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.

Changes include more frequent severe weather events such as:

  • extreme heat
  • extreme rain or snowfall
  • extreme drought
  • severe storms

Why is climate change happening?

  • 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 lead 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.
  • Most experts agree that average global temperatures could rise by 1 to 6.5°C over this century.

How could Toronto's climate be affected?

The City of Toronto used computer models to predict how our local climate may change by the year 2049.  The 2013 study predicts changes that include more rain storms and much higher temperatures:

Weather Extreme


Year 2000-2009

Year 2040-2049

Extreme Rain

Most rain likely in one day

66 mm

166 mm

Average of annual daily maximum rainfalls

48 mm

86 mm

Extreme Heat

Extreme Daily Maximum temperature



Number of Days with temperatures higher than 30C



Number of heat events with 3 consecutive days with temperatures greater than 32C




What can we do to reduce the pollution that causes climate change?

There are many things we can do to reduce the emissions of pollution that cause climate change, such as walking or taking transit instead of driving your vehicle. The City of Toronto's Livegreen initiative provides many programs to assist in taking actions to protect the environment. Toronto Public Health's 20/20 The Way to Clean Air Campaign helps Torontonians reduce energy use at home and on the road by 20%.

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 from flooding, power outages and disruption in government and business services.  The potential health impacts of climate change include:

Sickness from Heat

Extreme heat may cause:

  • dehydration
  • heat stroke, heat cramps and heat rash
  • fainting
  • worsening of existing medical problems, such as asthma and allergies.

Some people, such as the elderly and those without access to air conditioning, can be more vulnerable to extreme heat than the general population.  

Toronto Public Health has maps that show areas where seniors and the general population within the city may be more vulnerable to heat.  

Here are some way to protect your health and the health of others:
• Watch the news for heat alerts  
Find air conditioned places to keep cool.  
• Call or visit family, friends and neighbours, especially isolated seniors to make sure they are alright.
• If you're a landlord, you can follow these three steps to protect your tenants from stress and illness.

Sickness from poor air quality

Extreme heat contributes to air pollution. Increased air pollution causes:

  • eye, nose and throat irritation
  • shortness of breath
  • worsened respiratory conditions and cardiovascular disease
  • increase in risk for certain types of cancer and premature death.

The Air Quality Health Index is a tool designed to help protect from poor air quality.

Food and water contamination

Storms and flooding may 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. Extreme heat events may cause Torontonians to use their air conditioners more, which may cause power outages. There are many things that can be done to ensure food safety during a power outages and floods.

Infectious diseases from insects, ticks and rodents

Climate changes can increase infectious diseases passed on by insects, ticks and rodents in three ways, by increasing the:

  • amount of insect carriers (e.g. rodents)
  • amount of breeding habitat (such as standing water left after rainstorms) for some insects
  • length of transmission cycles (i.e. longer spring)
  • the immigration of insect carriers to new regions

West Nile Virus is a disease passed on through mosquitoes.  You can reduce your risk by preventing standing water on your property and using insect repellent.

Climate change may lead to new diseases as well as the return those that were previously wiped out. For example, Lyme disease (a disease that comes from ticks) is likely to increase. Although Lyme disease is currently uncommon in Canada, changes in temperature may cause an increase in the tick population and expand the geographical areas in which they live. Lyme disease may cause long term complications such as nerve damage and vision problems.

Mould and bacteria

Climate change will lead to increased flooding. Homes or buildings that are filled with flood or storm water or are exposed to a lot of dampness for a long time will have an increase in mould and bacteria growth. For some people, exposure to mould and bacteria can contribute to illnesses, such as:

  • respiratory distress
  • eye and nasal irritations
  • laryngitis
  • flu-like symptoms
  • asthma and allergy initiation and aggravation

You can reduce the risk of basement flooding.  If your basement floods, be sure to know how to clean up after the flood or call 3-1-1.

Who is at risk?

We all are. However, certain populations are at greater risk of climate change health impacts. This is due to:

  • exposure (e.g. a person with poor or no housing may have increased exposure during an extreme weather event);
  • sensitivity (someone with respiratory illness may be more sensitive to air pollution than others); and
  • inability to adapt to climate change (older people have a lower capacity to adapt to natural hazards to due to limited mobility).

Extreme heat or flooding may also cause power outages, damage infrastructure and disrupt 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.

Vulnerable groups include:

  • infants and children
  • women
  • seniors
  • people with underlying health problems
  • low income and homeless people
  • people living off the land
  • First Nation communities

Toronto Public Health and the Clean Air Partnership have written a report on climate change and health equity.

How can we protect ourselves?

We can reduce the amount of greenhouse gases we produce that contribute to climate change.  For example, we can:

There are rebates and incentives for homes and businesses to get you started.

We can also prepare for the expected changes in our climate.  For example, we can:
protect our homes from flooding and water damage
register to get heat alerts notices, so you can help vulnerable family members or neighbours cope, by preparing them for extreme heat or rain and visiting during these events.  

What is the City of Toronto doing to deal with climate change?

Toronto Public Health and other City divisions are conducting research and have programs to address climate change.  This work includes:
Toronto Public Health's Heat Alert Program and Hot Weather Response Plan to help people prepare for and cope with hot weather
LiveGreen Toronto supports individuals, school groups and businesses to go green
The Sustainable Energy Strategy aims to reduce the City's greenhouse gas emissions by 80 per cent from 1990 levels by 2050, and support more renewable and sustainable energy grid.