Scientists have uncovered how air pollution causes lung cancer

Air pollution is a hidden enemy that threatens everyone.

Polluted air has always been a by-product of human activity, from cooking the food we eat, to making things we need and getting to places we want to go. But new UK research shows just how much of a threat it presents to our health.

In 2019, almost all of us were living with higher levels of pollution than the strictest guidelines advise, according to the World Health Organization (WHO). And around seven million premature deaths around the world each year are caused by both ambient and household air pollution.

It is widely known that tiny particles in polluted air can cause breathing-related health problems such as asthma and chronic obstructive pulmonary disease and affect the heart. Studies have also found that particles released during the burning of fuel can pass into the brain, raising concerns about cognitive impairment and dementia risk.

But, for the first time, scientists are able to explain the link between pollution and lung cancer.

The British Lung Foundation defines particulate matter, or PM, as “a mix of solids and liquids, including carbon, complex organic chemicals, sulphates, nitrates, mineral dust, and water suspended in the air”.

Scientists at the UK’s Francis Crick Institute and University College London say they have found that exposure to PM2.5, which is 3% the width of a human hair, can promote the growth of cancer-causing mutations in the cells of the lung.

Their study is focused on a particular type of lung cancer known as epidermal growth factor receptor (EGFR) mutant lung cancer and is based on data derived from 400,000 people in the UK and some Asian countries.

The scientists discovered that people regularly exposed to higher levels of PM2.5 air pollution were at increased risk of EGFR mutant lung cancer and other cancers. In the case of non-smoking lung cancer, it is possible for these mutations to exist in healthy cells, they explain.

“EGFR mutations are an essential step towards cancer forming,” says Dr William Hill, a researcher at the Francis Crick Institute. “These cells are dormant until a trigger, such as air pollution, causes them to start growing. The mechanism we’ve identified may explain why there is an increased risk of cancer from air pollution, but the risk is much lower compared to smoking, which mutates DNA directly.”

The research team also believes the process could be triggered in other parts of the body.

In laboratory experiments, the researchers found that blocking an inflammatory molecule called Interleukin-1 Beta, which is released after PM2.5 exposure, stopped cancer from forming. It’s hoped this could pioneer a new wave of cancer-preventing medicines.

“The mechanism we’ve identified could ultimately help us to find better ways to prevent and treat lung cancers in never smokers. If we can stop cells from growing in response to air pollution, we can reduce the risk of lung cancer,” says Professor Charles Swanton, lead investigator for the study.

Cancer is one of the leading causes of death globally, accounting for almost 60% of deaths, according to the WHO. Lung cancer was the most lethal form of cancer in 2020, linked to 1.8 million deaths. It’s also the second most common cancer after breast cancer.

The availability of cancer treatment varies significantly. Around 90% of high-income countries offer comprehensive treatment compared with 15% of low-income countries. The WHO also says air pollution “disproportionately affects those living in developing nations and particularly the most vulnerable such as women, children and the elderly”.

Cutting levels of pollution in accordance with the WHO’s guidelines could reduce the number of deaths linked to the particulate by 80%, potentially saving more than three million lives worldwide.

A record 6,700 cities and communities in 117 countries are currently monitoring air quality. However, most of these are not aligned with WHO guidelines. “To attain clean air in cities, existing resources should be aligned to help countries develop and implement air quality management systems and improve health,” the organization says.