Researchers make a breakthrough discovery of the link between air pollution and lung cancer

Most cases of lung cancer are caused by smoking, however, one in ten cases in the UK is down to air pollution. In September, researchers at The Francis Crick Institute in London released their findings of a study into air pollution which radically changes our understanding of how tumours arise.

This breakthrough marks a new era as it may now be possible to develop drugs that stop cancers from forming as well as encourage more people to see the importance of diminishing air pollution.

Read on to find out more about the discovery.

What is Air Pollution?

Air pollution is caused when harmful gases and chemicals are released into the air, the majority of which are emitted through human activities such as burning fossil fuels, vehicle exhaust fumes, industry and using petrol-powered outdoor equipment. These particles are associated with non-small cell lung cancer (NSCLC) risk, which accounts for over 250,000 lung cancer deaths globally per year.

Many other health issues are caused by prolonged exposure to air pollution, including aggravated breathing conditions, and increased risk of asthma attacks, cancer, heart attacks and strokes. In fact, one in three deaths from strokes, lung cancer and chronic respiratory disease globally are caused by air pollution.

There is also a growing collection of research linking air pollution to other illnesses such as diabetes, child development issues, and suggested links to dementia.

The discovery

The researchers focused on a form of pollution called particulate matter 2.5 (known as PM2.5), which is far smaller than even the diameter of a human hair. They discovered some crucial findings through a series of detailed human and animal experiments.

• Places with higher levels of air pollution had more lung cancer cases in non-smokers
• Breathing in PM2.5 leads to the release of a chemical alarm known as Interleukin-1-Beta-in the lungs which causes inflammation and activates cells in the lungs to repair any damage
• Around one in every 600,000 cells in the lungs of a 50-year-old already contain potentially cancerous mutations. These are acquired through age and are healthy until activated by the chemical alarm to become cancerous.

Crucially, the researchers were able to stop cancers from forming in mice exposed to air pollution by using a drug to block the alarm signal. These results are therefore a breakthrough both for understanding the impact of air pollution as well as the prevention of lung cancer.

The Science

The discovery is based on research into mutations in a gene called EGFR which is seen in about half of people with lung cancer who have never smoked.

In a study of nearly half a million people living in England, South Korea and Taiwan, exposure to increasing levels of PM2.5 was linked to an increased risk of NSCLC with EGFR mutations.

The scientists also discovered that air pollution drives a rush of macrophages which release the chemical alarm and drive the expansion of cells with the EFGR mutations in response to exposure to PM2.5.

Air pollution & Smoking

The most concise summary of the findings is that very small pollutant particles in the air may trigger lung cancer in someone who has never smoked.

This means that the same particles in the air that come from the combustion of fossil fuels through human activities, and which are exacerbating climate change, are also directly causing 250,000 lung cancer deaths globally per year via a cancer-causing mechanism in the lung cells.

The risk of lung cancer from air pollution is lower than from smoking, however, the difference is that we have very limited control over the air we breathe with the sum of our contribution coming down to our environmental consciousness, such as choosing to ride to work than drive, or switching from using petrol powered garden tools to battery powered.

Globally, more people are exposed to unsafe levels of air pollution than they are to the toxic chemicals in cigarette smoke. This research, therefore, links the importance of addressing air pollution and overall climate health to improve human health.

Tackling Air Pollution

We now have a much better understanding of the driving forces behind lung cancer, however, as 99% of the world’s population live in places where air pollution levels exceed the World Health Organisations’ guidelines (The WHO) there is still much progress to be made in spreading the importance of reducing air pollution.

The WHO classifies Air Pollution as a Carcinogen, which is the highest of its four-level classification system. We have known about the link between air pollution and lung cancer for some time and now that we have a scientific explanation for it, we have a strong mandate–both environmental and health– for tackling air pollution and reducing carbon emissions.

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