Air pollution could be responsible for thousands of non-smokers dying from lung cancer every year, new UK research suggests.
A £14 million ($16.2m) research programme by Cancer Research UK looked at how lung cancer starts and evolves over time, in an effort to explore new treatments.
Although smoking is a well-known cause of lung cancer, the risk caused by air pollution was not fully understood until now.
Researchers involved with the Tracerx Lung Study investigated the theory that tiny pollutant particles in the air — about 3 per cent of the width of a human hair called PM2.5 — cause inflammation in the lungs that can lead to cancer.
Inactive cells in the lungs that carry cancer-causing mutations are ‘woken up’ by inflammation, causing cells to grow uncontrollably into tumours.
Prof Charles Swanton, chief clinician of scientists at the Francis Crick Institute and University College London, said the study fundamentally changed how lung cancer should be viewed in those who have never smoked.
“Cells with cancer-causing mutations accumulate naturally as we age, but they are normally inactive,” said Prof Swanton, who is also lead investigator on the Tracerx study.
“We’ve demonstrated that air pollution wakes these cells up in the lungs, encouraging them to grow and potentially form tumours.
“The mechanism we’ve identified could ultimately help us to find better ways to prevent and treat lung cancer in never smokers.
“If we can stop cells from growing in response to air pollution, we can reduce the risk of lung cancer.”
An estimated 6,000 non-smokers die of lung cancer in the UK each year, with outdoor air pollution thought to contribute or cause about 10 per cent of lung cancer cases.
Air pollution has also been linked to asthma, chronic obstructive pulmonary disease (Copd), heart disease and dementia.
While environmental agents such as ultraviolet light and tobacco smoke are known to directly mutate DNA, the study revealed how air pollution could have a similar effect.
Scientists examined a type of lung cancer called epidermal growth factor receptor (EGFR) mutant lung cancer, commonly found in the lung cancer of non-smokers.
Rates of EGFR were examined in data from 400,000 people in the UK and Asian countries, and compared with different levels of pollution.
The scientists found higher rates of the EGFR mutation, as well as other cancers in those living in areas with high PM2.5 pollution levels.
According to the Swiss IQAir pollution index in 2021, Bangladesh had the worst air quality index rating of 161, followed by Chad, Pakistan, Tajikistan and India.
Nations with the cleanest air were New Caledonia followed by the US Virgin Islands, Puerto Rico, Cape Verde and Bonaire, Saint Eustatius and Saba in the Caribbean.
“Even small changes in air pollution levels can affect human health,” said Dr Emilia Lim, co-author of the study.
“Ninety-nine per cent of the world’s population lives in areas which exceed annual World Health Organisation limits for PM2.5, underlining the public health challenges posed by air pollution across the globe.”