An English team announced on Saturday that it had discovered the mode of action of PM2.5, responsible for hundreds of thousands of deaths by lung cancer.
Air pollution linked to fine particles causes more than 250,000 deaths by lung cancers each year in the world. Even in people who have never smoked. The observation was known, but the causal explanation was missing.
By what mechanisms do these fine particles act? The answer was unveiled on Saturday September 10, during the annual congress of the European Medical Oncology Society (ESMO) which was held in Paris. “This study highlights an original model for cancer development,” comments Suzette Delaloge, medical oncologist, director of the personalized cancer prevention program at the Gustave Roussy Institute in Villejuif, who did not participate in this work. In the classic model, a toxic (like tobacco smoke) triggers mutations which, by accumulating, are enough to trigger cancer. But this is not the case here: “It takes an additional step, which is an inflammation.” The fine particles create this inflammatory process, which triggers the tumor transformation of certain cells of the respiratory tract only, those which bear mutations to Risk.
Present in the exhaust gases of motorized vehicles and in fumes from the combustion of fossil fuels, fine particles are invisible to the naked eye. Their diameter is less than or equal to 2.5 micrometers – hence their name “PM2.5” – or 20 to 30 times less than the diameter of a hair. “Because of this small size, they penetrate very far into the airways, especially in the lungs,” said Suzette Delaloge. these pm2.5 are responsible About 14 % of all deaths by lung cancer . Tobacco, for its part, alone causes approximately 63 % of these deaths.
in 2009, an American study estimated that 10 % at 15 % of lung cancers occurred in non-smokers , but “this proportion is increasing,” said Professor Charles Swanton, the Francis Crick Institute and the London University College (Kingdom- Uni), during a press conference at ESMO.
conducted by this renowned researcher, this study derives its strength from a combination of approaches and techniques, which range from epidemiology to cell and molecular biology, via animal and human models.
Epidemiology, first, confirms the association between the increase in concentrations of PM2.5 and the risk of different cancers. The authors analyzed the data of 463,679 people residing in England, South Korea and Taiwan. By crossing individual exposure data to PM2.5 – according to the place of residence – and individual health data, they find that the risk of lung cancer increases by 16 % for each increase of 1 microgram per cubic meter ‘Air (1mg/m 3 sup>) of the rate of PM2.5. But all the aerodigestive routes are concerned. The risk increases by 15 % for lip cancer, oral cavity and pharynx, by 26 % for larynx cancer, 30 % for small intestine cancer and 23 % for cancer of The anus. More surprising because unrelated to the aero-digestive tracks, it is increased by 19 % for multiple glioblastoma, cancer of the central nervous system.
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