New research deepens our understanding of how air pollution fosters the development of cancer.

The poor quality of the air that all of us breathe today has been the subject of various studies in the last decades. Such research has uncovered that air quality is decreasing steadily around the world and that rising levels of chemical pollution and particulate matter are linked with a greater incidence of respiratory issues and preventable death worldwide.

New research led by the Francis Crick Institute in London comes to further our understanding of how air pollution fosters the incidence of one disease in particular: cancer. The results, they write, completely transform our understanding of how tumors emerge.

Awakened by pollution

According to the researchers, air pollution doesn’t directly cause any damage to cells, which could lead to the formation of tumors. What it does do, however, is activate old, already-damaged cells — which can further mutate and degenerate into a cancerous state. Although the findings are based on research on air pollution, the findings are applicable to understanding how hundreds of cancer-causing substances interact with our bodies’ cells.

Our understanding of cancer so far is that it emerges from healthy cells that, over time, acquire more and more mutations — unintended changes in its genetic code. Upon reaching a certain tipping point, the weight of these mutations taken together cause the cell to grow and reproduce uncontrollably: at this point, it forms a cancerous tumor.

That being said, we don’t yet know how carcinogenic (cancer-promoting) substances fit into the picture. The main issue being that many of these substances, including air pollution, don’t cause direct damage to DNA.

In order to understand what’s going on, the team worked with non-smoking patients in the UK who have developed lung cancer. Although most lung cancers are caused by smoking, around 1 in 10 cases are caused by air pollution alone. According to the current paper, these substances act as chemical triggers. The mutations that eventually cause a cell to turn cancerous are produced as we age before they interact with the trigger.

The team reports that a particular form of pollution called particulate matter 2.5 (known as PM2.5) seems to be the main culprit. Places with higher concentrations of PM2.5 in the air have a higher incidence of lung cancers unrelated to smoking.

Inhaling PM2.5 leads to the release of interleukin-1-beta, a ‘chemical alarm’, in the tissues of the lungs. This leads to inflammation and leads to the activation of certain cells in the lungs that are meant to help repair the damage. However, in the lungs of every 50-year-old individual, around 1 in every 600,000 cells contains potentially-cancerous mutations acquired through normal aging processes.

Until such cells are activated by interleukin-1-beta, they are harmless. The chemical alarm, however, can cause them to become cancerous. The researchers showed that they can stop cancers from forming in mice exposed to high levels of air pollution by treating them with drugs that blocked the effect of interleukin-1-beta.

The results are quite important from two points of view. First, it allows us to better understand the link between air pollution and the formation of cancerous tumors. This is especially important in helping us understand cases of lung cancer that are not caused by smoking, helping to give some patients the answers they may need to come to grips with their situation.

They also help guide us to a possible means of preventing cancers from forming in the first place — the ability to do so would be of much greater benefit than knowing how to cure them after they develop.

“It’s super-important – 99% of people in the world live in places where air pollution exceeds the WHO guidelines so it really impacts all of us,” says Dr. Emilia Lim, co-firs author of the paper.

The findings showcase that one day, people living in heavily polluted areas could take a pill that prevents them from developing cancer. And, given how air quality is evolving around the world, that may be very many of us.

The findings have been presented at the Conference of the European Society for Medical Oncology.