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Degrees of Change – Human Health

2.0 The NRTEE’s Degrees of Change diagram: Illustrating the Impacts of Climate Change in Canada

Human Health

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This category refers to the overall health of Canadians, although the diagram’s focus is physical health. Health status is an important indicator of national prosperity. A country’s ability to innovate and remain productive depends on the characteristics and quality of its human capital, key elements of which are health, education, and skills. Promotion and enhancement of Canadians’ health is a national objective, with significant investment attached to it. Total health spending accounted for about 10% of Canada’s gross domestic product in 2008, a slightly higher proportion than the OECD average.[84]

Weather and climate directly and indirectly affect the health status of individuals or groups of individuals within a given community. For example, the 1998 ice storm in eastern Canada resulted in 28 deaths from trauma or hypothermia related to power outages, and a number of illnesses and injuries for which medical treatment was necessary.[85] In addition to direct health impacts, events such as these cause stress and affect mental and physical health. Consider the stress from temporary evacuations, extensive damage to homes and business assets, and subsequent insurance and rebuilding hassles. Lost productivity and the need for emergency services, such as medical services, are additional social costs tied to health impacts from the hazards of extreme weather.


Figure 8: Resource Industries


What we can expect



Extreme weather and climate events such as droughts, storms, heavy rainfall events, and heat waves increased over the last century, as did the number of injuries, the number of Canadians affected, and associated economic costs.[86] In a changing climate, these events will increase in frequency, intensity, and duration,[87] as could the health impacts and financial costs.[88] For example, as temperatures rise, the number of hot days exceeding 30°C is likely to as well. By the end of the century, communities in southern Canada could experience as many as four to six times more hot days during summer months than they did toward the end of the 20th century.[89] Annual heat-wave deaths for parts of southern Canada could double with global average temperatures between about 1.5°C and 2°C.[90]


Warmer global temperatures could affect air quality in Canada in several ways. Levels of ground-level ozone and particulate matter could increase, as could emissions of noxious chemical compounds from plants (volatile organic compounds) and soils (nitric oxide), production of pollens and other aeroallergens, and the number and duration of wildfires.[91] Studies project the severity and duration of air pollution episodes to increase in some areas of Canada because of a warming climate.[92] Air pollution can adversely affect cardiac and respiratory function, including damage to lung tissue, putting people with asthma or other breathing problems particularly at risk. In 2008, air pollution contributed to the death of more than 21,000 Canadians.[93] A rise in average local temperatures of 4°C could lead to a 5% increase in air pollutant-related health burdens on Canadian society relative to a 2002 baseline.[94]


Climate change is increasing Canadians’ exposure to infectious diseases transmitted via insects and mammals.[95] Warmer winters and warmer and more humid summers create conditions favourable for mosquitoes carrying West Nile.[96] The type of West Nile virus that first emerged in North America requires warmer temperatures than other strains; an increase in temperatures could result in higher levels of this type of virus.[97] Cold temperatures currently limit the geographic range of ticks carrying Lyme disease. Global temperatures at least 2°C over pre-industrial levels would accelerate the tick lifecycle and expand the northern limit of its range by 1,000 km, increasing the likelihood of transmitting Lyme disease to Canadians.[98] The introduction of new vector-borne diseases, such as Eastern Equine Encephalitis virus and St. Louis Encephalitis virus is possible. The risk of increased prevalence of tropical diseases such as malaria in Canada remains low in a changing climate.


Carried by ticks, Lyme disease, affects upward of 20,000 people annually in the United States. In a changing climate, warmer temperatures could expand the range of black-legged tick populations (I. scapularis) northward, exposing more Canadian to Lyme disease risks. Since 1997, new populations of the black-legged tick have been identified in southern Ontario, Nova Scotia, southeastern Manitoba, and New Brunswick, with data on Lyme disease cases suggesting a recent increase in the number of endemic cases in central and eastern Canada. In the decade prior to 2004, 15 cases were reported annually in these areas, but from 2004 to 2006, 69 cases were reported, with the annual incidence doubling in 2005 and 2006. As of this year, medical professionals must report cases of Lyme disease to the Public Health Agency of Canada by way of their regional public health systems.

