Are pollutants in the air we breathe likely to increase the risk of breast cancer in women? This is the entire purpose of the study launched at the initiative of the Léon-Bérard cancer center in Lyon and Rhône-Alpes, with the support of the ARC Foundation for cancer research. It is based on a sample of more than 10,000 women, ill and non-ill, followed between 1990 and 2011. “Although the genetic, reproductive and hormonal factors of breast cancer are well identified, they do not explain all caseshighlights the center’s “environmental cancer prevention” department. Epidemiological and experimental studies have suggested that exposure to environmental contaminants, especially those with endocrine-disrupting effects, may play a role in the development of breast cancer.
It is on the basis of this hypothesis and at the end of this unprecedented scientific program, called Xenair, that the researchers were able to establish a link between chronic, low-dose exposure to air pollutants and the risk of breast cancer. the most frequent female cancer in the world with 58,500 new cases in France in 2020. Of the eight air pollutants studied and classified for six of them as carcinogenic to humans by the International Center for Research on Cancer (Circ), five are implicated in the highest risk of the disease. NO2 or nitrogen dioxide, emitted mainly by road traffic, increases the risk of breast cancer by around 9% in women most exposed to pollutants. Same finding for particulate matter (PM10) and fine particulate matter (PM2.5), from the wood heating, road fuels, and construction and manufacturing sectors, with a risk of +8% and +13%, respectively. .
the benzo[a]Pyrene (BaP), found in coal tar, combustion fumes from wood and plants, cigarette smoke, exhaust fumes, or grilled meats (barbecues in particular ), increases the risk of tumors by approximately 15%. Finally, the fifth and last questioned, polychlorinated biphenyls (PCB153), from industrial combustion, reaches the highest percentage with approximately +19% risk. A daily danger that persists, despite the continuous and global decrease in exposure to these pollutants between 1990 and 2011.
To achieve these results, “We compared the exposure of sick women of the same age with those who were not sick in a given period (1990-2005 or 1990-2000 for example), estimating the average annual exposure of their places of residence to the different air pollutants, which which allowed us to estimate the risk they incur for each of the selected pollutants. Pollutants for which it was possible to estimate exposures retrospectively since 1990. details Delphine Praud, a researcher in environmental epidemiology who worked on the Xenair study. This was not the case at the time for ultrafine particles (UFP), which are now the subject of growing concern from health authorities, including the National Agency for Food Safety (Anses) and the World Health Organization (WHO). ).
In parallel, additional analyzes have shown an increased risk “in women who were exposed during their transition to menopause, a period of increased sensitivity, to BaP and PCB153, two contaminants classified as endocrine disruptors”, adds the study. In contrast, the latter does not establish a link between breast cancer and exposure to cadmium and dioxins, both from industrial processes, although cadmium has been identified as an important cause of breast cancer through food. Other ongoing analyzes concern exposure to ozone, the eighth and final pollutant considered in the Xenair study.
Faced with such results, improving air quality remains an important lever to contribute to the prevention of breast cancer in France. Proof : “If we take Europe’s thresholds for PM2.5 particles, PM10 particles and nitrogen dioxide (NO2) as a reference, almost 4%, 1% and 1% of the breast cancers of the women in our study could have been prevented, respectively.transmit the two scientists who are also currently working on the question of the combined effect of exposure to these multiple pollutants, with the support of the League against Cancer, the Environment and Energy Control Agency (Ademe) and ANSES. On the other hand, if exposure levels to NO2 or nitrogen dioxide were below the WHO recommendations by 2022, 7% of breast cancers in the Xenair population would have been prevented. Estimates that remain to be confirmed for PM2.5 and PM10 particles.
The cancers avoided would thus allow substantial savings in terms of treatment, care and costs for society. As a reminder, air pollution kills more than 48,000 people each year in France, according to ANSES, and around 7 million worldwide, according to the WHO.
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