Children born in Sarnia more likely to develop asthma than those in Windsor or London, study indicates

Children born in Sarnia, Ont., considered home to Chemical Valley, are more likely to develop asthma than those born in nearby cities, according to a population-based study by researchers at Lawson Health Research Institute and Western University.

Researchers followed 114,427 children in Sarnia, London and Windsor who were born between 1993 and 2009 for 10 years. By age 10, nearly a quarter of the study subjects in Sarnia were diagnosed with asthma, compared to 21 per cent in Windsor and 17 per cent in London. 

"It's known that cities in southwestern Ontario have varied levels of air pollution because of differences in industry and traffic," said researcher Dr. Dhenuka Radhakrishnan

"We wanted to see if children born in three cities had a different risk of developing asthma due to the differing air pollution levels in the three regions, even though the people living in these cities are otherwise comparable in many ways." 

The findings indicate air pollution exposure in the first year of life is associated with the development of asthma in children. Overall rates of new childhood asthma diagnosis in southwestern Ontario have been decreasing over time as air pollution levels drop.

Chemical Valley is one of Canada's most industrialized areas, with dozens of chemical plants and oil refineries clustered near Sarnia, at the southernmost tip of Lake Huron on the Ontario-Michigan border. 

Members of the Aamjiwnaang First Nation have for years warned about pollution in the Sarnia area and the higher levels of disease among its members. 

Researchers accounted for other risk factors associated with asthma, such as gender, socioeconomic status and urban versus rural setting. The findings were most apparent in the first two years of life, but persistent beyond age six.  

Asthma is the most common chronic disease in Canadian kids — and the leading cause of emergency department visits and hospital admissions — and has a significant impact on quality of life. 

"It's important to find strategies to prevent asthma development, and this study suggests that reducing air pollution exposure, including environmental causes, might reduce the number of children who suffer from asthma," said Dr. Salimah Shariff, a scientist at Lawson and professor at Western University.

There's also growing evidence that pollution exposure during pregnancy can influence whether children develop asthma, said Shariff. 

"We need to carefully examine how reducing air pollution exposures within a geographic area translates to reductions in asthma development," she said. "Understanding the amount of air pollution that a mother and infant are exposed to, and how this impacts their personal risk, could enable regions to target safer levels for their residents."