Wednesday, November 08, 2006

Industrial chemicals linked to Autism Spectrum Disorder

Industrial chemicals have caused a "silent pandemic" of brain disorders, according to a study published Tuesday in the British medical journal, the Lancet.
One in every six children has some kind of developmental disability, and most of these affect the nervous system.
Exposure to toxic chemicals during fetal development can be linked to autism, attention deficit disorder, cerebral palsy and developmental delays, say the study's authors.
"The human brain is a precious and vulnerable organ. And because optimal brain function depends on the integrity of the organ, even limited damage may have serious consequences," said Philippe Grandjean, adjunct professor at Harvard School of Public Health and the study's lead author.
Grandjean and his team described how industrial chemicals like lead, mercury, PCBs, arsenic and toluene are causing brain injury in developing babies.
The largest groups of chemicals that cause such problems are metals, solvents and pesticides. The team identifies 201 chemcials with toxic effects.
Developing babies are much more susceptible to brain injury caused by toxic agents than adults are. During the nine months of prenatal life, the human brain is developing from a strip of very sensitive cells.
The blood-brain barrier, which protects the adult brain from many toxic chemicals, is not fully formed until an infant is six months old.
Also, certain pesticides and industrial compounds accumulate in breast tissue. They are passed to an infant through its mother's breast milk. The result is infant exposure to these chemicals is 100 times the mother's exposure levels.
The study points out that damage caused by industrial chemicals is preventable; however the toxic effects of industrial chemicals are not regulated in a way that protects children.
Research showed preschool children living in agricultural communities and exposed to pesticides had more brain development problems than kids in urban communities.
Toxic exposure can also have delayed consequences as well, including Parkinson's disease or other neurodegenerative diseases in adults.
Recognizing the sensitivity of the developing brain has led to successful prevention programs in the past, such as eliminating lead additives in gasoline.
The study identifies roadblocks to more of such prevention programs.
Grandjean and his team say regulators need to test commonly used chemicals for their effects on the developing brain. The study says of the thousands of chemicals on the market, "fewer than half have been subjected to even token laboratory testing for toxicity."
The study also says new chemicals should be tested specifically for neural effects before they are allowed to be sold. Finally, the researchers say too much proof is required to demonstrate a chemical is risky.
Many scientists are speaking out in support of the research. One critic, however, says it does not take into account that many children affected by chemicals are exposed to much higher than average amounts of toxins, and that safe amounts do exist.
Warren Foster, director of the Centre of Reproductive Care at Ontario's McMaster University, cautions that these findings do not mean a ban on chemicals is necessary or helpful.
"We still need coolants, we still need plasticizers, we still need flame retardants, we still need solvents,'' Foster said. "So if we ban these, they're going to be replaced with something else. And just because something else comes along that we know nothing about doesn't mean it's safer.''