A new study has identified the mechanism by which air pollution leads to cancer. The nature of the discovery alters medical our understanding of how tumours arise.
The research was conducted at the Francis Crick Institute in London, and it finds that rather than causing direct damage, air pollution functions to cause old, damaged cells to move out of a state of ‘hibernation’.
This is based on the damage to a cell’s DNA forming as it ages. At some future point a trigger makes it cancerous. This may explain, for example, why non-smokers can develop lung cancer. Instead, air pollution is the mechanism in some cases.
This finding alters the established view of how cancer is formed. Here, cancer starts with a healthy cell. As the cell acquires more and more mutations in its genetic code it becomes a cancer and grows uncontrollably.
The finding potentially explains how hundreds of cancer-causing substances act on the body. Based on the discovery if may now become possible to develop drugs that stop certain cancers from forming.
The researchers looked at a type of pollution called particulate matter 2.5 (known as PM2.5). Particles in the PM2.5 size range are able to travel deeply into the respiratory tract, reaching the lungs. Exposure to fine particles can cause short-term health effects such as eye, nose, throat and lung irritation, coughing, sneezing, runny nose and shortness of breath.
In addition, exposure to these fine particles can also affect lung function and worsen medical conditions such as asthma and heart disease.
With the research, it was established that breathing in PM2.5 leads to the release of a chemical alarm – interleukin-1-beta – in the lungs. This causes inflammation and activates cells in the lungs to help repair any damage. However, around one in every 600,000 cells in the lungs of a 50-year-old already contains potentially cancerous mutations. This is a reason why air pollution has an association with an elevated cancer risk for some in the general population.
According to The Guardian, World Health Organisation guidelines state that say concentrations of PM2.5 should not exceed 5 micrograms per cubic metre on average over a year.
Lead researcher Dr Emilia Lim tells the BBC that understanding why people who had never smoked but developed lung cancer is of great importance: “To give them some clues about how this might work is really, really important. 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.”
