Scientists Discover How Air Pollution Causes Lung Cancer

Scientists say they have identified the mechanism by which air pollution triggers lung cancer in non-smokers, a finding that one expert has hailed as “a milestone for science – and for society”.

The research has illustrated the health risk posed by tiny particles produced by burning fossil fuels, prompting calls for more urgent action to tackle climate change.

It could also pave the way for a new area of ​​cancer prevention, according to Charles Swanton of the UK’s Francis Crick Institute.

Swanton presented the research, which has yet to be published in a peer-reviewed journal, at the annual conference of the European Society for Medical Oncology in Paris on Saturday.

Air pollution has long been thought to be linked to a higher risk of lung cancer in people who have never smoked.

Commuters make their way through smoggy conditions in New Delhi on November 20, 2021 [File: Prakash Singh/AFP]

“But we weren’t sure if the pollution directly caused lung cancer – or how,” Swanton told AFP news agency.

Traditionally, exposure to carcinogens, such as those from cigarette smoke or pollution, was thought to cause DNA mutations that then become cancerous.

But there was an ‘inconvenient truth’ with this model, Swanton said: Previous research has shown DNA mutations can be present without causing cancer – and most environmental carcinogens don’t cause the mutations. .

His study offers a different model.

A future cancer pill?

The research team from the Francis Crick Institute and University College London analyzed health data from more than 460,000 people in England, South Korea and Taiwan.

They found that exposure to tiny particles of PM2.5 pollution – which measure less than 2.5 micrometers (microns) in diameter – led to an increased risk of mutations in the epidermal growth factor receptor (EGFR) gene.

In laboratory studies in mice, the team showed that the particles caused changes in the EGFR gene as well as the Kirsten rat sarcoma virus (KRAS) gene, both of which have been linked to lung cancer.

Finally, they analyzed nearly 250 samples of human lung tissue never exposed to carcinogenic agents from smoking or heavy pollution.

Even though the lungs were healthy, they found DNA mutations in 18% of EGFR genes and 33% of KRAS genes.

High air pollution warning over London skyline
People enjoy a day in Primrose Hill as a high air pollution warning was issued for London on March 24, 2022 [File: Justin Tallis/AFP]

“They just sit there,” Swanton said, adding that mutations seem to increase with age.

“On their own, they are probably insufficient to lead to cancer,” he said.

But when a cell is exposed to pollution, it can trigger a “scarring response” that causes inflammation, Swanton said.

And if that cell “carries a mutation, then it will form a cancer,” he added.

“We have provided a biological mechanism behind what was previously an enigma,” he said.

In another experiment in mice, the researchers showed that an antibody could block the mediator – called interleukin 1 beta – that triggers inflammation, preventing cancer from developing in the first place.

Swanton said he hoped the discovery would “provide a successful foundation for a future of what could be molecular cancer prevention, where we can offer people a pill, maybe every day, to reduce the risk of cancer”.

A general view of Milad Tower following increased air pollution in Tehran, Iran
A general view of the Milad Tower following increased air pollution in Tehran, Iran on November 24, 2021. [File: Majid Asgaripour/WANA via Reuters]


Suzette Delaloge, who heads the cancer prevention program at France’s Gustave Roussy institute, said the research was “pretty groundbreaking, as we had virtually no prior demonstration of this alternative pathway of cancer formation”.

“The study is quite a milestone for science – and for society too, I hope,” she told AFP.

“This opens a big door, both for knowledge but also for new ways to prevent” the development of cancer, said Delaloge, who was not involved in the research but discussed it at the conference on Saturday. .

“This level of demonstration must compel the authorities to act on an international scale.”

Tony Mok, an oncologist at the Chinese University of Hong Kong, called the research “exciting”.

“This means we may wonder if in the future it will be possible to use lung scans to look for precancerous lesions in the lungs and try to reverse them with drugs such as interleukin 1 beta inhibitors. “, did he declare.

Swanton called air pollution a “hidden killer”, pointing to research estimating it is linked to the deaths of more than eight million people a year – almost the same number caused by tobacco.

smog in Kathmandu
A general view of part of the Kathmandu Valley during a smoggy day as air quality reaches dangerous levels, Nepal, April 6, 2021 [File: Navesh Chitrakar/Reuters]

Other research has linked PM2.5 to 250,000 deaths per year from lung cancer alone.

“You and I have a choice whether or not to smoke, but we don’t have a choice about the air we breathe,” said Swanton, who is also chief clinician at Cancer Research UK, which was the main funder. research funds. .

“Given that probably five times more people are exposed to unhealthy levels of pollution than tobacco, you can see this is a pretty major global problem,” he added.

“We can only address this if we recognize the really intimate links between climate health and human health.”

Scientists Discover How Air Pollution Causes Lung Cancer

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