Skip to Main Content

Climate Crisis

This guide provides information, resources, and data on the climate crisis

How Does Climate Changes Impact Our Air?

Clean air is one of the most critical environmental factors related to human health. Not only is it the air we breathe, but it is the air that plants and animals also depend on to grow, meaning polluted air impacts humanity in multiple ways. The effects of climate change on air quality are not consistent across the globe, leading to even more gaps in health equity between high income and low income regions of the world within marginalized communities within.

Climate change and air quality are inextricably linked; climate change can affect air quality, and certain air pollutants can also affect climate change,

Outdoor Air Pollution

Air pollution is one of the greatest environmental risk to health, affecting everyone in low-, middle-, and high-income countries. By reducing air pollution levels, countries can reduce the burden of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma. In 2019, 99% of the world’s population was living in places where the WHO air quality guidelines levels were not met. Ambient (outdoor) air pollution is estimated to have caused 4.2 million premature deaths worldwide in 2019.

Many of the sources of outdoor air pollution are also sources of high CO2 emissions. For example, the use of fossil fuels for power generation, industry and polluting transport are all major sources of both particulate matter and CO2.  

Other air pollutants, such as methane and black carbon, are powerful short-lived climate pollutants (SLCPs) that contribute to climate change and ill health . Although SLCPs persist in the atmosphere for short lifetimes, their global warming potential is often much greater than carbon dioxide (CO2).  

Black carbon, a component of fine particulate matter, is one of the largest contributors to global warming after CO2. Black carbon warms the earth’s atmosphere by absorbing sunlight, thereby accelerating the melting of snow and ice. Methane, another SLCP, is a potent greenhouse gas that is 84 times more powerful than CO2, and is a precursor to the air pollutant ozone. Ozone and black carbon affect weather processes and decrease agricultural yields, thus threatening food security. 

According to the Fourth National Climate Assessment, published in 2018, more than 100 million Americans live in areas with poor air quality. Weather patterns, and climate-driven extreme weather events can impact the air quality, especially in response to drought conditions which significantly increase the amount of ground-level ozone and particulate matter. This can exacerbate baseline air quality issues due to burning fossil fuels (transportation, factories, etc.).

Indoor Air Pollution

As outdoor air pollutants such as ground-level ozone and particulate matter increase, the amount of these pollutants that find their way indoors increases. These pollutants can enter buildings in many ways, through open doors and windows, ventilation systems, and even tiny cracks such as unsealed windows, doors, and vents.

Other indoor air pollutants, such as molds, dust mites, bacteria, and other allergens and pathogens can also increase in response to extreme weather events such as storms and flooding due to damp indoor environments where mold, bacteria, and other pollutants can form.

In many low and middle-income countries that rely on burning fuel (such as biomass, coal and kerosene) using inefficient devices for cooking, heating and lighting is a major contributor to premature death and disability. Exposure to household air pollution is associated with acute lower respiratory infection, chronic obstructive pulmonary disease, lung cancer, stroke, and cardiovascular disease. Households in poor rural areas, especially women and children who are primarily responsible for cooking and collecting fuel, are especially vulnerable. Around 2.4 billion people cook and heat their homes with polluting fuels and every year 3.2 million people die prematurely from household air pollution.

Wildfire Smoke

Climate change is already significantly impacting the length of wildfire season and the frequency of large-scale wildfires. This year's record-breaking Canadian wildfires are only the beginning of what is to come. During the month of May alone, Canada saw greater than 6.5 million acres (2.7 million hectares) burn, compared with an average of about 370,000 acres (150,00 hectares) during the month. Most of the May 2023 wildfires were in Western Canada (Alberta, British Columbia, and Saskatchewan). However, by June the wildfires, ignited by extreme heat, moved eastward across the country, including dozens of fires in Nova Scotia and Quebec.

On June 8, 2023, the White House briefed the American public on the historic wildfire and smoke conditions impacting the East Coast of the United States. "More than 100 million Americans are under Air Quality Index Alerts due to smoke drift from historic wildfire activity throughout Canada, which is facing one of its worst wildfire seasons on record.  There are over 425 active wildfires in Canada and nearly 10 million acres have burned, 17 times the 20-year average.  Since January 1, 2023, 19,574 wildfires have burned 616,486 acres across the United States.  Most current large fire activity in the United States is concentrated in the Southwest."

