"Concern for human health is one of the most compelling reasons to study the effects of global climate change. Health reflects the combined impacts of climate change on the physical environment, ecosystems, the economic environment, and society..." ⁽¹⁾

Good health, which requires physical, mental and social well-being, is a key determinant of quality of life. As a result, health and health services are extremely important to Canadians. The health care and social services sector employs more than 1.5 million Canadians, and over $102 billion per year is spent on health services.⁽²⁾ This spending on health care accounts for about 9.3% of the total annual value of goods and services produced in Canada (Gross Domestic Product). This represents an average of approximately $3,300 per person per year.⁽²⁾

At a very basic level, the relationship between health and climate in Canada is demonstrated by the strong seasonal variability in the incidence of infectious diseases^{(3, 4)} and the persistent seasonal pattern in mortality (Figure 1; reference 5). The monthly number of deaths tends to reach a low in August, then rises to a peak in January and declines again during the spring and summer months. Many of the winter deaths result from pneumonia,⁽⁵⁾ suggesting that seasonal changes in weather and climatic conditions influence respiratory infections. Deaths from heart attacks and strokes likewise show strong seasonal fluctuations, with peaks in both summer and winter.⁽⁵⁾

Figure 1: Seasonality of deaths in Canada, 1974-1994 (adapted from Statistics Canada Web site, March 2003) larger image [JPEG, 57.2 kb, 800 X 388, notice]

Another strong linkage between climate and human health is seen in the impacts of extreme climate events and weather disasters. Flooding, drought, severe storms and other climate-related natural hazards can damage health and social well-being by leading to an increased risk of injury, illness, stress-related disorders and death. In recent years, this has been dramatically demonstrated by the effects of the 1996 flood in the Saguenay region of Quebec, the 1997 Red River flood in Manitoba, and the 1998 ice storm in eastern Ontario, southern Quebec and parts of the Maritime Provinces.^{(6, 7, 8, 9)}

Trends in illnesses and deaths associated with air pollution, extreme weather events, allergies, respiratory diseases, and vector-, food- and water-borne diseases all illustrate that weather and climatic factors influence health and well-being.^{(10, 11, 12)} Therefore, there is concern that climate change of the magnitude projected for the present century by the Intergovernmental Panel on Climate Change (1.4-5.8°C increase in mean global temperature; reference 13) may have significant consequences for health and the health care sector in Canada. Indeed, results of climate modelling exercises,⁽¹⁴⁾ assessments of regional environmental and resource vulnerabilities,⁽¹⁵⁾ and climate abnormalities experienced across the country in recent years all indicate that changes in climate could make it more difficult to maintain our health and well-being in the future.

The potential impacts of climate change are classified as either direct (e.g., changes in temperature-related morbidity and mortality) or indirect (e.g., shifts in vector- and rodent-borne diseases).⁽¹⁶⁾ Of particular concern are the effects on more vulnerable population groups, including the elderly, the infirm, the poor and children. Rural residents, who may have to travel farther for health care, and those relying directly on natural resources for their livelihood (e.g., some aboriginal communities), are also considered to be potentially more vulnerable. Overall, health effects will be a function of the nature of climatic changes, exposure to changes, and our ability to mitigate exposure. Although most of the literature focuses on the negative impacts of climate change on human health, certain benefits, such as decreases in illness and mortality related to extreme cold, are also expected.⁽¹⁷⁾ Some of the key issues related to health and climate change in Canada are listed in Table 1.

Although Canadians are generally considered to be well adapted to average conditions, we continue to be challenged by extreme climate events, which sometimes fall outside our current coping range. There are concerns that future climate change will cause this to happen more frequently, and further limit our ability to cope. In fact, any environmental and socio-economic impact resulting from climate change would place additional stress on a health infrastructure that is already dealing with a wide range of challenges. Strategies that serve to reduce the negative impacts of climate change on the Canadian health sector are therefore required. Determining which adaptation options are most appropriate will require an assessment of the vulnerabilities and adaptive capacities of different regions, communities and population groups.

This chapter presents an overview of the major potential impacts of climate change on human health and well-being, and highlights some initiatives that have already been undertaken to better understand the impacts on Canadians and help provide information for the development of adaptation strategies.