Cause of death: weather

Dr Karen Smoyer

Dr. Karen Smoyer conjures up a tempting scenario, as wind-whipped snow lashes at people scurrying past the building where she delivers a seminar on climate change and health.

"Imagine it's the year 2050," she begins, "and mean global surface temperatures have increased 2 C above what they were in 1999."

Then her description takes a sinister turn. "Another heatwave has hit Edmonton and an elderly neighbor has died of heatstroke," she continues. "You're concerned about your own health because while visiting Toronto, you were bitten by a mosquito and malaria has been on the horizon in Toronto over the past few decades."

Can we expect an outbreak of malaria in Canada as the climate heats up? Not likely, says Smoyer. But in areas where malaria-carrying mosquitoes can survive in a warmer world, and where humans don't adapt to climate change, we will have "more cases of malaria." Of even greater concern, though, is the probability of more heat-related deaths.

A geographer in the Department of Earth and Atmospheric Sciences, Smoyer summarized the research and debates in the medical community about possible effects of climate change on human health. Hers was the third seminar in a series sponsored by the Environmental Research and Studies Centre and funded by TransAlta Corporation.

Smoyer discussed the circumstances that make us vulnerable to climate change, and how we adapt to reduce our vulnerability and limit its impact. Her message is one we should heed, but often don't - weather can kill.

Internationally, concerns are growing about direct health impacts of climate change, such as heat-related deaths and cancer-causing air pollutants, and indirect impacts, such as diseases transmitted by water, insects or animals. North American medical opinion about the threat of global warming to human health ranges from "dire warnings to skepticism," she says. The dire-warning camp tends to base their estimates on climate change alone, rather than adjusting for public health measures. Skeptics, in contrast, ask why outbreaks of malaria have never been seen in North America. Smoyer counters they have, but are rare due to the advantages of better sanitation, screened windows and public health interventions.

She points out unusual weather caused more than 500 deaths in the 1995 Chicago-area heatwave, was responsible for outbreaks of rodent-borne Hantavirus in southwestern United States, and mosquito-borne dengue, a flu-like and potentially debilitating illness, in Latin America.

Alarming as these events are, they do not predict what will happen as climate changes over time. "We're seeing examples of extreme climate variability," says Smoyer, and humans adapt better to "gradual shifts in precipitation and temperature." However, if heat waves arrive more often, last longer and become more intense as the climate warms, "We can expect to see health problems in cities at risk." Says Smoyer: "Adaptation is going to be more difficult."

The preliminary results of her latest research confirm heat extremes can prove deadly. Smoyer and her colleagues found higher death rates among the elderly on "heat-stress days" (more than 32 C) than they did on "non-heat stress days" in almost all areas of the Toronto-Windsor corridor of Ontario. Their findings resemble those in their earlier studies of heat-related deaths in St. Louis, Mo., and the New York area. All three regions experience hot and humid summers and cold winters. Heat wave death rates were highest in densely populated urban areas where air conditioning use was low and poverty levels were high.

When tackling exposure to heat extremes in Canada, we need to consider these results and other factors, including potential changes to our health care system, says Smoyer. "If Canada does go to a privatized U.S. model, we could see more vulnerability." But other conditions - an aging population, urban sprawl, air pollution, auto use and an increase in low-income families - may contribute to our health risk."

These factors "are not static," she says. Our vulnerability changes with each shuffle of the social, economic and political cards. And we can adapt.

"When people are exposed to hot weather for a long time, the body acclimatizes." We can even acclimatize our behavior. "In the southern U.S. people don't mow their yard or go for a run at noon on a hot day," she notes. Housing type, air conditioning and rooftop gardening could reduce urban temperature, and public warning systems could be implemented.

"Heat waves are predictable and heat-wave mortality is preventable," insists Smoyer. Unfortunately, "people don't regard weather as a hazard because heatwaves don't destroy buildings."

Now if only we could adapt our thinking.