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The air we breathe may contain toxins and harmful particulate matter, which can be dangerous to human health. Burak GULER/Getty Images
  • Recent and ongoing wildfires have highlighted how climate change contributes to poor air quality.
  • Air pollutants are also caused by vehicle emissions, and industrial and agricultural practices, and may also arise indoors.
  • Each year, an estimated 7 million premature deaths are attributed to air pollution.
  • Breathing in harmful particulate matter can increase the risk of health concerns, including heart disease, respiratory distress, and cancer.
  • You can reduce your exposure to air pollution by wearing a face mask or refraining from exercising outdoors when the Air Quality Index (AQI) reaches high levels.

On average, adults take 12–20 breaths per minute.

The air we breathe contains much more than vital oxygen — it comprises toxins and particulate matter (PM), high levels of which can harm health.

Poor air quality is exacerbated daily by multiple pollutants, which could increase the risks of health concerns ranging from heart disease to COPD, cancer, and even dementia. Unhealthy air quality is also associated with premature death.

We might not give the air we’re breathing much thought until we see noticeable changes in the air around us, such as during wildfire season, when the sky turns burnt orange and the Air Quality Index (AQI) reaches dangerously high levels.

“Many people may not think about the fact that air that looks clean (has good visibility) still contains pollutants that are harmful to health,” said Shahir Masri, ScD, a specialist in air pollution exposure at the Department of Environmental & Occupational Health at the University of California, Irvine.

If you’re concerned about the health effects of air pollution, it’s important to understand how to protect yourself.

Particulate matter (PM), also known as atmospheric aerosol particles, contain microscopic solid or liquid molecules that are found in the air we breathe.

One type of particle pollution that is especially harmful to health is PM2.5, a fine particulate matter measuring just 2.5 microns or less in diameter. The microscopic size of PM2.5 allows it to enter deep into the body once breathed in.

“The reason [PM2.5 particulates] are particularly virulent is they float with the air through your upper respiratory system, deep into your lungs into the alveoli [air sacs], where they lodge,” explained Russell Dickerson, PhD, a researcher and professor at the Department of Atmospheric and Oceanic Science at University of Maryland, College Park.

Dickerson explained that when you breathe PM2.5 matter it can pass through the sacs’ membrane and into your blood. As a result, inflammation and oxidative stress can occur, leading to various health concerns.

According to Neil Donahue, PhD, a professor of chemical engineering at the College of Engineering at Carnegie Mellon University, PM2.5 “causes more than 10% of all deaths around the world.”

Indeed, the World Health Organization (WHO) estimates around 7 million premature deaths are caused by indoor and outdoor air pollution each year.

Donahue told Healthline that air quality in the United States is “really quite good compared to other places,” but noted the number of related deaths remains high.

He said around 3.5 million deaths occur in the U.S. each year, 100,000 of which (about 3%) can be attributed to air pollution.

“[This is] not that far off the pandemic and way more than homicide and automobile deaths combined,” Donahue noted.

Air pollution from dangerous particulate matter like PM2.5 could have significant effects on health and well-being, which may vary depending on where you live.

Cardiovascular events

Guanyu Huang, PhD, assistant professor of environmental and health sciences at Spelman College, told Healthline that air pollution increases the risk of heart attack and stroke.

In fact, Research shows nearly half of PM2.5-related deaths may be attributed to cardiovascular disease.

What’s more, heart disease has been found to occur from long-term PM2.5 exposure, even when pollution levels are below ambient levels of 12 micrograms (μg) per cubic meter (m3).

Respiratory disease

Huang said another major health concern of air pollution exposure is respiratory disease, the short-term impacts of which may include:

  • coughing
  • wheezing
  • shortness of breath

Air pollution exposure may also lead to and exacerbate chronic concerns, such as chronic obstructive pulmonary disease (COPD).

One meta-analysis found that a 10 μg/m3 increase in PM2.5 led to higher hospital visits and admissions among COPD patients. Huang added that air pollution may also lead to respiratory conditions like asthma and lung cancer.


Lung cancer isn’t the only cancer associated with air pollution.

Previous studies have linked long-term exposure to PM2.5 to breast cancer, digestive cancers (such as stomach and liver), and laryngeal (throat) cancer.

Neurological, cognitive, and mental health

Air pollution may also impact brain health in various ways.

Recent studies show close links between dementia and extended PM2.5 exposure.

There are also effects on cognitive well-being.

A 2023 study of over 389,000 individuals in the United Kingdom found that long-term exposure to multiple pollutants — including PM2.5, nitrogen dioxide, and nitric oxide — can increase the risk of mental health conditions depression and anxiety.

While it’s impossible to avoid air pollutants entirely, you can take measures to help minimize your exposure.

According to experts like Masri and Jennifer Vanos, PhD, a scientist at the Julie Ann Wrigley Global Futures Laboratory and associate professor in the School of Sustainability at Arizona State University, these include:

  • Wear a face mask outdoors when pollution is high. Make sure it sits tightly against the face; facial hair will prevent effective sealing.
  • Don’t exercise outdoors if pollution is bad, and always try to avoid exercising alongside major roads.
  • Use an air purifier to reduce pollution in the home (ensure it is suitable for the room size). Place somewhere you spend a lot of time, such as the bedroom, and ensure windows are closed.
  • Be aware that events with lots of fireworks (such as the Fourth of July in the U.S.) can increase air pollution.
  • Use tape around older windows to seal gaps and prevent fine PM from seeping through.
  • If you’re in high pollution areas, change your clothes after returning home.
  • When using central air conditioning, switch the setting to recirculate air.
  • If possible, live away from industrial areas and major roads.