Changing precipitation patterns heighten exposure risk to diseases transmitted via water. Prolonged drought followed by excess rainfalls was determined to be one of the factors contributing to the E. Coli outbreak in Walkerton, Ontario, in 2000 in which 2,300 people became sick and seven people died. Similar conditions contributed to a toxoplasmosis outbreak in Victoria, British Columbia, in 1994–1995 and a Cryptosporidium outbreak (causing gastrointestinal illness) in Milwaukee (United States) in 1993. In 2006, a million people in Vancouver, British Columbia, were subject to boil water advisories for nearly two weeks due to increased turbidity and the unacceptable quality of drinking water following a major rainstorm that affected three reservoirs in the area.

Sources: Mackenzie et al. (1994); Bowie et al. (1997); BGOSHU (2000); Auld et al, (2001); Centers for Disease Control and Prevention (2003); Ogden et al. (2004); Ogden et al. (2005); Berrang-Ford (2006); CBC News (2006); and, Ogden et al. (2008);Lyme Disease fact Sheet.


Higher temperatures and changing patterns of intense rainfall events are associated with higher rates of water- and food-borne disease, particularly during summer months.[99] Higher temperatures increase the abundance of pathogens, such as bacteria, and intense rainfall events increase the odds of well water contamination. Pathogens currently contributing to outbreaks of water-borne diseases in North America include Escherichia coli, Giardia, Cryptosporidium and Toxoplasma. By crossing key thresholds, climate change may result in conditions favourable to more frequent and intense outbreaks of water-borne diseases. A 5°C increase in maximum daily temperature over a 42-day period quadruples the risk of disease outbreak.[100] Climate change may also allow the re-establishment of diseases previously eradicated in Canada such as leptospirosis and cholera.[101]

Food-borne diseases result from the ingestion of contaminated food, with Salmonella, Campylobacter, and E. coli being the most common food-borne pathogens in Canada.[102] Canada has an excellent food safety system in place, yet food production chains are sensitive to changes in climate conditions. Within limits, ambient temperatures influence survival rate of bacteria and parasites transmitted via food.[103] Longer summers with hotter temperatures, conditions expected in a changing climate, are likely to increase the number of cases of food-borne disease and lengthen the period over which they take place.

What we can do about it

Canada already has measures in place and the ability to protect the health of its population from hazards linked to environmental conditions. These safeguards include safe water (treatment); air and food regulations; high-quality public infrastructure such as storm sewer, drainage and sanitation systems; health infrastructures and services, including disease surveillance, public health programs, and vaccinations; and adequate income, housing and clothing to handle environmental conditions such as heat, cold, and pests. A changing climate will place increased demands on emergency hospital services and the health care system generally. Attaining public health standards will require adjustments in the health system to take into account future climate change impacts and their effect on vulnerable populations, such as low-income Canadians, Aboriginal Canadians, children, the elderly, and those with heart, breathing, and immunity problems. Understanding the health implications of climate change impacts in other sectors — such as public infrastructure systems — is also important.

Adaptive strategies include preventative and reactive measures. Some preventative strategies have less to do with the health system and more to do with land use, energy planning, and environmental policy. They include increasing albedo and planting trees to counteract the urban heat-island effect, and reducing emission of air pollutants. The first example addresses health impacts from extreme heat and the second from poor air quality. Other preventative strategies generally involve public information, early warning systems, and health services planning, and include heat alert and response systems, infectious disease surveillance and response plans, air quality indices, and smog advisories. Rather than taking action to prevent, avoid, or reduce health impacts, reactive approaches involve treating health impacts such as illness from heat-related events as they arise.


