Canada — As wildfires tore away at Kelowna, B.C., in the summer of 2003 consuming 25,000 hectares, uprooting 33,000 people, and engulfing 238 homes concerns centred on the immediate safety of residents and firefighters.
But an exhaustive new study has discovered a less obvious threat from that disastrous event: the inhalation of fine particles in the smoky air that filled the Okanagan Valley.
The study shows a close correlation between elevated particulate matter in the air and increased visits to physicians and hospitals due to respiratory problems.
And with scientists predicting an increase in the frequency and intensity of wildfires under global warming, the threat to human health may only get worse.
“This is going to become commonplace,” said Michael Brauer, a professor in the school of population and public health at the University of British Columbia. “There are definitely some climate links, which doesn’t look good for the future.”
Published in the journal Environmental Health Perspectives, the study results are being presented at the annual meeting of the American Association for the Advancement of Science in Vancouver.
The University of British C’s school of environmental health also participated in the study.
An increase of 10 micrograms of particulate per cubic metre of air resulted in a five per cent increase in respiratory hospital admissions and a six per cent increase in the odds of an asthma-specific physician visit.
Kelowna residents experienced increases in particulate levels 10 times that amount, resulting in an increase of about 80 per cent in visits to physicians.
In B.C. in 2010, a total of 1,673 fires cost $212 million and destroyed 331,108 hectares, according to the province’s wildlife management branch.
The annual average over the past decade was 1,969 fires, 98,541 hectares destroyed, and $144 million in damage. Of those, 41 per cent were caused by people and 59 per cent by lightning.
While most studies use particulate data from routine air-quality monitoring to estimate population exposure, the Kelowna fires provided an ideal scenario for measuring human-health impacts, especially in urban settings.
Chronic exposure to air pollution increases the risk of cardiovascular disease, including heart attacks.
The study found that the “effects of chronic exposure to wildfire smoke have yet to be studied but could pose a considerable health risk in areas where annual burning is practised.”
The study area extended beyond the Kelowna area to include fires that occurred in 2003 throughout southeastern B.C. to the U.S. and Alberta borders for the 92-day period ending Sept. 30 of that year. About 640,000 people in the area were potentially exposed to smoke pollution.
Data on particulate levels was obtained from provincial and federal air-quality instruments in Kelowna, Kamloops, Vernon, Creston, Revelstoke, and Golden.
The U.S. National Oceanic and Atmospheric Administration hazard mapping system also provided information on the shape of smoke plumes based on expert reviews of satellite imagery.
The study involved 281,711 people. Middle-aged adults had most of the complications not children or the elderly, as one might expect.
Of the 34,771 respiratory physician visits, 16 per cent were for asthma; about 21 per cent were for acute bronchitis or acute upper respiratory infection.
The study observed no clear differences by sex, socioeconomic status, or possible pre-existing sensitivity.
Brauer also noted that a fire-smoke forecasting system, operated by the B.C. Ministry of Environment, is doing a “reasonable job of predicting where smoke will go” and the potential for increased respiratory health problems.