Infants who are exposed to higher levels of air pollution are at
increased risk for bronchiolitis, according to a new study.
The study appears in the November 15 issue of the American
Thoracic Society's American Journal of Respiratory and Critical
Care Medicine.
"There has been very little study of the consequences of early
life exposure to air pollution," said Catherine Karr, M.D. PhD,
assistant professor of pediatrics at the University of Washington
and the paper's lead author. "This study is unique in that we were
able to look at multiple sources including wood smoke in a region
with relatively low concentrations of ambient air pollution
overall."
The researchers analyzed nearly 12,000 diagnoses of infant
bronchiolitis between 1999 and 2002 in southwestern British
Columbia, with respect to the individual's ambient pollution
exposure based on monitored levels of nitric oxide (NO), nitrogen
dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), and
particulate matter from monitoring stations within 10 km of the
infants' homes. They also used land-use regression maps to assess
concentrations of ambient pollution with respect to traffic and
wood smoke. They analyzed pollution exposure by dividing subjects
into four categories, or quartiles, of concentration.
After accounting for confounding variables including sex,
gestational age, maternal smoking and breastfeeding, they found
that a diagnosis of bronchiolitis was significantly linked to
increased lifetime exposure to specific pollutants. An
interquartile increase in exposure to NO, NO2, SO2 and CO increased
bronchiolitis risk by 8, 12, 4 and 13 percent respectively. Infants
who lived within 50 meters of a highway had an increased risk of
six percent; those who lived in a higher wood smoke exposure area
had an increase of eight percent in their risk of
bronchiolitis.
"In general, we found that traffic-derived air pollutants were
associated with infant bronchiolitis as well as wood smoke and
industrial emissions," said Dr. Karr. "The magnitude of the effect
is modest, but is comparable to most air pollution studies in North
America. The importance of these small magnitude effects become
significant when you consider that they affect a great number of
children because these exposures are so ubiquitous."
"This study adds to a growing body of research showing a link
between neighborhood air pollution hotspots and pediatric
respiratory disease. We were specifically interested in
bronchiolitis, the main reason for children to be hospitalized in
their first year, as it is an important and costly childhood
illness. Reducing exposure to air pollution may be one approach to
decrease bronchiolitis occurrence," said Michael Brauer, Sc.D.,
professor at the School of Environmental Health at the University
of British Columbia and principal investigator on the study.
Dr. Karr, who is a pediatrician, also noted that the current
research might help guide the conversations that doctors have with
patients. "I think we have a role in educating parents about
concerns regarding air pollution and promoting precautionary
approaches where feasible. Encouraging avoidance of the use of wood
burning appliances or avoiding residing in close proximity to
highways would be examples."
Furthermore, she says, policies should address exposure to air
pollution in residential settings, school settings, and daycares.
"Places where kids spend a lot of time shouldn't be right next to
major highways," said Dr. Karr.
The research strengthens the connection between ambient air
pollution and respiratory disease among children, although more
research needs to be done to elucidate the precise nature of that
link. Dr. Karr noted that the National Children's Study, a new
project of the NIH, CDC and EPA, which is designed to follow
100,000 mothers and their children from birth to adulthood will
expand our understanding further. This prospective study will allow
exploration of the role of environmental exposures such as air
pollution in the context of other influences on child health such
as genes and gene-environment interactions.
SOURCE