The cancer discovery should serve as a “wake-up call” about the risks of air pollution. In ground-breaking research that has the potential to rewrite our understanding of lung cancer, scientists have discovered how air pollution causes the disease.
The results explain how car exhaust’s fine particulates “awaken” latent mutations in lung cells, pushing them over the edge into a cancerous condition. This study is a “wake-up call” about the negative effects of pollution on human health and sheds light on why so many people who don’t smoke get lung cancer.
Prof. Charles Swanton of the Francis Crick Institute, who presented the findings at the European Society for Medical Oncology conference in Paris on Saturday, said, “The risk of lung cancer from air pollution is lower than from smoking, but we have no control over what we all breathe.”
Recent findings “link the importance of addressing climate health to improving human health,” as “globally, more people are exposed to unsafe levels of air pollution than to toxic chemicals in cigarette smoke.”
Although smoking is still the leading cause of lung cancer, outdoor air pollution is estimated to be responsible for about one in ten cases in the UK, and 6,000 people who have never smoked are estimated to die from lung cancer each year. Air pollution containing fine particulate matter (PM2.5) is responsible for approximately 300,000 cases of lung cancer and 2019 deaths worldwide.
Air pollution has been linked to cancer, but the underlying biological mechanisms behind this association are not well understood. Air pollution does not cause cancer by triggering DNA mutations like those caused by smoking or sun exposure, which is linked to lung and skin cancer.
As a result, people with non-smoking lung cancer are more likely to have the same kinds of mutations found in healthy lung tissue. These mutations are the result of the normal, gradual accumulation of small, harmless mistakes in our DNA that occurs throughout our lives.
“Clearly these patients are getting cancer without having mutations, so there’s got to be something else going on,” said Swanton, who is also the chief clinician at Cancer Research UK. However, the mechanisms linking air pollution and lung cancer have been largely disregarded.
Through a series of careful experiments, the most recent research reveals how PM2.5 particles can activate dormant mutations in cells, transforming them into cancer. The pollutant acts like a spark on a gas stove.
Laboratory experiments conducted by Swanton’s group demonstrated that mice genetically engineered to carry mutations in the EGFR gene (which is associated with lung cancer) were significantly more susceptible to developing cancer when exposed to the pollutant particles.
Interleukin-1 beta (IL1B), an inflammatory protein, is released as part of the body’s immune response to PM2.5 exposure, and the researchers found that this protein mediates the risk. Drugs that inhibited the protein made the mice more resistant to the toxins.
The work explains an observation made by chance in a clinical trial of a Novartis drug for heart disease: that patients taking the drug, an IL1B-inhibitor, had a significantly lower risk of developing lung cancer. Swanton thinks this could pave the way for a new generation of drugs to prevent cancer.
The EGFR mutation was also detected in 20% of the normal lung tissue samples analyzed by the team during patient biopsies. This indicates that everyone has latent cancer-causing mutations in their cells and that the risk of developing cancer is increased by prolonged exposure to air pollution.
After her daughter, Ella, age 9, died in 2013 from exposure to illegal levels of air pollution, Rosamund Kissi-Debrah said there is still a “lack of joined-up thinking” about pollution and health.
She warned that despite increased funding for the National Health Service (NHS), more people will continue to get sick unless air pollution is reduced. Every year we produce the numbers — air pollution causes nine million premature deaths — but no one is held accountable, and that worries me about global health.
We have known about the link between pollution and lung cancer for a long time, and we now have a possible explanation for it,” said Professor Tony Mok of the Chinese University of Hong Kong, who was not involved in the research.
Since pollution and carbon emissions are inextricably linked to fossil fuel use, we have an urgent responsibility to address these problems for the sake of the environment and human health.
Cancer geneticist Professor Allan Balmain from the University of California, San Francisco, said the results could also shed light on the link between smoking and the disease.
Both environmental pollutants and cigarette smoke are loaded with health-impairing chemicals. This has been known since the 1960s, but “everyone was focused on mutations,” so it has been largely overlooked. Tobacco companies are now advising their customers to switch to e-cigarettes because they pose less of a risk of cancer due to the reduced exposure to mutagens.
Although cell mutations are inevitable, there is mounting evidence that vaping, like promoters, can cause lung disease and inflammation.