Air pollutants linked to lung condition in kids
Infants exposed to outdoor air pollution even at levels that fall within regulatory limits have a higher risk of getting admitted to hospital for bronchiolitis, according to a study published in the November 2009 issue of the American Journal of Respiratory and Critical Care Medicine.
It is thought that ambient air pollution makes lungs more susceptible to bronchiolitis, which is the leading cause of morbidity in infants. Yet little is known about how exposure to air pollutants can influence the chances of developing the condition, and specifically about the risks of early-life exposure.
The team of researchers from the USA and Canada, led by Catherine Karr, evaluated the impact of several air pollutants and their sources on hospital admissions for bronchiolitis among infants in southwestern British Columbia. They looked at data for 11,675 young children who received their first hospital treatment for bronchiolitis between the second and twelfth month of life. For each patient, 10 infants without the condition were matched for month and year of birth.
Using various methods the authors estimated exposure to pollutants from traffic, industrial emissions and wood smoke, and then linked these estimates to information on where the infants resided. Levels of nitric oxide (NO), nitrogen dioxide (N02), carbon monoxide (CO), sulfur dioxide (SO2), ozone (O3) and particulate matter (PM2.5 and PM10) were tracked at air-monitoring stations within 10km of the infants” homes. Exposure to traffic fumes was assessed using land-use regression models of NO2, NO and PM, and with information on the residences’ proximity to highways.
After adjusting for variables such as gender, maternal age, smoking and breastfeeding, the authors found that a rise in exposure by a quartile unit was associated with a higher risk of bronchiolitis. The link was statistically significant for exposures — both over a lifetime and in the month before an illness episode — to NO2, NO, SO2, CO and, for the first time, wood smoke. Infants who lived within 50 metres of a major highway were 6% more likely to have the condition compared to those who lived further away.
“The findings add to our increasing understanding of infants and children as susceptible to health risks from low level, day in day out exposure to environmental contaminants,” says lead author Catherine Karr, Director of the Pediatric Environmental Health Specialty Unit at the University of Washington, USA.
Although the magnitude of the risk in this and previous studies of air pollution health effects is “modest”, say the researchers, the public health impact is significant because virtually everyone is exposed to these air pollutants at low levels. The area studied had “low to moderate” concentrations of air pollutants that, on average, did not exceed US standards or guidelines.
But the study’s findings are relevant for most parts of the world because exposure to traffic is ubiquitous and, in many countries, biomass burning for heating and cooking indoors leads to extremely high exposures to wood smoke, adds Karr. “In many rapidly developing cities, air pollution concentrations far exceed those observed in our region.”
The researchers call for further investigation of the link, pointing to limitations of their study. “The biggest difficulty with large studies like these is the ability to have perfect representation of exposure to the contaminant of interest as well as other exposures and all of the other factors that influence health, such as genetic predisposition,” explains Karr.
Reference – Karr CJ, Demers PA, Koehoorn MW, Lencar CC, Tamburic L, Brauer M. Influence of ambient air pollutant sources on clinical encounters for infant bronchiolitis. Am J Respir Crit Care Med 2009, 180:995–1001. doi: 10.1164/rccm.200901-0117OC
Source – http://www.eht-forum.org/news.html?fileId=news091106021341&from=home&id=0
