Environmental Factor – November 2021: Growing evidence links air pollution to breast cancer
“Given the high incidence of breast cancer and the pervasive nature of environmental exposures, such as air pollution, our research has the potential for substantial public health impact,” said Alexandra White, Ph.D., who heads the Environment and Cancer Epidemiology group at NIEHS.
Breast cancer accounts for 30% of newly diagnosed invasive cancers in women, reports the American Cancer Society. In addition, population-based data shows significant and constant increases in breast cancer from 1935 to 2015, especially among younger women (25-39 years).
The condition has known or suspected links to many environmental factors.
âThese factors need to be further considered as contributors to these higher rates,â White said. “There has been no significant progress in reducing the incidence of breast cancer with the risk factors that have been identified.”
The conundrum for scientists and health professionals is that even established risk factors, such as postmenopausal obesity and alcohol consumption, have little effects on the overall risk of developing breast cancer.
“However, these modest effects do not necessarily translate into a lack of public health significance,” White said. âTo better understand how the environment contributes to breast cancer risk, we need to understand how different environmental factors can work together. This will help us identify the key factors. Then, hopefully, we can make progress by reducing the most important exposures. “
Documenting the effects of air pollution
According to recent research, air pollution could be one of these key exposures. Present all over the world, this pollution is a complex mixture of particles and solid and liquid gases.
In 2018, White co-wrote a review the article which identified 17 studies on the risk of breast cancer associated with air pollution. Nitrogen dioxide (NO2) and nitrogen oxides – two indicators of traffic-related air pollution – have been linked to breast cancer.
Three years later, the findings of an updated review showed that a decrease in long-term NO2 exposure could a lower incidence of breast cancer.
The NIEHS Sister study is a leading resource for research on environmental factors and breast cancer. In this study, White and her group found that women who live in areas of higher air pollution had a higher risk of developing breast cancer. The risk varied geographically due to the different sources of pollution in the United States (see sidebar for more results.)
“Among the many different compounds in air pollution, some act as endocrine disruptors and can affect hormonal pathways,” she said. âThe scientific literature is quite clear that endocrine disruption can affect the development of breast cancer. “
“We want to know whether exposure to certain endocrine disrupting and carcinogenic chemicals in air pollution leads to an increased risk of breast cancer later in life,” noted White.
Because breast cancer can take a long time to develop, the most recent exposures may not be the most relevant. In addition, studies that only examine exposure to air pollution at a later stage of life may not take into account the effects of previous exposures.
White is interested in breast cancer studies that take into account historical levels of exposure to pollutants. Her team plans to study how exposure to air pollution, especially during the childbearing years, might be linked to breast cancer risk decades later.
She noted that black women need better representation in these studies.
Increasingly, his team will consider multiple sources of exposure and interactions between different compounds over time. This approach will be applied in a project examining residential exposure to industrial carcinogenic emissions and how certain types of emissions can act together to influence breast cancer risk.
White explained in more detail the goals of future research.
- Characterize mixtures of air pollutants and their contributions to breast cancer risk.
- Explore racial and ethnic disparities in health.
- Consider the effects of air pollutants throughout life, especially early in life.
These considerations could lead to a better understanding of how air pollution affects breast cancer risk, according to White.
At NIEHS, White’s team seeks to identify exposures that can be reduced either through policy changes or through actions women can take on their own.
The concept of place-based health is important, according to White. Where people live can be critical in assessing their risk of developing breast cancer, receiving adequate treatment, and estimating short- and long-term survival after diagnosis.
âAs a result of our work, I would like us to recognize more widely that air pollution plays a role in the risk of breast cancer,â she said. “This recognition could influence policies related to acceptable levels of exposure to air pollution, which could help reduce the incidence of breast cancer.”
AJ white. 2021. Invited Perspective: Air Pollution and Breast Cancer Risk: Current State of Evidence and Next Steps. A look at the health of the environment. 129 (5): 51302.
Gabet S, Lemarchand C, GuÃ©nel P, Slama R. 2021. Breast cancer risk associated with exposure to air pollution: a meta-analysis of effect estimates followed by a health impact assessment. A look at the health of the environment. 129 (5): 57012.
Lima SM, Kehm RD, Swett K, Gonsalves L, Terry MB. 2020. Trends in breast cancer parity and incidence among US women under 40 from 1935 to 2015. JAMA Netw Open. 2.3 (3): e200929.
White AJ, Keller JP, Zhao S, Carroll R, Kaufman JD, Sandler DP. 2019. Air Pollution, Clustering of Particle Components, and Breast Cancer in the Sister Study: A US-Wide Cohort. A look at the health of the environment. 127 (10): 107002.
White AJ, Bradshaw PT, Hamra GB. 2018. Air pollution and breast cancer: a review. Curr Epidemiol Rep. 5 (2): 92-100.
(Carol Kelly is editor-in-chief of the NIEHS Office of Communications and Public Liaison.)