Tiny air pollution particles may be increasing the risk of lung cancer in women who have never smoked, doctors have discovered.
Exposure to tiny particles of fumes emitted from car exhausts and burning wood can increase the risk of a DNA mutation known to trigger lung tumours, according to research presented today at the International Association for the Study of Lung Cancer (IASLC).
Although smoking remains the biggest risk factor for lung cancer, it’s estimated that nearly 6,000 people who have never smoked die of the disease each year.
While smoking rates are decreasing, some studies show that cases in young women and non-smokers are increasing.
Lung cancer in UK never-smokers doubled between 2008 and 2014, according to one 2017 study.
Although smoking remains the biggest risk factor for lung cancer, it’s estimated that nearly 6,000 people who have never smoked die of lung cancer each year, some of which may be due to air pollution exposure
Another 2023 report by the American Cancer Society found 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 increasingly younger case load.
Researchers at British Columbia Cancer Research Institute in Vancouver, Canada collected data collected from 255 lung cancer patients who never smoked — including where they lived since birth.
Levels of pollution were then analysed at their home addresses using satellite data, air pollution forecasts, and ground measurements within a 10 kilometer area.
The team obtained annual exposure data going back to 1996 when accurate air pollution information became available globally.
Researchers also noted whether patients developed a change in their DNA that is known to increase the risk of lung cancer, called an EGFR mutation.
The genetic mutation — which is not usually present at birth — accelerates the activity of a protein called epidermal growth factor receptor (EGFR), which helps cells grow and divide.
The extreme division of cells is what causes cancers to develop over time.
Although small, these particles are thought to cause inflammation in the lungs which can wake up normally inactive cells which can lead to cancer-causing mutations and tumours
Researchers found patients diagnosed with stage four lung cancer were far more likely to have EGFR mutations compared to those without the disease.
But they also found women were more likely to have EGFR mutations if they were exposed to at least three years of pollutant particles smaller than 2.5 micrometers, also known as PM2.5.
This was true regardless of whether a woman smoked or not.
This was also the case for patients who had been exposed to the pollution for five years prior to diagnosis.
Surprisingly, these associations were not evident in men who never smoked.
PM2.5 are soot particles in the air invisible to the human eye that can enter into blood and penetrate deep into the lung.
They can be emitted by vehicle engines, wood burning and smoking.
Although small, these particles are thought to cause inflammation in the lungs that can wake up normally inactive cells, leading to cancer-causing genetic mutations.
The International Agency for Research on Cancer (IARC) categorised outdoor air pollution and its key component, particulate matter PM 2.5, as a Group 1 carcinogens in 2013 — indicating that they cause lung cancer.
Although smoking is the leading cause of cancer, researchers and public health experts have not been able to identify an association that explains why individuals who do not smoke or have never smoked are diagnosed with the disease.
Lung cancer is the third most common cancer in the UK with around 48,500 people diagnosed every year.
Symptoms include a persistent cough, chest infections and aches in the chest or shoulder.
About 70 per cent of cases are caused by smoking, while other risk factors can include exposure to radon gas, certain chemicals and a family history of lung cancer.
Although lung cancer is rare in young people younger than 40, overall there are around 2,300 new cancer cases in young people in the UK every year, according to Cancer Research UK.
But study authors say more research is needed to asses air pollution as a lung cancer risk.
‘These findings suggest a potential impact of recent exposure to PM2.5 on lung cancer in people who never smoked, particularly among women,’ wrote the study authors.
