“Autism spectrum disorders are lifelong conditions for which there
is no cure and limited treatment options, so there is an urgent need to
identify any risk factors that we could mitigate, such as pollution,”
said lead author Evelyn Talbott, Dr.P.H., professor of epidemiology at
Pitt Public Health. “Our findings reflect an association, but do not
prove causality. Further investigation is needed to determine possible
biological mechanisms for such an association.”
Dr. Talbott and her colleagues performed a population-based,
case-control study of families with and without ASD living in six
southwestern Pennsylvania counties. They obtained detailed information
about where the mothers lived before, during and after pregnancy and,
using a model developed by Pitt Public Health assistant professor and
study co-author Jane Clougherty, Sc.D., were able to estimate individual exposure to a type of air pollution called PM2.5.
This type of pollution refers to particles found in the air that
are less than 2.5 micrometers in diameter, or 1/30th the average width
of a human hair. PM2.5 includes dust, dirt, soot and smoke. Because of its small size, PM2.5
can reach deeply into the lungs and get into the blood stream.
Southwestern Pennsylvania has consistently ranked among the nation’s
worst regions for PM2.5 levels, according to data collected by the American Lung Association.
“There is increasing and compelling evidence that points to
associations between Pittsburgh’s poor air quality and health problems,
especially those affecting our children and including issues such as
autism spectrum disorder and asthma,” said Grant Oliphant, president of
The Heinz Endowments. “While we recognize that further study is needed,
we must remain vigilant about the need to improve our air quality and to
protect the vulnerable. Our community deserves a healthy environment
and clean air.”
Autism spectrum disorders are
a range of conditions characterized by social deficits and
communication difficulties that typically become apparent early in
childhood. Reported cases of ASD have risen nearly eight-fold in the
last two decades. While previous studies have shown the increase to be
partially due to changes in diagnostic practices and greater public
awareness of autism, this does not fully explain the increased
prevalence. Both genetic and environmental factors are believed to be
responsible.
Dr. Talbott and her team interviewed the families of 211 children
with ASD and 219 children without ASD born between 2005 and 2009. The
families lived in Allegheny, Armstrong, Beaver, Butler, Washington and
Westmoreland counties. Estimated average exposure to PM2.5 before, during and after pregnancy was compared between children with and without ASD.
Based on the child’s exposure to concentrations of PM2.5
during the mother’s pregnancy and the first two years of life, the Pitt
Public Health team found that children who fell into higher exposure
groups were at an approximate 1.5-fold greater risk of ASD after
accounting for other factors associated with the child’s risk for ASD –
such as the mother’s age, education and smoking during pregnancy. This
risk estimate is in agreement with several other recent investigations
of PM2.5 and autism.
A previous Pitt Public Health analysis of the study population revealed an association between ASD and increased levels of air toxics,
including chromium and styrene. Studies by other institutions using
different populations also have associated pollutants with ASD.
“Air pollution levels have been declining since the 1990s; however,
we know that pockets of increased levels of air pollution remain
throughout our region and other areas,” said Dr. Talbott. “Our study
builds on previous work in other regions showing that pollution
exposures may be involved in ASD. Going forward, I would like to see
studies that explore the biological mechanisms that may underlie this
association.”