How air quality affects breast cancer

Breast cancer is the most commonly diagnosed cancer among women worldwide.

While it's usually treated as a disease of genetics and lifestyle, eighty percent of breast cancer cases can't be explained by family history, age, or lifestyle (1)(2). A growing body of research points to another factor: air quality. The air a woman breathes can shape that risk years before any diagnosis is made.

In recent years, a number of research studies have linked long-term exposure to fine particulate matter (PM2.5) and nitrogen dioxide (NO₂) to an increased risk of breast cancer. These findings have drawn attention to the potential role of air pollution as an environmental risk factor in breast cancer development. Because exposure to these pollutants can occur in everyday settings, understanding their long-term health effects is an important step toward identifying opportunities for prevention.

How researchers linked air pollution with breast cancer

Over time, breast cancer and air pollution research has grown to include larger participant pools, differing community environments, and specific analysis of airborne pollutant particles.

In 2023, researchers at the National Institutes of Health (NIH), a U.S. government agency responsible for biomedical and public health research, found that women living in areas with higher historical PM2.5 concentrations had an 8% increase in breast cancer incidence for every 10 µg/m³ of long-term pollutant exposure (3). The study included one of the largest participant pools for cancer research to date, following 500,000 men and women across the United States. Participants received questionnaires over the course of 20 years, during which 15,870 breast cancer cases were identified.

In cities, traffic emissions are one of the biggest contributors to outdoor air pollution. A 2025 research project combining five large U.S. breast cancer studies found that a 10-parts-per-billion increase in NO2, a proxy for vehicle emissions, corresponded to a 3% increase in overall breast cancer incidence. Set against the roughly 316,950 U.S. breast cancer cases expected each year, that increase would account for about 9,500 cases (4).

The association between long-term air pollution exposure and breast cancer incidence has also been consistently reported across studies conducted outside the U.S. A 2026 research study observed nearly 100,000 French women through a series of questionnaires over the course of 21 years and identified 5,222 cases of breast cancer. The research analyzed annual PM2.5 and PM10 levels within participant’s regions, linking increased local air pollution to elevated risk rates for breast cancer (5).

How can airborne pollutants influence breast tissue and health?

Cancer begins with genetic changes and cell signaling gone wrong. Airborne pollutants can contribute to both (6).

Fine particulate matter is small enough to be inhaled deep into the lungs, where its chemical cargo of carcinogens, metals, and microplastics can pass into the bloodstream. Inhaled toxicants have been measured in breast fluid – evidence that these compounds physically reach breast tissue and directly impact cell systems (7).

The most common outdoor pollutants include:

• Diesel exhaust
• Arsenic
• Nickel
• Nitrogen dioxide (NO2)
• Polycyclic aromatic hydrocarbons (PAHs)
• Volatile organic compounds (VOCs)
• PM2.5, particulates measuring 2.5 microns in diameter or smaller
• PM10, particulates measuring 10 microns in diameter or smaller

Once inhaled, these pollutants can disrupt several cellular processes at once, including DNA integrity and hormone signaling. PAHs can bind directly to DNA and form adducts, initiating genetic damage that can start a cell down the path toward cancer. Many of the same pollutants mimic or interfere with estrogen, the hormone that drives the growth of most breast tumors (8).

Inflammation plays a role as well. Pollutants drive systemic inflammation and oxidative stress, conditions that damage cells and make tissue more hospitable to tumors (9). Long-term exposure can increase breast cancer risks over time through sustained inflammation and repeated inhalation of pollutants that enter the bloodstream.

Where is the risk most visible?

The risk does not fall evenly across communities or global environments. Cancer cases often concentrate where traffic, industry, and housing overlap.

In a 2025 multiethnic study, which followed more than 58,000 California women for an average of 19 years, satellite-based PM2.5 estimates were associated with a 28% increase in breast cancer incidence per 10 µg/m³ increase (10). African American and Latino participants in the study were at the highest risk for breast cancer.

In a 2023 study performed in Denmark, researchers analyzed 55,745 of the nation’s breast cancer cases against annual PM2.5 and NO2 levels in the region. Although the study measured a connection between breast cancer and both types of airborne pollutants, researchers found the strongest risk association to be with atmospheric PM2.5 particles (11).

Breast cancer rates vary globally. In a 2024 study performed in Beijing, researchers found a connection between breast cancer cases and regional black carbon exposure from coal burning pollution (12). Breast cancer incidence is rising fastest in low- and middle-income countries, where pollution levels are elevated and air quality regulation is limited.

How to promote air quality and breast cancer protection

Reducing the risk of pollution-related breast cancer requires action on two levels: individual measures to reduce exposure at home and government policies and regulations to control pollution at its source.

What individuals and families can do

Households and individuals can cut their own exposure and build community awareness through daily lifestyle choices. A few habits can make the biggest difference:

• Check local air quality forecasts daily and plan outdoor activities around pollution peaks.
• Monitor PM2.5 levels inside the home with indoor air quality monitors.
• Wear masks and use air purifiers during high-pollution days and wildfire smoke events for ultrafine particle protection.
• Keep windows closed when outdoor air quality is poor and consider upgrading filtration in home air conditioning systems in regions with high concentrations of air pollution.
• Avoid exercising near high-traffic roads, where NO2 and ultrafine particle concentrations spike.
• Support cleaner air policies in your community.
• Keep up regular breast cancer screening, as early detection can improve treatment outcomes.

What communities and governments can do

The largest impact can be made by governments, health organizations, and community leaders, who can reduce pollution-related breast cancer risk. Several policy choices can help:

• Enact and enforce stricter air quality standards for PM2.5, NO2, and other pollutants.
• Invest in public transportation and electric vehicle infrastructure to cut traffic emissions.
• Create buffer zones between residential areas and high-emission industrial or traffic corridors.
• Fund continued research into environmental risk factors for breast cancer.
• Expand access to air quality monitoring networks in underserved communities.
• Support public health campaigns that educate residents about pollution and cancer risk.
• Integrate air quality considerations into urban planning and public health policy.

Conclusion

As awareness of the potential health risks of air pollution grow, individual actions to reduce exposure can help protect women’s health and support breast cancer prevention efforts.

Each October, Breast Cancer Awareness Month brings people together to raise awareness, promote early detection, and support those affected by the disease.

Although breast cancer has no single cause and genetic factors cannot be changed, reducing exposure to air pollution is one potentially modifiable environmental measure that may help protect women’s health over the long term.