Airborne Allergens

As climate change shifts seasons, with expected earlier onset of spring, longer summers, shorter and warmer winters, and extreme precipitation changes, allergen exposure shifts and extends leading to increased risk of allergy-related illnesses such as asthma, hayfever, and other respiratory conditions.

What's in Our Air?

Ambient and household air pollution can come from similar processes such as incomplete combustion of fuels or chemical reactions between gases. However, the specific source of the combustion process can vary. Health problems can occur as a result of both short- and long-term exposure to these various pollutants. For some pollutants, there are no thresholds below which adverse effects do not occur. 

Particulate matter (PM) refers to inhalable particles, composed of sulphate, nitrates, ammonia, sodium chloride, black carbon, mineral dust or water. PM can be of different size and is generally defined by their aerodynamic diameter (in microns/micrometers), with PM2.and PM10 the most common in the regulatory framework and relevant for health.

Particulate matter is capable of penetrating deep into the lung and enter the bloodstream causing cardiovascular (ischaemic heart disease), cerebrovascular (stroke) and respiratory impacts. Both long-term and short-term exposure to particulate matter is associated with morbidity and mortality from cardiovascular and respiratory diseases. Long-term exposure has been further linked to adverse perinatal outcomes and lung cancer.

Course Particles

Course particles (PM10) are those with a diameter between 2.5 µm and 10 µm. This larger particulate matter is visible to the naked eye. It can include such things as pollen, sea-spray, and wind-blown dust.

Fine Particles

Fine particles (PM2.5) are those with a diameter less than 2.5 µm. These microscopic particles can come from both primary sources (combustion in power plants, vehicles, and factories), or secondary sources (chemical reactions between two or more gases).

Ultrafine Particles

Ultrafine particles (UFP) are  particulate matter with a diameter less than or equal to 0.1 µm. UFP are commonly found in transportation combustion processes, power plants, and residential heating. Exposure to UFP can increase the likelihood of pulmonary, cardiovascular and ischaemic heart diseases.

Ozone in our atmosphere is a good thing, and greenhouse gases have been eroding the "ozone layer" that protects us from harmful UV radiation from the sun. However, when ozone is near the surface it takes on a completely different role. Ground-level ozone (O3) is a major component of smog. It is formed from photochemical reactions with pollutants such volatile organic compounds (carbon monoxide and nitrogen oxides) emitted from vehicles, and industry. Due to the photochemical nature, the highest levels of ozone are seen during periods of sunny weather.

It is worth mentioning that ozone can also be generated by household equipment, such as certain portable air cleaners.  

Exposure to excessive ozone can cause problems breathing, trigger asthma, reduce lung function and lead to lung disease.   

Carbon monoxide (CO) is a colorless, odorless gas produced by the incomplete combustion of carbonaceous fuels such as wood, petrol, coal, natural gas and kerosene in simple stoves, open fires, wick lamps, furnaces, fireplaces. The predominant source of carbon monoxide (CO) in ambient air is from motor vehicles.

Carbon monoxide diffuses across the lung tissues and into the bloodstream, making it difficult for the body’s cells to bind to oxygen. This lack of oxygen damages tissues and cells. Exposure to carbon monoxide can cause difficulties breathing, exhaustion, dizziness, and other flu-like symptoms. Exposure to high levels of carbon monoxide can be deadly.

Black carbon is a major component of PM2.5 and it is sometimes referred to as soot and its main sources are from incomplete combustion of fossil fuels, biofuels and biomass. It can be emitted both from anthropogenic (e.g. diesel vehicles, biomass cookstoves) and natural (e.g. wildfires) sources. It is also a potent warming agent in the atmosphere and contributes to regional environmental disruption and accelerates glacier melting. 

Short- and long-term exposure to black carbon has been associated with cardiovascular health effects and premature mortality.

Nitrogen Dioxide

Nitrogen dioxide (NO2) is a reddish-brown gas that is soluble in water, and a strong oxidant. Nitrogen dioxide occurs from high-temperature fuel combustion found in processes such as heating (furnaces, fireplaces), transportation, power generation, and cooking (gas stoves/ovens).

Exposure to nitrogen dioxide can irritate airways and aggravate respiratory diseases. NO2 is an important ozone precursor, a pollutant closely linked to asthma and other respiratory conditions.

