Can air pollution cause lung cancer?  Scientists explain

Can air pollution cause lung cancer? Scientists explain

The study marks an “important step for science and society”, according to experts.

Climate change

AFP

The study marks an “important step for science and society”, according to experts.

As a “hidden killer”, air pollutants can cause lung cancer in non-smokers through a mechanism revealed in a study released this Saturday, which marks an “important step for science – and for society”, according to experts.

Already implicated in climate change, fine particles – less than 2.5 microns, roughly the diameter of a hair – are believed to be responsible for cancerous changes in cells in the respiratory tract, according to scientists at the Francis-Crick Institute and the University College London.

Found in exhaust fumes, dust from vehicle brakes and fumes from fossil fuels, the fine particles are “a hidden killer”, Charles Swanton of the Francis-Crick Institute told AFP, in charge of presenting this investigation, which has not yet been peer-reviewed at the annual congress of the European Society of Medical Oncology, which runs until 13 September in Paris.



The UN General Assembly adopted a resolution that for the first time universally enshrines the human right to a “clean, healthy and sustainable” environment.


While air pollution has long been suspected, “we didn’t really know if and how it directly caused lung cancer,” Swanton said.

The researchers explored data from more than 460,000 people in England, South Korea and Taiwan, and showed that exposure to increasing concentrations of fine particles was linked to an increased risk of lung cancer.

The big discovery is the mechanism by which these pollutants can trigger lung cancer in non-smokers.

In laboratory studies of mice, the researchers showed that the particles caused changes in two genes (EGFR and KRAS), which are already linked to lung cancer.

Next, they analyzed nearly 250 samples of healthy human lung tissue, never exposed to tobacco carcinogens or heavy pollution. Mutations in the EGFR gene were found in 18% of the samples, and changes in KRAS in 33%.

“An Enigma”

“By themselves, these mutations are probably not enough to lead to cancer. But when a cell is exposed to pollution, it probably stimulates some kind of inflammatory response”, and if “the cell harbors a mutation, it will form cancer”, summarizes the Professor Swanton.



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It is a “deciphering of the biological mechanism of what was an enigma” but “quite confusing”, admits this chief physician of Cancer Research UK, the main funder of the study.

Traditionally, exposure to carcinogens, such as those from cigarette smoke or pollution, was thought to cause genetic mutations in cells, making them tumorous and proliferating.

For Suzette Delaloge, director of the cancer prevention program at the Gustave-Roussy Institute, “this is quite revolutionary because there has been virtually no previous demonstration of this alternative carcinogenesis.”

“This study is a very important step for science – and also for society, I hope,” the oncologist, who was in charge of discussing the study at the congress, told AFP. “It opens a great door for knowledge, but also for prevention”.

The next step will be “to understand why some altered lung cells become cancerous after exposure to pollutants,” according to Swanton.

More than 90% of the world population exposed

This study confirms that reducing air pollution is also crucial for health, insist several researchers.


A woman places trays of tobacco to dry in Sumedan, Indonesia.  Known as the Village of Tobacco, it is common to see large quantities of this raw material drying in the sun, filling the streets, roofs and terraces of the village's houses.

Tobacco cultivation is where food for poor populations should be, warns the World Health Organization.


“We have a choice about whether or not we smoke, but not about the air we breathe. With probably five times more people exposed to unhealthy levels of pollution than tobacco, this is a major global problem,” said Professor Swanton.

More than 90% of the world’s population is exposed to what the WHO considers to be excessive levels of fine particulate pollutants.

This investigation also offers hope for new approaches to prevention and treatment.

To detect and prevent, Suzette Delaloge foresees several ways but “not for tomorrow”: “personal assessment of our exposure to pollutants”, detection – not yet possible – of the EGFR gene mutation, etc.


Image captured on October 15, 2021 shows a cloud of pollution over Lyon, France

The information was released this Friday by the European Environment Agency.


For Tony Mok, from the University of Hong Kong, quoted in an ESMO press release, this research, “as intriguing as it is promising”, “makes it possible one day to look for precancerous lesions in the lungs through imaging, and then try to treat them.” with drugs such as interleukin-1 inhibitors”.

Swanton imagines “what molecular cancer prevention could look like in the future, with a pill, perhaps every day, to reduce the risk of cancer in high-risk areas.”

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