The risk of air pollution depends on the hazard of the pollutant and the exposure to that pollutant. Image by Janak Bhatta (CC BY-SA 4.0)
A new study has identified the mechanism by which air pollution leads to cancer. The nature of the discovery is changing our medical understanding of how tumors arise.
A study conducted at the Francis Crick Institute in London showed that air pollution does not cause direct damage, but causes old, damaged cells to come out of a state of “hibernation”.
This is based on damage to the cell’s DNA, which is formed as it ages. At some point in the future, the trigger makes it cancerous. This could explain, for example, why non-smokers can develop lung cancer. Instead, in some cases, air pollution is the mechanism.
This conclusion changes established understanding of how cancer develops. Here cancer begins with a healthy cell. As a cell acquires more and more mutations in its genetic code, it becomes cancerous and grows uncontrollably.
The discovery potentially explains like hundreds of cancer-causing substances act on the body. Based on the discovery, it is now possible to develop drugs that stop the formation of certain types of cancer.
Researchers have studied the type of pollution called particulate matter 2.5 (known as PM2.5). PM2.5 particles are able to penetrate deep 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 conditions such as asthma and heart disease.
Research has found that inhaling PM2.5 triggers the release of a chemical alarm signal, interleukin-1-beta, into the lungs. This causes inflammation and activates cells in the lungs to help repair any damage. However, about one out of every 600,000 cells in the lungs of a 50-year-old person already contains potentially cancerous mutations. This is the reason why air pollution is associated with an increased risk of cancer in some members of the general population.
According to The GuardianWorld Health Organization guidelines state that PM2.5 concentrations should not exceed 5 micrograms per cubic meter on average throughout the year.
Lead Investigator Dr. Emilia Lim tells the BBC that understanding why people who have never smoked but have developed lung cancer goes a long way: “Giving them some clues about how this might work is very, very important. This is very important – 99% of the world’s people live in places where air pollution exceeds WHO guidelines, so it really affects all of us.”