Are pollutants in the air we breathe likely to increase the risk of breast cancer in women? This is the whole purpose of the study launched on 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, sick and not sick, followed between 1990 and 2011. “While the genetic, reproductive and hormonal factors of breast cancer are well identified, they do not explain all the casesemphasizes the centre’s “environmental cancer prevention” department. Epidemiological and experimental studies have suggested that exposure to environmental pollutants, particularly those with endocrine disrupting effects, may have 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 exposure – at low doses – to atmospheric pollutants and the risk of cancer of the breast, 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 for humans by the International Center for Research on cancer (Circ), five are implicated in the increased risk of the disease. NO2 or nitrogen dioxide, mainly emitted by road traffic, increases the risk of breast cancer by around 9% in women most exposed to pollutants. Same finding for particles (PM10) and fine particles (PM2.5), from wood heating, road fuels and the construction and manufacturing industry sectors, with respectively +8% and +13% risk .
The benzo[a]pyrene (BaP), found in coal tar, combustion fumes from wood and plants, cigarette smoke, fumes from exhaust pipes or grilled meats (on the barbecue in particular), increases the tumor risk of about 15%. Finally, the fifth and last questioned, polychlorinated biphenyls (PCB153), coming from industrial combustion, reaches the highest percentage with approximately +19% risk. A daily danger that persists, despite the continuous and global decline 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 over a given period (1990-2005 or 1990-2000 for example), by estimating the average annual exposure of their places of residence for the various atmospheric pollutants, this 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, researcher in environmental epidemiology who worked on the Xenair study. This was not the case at the time of ultrafine particles (UFP) which are now the subject of growing concern from health authorities, including the National Food Safety Agency (Anses) and the World Health Organization (WHO).
In parallel, additional analyzes have demonstrated a higher risk “in women who were exposed during their menopausal transition – a period of heightened sensitivity – to BaP and PCB153, two pollutants classified as endocrine disruptors”, adds the study. Conversely, the latter does not make 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 taken into account in the Xenair study.
Faced with such results, improving air quality therefore remains a major lever for contributing 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, respectively nearly 4%, 1% and 1% of women’s breast cancers of our study could have been avoidedrelay the two scientists who are also currently working on the question of the combined effect of exposure to these multiple pollutants, with support from the League against Cancer, the Environment Agency and the control of l energy (Ademe) and ANSES. On the other hand, if the levels of exposure to NO2 or nitrogen dioxide were below the WHO recommendations for 2022, 7% of breast cancers in the Xenair population would have been avoided. Estimates that remain to be confirmed for PM2.5 particles and PM10 particles.
The cancers avoided would thus make it possible to make 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.