Silent threat that could unravel the mystery of lung cancer in non-smokers
Doctors have discovered that tiny air pollution particles may increase the risk of lung cancer in women who have never smoked.
Exposure to tiny particles of smoke released from car exhaust and burning wood may increase the risk of a DNA mutation known to cause lung tumors, according to research presented today by the International Association for the Study of Lung Cancer (IASLC).
Although smoking remains the greatest risk factor for lung cancer, it is estimated that nearly 6,000 people who have never smoked die from the disease each year.
Although the number of smokers is decreasing, some studies show that the number of cases is increasing among young women and non-smokers.
According to a 2017 study, the number of lung cancer cases among non-smokers in the UK doubled between 2008 and 2014.
Although smoking remains the greatest risk factor for lung cancer, it is estimated that nearly 6,000 people who have never smoked die from lung cancer each year, some of which may be due to exposure to air pollution.
Another 2023 report from the American Cancer Society found that more women between the ages of 35 and 54 are now diagnosed with lung cancer than men of the same age.
Meanwhile, lung cancer doctors in the US have reported an increasing number of cases younger caseload.
Researchers at the British Columbia Cancer Research Institute in Vancouver, Canada, collected data from 255 lung cancer patients who had never smoked, including where they had lived since birth.
The pollution level at their residential address was then analysed using satellite data, air pollution forecasts and ground measurements within a 10-kilometre area.
The team collected annual exposure data dating back to 1996, when accurate information on air pollution became available worldwide.
Researchers also looked at whether patients developed a change in their DNA known to increase the risk of lung cancer, called an EGFR mutation.
The genetic mutation, which is not normally present at birth, speeds up the activity of a protein called epidermal growth factor receptor (EGFR), which helps cells grow and divide.
The extreme division of cells causes cancer to develop over time.
Although small, these particles are thought to cause inflammation in the lungs, potentially reviving normally dormant cells that can lead to cancer-causing mutations and tumors.
Researchers found that patients with stage four lung cancer were much more likely to have EGFR mutations than patients without the disease.
But they also found that women were more likely to have EGFR mutations if they were exposed to pollutants smaller than 2.5 micrometers, also known as PM2.5, for at least three years.
This was true regardless of whether a woman smoked or not.
This was also the case in patients who had been exposed to the pollution five years before diagnosis.
Surprisingly, these associations were not seen in men who had never smoked.
PM2.5 are soot particles in the air that are invisible to the human eye, but can penetrate the blood and penetrate deep into the lungs.
They can be emitted by car engines, wood burning and smoking.
Although these particles are small, they are thought to cause inflammation in the lungs. This can cause normally dormant cells to come back to life, which can lead to genetic mutations that cause cancer.
In 2013, the International Agency for Research on Cancer (IARC) classified outdoor air pollution and its main component, fine particulate matter (PM 2.5), as a Group 1 carcinogen. This means that it causes lung cancer.
Although smoking is the leading cause of cancer, researchers and public health experts have not yet been able to find a link that explains why people who do not smoke or have never smoked are still diagnosed with cancer.
Lung cancer is the third most common cancer in the UK, with around 48,500 people diagnosed each year.
Symptoms include persistent cough, chest infections, and chest or shoulder pain.
About 70 percent of cases are caused by smoking. Other risk factors include exposure to radon gas, certain chemicals, and a family history of lung cancer.
Although lung cancer is rare in young people under 40, it is generally According to Cancer Research UK, there are around 2,300 new cases of cancer in young people each year in the UK.
However, the study authors say more research is needed to assess air pollution as a risk for lung cancer.
“These findings suggest that recent exposure to PM2.5 may influence lung cancer in never smokers, especially women,” the study authors wrote.