1 in 70 boys and 1 in 315 girls in the U.S. now have an autism spectrum
disorder (ASD), according to a 2009 study by the Centers for Disease Control
and Prevention. Increased awareness and detection as well as earlier diagnoses
cannot alone account for the steep increase over the past few decades, experts
now widely believed to be caused by a combination of genetics and environmental
factors. "Research indicates that even low-dose environmental exposures during pregnancy and early childhood have an effect on the developing brain," said Linda S.
Birnbaum, Ph.D., director of the National Institute of Environmental and Health
Sciences, at a congressional hearing last August.
of young children and fetuses are less able than those of adults to detoxify
harmful substances and repair damage, and fetal exposure is of utmost concern,
explains Santa Monica, Calif., pediatrician Harvey Karp, M.D. "The brain
quadruples in size during the last trimester," he says. "There are windows of
vulnerability during this time where even miniscule amounts of chemicals could
repeatedly ruled out vaccines as a cause of autism. Currently, indoor and
outdoor air pollution, endocrine-disrupting chemicals such as bisphenol-A (BPA)
and PBDEs, smoking, alcohol use, medications and infections are being
investigated. Already, a 2010 study at the University of Southern California
found that children of women who lived within 1,000 feet of a freeway during
the third trimester were more than twice as likely to have autism. And research
from Columbia University's Mailman School of Public Health in New York found
that babies with higher concentrations of the pesticide chlorpyriphos or PBDEs
in their umbilical cord blood experience developmental delays later.
steps to protect children need to be taken federally, says Bruce P. Lanphear,
M.D., M.P.H., senior scientist at the Child & Family Research Institute and
professor of health sciences at Simon Fraser University in Vancouver, British
Columbia. "Currently, each chemical has to individually be proven toxic in
animal and human studies before it's regulated," he explains. "Eventually, we
should require companies to prove their products are safe."