in problems between 2008 and 2016 was likely due to the chemicals being phased out of use in 2004 due to public concern. Despite crackdowns, children may still come into contact with these chemicals because of bioaccumulation and their persistence in the environment meaning they could be found in dust and food. PBDEs were followed by lead at 330,684 cases.
“Leaded paint may no longer be used, but dust from remaining paint layers poses a major risk for lead inhalation and ingestion, especially among young children,” the authors wrote. “The lead crisis in Flint, Michigan makes evident that lead exposure from water is not obsolete either.”
OPs accounted for 111,830 cases, and methylmercury which comes from coal-fired electric power generation facilities, was linked to 8,860. Regulations to stop the plants pumping out mercury were finalized in 2011, but some plants still exist, the authors said.
These chemicals led to a cost of over $6 trillion in a loss of IQ points among children, the authors believe.
More positively, the team also found a huge drop in the estimated loss of IQ points among children from 27 million in 2001 and 2002 to 9 million IQ points in 2015 and 2016.
The team acknowledged limitations to their study, including that the exposure-response relationships might not relate to all populations, and the cost of chronic diseases can change over time.
Lead author Abigail Gaylord, a doctoral candidate in the Department of Population Health at NYU Langone commented: “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 said.
Senior study author Dr. Leonardo Trasande, Professor at NYU Langone Health, commented in a statement: “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, who is chief of environmental pediatrics in the Department of Pediatrics at NYU Langone, added: “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.”