Air pollution associated with fine particles causes more than 250,000 deaths from lung cancer annually worldwide. And this, even in people who have never smoked. The observation was made, but a causal explanation was missing.
What are the mechanisms by which these microparticles act? The answer was revealed on Saturday, September 10, during the annual conference of the European Society of Medical Oncology, ESMO, held in Paris. This study highlights an archetype of cancer development., comments Suzette Delalog, MD, medical oncologist, director of the Personal Cancer Prevention Program at the Gustave Roussy Institute, Villejuif, who was not involved in this work. In the classic model, a toxin (such as tobacco smoke) causes mutations that, when accumulated, are enough to cause cancer. But this is not the case for the people observed in this study: “It takes an extra step, which is inflammation.” Microparticles create this inflammatory process, which leads to the transformation of the tumor in only certain cells of the bronchi, which carry dangerous mutations.
Fine particles are present in automobile exhaust gases and in fumes from the combustion of fossil fuels, and are invisible to the naked eye. Its diameter is less than or equal to 2.5 micrometers – hence the name “PM2.5” – twenty to thirty times less than the diameter of a hair. “Because of its small size, it penetrates the airways for very long distances, especially the lungs”Susette Dialog explains. PM2.5 is responsible for about 14% of all lung cancer deaths. Tobacco, for its part, causes about 63% of these deaths.
Ratio increase
In 2009, an American study estimated that 10% to 15% of lung cancers occur in non-smokers, but This percentage is increasing.Professor Charles Swanton, from the Francis Crick Institute and University College London (UK), said during a press conference at ESMO.
The study by this renowned researcher draws its strength from a range of methods and techniques, ranging from epidemiology to cellular and molecular biology, including animal and human models.
First, epidemiology confirms the association between increased PM2.5 concentrations and the risk of various types of cancers. The authors analyzed data from 463,679 people residing in England, South Korea, and Taiwan. By crossing individual PM2.5 exposure data—depending on where you live—and individual health data, they found a 16% increase in lung cancer risk for every 1 microgram per cubic meter increase in PM2.5. In addition, all airways are involved. The risk of developing cancer of the lips, oral cavity and pharynx increases by 15%, cancer of the larynx by 26%, cancer of the small intestine by 30%, and cancer of the anus by 23%. Even more surprising, because it had nothing to do with the digestive system, it increased by 19% for glioblastoma multiforme, a cancer of the central nervous system.
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