Lung cancer is diagnosed more than any other cancer in the world among men, and it’s the third most commonly diagnosed cancer in women. While around 80 percent of lung cancer deaths are directly attributable to smoking, the Global Burden of Diseases, Injuries, and Risk Factors Study reported that in 2017, air pollution was responsible for 14 percent of all lung cancer deaths.

The International Agency for Research on Cancer, a division of the World Health Organization, declared outdoor air pollution a direct threat to public health and labeled it a carcinogen (a substance that causes cancer) in 2013.

What Is Air Pollution?

Air pollution is a combination of several different hazardous substances that contaminate the air, both indoors and outdoors. Air pollution can be caused by people or occur naturally.

Outdoor Air Pollution

Naturally occurring sources of outdoor air pollution can include gas and ash from volcanic eruptions, methane from natural wetlands, and smoke from wildfires.

Most outdoor air pollution (called ambient air pollution) comes from human-made sources such as vehicle emissions, power generation byproducts from coal power plants, and manufacturing and industrial facility byproducts. Air pollution from these sources generally includes:

• Ground-level ozone
• Noxious gases like carbon dioxide, carbon monoxide, sulfur oxides, and nitrogen oxides
• Particulate matter like chemicals, dust, and metals

The U.S. Environmental Protection Agency (EPA) divides particulate matter into two categories based on size: inhalable coarse particles and fine particles. Inhalable coarse particles are between 2.5 and 10 micrometers (PM₁₀) in diameter and are often found near roadways and industries that produce dust. Fine particles are smaller than 2.5 micrometers in diameter (PM_2.5) and can be found in the haze that sometimes hangs over cities, as well as in smoke from fires. These particles are so small that a single strand of human hair is 30 times larger than the largest fine particle.

This fine particulate matter is tiny enough to be inhaled through the nose and throat and pass into the lungs. Once in the lungs, these particles can cause serious health problems. Epidemiological studies point to a correlation in particulate air pollution and an increase in heart disease, lung disease, and reproductive diseases and their associated causes of death. Lung cancer research has also shown an increased risk of cancer incidence associated with long-term exposure to ambient air pollution.

Indoor Air Pollution

Indoor air quality can be affected by pollution as well. According to the EPA, Americans spend about 90 percent of their time indoors. Those who are in higher risk categories of being affected by outdoor pollution (individuals with respiratory and cardiovascular disease, for example) may spend even more of their time indoors. Elevated concentrations of indoor pollutants in an office building, home, or school can impact a person’s lung health.

Indoor air pollutants can come from:

• Tobacco smoke
• Combustion appliances, such as wood-burning stoves and gas water heaters
• Pet dander
• Mold and mildew
• Asbestos
• Ozone from some air cleaners
• Off-gassing from furniture, carpet, and other household items
• Dust, mite debris, and pollen
• Outdoor pollution from nearby roads or sources of exhaust emissions
• Radon

According to the American Lung Association, radon is the second leading cause of lung cancer in the United States. It’s also the leading cause of lung cancer in nonsmokers, according to EPA estimates.

Radon is a colorless, odorless, tasteless gas that is usually found in the highest concentrations in the basement or crawl spaces of homes. Radon is a radioactive gas that occurs naturally from the decay of certain elements in the soil. While short-term exposure to radon isn’t dangerous, long-term exposure can increase the incidence of lung cancer.

Read more about radon and lung cancer risk.

Why Does Air Pollution Affect the Risk of Lung Cancer?

Air pollution particles can be inhaled deep into the lungs. The body detects these foreign particles and organizes an inflammatory response in an effort to get rid of these tiny substances. Chronic inflammatory responses and repeated deposits of particulates can interfere with the lung cells’ capability to repair themselves, damaging their DNA and increasing the risk of cancer.

How Can You Reduce Your Exposure to Air Pollution?

There are steps you can take to cut down on your exposure to air pollution, both indoors and outdoors.

Indoor Exposure

The EPA suggests the following to reduce your exposure to indoor air pollution:

• Do not smoke inside your house or your car.
• Vacuum and clean bedding, carpets, and furniture often.
• Ventilate rooms that have fireplaces.
• Use a ventilation fan in the bathroom to prevent mold growth.
• Consider purchasing household cleaners without volatile organic compounds.

To reduce your risk of radon exposure, the Centers for Disease Control and Prevention recommends:

• Test your home’s radon levels. If tests show that areas of your home contain radon, have a qualified contractor make repairs that fix the issue. Reducing levels of radon in your home requires specific knowledge and skill sets.
• Increase air ventilation by opening windows and doors when possible. Use fans and vents to circulate air when the outside weather is not conducive to opening up the home.
• Seal cracks in floors and walls with material specifically designed to block radon transmission.

Outdoor Exposure

Limit your outdoor activity when air quality levels are unhealthy. MyLungCancerTeam members report they check both weather and air quality frequently. One member wrote, “I check air quality every day! Finally got back to walking the last few weeks now that temps are lower and air quality is better.”

Other ways to reduce your exposure include:

• Avoid exercising in or around high-traffic areas.
• Use a mask with an N95 air filter if you need to go out when air quality is unhealthy.
• Don’t burn wood or trash.
• Use hand-powered or electric-powered lawn equipment.

If you are concerned about your indoor or outdoor exposure to air pollution, talk with your health care provider for more information.

Talk With Others Who Understand

MyLungCancerTeam is the social network for people with lung cancer. On MyLungCancerTeam, more than 5,000 members come together to ask questions, give advice, and share their stories with others who understand life with lung cancer.

Are you living with lung cancer and wondering how air pollution affects lung cancer risk? Share your experience in the comments below, or start a conversation by posting on your Activities page.