The United States Environmental Protection Agency (EPA) and the World Health Organization have different levels of “maximum” acceptable air pollution.

EPA states PM2.5 levels should not exceed 35 μg/m3 in 24 hours. WHO’s limit is lower, at 15 μg/m3 per 24 hours.

To put this into perspective, the average PM2.5 level in the U.S. in 2022 was 7.8 μg/m3. During the June 2023 Canadian wildfires, PM2.5 in New York reached 117 μg/m3.

The situation is consistently worse in other countries. In India, for instance, the average individual is regularly exposed to PM2.5 at 75-100 μg/m3.

However, without smog or significant smoke, it’s almost impossible to visualize how much pollution is in the air.

To check PM2.5 and ozone levels in your area, the U.S. government maintains an Air Quality Index (AQI) called Air Now.

“[Air Now] allows residents to input their zip code to identify their local air quality and determine whether the air is healthy for outdoor activity, and so on,” Masri explained.

The World Air Quality Index Project’s interactive map also shows levels of PM2.5 and ozone in towns and cities across the globe.

But technological developments mean you can check air quality from your backyard using small air sensors, typically costing $100–300.

Masri noted that companies like PurpleAir sell “low cost air quality sensors which provide real-time PM2.5 data throughout the U.S. and abroad.”

“The AtmoTube company also sells small mobile sensors at a similar cost. Both devices have been validated for their accuracy in monitoring PM2.5,” Masri added.

Air pollution is most often associated with outdoor pollutants, but pollutants can occur indoors as well. Indoor Air Quality (IAQ) can be found in buildings, structures, and even the home.

Although many pollutants are in the air (including “natural” ones, such as pollen), two types have the greatest effects on health.

Fine particulate matter

Microscopic PM2.5 particles are so small they measure about 1/40th of the width of a human hair, Masri told Healthline.

Various sources release chemicals and toxins that contribute to PM2.5, Dickerson said. These particularly include those which involve the burning of fossil fuels, such as:

  • cars and trucks
  • industries (i.e., electricity, steel production, manufacturing)
  • agriculture
  • fires

Some forms of PM2.5 are more harmful than others, Vanos noted.

“PM2.5 from wildfires are of greatest concern [to health] due to a more toxic composition (which depends on what is being burned in addition to trees; e.g., houses, cars) than other types of PM2.5,” she told Healthline.

Ozone gases

You’ve likely heard of the “good” ozone layer, which sits in the Earth’s stratosphere and helps block the sun’s harmful UV rays.

However, ozone gases also float at ground level — and Masri noted these are known as a “secondary pollutant.” This is because they aren’t emitted directly from sources such as cars.

Instead, they form “after vehicle emissions linger in the atmosphere for a while and react with sunlight and other pollution (volatile organic compounds, also known as VOCs),” he said.

Wildfires in recent years have been a prime example of how climate change contributes to poor air quality.

Driven by rising global temperatures and drier landscapes, the number of wildfires is estimated to double by the end of the century.

Wildfires release a mass of toxic gases. Wildfire smoke is believed to account for around one-fifth of all PM2.5 in the air.

A 2023 study links wildfire smoke to an increased risk of all-cause, non-accidental, and neoplasm (abnormal excess tissue growth) mortalities.

Donahue explained it’s the dense volume of PM2.5 that causes the reddish smoke haze following wildfires.

But it isn’t the only climate change factor exacerbating air pollution.

Burning fossil fuels releases carbon dioxide and acts as a precursor for PM2.5 and ozone, Donahue said.

Ozone pollution is also known to worsen in high temperatures. This is because the chemical reaction in ozone generation occurs when it’s very sunny, through a process called photochemistry, explained Dickerson.

“When it’s very hot, [the air is] stagnant, and winds are very weak,” he continued, “and that exacerbates the problem.”

These weather conditions also cause high pressure, said Dickerson, which means air cannot move vertically as much, preventing pollution from “escaping” upward. Furthermore, hot weather causes some chemical reactions in pollutant creation to occur much faster.

Finally, as temperatures rise, so does electricity consumption — thanks to reliance on cooling systems. This involves even more burning of fossil fuels, which “contributes to higher sulfur and nitrogen pollution of the atmosphere, [and] higher PM2.5 pollution,” Masri shared.

While a solution to our growing air pollution problem has yet to be determined, the future isn’t all doom and gloom.

North America and Europe have made “huge progress” in reducing air pollution over the past couple of decades, said Dickerson — with EPA data revealing that PM2.5 levels decreased 42% between 2000 and 2022.

Ozone levels have also dropped, although not quite to the same degree: decreasing 29% between 1980 and the present day.

“Other pollutants, such as carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead, are much less of a problem than they once were over,” Donahue noted. “This is a huge success story of clean air regulation.”

He added that reformulations of fuel and catalytic converters in vehicles have also led to notable reductions in harmful auto emissions.

That said, it’s no excuse for complacency. The burning of fossil fuels remains high, accounting for 80% of the world’s energy supply.

Plus, noted Dickerson, “we’ve not made much progress on greenhouse gases” — the key driver behind climate change.

“As the climate changes, air quality is going to get worse,” he said. “They’re very tightly linked.”