"Climate change is likely to have wide-ranging and mostly adverse impacts on human health." ⁽¹⁹⁾

In their summary of research as part of the Canada Country Study, Duncan et al.⁽¹⁷⁾ identified a range of health-related climate change impacts, and discussed the role of potential adaptation strategies. Key concerns included the effects of climate change on heat- and cold-related mortality, a possible northward expansion of vector-borne diseases, an increase in food-borne diseases, changes in the amounts and quality of available water resources, and weaknesses in the public health infrastructure.

Table 1: Possible health impacts from climate change and variability in Canada⁽¹⁸⁾

Particular attention was paid to the effects of high temperature combined with poor air quality in large southern Canadian cities. It was concluded that, in cities such as Toronto, Ottawa and Montréal, the degree of warming projected over the next few decades could lead to a significant increase in the number of deaths during severe heat waves, particularly among the elderly and the infirm.

The Canada Country Study also drew attention to potential increases in disease transmission and bacterial contamination due to climate change. For example, heavy rainfalls could increase outbreaks of infectious diseases such as cryptosporidiosis and giardiasis ('beaver fever'). Warmer temperatures would generally favour the survival of cholera bacteria, as well as the growth of certain algae that release toxins that can accumulate in fish or shellfish. A warmer environment resulting from climate change could also enhance the prevalence of food-borne diseases from enteric bacteria and viruses, favour the northward spread of mosquitoes and ticks capable of transmitting disease (e.g., dengue fever, yellow fever and malaria), and increase the number of disease-carrying rodents and their contact with humans.

Duncan et al.⁽¹⁷⁾ also discussed the need for both short- and long-term adaptations that would reduce the health impacts of climate change. Such adaptation measures include introducing weather-watch warning systems, assisting acclimatization to extreme heat, and improving public outreach and education. The need for increased research, including interdisciplinary studies, was also stressed.