A laundry list of common industrial chemicals could be responsible for a silent pandemic that already has resulted in brain impairment in millions of children worldwide, according to a study published today in the British medical journal The Lancet.
The chemicals, which are released into the environment by various industries, turn up in various forms -- from methylmercury in fish, arsenic and PCBs in drinking water, to lead in certain types of paints and glazes.
Some researchers argue that conclusive evidence of a connection between the chemicals and brain impairment is limited, in many cases. But authors of the study still believe that the total impact of exposure to industrial chemicals is much greater than currently recognized, and raises the question of whether enough is being done to protect children from exposure.
"The human brain is a precious and vulnerable organ," said study author Dr. Philippe Grandjean, an adjunct professor at Harvard School of Public Health in Boston. "And because optimal brain function depends on the integrity of the organ, even limited damage may have serious consequences."
Among the possible consequences, the authors note, are decreases in intelligence or changes in behavior, which are important but aren't something a doctor might notice during an office visit.
"What prompted our study," said study co-author Dr. Philip J. Landrigan, a professor at Mount Sinai School of Medicine in New York, "was the realization that has been growing over the past several decades that there are a small number of chemicals that we know with absolute certainty can cause brain injury if exposure occurs during the fetal life or in the first several years after birth."
"Our big worry is this: If we know there are four or five or six chemicals out there capable of causing brain injury, what about the other chemicals, to this time, that have not been adequately tested?" he said.
The idea that industrial chemicals have detrimental effects on developing brains is not a new one.
However, the authors say insufficient research has been conducted into the toxic effects of industrial chemicals on children. Moreover, they say, lax governmental requirements for testing and control have caused the problem to be overlooked.
A Call for Action on Chemicals?
Some experts point to the study as a call to action for additional research into the detrimental effects of the chemicals on child development, as well as more stringent government regulation of a wider range of industrial chemicals.
"All high-production volume chemicals should undergo a rigorous registration and evaluation process, with chemicals used in close proximity with pregnant women and children being prioritized," said Dr. Bruce Lanphear, Sloan professor of children's environmental health at Cincinnati Children's Hospital Medical Center in Cincinnati.
"These chemicals are potent risk factors for numerous learning and behavioral problems," he said. "Until society recognizes, tests and regulates these chemicals for neurotoxicity, we will fail to protect children."
Some experts suggest that what they don't know about the chemicals may be even scarier than what they know.
"What we find out will probably be more disturbing yet," said Marc Gillespie of the department of pharmaceutical sciences at the College of Pharmacy and Allied Health Professions in Queens, N.Y.
Not all experts agree, however, that the findings warrant action.
"[The study] is inflammatory, and to follow its recommendations would only add an unnecessary burden to the approval process," said Charles Santerre, professor of food toxicology at Purdue University in West Lafayette, Ind.
Santerre also argues that average consumers today are exposed to much lower levels of the industrial chemicals mentioned in the study than they were decades ago. He says that the general public's exposure to brain-impairing chemicals known as polychlorinated biphenyls (PCBs) are 10 percent of what they were three decades ago, and exposure to lead is also much lower.
Santerre also says that the recommendations of the study, which include the adoption of strong governmental regulations that could later be relaxed if the chemicals were found to be less harmful, place an unneeded burden on regulators and corporations.
ADHD and Autism -- a Chemical Link?
Among potential neurological consequences, the study lists attention deficit disorder (ADHD), autism and mental retardation. Landrigan says though the jury is still out with regard to the exact causes of these neurological conditions, industrial chemicals are a likely culprit.
"Autism is a complicated disease for many causes; part of causation is genetic," he said. "But at the same time it's very clear genetics is not the whole story, even in families that have a tendency for autism."
"Some children have genes that predispose them to autism, but other children develop autism in the absence of those genes," he said. "That suggests very strongly to my colleagues and me that factors in the environment that need badly to be identified are almost certainly contributing to the causation of autism."
However, while some research exists linking certain chemicals to these conditions, experts say that the link between such exposure and these conditions is tenuous at best.
"It's a worry, not a fact," said Dr. Alan Ducatman, professor and chair of the department of community medicine at the West Virginia University School of Medicine in South Morgantown, W.Va.
Ducatman says the appropriate response to the study involves regulation on an exposure-specific basis -- that is, find out which sources children are exposed to and eliminate them.
"This is not about absolute toxicity, but about the likelihood of encounter," he said. "We should find financial and regulatory means to replace products that can leach or directly expose these products to children. That is the priority. Does the baby's binky still have phthalates? Those are the kinds of simple regulatory questions we need to ask."