Air Quality Alert: Polluted Air Percentage

Air pollution is a significant global issue that poses risks to both human health and the planet. It is caused by the release of pollutants into the atmosphere, which can be detrimental to people's health and the environment. According to the World Health Organization (WHO), air pollution is responsible for approximately seven million premature deaths worldwide each year, making it the world's fourth-largest risk factor for early death. The sources of air pollution are diverse and context-specific, including indoor and outdoor sources such as household combustion devices, motor vehicles, industrial activities, and natural phenomena. While air pollution is a global issue, low- and middle-income countries tend to be disproportionately affected, with 99% of people worldwide breathing air that exceeds the WHO's recommended limits for pollutants.

Air pollution's impact on health

Air pollution is defined as the presence of one or more contaminants in the atmosphere, such as dust, fumes, gas, mist, odour, smoke or vapour, in quantities and durations that can be harmful to human health. According to the World Health Organization (WHO), around seven million deaths worldwide are caused by indoor and outdoor air pollution each year. Ninety-nine per cent of human beings currently breathe air that exceeds the WHO's guideline limits for pollutants, with those living in low- and middle-income countries suffering the most.

The main pathway of exposure from air pollution is through the respiratory tract. Pollutants cause inflammation, oxidative stress, immunosuppression, and mutagenicity in cells throughout the body, impacting the lungs, heart, brain and other organs. Some pollutants are small enough to penetrate the bloodstream via the lungs and circulate throughout the body, leading to systemic inflammation and carcinogenicity. Fine particulate matter, such as soot, is especially dangerous as it can cause damage to tissues and cells. Short-term exposure to fine particulate matter can lead to reduced lung function, respiratory infections and aggravated asthma, while long-term exposure increases the risk of noncommunicable diseases such as stroke, heart disease, chronic obstructive pulmonary disease and cancer.

Maternal exposure to air pollution is associated with adverse birth outcomes, including low birth weight, pre-term birth and small gestational age births. Air pollution can also cause harm to the brain and slow a baby's brain and behavioural development. Studies have also shown a strong link between air quality and mental health, with people living in areas with poor air quality experiencing higher rates of bipolar disorder and major depression.

In addition to the direct health impacts, air pollution also has economic costs. In Canada, the total economic cost of all health impacts attributable to air pollution for one year was $120 billion (2016 CAD), equivalent to approximately 6% of Canada's 2016 real gross domestic product.

While there has been progress in reducing air pollution, climate change is making it harder to maintain these improvements. Extreme heat, drought and wildfires are contributing to worsening levels of air pollution, exposing a growing proportion of the population to harmful pollutants. Communities of colour are disproportionately exposed to unhealthy air and are also more likely to be living with chronic conditions that make them more vulnerable to air pollution.

Sources of air pollution

Air pollution is responsible for nearly seven million deaths worldwide each year, according to the World Health Organization (WHO). It is the fourth-largest risk factor for premature death globally. In the United States, 46% of the population, or 156.1 million people, live in areas with unhealthy levels of ozone or particle pollution, according to the 2025 "State of the Air" report by the American Lung Association. This is an increase of nearly 25 million people compared to the previous year's report.

There are four main types of air pollution sources: mobile, stationary, area, and natural. Mobile sources, such as cars, trucks, planes, and trains, account for more than half of all air pollution in the United States, with automobiles being the primary contributor. Stationary sources, such as power plants, oil refineries, industrial facilities, and factories, emit large amounts of pollution from a single location. Area sources include agricultural areas, cities, and wood-burning fireplaces, which collectively contribute significantly to air pollution. Natural sources, such as wind-blown dust, wildfires, and volcanoes, can also contribute to air pollution, although they typically do not create ongoing pollution problems like the other source types.

Motor vehicles are a significant contributor to air pollution, emitting pollutants such as carbon dioxide, carbon monoxide, nitrogen oxides, and sulfur oxides. Older diesel engines, in particular, produce significantly more fine particulate pollution than newer models. The combustion of fossil fuels, such as coal, gasoline, and natural gas, releases harmful chemicals and gases into the air, contributing to smog formation. Smog, or ground-level ozone, irritates the eyes and throat and damages the lungs, especially in children, the elderly, and those with asthma or allergies.

Industrial processes are another major source of air pollution. Power plants, industrial boilers, refineries, and factories release pollutants that contribute to smog and particulate matter formation. Particulate matter, composed of chemicals such as sulfates, nitrates, carbon, or mineral dusts, can penetrate deep into the lungs and lead to serious health issues. Fine particulate matter (PM2.5) has been linked to an increased risk of cardiovascular disease, respiratory diseases, and neurological disorders.

Agricultural emissions, including the burning of agricultural waste and the use of diesel engines in agricultural equipment, contribute to air pollution. Residential wood burning, primarily for home heating, is also a significant source of fine particle emissions, especially in states like Minnesota. Wildfires, which are becoming more frequent and severe due to climate change, release particulate matter and gases that contribute to air pollution over vast areas.

Air pollution by country

Air pollution is defined as the release of pollutants into the atmosphere that are detrimental to human health and the planet. According to the World Health Organization (WHO), air pollution is responsible for around seven million deaths annually across the globe. Furthermore, 99% of humans currently breathe air that exceeds the WHO's guideline limits for pollutants, with those in low- and middle-income countries suffering the most.

The countries with the worst air pollution vary from year to year, but some nations consistently appear in the rankings. For instance, Pakistan has struggled with air quality for several years, with urban areas such as Lahore and Karachi acting as hotspots for hazardous air. The Pakistani government has faced criticism for not doing enough to combat the crisis.

