Researchers have found a possible explanation for the rising rate of lung cancer in those who have never smoked: exposure to car exhaust.
Researchers have found the missing link between air pollution and lung cancer, a finding that could rewrite our knowledge of the disease.
The results explain how the small particles found in car exhaust “awaken” dormant abnormalities in lung cells, pushing them over the edge into a malignant condition. This study is a “wake-up call” concerning 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, stated, “The risk of lung cancer from air pollution is lower than from smoking, but we have no control over what we all breathe.”
New findings “connect the importance of addressing climate health to improving human health” because “globally, more individuals are exposed to dangerous levels of air pollution than to toxic compounds in cigarette smoking.”
While smoking is still the leading cause of lung cancer, outdoor air pollution accounts for around one in ten cases in the UK, and 6,000 people who have never smoked die from lung cancer each year. Three hundred thousand cases of lung cancer will be diagnosed this year because of exposure to PM2.5, a small particulate matter found in air pollution.
To yet, however, the biological mechanisms by which air pollution promotes cancer have remained unknown. Air pollution does not cause cancer by causing DNA mutations like those caused by smoking or sun exposure, which are directly connected to lung and skin cancers.
To the contrary, those with nonsmoking lung cancer are more likely to have mutations that are also present in healthy lung tissue. These mutations are the result of normal human DNA damage accumulation.
“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. Although there is the evidence between air pollution and lung cancer, the processes behind this association have been largely neglected.
Through a series of careful trials, the most recent research reveals how PM2.5 particles can activate dormant mutations in cells, transforming them into cancer. Like the spark on a gas stove, the pollutant is essential for getting the fire started.
Swanton’s team conducted experiments in which mice modified to possess mutations in a gene called EGFR, linked to lung cancer, were exposed to the pollutant particles and found that the animals were significantly more likely to acquire cancer. In addition, they found that interleukin-1 beta (IL1B), an inflammatory protein secreted as part of the body’s immunological response to PM2.5 exposure, mediates the risk. Treatment with medicines that inhibited the protein made the animals more resistant to the toxins.
This work provides an explanation for an unexpected discovery made during a clinical trial of an IL1B-inhibitor used by Novartis to treat heart disease: the patients taking the medicine had a dramatic decrease in the rate at which they developed lung cancer. According to Swanton, this could lead to a new generation of drugs that actively target and destroy cancer cells.
One in five of the normal lung samples analyzed by the study had the EGFR mutation, which was also discovered in samples of healthy lung tissue collected during biopsies of patients. Apparently, we all have latent cancer-causing mutations lying dormant in our bodies, and prolonged exposure to air pollution makes that risk much higher.
According to Swanton, “it’s a wake-up call on the impact of pollution on human health.” To disregard climate health is irresponsible. Human health can’t be improved without also improving the health of our planet.
According to Rosamund Kissi-Debrah, whose daughter Ella, age nine, died from exposure to prohibited levels of air pollution in 2013, there is still a “lack of joined-up thinking” on 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 was 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 world health.
We have known about the link between pollution and lung cancer for a long time, and we now have a probable explanation for it,” said Prof. 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 the burning of fossil fuels, it is imperative that we find solutions to 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 possibly shed light on the link between smoking and the disease. Air pollution and cigarette smoke are both rich in promoting chemicals. Everyone was so preoccupied with mutations that this fact, which has been known since the 1960s, was largely overlooked.
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Since switching to vaping minimizes exposure to mutagens, the tobacco industry claims, cancer risks associated with smoking will be eliminated. The truth is that cell mutation occurs naturally in the human body, and there is mounting evidence that vaping, like promoters, can lead to lung illness and inflammation.
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