Sulfer Dioxide

Sulfur dioxide (SO2) is a colorless gas that is readily soluble in water. It is predominantly derived from the combustion of fossil fuels for domestic heating, industries and power generation.

Exposure to SO2 is associated with asthma hospital admissions and emergency room visits.

Polycyclic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAH) are present in the atmosphere in particulate form. They are a group of chemicals formed primarily from incomplete combustion of organic matter (e.g. cooking of meat) as well as fossil fuels in coke ovens, diesel engines and wood-burning stoves.  They are also emitted from tobacco smoke.

Short-term exposure can irritate eyes and breathing passages. Long-term exposure to PAH has been linked to lung cancer.


Lead (Pb) and lead particulate compounds can be found in the home in contaminated dust from products such as paints, ceramics, pipes and plumbing materials, solders, gasoline, batteries, ammunition, and cosmetics. Lead can also be found in ambient air from vehicle exhaust of fuel with lead.

Lead poses health risks of particular concern for children and pregnant women. The health impacts for children exposed to lead include behaviour and learning problems, lower IQ and hyperactivity, slowed growth, hearing problems, and anemia. In rare cases, ingestion of lead can cause seizures, coma and even death. For pregnant women, health risks include reduced growth of the fetus and premature birth.

Adults exposed to lead also have a higher risk of cardiovascular effects increased blood pressure, the incidence of hypertension, decreased kidney function and risk of reproductive problems in both men and women.


Formaldehyde is a colorless gas with a pungent smell. It is one of the most common volatile organic compounds (VOCs) found indoors. Formaldehyde is emitted from building materials (e.g. particleboard, plywood, glue, paints) as well as household and personal care products (e.g. drapes, carpets, cleaning products, hair sprays). Additional indoor sources may be combustion processes such as smoking, heating, cooking, or candle or incense burning.

Short-term exposure to formaldehyde can lead to eye, nose and throat irritation as well as increased allergic sensitization. However, long-term exposure to formaldehyde has been associated with nasopharyngeal cancer.  


Radon (Rn) is a radioactive gas that emanates from certain rock and soil formations, concentrating in the basement or ground levels of homes, in the absence of inadequate ventilation or evacuation systems.

Recent studies on indoor radon in Europe, North America and Asia indicate that lung cancers attributable to radon may range from 3% to 14%, making radon the leading cause of lung cancer among non-smokers.

Air Quality Equity

Population Inequality

The level of health risk varies between populations. People living in low and middle-income countries are typically more vulnerable to air pollution due to the higher levels of air pollution they are exposed to each day, and the higher prevalence rates of diseases that are negatively affected by air pollution exposure, like asthma. Populations living in slums or near busy highways or roads, lacking access to clean cooking, or in certain occupations are other examples of populations more vulnerable to the adverse impacts of air pollution.  

Energy Poverty

The health risks of household air pollution are strongly correlated with poverty. These risks are not distributed evenly across countries, or even within countries. People in sub-Saharan Africa, South-East Asia and the Western Pacific experience the highest rates of health problems from exposure to indoor pollutants related to household energy use. Within these regions, the burden of disease falls most heavily on rural households. Because they lack the resources to obtain cleaner fuels and devices, people in lower-income households rely mostly on fuels that they can freely gather, such as wood and dung and more traditional inefficient cooking stoves.  

Women and Children

Within poorer households, women, children, and the elderly bear the brunt of health and other impacts of household air pollution. In most low- and middle-countries, women and children perform the domestic tasks related to household energy provision including gathering and processing fuel, tending the hearth and cooking meals; all of which led to chronic strain and injury. As they spend the most time in the kitchen or in polluted living spaces, women and children have higher rates of exposure to particulate matter and other pollutants emitted by stoves and open fires. 

Vicious Cycles

Additionally, reliance on inefficient household fuels and devices limits the time available, especially to women, for income generation, schooling, and other opportunities for economic development. Similarly, households with limited or no access to a clean and reliable source of lighting (e.g. electricity) can lose opportunities for educational and income-generating activities outside of daylight hours. 

Energy poverty thus locks people in a vicious cycle, sapping them of time, damaging their health, and limiting their access to better livelihoods, education, and other paths out of poverty.