Children today may be at a greater risk of developing cognitive and behavioral issues including autism, ADHD and dyslexia, due to exposure to "new" chemicals, reveals an unsettling new study.
The study, published in The Lancet Neurology, finds a list of common chemicals are likely contributing to what the researchers are calling the “global, silent pandemic of neurodevelopmental toxicity” in children, reports Forbes.
Five neurotoxins were pinpointed in 2006 by the researchers as contributing to cognitive deficits and attention problems (lead, methylmercury, polychlorinated biphenyls, arsenic, and toluene). The team has now added six more chemicals to the list: manganese, fluoride, chlorpyrifos, dichlorodiphenyltrichloroethane, tetrachloroethylene, and the polybrominated diphenyl ethers. “The greatest concern is the large numbers of children who are affected by toxic damage to brain development in the absence of a formal diagnosis,” study author Philippe Grandjean, of the Harvard School of Public Health told Forbes. “They suffer reduced attention span, delayed development, and poor school performance. Industrial chemicals are now emerging as likely causes.”
The team says that while genes do play a part in neurobehavioral problems like autism, ADHD, and dyslexia, genetics only account for about 30 to 40 percent of the cases; therefore, environment—and specifically chemicals in the environment—must be considered in the majority of the issues.
"The developing human brain is incredibly vulnerable to chemical exposures, both in utero and in early childhood, and these changes can be lifelong," notes Forbes. “During these sensitive life stages,” say the authors, “chemicals can cause permanent brain injury at low levels of exposure that would have little or no adverse effect in an adult.”
Calling it a "pandemic" level of exposure, the study authors are urging for stricter mandatory testing for chemicals before approved for use. "One common complaint has been that when one compound does finally become banned, another equally toxic and often untested chemical may take its place," reports Forbes. "More rigorous testing, though complicated to carry out, might address this major issue."
The 11 chemicals and their effects (via Forbes):
Lead–This is one of the most extensively researched compounds in terms of neurodevelopment, and has been consistently linked to serious deficits, including low IQ. Its effects seem to be permanent, leading to the conclusion that there is no safe level of exposure.
Methylmercury–Affecting the neurological development of the fetus,exposure often comes from maternal intake of fish containing high levels of mercury, according to the World Health Organization and the EPA.
Polychlorinated biphenyls (PCB) – This family of chemicals has routinely been associated with reduced cognitive function in infancy and childhood. It is often present in foods, particularly fish, and can be passed along in breast milk.
Arsenic – When absorbed through drinking water, this chemical has been linked to reduced cognitive function in schoolchildren. Follow-up studies from the Morinaga milk poisoning incident have linked it to neurological disease in adulthood.
Toluene – Used as a solvent, maternal exposure has been linked to brain development problems and attention deficit in the child, according to the EPA and OSHA.
Manganese – In the drinking water in Bangladesh, for example, this chemical has been linked to lower scores in math, diminished intellectual function, and ADHD.
Fluoride – Higher levels of this chemical has been connected with a 7-point decrease in IQ in children.
Chlorpyrifos and DDT (pesticides) – Linked to structural abnormalities of the brain and neurodevelopmental problems that persist up to age 7. These pesticides are banned in many parts of the world (U.S. included), but still used in many lower-income countries. They have recently been linked to Alzheimer’s disease as well.
Tetrachloroethylene (AKAperchlorethylene)– These solvents have been linked to hyperactivity and aggressive behavior, and increased risk of psychiatric diagnosis. Mothers in certain professional roles, like nurse, chemist, cleaner, hairdresser, and beautician had higher levels of exposure.
The polybrominateddiphenyl ethers – These flame retardants are banned now, but believed to be neurotoxins. Prenatal exposure has been linked to neurodevelopmental disorders in the child.
And the researchers found two more "compounds of concern": BPA (bisphenol A), which is a common plastic additive in canned goods, thermal register receipts and hard plastics; and phthalates, which are commonly found in personal care products including deodorants and nail polish.
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