Everyone is susceptible to extreme heat, but it does not affect the health of all members of society equally. Those particularly vulnerable to heat include infants and young children, seniors, people with underlying medical conditions (such as heart or lung problems) and people who are economically disadvantaged, live in substandard housing, or do not have access to air conditioning.
Geographical differences also play a role in the effects of heat, which appear to be greater in cities than in rural areas. Urban settings typically include high-rise apartments, where people residing on the top floors are at greater risk of heat exposure. Residents of the older structures common in many cities—usually multi-family brick dwellings with poor ventilation and a high heat load—are especially at risk. Finally, the presence of urban heat islands can have a dramatic effect on city dwellers (Figure 1).1 These areas are often warmer than their surroundings because concrete and asphalt retain heat.
Public Health Responses
To mitigate the harmful effects of extreme heat, public health practitioners and policymakers are working to improve surveillance and intervention strategies. Some cities, including Toronto and Montreal, have implemented heat alert and response systems that issue warnings when meteorological forecasts predict unusually hot weather. Response plans may include media announcements, activation of buddy systems, operation of telephone helplines, and opening of “cooling” centres. However, one of the challenges public health practitioners face in developing interventions for heat-related illness is locating vulnerable populations within larger communities. Once the location of vulnerable people is known, then public health officials can use targeted interventions to prevent heat-related illness.
Currently, several cities are conducting heat vulnerability assessments to map locations where interventions will likely be needed during a heat wave. Researchers are helping with this by creating indices of vulnerability2 using census and health data to identify the proportion of residents in an area who are at risk (Figure 2).
- 1. The reproduction is a copy of an official work that is published by the Government of Canada. This reproduction has not been produced in affiliation with, or with the endorsement of the Government of Canada.
- 2. Reid CE, O’Neill MS, Gronlund CJ, et al. Mapping Community Determinants of Heat Vulnerability. Environ Health Perspect. 2009; 117(11): 1730–1736.