Fine particulate matter is gaining significance as a potential cause of lung cancer in non-smokers, according to recent studies.

16.06.2025

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Leading Medicine Guide Editors

The diagnosis of lung cancer is increasingly affecting non-smokers. Globally, it has now become the fifth most common cancer-related cause of death. As early as April 2023, the journal Nature published an international study investigating the link between fine particulate matter exposure and lung cancer in non-smokers.

In 2025, a team of researchers from the University of Miami stated in the journal EClinicalMedicine that globally, 20 percent of all lung cancer cases are caused by polluted outdoor air. In countries such as China, India, Pakistan, Bangladesh, and Nigeria, the figure is estimated to be as high as 25 percent. How does fine particulate matter promote lung cancer? How can lung disease be prevented?

What is fine particulate matter made of, and how does it enter the respiratory system?

Smoking is still considered the number one risk factor for lung cancer. However, the fact remains that bronchial carcinoma is also being diagnosed in non-smokers—and the trend is rising. In most cases, these patients develop adenocarcinoma, a type of cancer classified as non-small cell lung cancer. But how does toxic fine particulate matter reach their lungs, and what exactly are these particles composed of?

Most PM10—particulate matter with a diameter smaller than ten micrometers—and PM2.5 are generated through human activities, primarily through traffic, agriculture, and heating:

diesel engines
abrasion from tires, brakes, and road surfaces
agricultural machinery
fertilizers
intensive livestock farming, which produces large amounts of ammonia that form secondary fine particles
heating systems and stoves in homes, apartments, and buildings

These particles can also occasionally originate from natural sources, though only under certain conditions (e.g., smog or thermal inversions):

soil erosion
volcanic eruptions
bushfires

Due to their small size, these harmful airborne particles can easily enter the human respiratory system. PM2.5 particles are so small that they can even reach the alveoli in the lungs.

To minimize exposure, limit values have been established, though they vary internationally. In Germany, current annual average limits are set at 40 µg/m³ for PM10 (24-hour limit value) and 25 µg/m³ for PM2.5 (annual target value). These levels are significantly above the WHO’s recommended values of 15 and 5 µg/m³, respectively.

Feinstaub der Größe PM2,5 kann sogar direkt die Lungenbläschen erreichen.

How can fine particulate matter contribute to the development of lung cancer?

Initially, scientists believed that particulate matter could alter the genetic material of lung cells. This is because a large proportion of those with adenocarcinoma exhibit a specific genetic mutation in a protein known as the epidermal growth factor receptor (EGFR), which can lead to uncontrolled tumor cell growth.

In their 2023 study, researchers used epidemiological data from four population groups in the United Kingdom, Canada, Taiwan, and South Korea to demonstrate a link between lung cancer and PM2.5 exposure. Follow-up experiments in mice showed that the fine particles do not directly cause the EGFR mutation, but that the mutation must already exist—at least in part—within the body. However, and this is the key point, the combination of the altered receptor and particulate matter exposure significantly promoted tumor growth in the animals. This was due to prolonged inflammatory reactions in the lung tissue triggered by the fine particles.

The role of a signaling molecule

In this context, scientists also discovered that interleukin-1β, a signaling molecule of the immune system, plays a crucial role. Mice treated with antibodies before being exposed to particulate matter developed lung cancer less frequently than untreated counterparts. This suggests that interleukin-1β might serve as a preventive treatment option for people living in regions with particularly high levels of air pollution. However, Prof. Dr. Martin Göttlicher, director of the Institute of Molecular Toxicology and Pharmacology at the Helmholtz Center in Munich, does not view this as a viable preventive approach. Instead, he advocates for further reductions in permissible particulate matter levels.

Indeed, a new European air quality directive was drafted last year, including updated PM10 and PM2.5 limit values set to take effect in 2030. It officially went into force at the end of 2024.

Conclusion

Smokers still have approximately ten times the risk of developing lung cancer compared to non-smokers, according to Prof. Dr. Martin Göttlicher. However, the urgency for a revised approach to managing particulate matter exposure worldwide is underlined by further studies. These also indicate that air pollution increases the risk for additional conditions such as cardiovascular diseases and Alzheimer’s disease.

What’s crucial is a global reduction in fine particulate emissions. As a weather phenomenon in Poland and Germany in March of this year clearly demonstrated, air pollution from neighboring countries can drift across borders. Certain wind patterns can carry fine particulate clouds over great distances. Additionally, persistent high-pressure systems can prevent air from circulating, allowing particulate matter to pollute the air for extended periods. In Germany, the Federal Environment Agency provides information on current air quality levels.

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