Built Environment

Climate Change and Health

What is climate change?

Climate change is a permanent change in weather patterns over time. This change in weather patterns can impact human health. Climate change is caused mostly by the burning of fossil fuels (oil, gas and coal), which releases pollutants called greenhouse gases into the atmosphere. Other sources of greenhouse gases include agriculture, waste, industrial processes and fugitive emissions (e.g. vapours that escape from storage tanks, pipelines or during transfer of fuels). These pollutants trap heat from the sun, which has led to an increase in the earth's temperatures. Changes in temperature affect ocean currents, air movement, evaporation and precipitation – all factors that affect the weather.

How does climate change affect our health?

Climate change can have both a direct and an indirect impact on human health. Direct impacts include sickness from extreme heat or poor air quality. Health may also be indirectly impacted by extreme heat or flooding resulting in power outages, damage to infrastructure and disruption to transportation and telecommunications.  Such disturbances may increase risks of food contamination, displace people from their homes and jobs, disrupt social support networks, create challenges for accessing healthy food, and increase psychosocial stress.

In Toronto, potential health impacts of climate change include:

• Increased incidence of heat/cold-related illness and premature death

• Severe weather resulting in direct impacts such as injury and indirect impacts such as  water-borne diseases

• Increases in vector-borne diseases

• Food system impacts including food insecurity and food-borne illness

• Degraded air quality increasing cardiovascular and respiratory illness

Who is at risk?

We all are. However, certain populations are at greater risk of climate change health impacts. Vulnerable groups include infants and children, women, seniors, people with underlying health problems, low income and homeless people, people living off the land and First Nation communities. For more information, consult Toronto Public Health's and the Clean Air Partnership's report on climate change and health equity.


This work will be supported alongside City-wide efforts to achieve an 80% reduction in greenhouse gas emission by 2050, through the TransformTO.

ExpandProtecting Health in Cold Weather

Two people crossing a major street in Toronto during a snow stormClimate change is associated with volatile swings in weather and while cold may become less common overall, unusual cold spells may occur more frequently. Various health effects arise from periods of cold weather exposure, including frostnip, frostbite and hypothermia. Toronto Public Health's work on extreme cold is focused on better understanding the relationship between extreme cold and adverse health impacts with a focus on protecting vulnerable populations, including the homeless. This work will contribute to TPH's work in managing the Cold Weather Response Plan.

ExpandProtecting Health in Extreme Heat

picture of a cooling centre when its hot outsideRising global temperatures were recognized early as the result of a changing climate, as were their direct and indirect health effects. The extended heat waves that affected Europe in 2003 and Russia in 2010 were linked to 70,000 and 55,000 deaths respectively and highlighted the significant effect extreme heat can have on morbidity and mortality, even in developed countries.

Efforts to address the health effects of extreme heat ultimately support Toronto Public Health's Heat Alert Program to help people prepare for and cope with hot weather

ExpandPreventing the Health Impacts of Severe Weather

 In Branches encased in ice following an ice-stormthe past few years Toronto has been affected by severe weather events such as flooding and ice storms. These events had significant economic impact on the City and also had direct and indirect effects of the health of Toronto's population.

Severe weather can impact health in a variety of ways. For example, severe rainfall events can result in flooded buildings. The dampness associated with flooded buildings can lead to increases in mould and bacteria growth. Storms and flooding may also contaminate food and drinking water, which may lead to illnesses such as diarrhoeal and intestinal diseases. Water and food-borne illnesses also increase when food is not refrigerated. Toronto Public Health's work in this area is focused on better understanding the acute and chronic health impacts, including mental health impacts of severe weather. Research and action will focus on enhancing resilience and protecting health from the effects of severe weather.

ExpandAir Quality and Climate Change

Small boy sneezingWhile air quality has improved in the last decade, air pollution still gives rise to around 1,300 premature deaths and 3,550 hospitalizations each year in Toronto. Climate change is expected to affect, pollination and consequently, people who suffer from asthma and seasonal allergies.

Toronto Public Health's efforts to address the health effects of air pollution  build on existing efforts in this area, including the promotion of the the Air Quality Health Index a tool designed to help protect people from the effects of poor air quality.

ExpandThe Built Environment and Climate Change

The Toronto skyline with the CN Tower in the background

The built environment means the buildings, transportation systems, energy systems, open space, and agricultural lands that make up and support our communities. The built environment can have a significant impact on human health. In light of climate change, we need to consider the health impacts associated with the way we design, plan and build our cities.

Toronto Public Health's work on the built environment will help mitigate the impacts of climate, adapt to a changed climate, transition to low-carbon while enhancing climate resilience and improving health. Examples of this work include an exploration of the health benefits of expanding green space in the City and the implementation of theActive City Principles.

ExpandPreventing Vector-Borne Diseases

A warning sign for ticks attached to a tree in a campsiteClimate changes can increase infectious diseases passed on by insects, ticks and rodents in various ways, by increasing the amount of insect carriers (e.g. rodents), the amount of breeding habitat (such as standing water left after rainstorms) for some insects, the length of transmission cycles (i.e. longer spring) and the immigration of insect carriers to new regions.

In recent years, West Nile Virus (WNV) and Lyme disease have seen their geographic range expanded northward and pose increased risks to human health in Toronto. The strategy is focused on better understanding the impact climate change may have on the presence and risk of existing and emerging vector-borne disease in Toronto and ultimately, on actions to reduce risk and prevent health impacts.

ExpandWater, Climate Change and Health

Three glasses of water, one empty, one half-ful and one completely full

Climate change is expected to result in changes to the availability and quality of water. In some instances this may mean more water (flooding) or less (drought). The quality and quantity of available water can have impacts on health and sanitation, agricultural productivity, the economy, the natural environment, water-borne disease and important cultural and recreational activities. In light of the fundamental relationship between the availability of clean water and health, the strategy focuses on identifying specific health risks associated with the impacts of climate change on Toronto’s water supply and other processes, services and activities.

ExpandFood and Climate Change

A large stand covered with a variety of fruits and vegetables

Climate change and health are linked across the food system, from production to processing, distribution to storage, consumption to waste disposal. As an example, climate change could affect the availability of some foods as weather events such as flooding, drought and heat can impact agriculture. This could increase food costs and reduce accessibility for people, especially those with low incomes. Toronto Public Health's work in this area builds on projects such as the Toronto Food Strategy and is focused on promoting a sustainable, low carbon food system that promotes access to healthy food and local food production.