In 2022, Chad became the world's most polluted country, with a PM2.5 concentration of 89.7, a notable increase from 75.9 in 2021. This crisis has been driven by desert dust, vehicle emissions, and biomass burning. Iraq has also seen a sharp increase in pollution, with a PM2.5 concentration of 80.1 in 2022, up from 39.6 in 2019. This rise is attributed to industrial growth, traffic congestion, and dust storms, with the oil sector's gas flaring practices playing a significant role.

In contrast, Switzerland, France, and Denmark are considered the cleanest countries globally, with high air quality, clean water, and robust environmentally friendly policies and initiatives.

Air Pollution in the United States

The United States has made significant progress in improving air quality over the years. The Clean Air Act, established in 1970, has led to a reduction in emissions from transportation, power plants, and manufacturing. Between 1970 and 2023, total emissions of the six principal air pollutants dropped by 78%. However, the "State of the Air" report for 2025 found that 46% of Americans (approximately 156.1 million people) live in areas with failing grades for unhealthy levels of ozone or particle pollution. This issue disproportionately affects communities of color, who are more vulnerable due to higher rates of chronic conditions such as asthma, diabetes, and heart disease.

While the US has made strides in reducing air pollution, the changing climate is making it more challenging to maintain this progress. Extreme heat, drought, and wildfires are contributing to worsening air quality, and the geographic distribution of pollution is shifting back east.

Efforts to reduce air pollution

According to the World Health Organization (WHO), 99% of humans currently breathe air that exceeds the guideline limits for pollutants, with those living in low- and middle-income countries suffering the most. Air pollution is now the world's fourth-largest risk factor for early death, with an estimated 4.2 million premature deaths a year, according to the WHO. When indoor air quality is considered, that number rises to an estimated 2.9 to 7 million deaths per year.

Despite these dire statistics, there have been some successes in reducing air pollution. For instance, the "State of the Air" 2025 report found that even after decades of successful efforts to reduce sources of air pollution, 46% of Americans—nearly 25 million more people than the previous year—are living in places with unhealthy levels of ozone or particle pollution. This increase is largely due to extreme heat, drought, and wildfires, which are exposing a growing proportion of the population to harmful pollutants.

To address air pollution, several interventions and initiatives have been implemented worldwide. Here are some efforts to reduce air pollution:

• The Clean Air Act, established in 1970 in the United States, authorizes the U.S. Environmental Protection Agency (EPA) to regulate the emissions of harmful air pollutants. As a result, total emissions of the six principal air pollutants in the U.S. dropped by 78% between 1970 and 2023.
• The Climate and Clean Air Coalition (CCAC), a global network of governments, intergovernmental organizations, businesses, scientific institutions, and civil society organizations, was created in 2012 to improve air quality and protect the climate. The CCAC has developed initiatives to reduce short-lived climate pollutant emissions, such as replacing wood stoves with pellet stoves and banning open-field burning of agricultural waste.
• Electrifying public transport is another way to lower both air pollution and carbon emissions.
• Phasing out the use of coal and other fossil fuels for power generation is crucial. Coal-fired power plants are one of the largest contributors to air pollution and climate change.
• The National Emission Reduction Commitments (NEC) Directive in the EU aims to improve air quality and reduce premature deaths resulting from air pollution exposure.
• In 2020, the EEA published a briefing on the progress made by EU Member States toward meeting the 2010 emission ceilings under the NEC Directive.
• Awareness campaigns in Arctic countries aim to reduce the impact of household emission sources on local air pollution.

Air pollution and climate change

Air pollution is defined as the contamination of the air by toxic or polluting particles and gases. It is detrimental to human health and the planet as a whole. According to the World Health Organization (WHO), approximately 7 million deaths occur annually due to indoor and outdoor air pollution. Furthermore, 99% of humans currently breathe air that exceeds the WHO's guideline limits for pollutants, with those in low- and middle-income countries suffering the most.

The primary sources of air pollution are energy use and production, which involve the burning of fossil fuels. This includes driving cars on gasoline, heating homes with oil, and running power plants on fracked gas. When fossil fuels are burned, harmful chemicals and gases are released into the air. Two prevalent types of air pollution are smog (ground-level ozone) and soot (particulate matter). Smog is formed when emissions from combusting fossil fuels react with sunlight, irritating the eyes and throat and damaging the lungs. Soot, on the other hand, is composed of tiny particles of chemicals, soil, smoke, dust, or allergens that are carried in the air. Both smog and soot have similar sources, including cars, trucks, factories, power plants, and anything that combusts fossil fuels.

Climate change and air pollution are closely interconnected, sharing many of the same causes and solutions. Burning fossil fuels, transport emissions, industrial emissions, agriculture, crop burning, and residential heating contribute to both climate change and air pollution. Short-Lived Climate Pollutants (SLCPs), such as methane, black carbon (soot), and tropospheric ozone, are super pollutants that contribute to global warming, local environmental degradation, ecosystem damage, biodiversity loss, and adverse health effects.

The impacts of climate change on air quality vary by region. In many areas of the United States, climate change is expected to worsen ground-level ozone levels, increase exposure to allergens like pollen, and contribute to declining air quality. Warmer temperatures can intensify smog formation, and drought conditions can increase particulate matter in the air. Additionally, climate change-induced extreme weather events, such as wildfires, can further degrade air quality.

Regulatory initiatives, partnership programs, and individual actions can help reduce air pollutants and mitigate their impact on both human health and the environment. Prioritizing air quality action alongside climate change solutions offers a "win-win" strategy, improving respiratory and cardiovascular health while also reducing emissions of carbon dioxide (CO2) and SLCPs, thereby contributing to the mitigation of climate change in the near and long term.

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