Results from a long-term case-controlled study investigating the impact of both residential and workplace exposure to air pollution and the risk of developing breast cancer, showed that women living and working in places with higher levels of fine particle air pollution are more likely to get breast cancer than those living and working in less polluted areas.
The results of the study, which was conducted between 1990 and 2011, is the first study to take account of the effects of both residential and workplace exposure to air pollution on breast cancer risk, has been presented at the annual meeting of the European Society for Medical Oncology (ESMO Congress 2023) held October 20 – 24, 2023 in Madrid, Spain. 
“Our data showed a statistically significant association between long term exposure to fine particle air pollution, at home and at work, and risk of breast cancer. This contrasts with previous research which looked only at fine particle exposure where women were living, and showed small or no effects on breast cancer risk,” noted Professor Béatrice Fervers, Head of Prevention Cancer Environment Department, Léon Bérard Comprehensive Cancer Centre, France.
In the study, home and workplace exposure to pollution in 2419 women with breast cancer was compared to that in 2984 women without breast cancer over the period 1990-2011. The results showed that breast cancer risk increased by 28% when exposure to fine particle (PM2.5) air pollution increased by 10 µg/m3 – approximately equivalent to the difference inPM2.5 particle concentration typically seen in rural versus urban areas of Europe. Smaller increases in breast cancer risk were also recorded in women exposed to high levels of larger particle air pollution (PM10 and nitrogen dioxide).
As a follow-up, Fervers and colleagues plan to investigate the effects of pollution exposure during commuting to get a complete picture of effects on breast cancer risk.
Lung cancer in non-smokers
Updated results from a study by Professor Charles Swanton, the Francis Crick Institute, London, UK, whose research suggests how PM2.5 particles may trigger lung cancer in non-smokers, were also presented at annual ESMO meeting. 
Swanton stressed the importance of the new findings with breast cancer: “These very small particles can penetrate deep into the lung and get into the bloodstream from where they are absorbed into breast and other tissues.”
“There is already evidence that air pollutants can change the architecture of the breast . It will be important to test if pollutants allow cells in breast tissue with pre-existing mutations to expand and drive tumor promotion possibly through inflammatory processes, similar to our observations in non-smokers with lung cancer,” he explained.
“It is very concerning that small pollutant particles in the air and indeed microplastic particles of similar size are getting into the environment when we don’t yet understand their potential to promote cancer. There is an urgent need to set up laboratory studies to investigate the effects of these small air pollutant particles on the latency, grade, aggression and progression of breast tumor’s,” Swanton continued.
Strong epidemiological and biological evidence
“There is now strong epidemiological and biological evidence for the link between PM2.5 particle exposure and cancer, and there are good clinical and economic reasons for reducing pollution in order to prevent cancers,” noted Professor Jean-Yves Blay, ESMO Director of Public Policy.
Following on a proposal from the European Commission in October 2022 to reduce the limit for PM2.5 particles in the air from the current 25 µg/m3 to 10 µg/m3 by 2030, ESMO urged a reduction in the PM2.5 limit still further to 5 µg/m3, in line with the World Health Organization’s air quality guidance. 
“Reducing PM2.5 particles in the air to the WHO recommended level is critical because of their association with a variety of tumor types, including breast cancer,” Blay explained.
“We have a responsibility to push for this change, not only for people in Europe but worldwide where there are big variations in the pollution landscape.”
The lower limit was indeed adopted by the European Parliament’s Environment, Public Health and Food Safety Committee in June 2023.
More recently, in September 2023, the European Parliament adopted in plenary session its report on the ongoing revision of the EU Ambient Air Quality Directives, which reflects ESMO’s recommendations to set the annual limit value for Fine Particulate Matter (PM2.5) at 5 µg/m³, and requires all EU Member States to take appropriate measures to ensure compliance with the limit and target values within a specified deadline and/or to maintain compliance once the limit and target values have been met. This adoption opens interinstitutional negotiations between the co-legislators – European Parliament, European Commission and EU Council – to agree on the final text of the directive. 
“By supporting our requests with solid scientific evidence, we are offering a new dimension to health public policy. The work is not over, and change will not happen overnight, but we are moving in the right direction,” Jean-Yves Blay concluded.
 Fervers B et al. Longterm residential and workplace exposure to air pollution and breast cancer risk: A case-control study nested in the French E3N cohort from 1990 to 2011 will be presented by Fervers B. during the Mini Oral Session on Monday, 23 October 2023, 16:30-18:00 CEST, at ESMO Congress 2023, Madrid (Bilbao Auditorium).
 Swanton C et al. Mechanism of action and an actionable inflammatory axis for air pollution induced non-small cell lung cancer: Towards molecular cancer prevention. Presented at ESMO Congress 2022, Paris, France Presidential Symposium 1, LBA1
 Niehoff NM et al. Outdoor air pollution and terminal duct lobular involution of the normal breast. Breast Cancer Res 2020; 22,100.
 Kotake R et al. An association between mammographic breast density and fine particulate matter among postmenopausal women. Environ Sci Pollut Res Int. 2023 Feb;30(10):25953-25958.
 WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide.
 European Parliament. Revision of the ambient air quality directives.
 European Parliament. Towards cleaner air for Europe.