Health and health services are extremely important to Canadians. Physical, mental and social well-being are key indicators of quality of life, and more than $100 billion is spent each year on health services. Although health is influenced by a range of social and economic factors, our country's variable climatic conditions also play a role. Seasonal trends are apparent in illness and death, while extreme climate events and weather disasters have both acute and chronic health effects.

The impacts of future climate change on health and the healthcare sector in Canada would be both direct (e.g., changes in temperature-related morbidity and mortality) and indirect (e.g., shifts in vector-borne diseases). There would be some benefits for human health, as well as many challenges (see Table 2). It is expected that climate change would make it more difficult to maintain our health and well-being in the future. The impacts on the more vulnerable groups of the population, including the elderly, the young, the infirm and the poor, are of particular concern.

Higher temperatures are expected to increase the occurrence of heat-related illnesses such as heat exhaustion and heat stroke, and exacerbate existing conditions related to circulatory-, respiratory- and nervous-system problems. An increase in heat waves, particularly in urban areas, could cause significant increases in the number of deaths.

Higher overnight temperatures during heat waves are also a concern for human health, as cooler temperatures at night offer much-needed relief from the heat of the day. With respect to beneficial impacts, a decrease in extreme cold events during the winter would decrease cold-weather mortality, especially among the homeless.

Respiratory disorders, such as asthma, would be affected by changes in average and peak air pollution levels. Higher temperatures could lead to an increase in background ground-level ozone concentrations, and increase the occurrence of smog episodes. Air pollution would also be affected by an increase in airborne particulates, resulting from more frequent and intense forest fires. Airborne particulates have been shown to cause nasal, throat, respiratory and eye problems.

Table 2: Potential health impacts from climate change and variability

Another concern is the potential impact of higher temperatures and heavier rainfall events on waterborne diseases. Heavy rainfall and associated flooding can flush bacteria, sewage, fertilizers and other organic wastes into waterways and aquifers. A significant number of waterborne disease outbreaks across North America, including the E. coli outbreak in Walkerton, Ontario in 2000, were preceded by extreme precipitation events. Higher temperatures tend to increase bacterial levels and can encourage the growth of toxic organisms, including those responsible for red tides (toxic algal outbreaks).

Warmer weather may also make conditions more favourable for the establishment and proliferation of vector-borne diseases by encouraging the northward migration of species of mosquitoes, ticks and fleas, and by speeding pathogen development rates. Some diseases of potential concern include malaria, West Nile virus, Lyme disease, and Eastern and Western Equine Encephalitis. Mosquito-borne diseases, such as West Nile virus and malaria, may also be able to exploit an increase in breeding grounds resulting from increased flooding.

Communities in northern Canada would face additional health-related issues due to the impacts of climate change on the distribution and characteristics of permafrost, sea ice and snow cover. In fact, there is strong evidence that northern regions are already experiencing the impacts of climate change. Some key concerns include the consequences of these changes on travel safety, ability to hunt traditional food, access to clean drinking water and fish contamination.

Some emerging issues with respect to climate change and health include potential effects on allergens and human behaviour. Increased temperatures, elevated atmospheric CO2 concentrations and longer growing seasons would encourage plant growth and pollen production. Human behaviour could be affected by increases in natural hazards and extreme climate events, as these can lead to psychological stresses, including elevated anxiety levels and depression.

Although Canadians are already adjusted to a variable climate, climate change would place new stresses on the health sector, which would require additional adaptations. To maximize the effectiveness of climate change adaptations, climate change should be incorporated into existing population health frameworks. Integrating efforts between different groups to develop a co-ordinated response to climate change and health, and expanding monitoring and outreach initiatives, is also important.

Adaptation has the potential to significantly reduce health-related vulnerabilities to climate change. Some adaptation initiatives include the development of vaccines against emerging diseases, public education programs aimed at reducing the risk of disease exposure and transmission, and improving disaster management plans so as to enhance emergency preparedness. The implementation of early warning systems for extreme heat and cold is another effective adaptation strategy, which has recently been introduced in Toronto, Ontario. Reducing the heat island effect in urban areas would also reduce future climate change impacts.