Worldwide, smoke from landscape fires contributed to an average of 339,000 deaths per year between 1997 and 2006, according to new research published in Environmental Health Perspectives and released today during the Annual Meeting of the American Association for the Advancement of Science (AAAS).

Sub-Saharan Africa and Southeast Asia were the hardest hit by fire-smoke deaths, with an estimated annual average of 157,000 and 110,000 deaths, respectively, attributable to landscape fire smoke exposure, said researcher Fay Johnston, who represented a global team at the 2012 AAAS Annual Meeting in Vancouver, Canada.

"It's time to look at deforestation impacts on fires, which in turn affect human health," said Johnston, a research fellow at the Menzies Research Institute, University of Tasmania, Hobart, Australia.

Johnston and her co-authors specifically assessed the health impacts of particulate matter smaller than 2.5 micrometers, an important byproduct of landscape fire smoke. First, they looked at satellite data to gather information on areas burned each year during the study period; particulate matter exposures were estimated using a chemical transport model, satellite-based observations, and other data.

They applied an accepted World Health Organization framework for determining annual mortality in different regions, and they used results from previous research on the health effects of smoke-related particulate matter to estimate deaths attributable to fire smoke.

They further calculated annual mortality during a La Nina period, and an El Nino period. Worldwide, deaths from fire smoke during those periods were estimated at 262,000 and 532,000, respectively, compared with an estimated 10-year global average of 339,000 deaths.

"Fire emissions are an important contributor to global mortality," the EHP article concludes. "Adverse health outcomes associated with landscape fire smoke could be substantially reduced by curtailing burning of tropical rainforests, which rarely burn naturally. The large estimated influence of El Nino suggests a relationship between climate and the burden of mortality attributable to landscape fire smoke."

Johnston noted that fire scorches 350 to 400 million hectares of land every year-an area larger than the size of India-emitting greenhouse gases as well as fine particulate matter that can be harmful to people and animals. As global warming continues, vegetation becomes dryer, lightning strikes more frequently, and fire seasons change.

Woolford's research reveals, for example, that the fire season now begins earlier and ends later in Alberta than it did in 1960. Climate change affects the frequency of extreme weather, too, causing unusually warm events to happen more often.

Also during the AAAS news briefing, Mike Flannigan released new predictions of future global fire severity, based on three specific climate-change scenarios. He further discussed concerns about the increasing number of peat fires, which release significant amounts of greenhouse gases as well as high levels of mercury.

Brauer discussed approaches for estimating population exposure to forest fire smoke and the evaluation of a smoke forecasting tool for public health preparedness. He summarized studies of health impacts of fire smoke exposure in Canada and evaluated the effectiveness of room air cleaners in reducing exposure to fire smoke.

Johnston's co-authors on the EHP paper, "Estimated Global Mortality Attributable to Smoke from Landscape Fires," were Sarah B. Henderson, Yang Chen, James T. Randerson, Miriam Marlier, Ruth S. DeFries, Patrick Kinney, David M.I.S. Bowman, and Michael Brauer. Environmental Health Perspectives is published by the U.S. National Institute of Environmental Health Sciences, one of the National Institutes of Health. Funding for the research was provided by the Australian Research Council, the University of Tasmania, and NASA.