The number of industrial chemicals, heavy metals and pesticides proven capable of derailing normal brain development -- and robbing children and society of dollars, IQ points and future potential -- has doubled over the last several years, according to a new paper published Friday.
Dr. Philippe Grandjean, one of the co-authors, suggested that the world is facing a "silent pandemic" of "chemical brain drain."
"We have an ethical duty to protect the next generation," he said. "In particular, the next generation’s brains."
As a medical student in the 1970s, Grandjean remembers watching a young Japanese teenager, Shinobu Sakamoto, on the TV news. Sakamoto struggled to walk and talk, but was determined to let the world know about her people's plight. Many in her fishing village of Minamata had unknowingly consumed seafood heavily tainted with methylmercury. Her mom had done so while Sakamoto was in her womb.
"I was shocked, as they didn't teach us anything about the effects of pollution on human health" in medical school, recalled Grandjean, chair of environmental medicine at the University of Southern Denmark and an adjunct professor at the Harvard School of Public Health. "That was the moment I decided to do something about it."
Grandjean has spent the decades since investigating chemicals capable of damaging the developing brain. He started with lead, then mercury. "Every time I turned over a stone, I found something new," he said.
The line-up has now grown to a dozen "bona fide brain drainers," said Grandjean. That's twice as many chemicals as he and co-author Philip Landrigan, chairman of the department of preventative medicine at the Mount Sinai School of Medicine in New York City, listed in their first review of the science in 2006.
Joining methylmercury, lead, arsenic, PCBs, toluene and ethanol, according to the authors' updated list, are manganese, fluoride, DDT, chlorpyrifos, tetrachloroethylene and polybrominated biphenyl ethers.
The consequences of exposure in the womb or during the first years of life to any of these heavy metals, pesticides, solvents, flame retardants and other industrial compounds may not always be as obvious as they were for Sakamoto. But the effects on society, experts warn, can be profound.
An estimated one in six children in the U.S. is now affected by a cognitive or behavioral disorder, and that rate appears to be on the rise. Experts suggest that increases in the number of kids with autism and attention deficit hyperactivity disorder, for example, can't be explained by increased awareness or surveillance alone. Environmental pollutants are among the suspects.
Still, the new paper's concerns go much further.
Reduce one child's IQ by five points and the difference may be imperceptible. The child might be just a little slower to learn, a little shorter of attention and a little less successful on tests and at work -- which economists estimate could equate to $90,000 in lost lifetime earnings.
Reduce the average IQ among all children in the U.S. by five points, however, and the impact is striking: About half as many members of that generation will be "intellectually gifted," twice as many will be "intellectually impaired," and billions of dollars of productivity will be lost. And that doesn't take into account the costs of diagnosis, treatment, special education, incarceration and other indirect costs, such as an estimated rise in traffic accidents attributed to more distracted drivers.
A potential shifting of the bell curve should ring alarms for policymakers, business leaders and parents alike, experts say. They add that the current list of chemical culprits likely represents just the tip of the iceberg.
"The number is going to increase. Right now, it's just a matter of not having data available," said David Bellinger, an expert in children's environmental health at Harvard, who has found associations between three of the brain poisons -- lead, methylmercury and organophosphate pesticides (a class that includes the newly added chlorpyrifos) -- and drops in the combined nationwide IQ of 23 million, 17 million and 0.3 million points, respectively.
Adding to the problem, Bellinger added, is that "the regulatory process in this country is inherently conservative: You have to prove something is bad [before you can ban it] rather than prove something is good [before you can authorize it]."
Representatives of the chemical industry, meanwhile, called the new paper "flawed."
"The authors focus largely on chemicals and heavy metals that are well understood to be inappropriate for children's exposure, highly regulated and/or are restricted or being phased out," the American Chemistry Council told HuffPost in an emailed statement. "They then extrapolate that similar conclusions should be applied to chemicals that are more widely used in consumer products without evidence to support their claims."
The industry group further emphasized that its members "go to great lengths to ensure products are safe."
Most of today's knowledge about chemicals and their effects on the human brain is based on the study of adults -- typically those who have suffered occupational exposures or tried to kill themselves. With these data, scientists have tallied a total of 214 neurotoxic chemicals. Another thousand chemicals have been shown to be toxic to animals' brains, while thousands more have yet to be studied for neurotoxicity.
Science has come a long way since Grandjean’s medical school days, when his professors taught that the fetus is well protected inside the mother’s womb. Scientists now know that hundreds of chemicals can course through umbilical cord blood.
But proving that a specific chemical can harm a child's growing gray matter is extremely difficult and time-consuming, which experts suggest is why the list currently stands at only 12.
"The default assumption is that if it's not good for the adult brain, it's even worse for the child's," said Bellinger.
Timing is critical. At certain times while the baby is still inside the womb, brain cells are added at a rate of 250,000 every minute -- with each neuron migrating to a specific location in the brain, where it begins building intricate networks with other cells. During the first few years of a baby's life, 700 new neural connections are formed every second.
"The brain has to go through very complicated and delicate stages of development that have to happen at the right time and in the right sequence. If that doesn't happen, you don't get a second chance," said Grandjean, who has recently published a book on the topic titled Only One Chance.
"That kid is stuck with that brain the rest of his or her life," Grandjean added.
Some children may be more at risk than others, noted Bruce Lanphear, an environmental health expert at Simon Frasier University in British Columbia. "If you grow up in an impoverished neighborhood, you could be exposed to lead, airborne pollutants, tobacco smoke and high levels of pesticides," he said. "Each of these can chip away at learning abilities or elevate risks of ADHD."
What's more, some of these chemicals may magnify the effects of others. Lead, for example, has been shown to cause more harm in children who are also exposed to tobacco smoke or manganese.
Sheela Sathyanarayana, a pediatric environmental health expert at Seattle Children's Hospital, noted at least a few things that parents and expecting parents can do to reduce potential neurotoxic exposures inside their home. She recommended avoiding fish known to contain high levels of mercury, such as tuna, as well as minimizing dust, removing shoes when coming indoors and keeping windowsills clean.
She also welcomed the paper's recommendation of a new agency -- much like the World Health Organization's International Agency for Research on Cancer -- that could coordinate research and grade the evidence for a chemical's propensity to wreak havoc on the developing brain.
Some progress has already been made, including the newly adopted Minamata Convention on Mercury, which addresses human activities contributing to widespread mercury pollution and was inspired by the tragedy in Sakamoto's village. But, as Grandjean noted, even chemicals long-banned in the U.S., such as chlorpyrifos, are still turning up inside American homes or being exported to developing countries.
"This is like climate change," he said. "We just can’t afford to do this experiment. Once we finally get enough evidence, it's too late."
Grandjean added his fear of a potentially ironic "vicious cycle."
"If the next generation does not have the cognitive skills that we hope they will have," said Grandjean, "they will not be able to clean up after us ... or care for us."