We're going to need all the brains we can get to navigate through
an uncertain future; our kids are going to need theirs more. So, maybe we need to take better care of them. In that regard, I'm drawing your attention to
this article from the February 2006 issue of Environmental Health Perspectives. It highlights the importance of understanding the effects of environmental contaminants on our kids brains.
In 1994, about 17% of school-age children in the United States reportedly suffered from a disability that affected their behavior, memory, or ability to learn. These include attention deficit/hyperactivity disorder (ADHD), autistic spectrum disorders, epilepsy, Tourette syndrome, and other general disorders such as mental retardation and cerebral palsy. These are thought to arise from abnormal brain development occurring in utero or in young children. Beyond the heartbreak, stress and economic disruption to the families, there are enormous societal costs from these behavioral disorders. Children with these disorders experience higher rates of mental illness and suicide, and are more likely to engage in substance abuse and to commit crimes as adults. The overall economic cost of neurodevelopmental disorders in the United States is estimated to be $81.5 to $167 billion each year.
Controversy abounds about whether or not the trends in childhood neurodevelopmental disorders are increasing or not. However, some researchers are looking at some widespread low-level environmental contaminants as having a role in these disorders.
The tendency for neurodevelopmental disorders to occur in some children may arise through a gene-environment interaction. Some kids might be genetically predisposed to developmental disorders that might not produce any significant effects, in the absence of "hits" from environmental chemicals. However, children in industrialized countries grow up in a veritable sea of low levels of potentially toxic chemical substances. While our bodies have defense mechanisms against many of the effects of chemical exposure, inborn genetic abnormalities coupled with genetic abnormalities caused by chemical exposure might weaken these defenses, amplify developmental disorders, or both, producing behavioral or learning problems.
Some examples of what the article refers to as the neurodevelopmental toxicant hit parade:
Lead - it's been long known that children exposed to lead experience deficits in intelligence and ability to learn. Over time, public health authorities have been reducing the blood-lead level triggering intervention to reduce childhood exposure. Overall, blood-lead levels in children have been decreasing; however, children in black or Mexican-American families, who are poor and living in urban areas in old or substandard housing are still at risk.
Mercury - In 2003, EPA researchers concluded that upwards of 300,000 newborns per year are at risk of adverse neurodevelopmental effects from their mothers' blood-mercury levels. However, EPA also appears to have dragged its feet on regulating emissions from coal-fired power plants. A study reported last year calculated that lost productivity from IQ deficits potentially associated with neurodevelopmental effects from childhood mercury exposure could cost the U.S. $8.7 billion per year, with $1.3 billion from power plant emissions alone. The authors made the point, which could apply to all of these neurodevelopmental toxicants of this representing a threat the economic health and security of the U.S.
Exposure to certain synthetic organic chemicals such as PCBs are thought to be associated with development delays and reductions in IQ. One class of chemicals that are particularly worrisome in this regard are the class of fire retardants know as polybrominated diphenyl ethers or PBDEs. These are of concern because of recent data showing that trends in PBDE exposure are increasing over time are found in breast milk and produce adverse developmental effects in laboratory animals, at levels of exposure not much higher than those found in humans. Steps have been taken to reduce PBDE use in commerce, but we're probably going to be living with these substances for a long time.
Next time: some of the actions we can all start taking to address this environmental health issue.