Health Canada and Environment Canada have recently developed an Air Quality Health Index (AQHI), a national index that provides information relating air pollution to health risk, disseminated with weather forecasts. A collaborative effort between federal, provincial, and local environmental health authorities, the AQHI is a tool to help Canadians protect their own health by limiting short-term exposure to adverse air quality and adjusting activity levels during air quality episodes. At present, the AQHI is tailored to local conditions in selected communities across all provinces but Alberta, and its reach is expected to expand over time. Measures to reduce chronic or long-term exposure to air pollutants are complementary to initiatives such as the AQHI.

Box 10: The Air Quality Health Index







84 OECD Health Data 2010 (under “frequently requested data”), retrieved on July 30, 2010 from:,3343,en_2649_34631_12968734_1_1_1_1,00.html

85 Retrieved July 30, 2010

86 See Berry et al. (2008) for a comprehensive assessment of the health impacts of climate change-related natural hazards. Analyzing data the Public Safety disaster database suggests an upward trend in weather and climate-related disasters: we estimated that the ten-year average number of disasters from weather and climate-related hazards increased from about four to fourteen between 1950 and 2001.

87 See Table 6 in Warren & Egginton (2008).

88 Etkin et al. (2004).

89 Hengeveld et al. (2005) reported a four to six-fold increase in number of hot days over 30°C for six Canadian southern cities by the last couple of decades of this century, compared to a 1961–1990 baseline.

90 Cheng et al. (2005) found that heat wave deaths are expected to more than double by the 2050s and triple by the 2080s (based on IS92a and SRES A2 and B2); current annual average heat wave deaths in only four cities are 320, including other cities across Canada, in addition to population growth, results in an estimate of 3000 heat wave deaths per year for 2080s. In the Degrees of Change diagram, we plot this impact along the global temperature scale using best estimates for 2050s for IS92a (low) and A2 (high), two of the scenarios used by Cheng et al.

91 Prather et al. (2003); Hogrefe et al.( 2004); Lagner et al.( 2005);  Seguin (2008); Lamy & Bouchet (2008).

92 Mickley et al. (2004), Leung & Gustafson Jr. (2005).

93 Canadian Medical Association (2008).

94 Lamy & Bouchet (2008) assessed the national health impacts of air quality changes from a 4° C increase in ambient temperatures, considering changes in ground level ozone and particulate matter.  Relative to a 2002 baseline incidence, they found a 5% increase in air pollutant-related health burden to Canadian society.  In the degrees of change diagram, we plot this impact along the global temperature scale at 2.7°C (which accounts for Lamy and Bouchet’s use of local temperatures as bases for scenarios).  IPCC (2007) Working Group II technical summary Table TS4 highlights “about 70% increase in hazardous ozone days” for North America between 2.5-4°C above pre-industrial temperatures.

95 For a comprehensive review of the state of knowledge of Canadians’ vulnerability to vector, food, and water-borne disease linked to a changing climate, see Charron et al. (2008). Increased exposure to infectious diseases in connection to climate change is not only a concern for humans. Purse et al. (2005) describe a resurgence in bluetongue disease, a devastating illness affecting ruminants (such as cattle), in Europe.

96 Charron et al. (2008)

97 Public Health Agency of Canada (2007)

98 Ogden et al. (2006) project an expansion of the tick’s range by 1000km in 2080s, using an A2 scenario (this corresponds to a likely range of 2–4.6°C global temperature rise above pre-industrial levels).

99 Curriero et al. (2002); Charron et al. 2008.

100 See Thomas et al. ((2006) for details on this relationship and its implications. In the degrees of change diagram, we plot the impact related to water-borne diseases along a temperature range that reflects the potential for poorer water quality in some regions and vulnerability due to increased extreme rainfall events (1–3.9°C).

101 Charron et al. (2008).

102 Public Health Agency of Canada (2003).

103 Hall et al. (2002).