Could Air Pollution and Racism Be Hidden Causes of Breast Cancer?
Known risk factors account for less than half of all breast cancer cases. Is the environment to blame for the rest?
WHY YOU SHOULD CARE
Because breast cancer may have much to do with where you live.
Breast cancer struck Joan Venticinque twice: first when she was 44, and again five years later. The second time, she underwent surgery to remove both breasts, as well as her ovaries. “What did I do to get this?” she wondered. Now 64, the patient advocate and graphic designer in Redwood City, California, had no family history of the disease and exercised avidly. Plus, she was on the young side; breast cancer is more common in women over 50. Venticinque recalled the solvents and chemicals she had used in art school and while working at a local science museum. Did they cause her cancer?
Many women who get breast cancer are like Venticinque. Their cases aren’t explained by established risk factors, such as inherited genetic mutations, family history or obesity. Scientists have studied these factors for decades, yet together they account for around 30 to 40 percent of breast cancer cases. What could explain the rest? A growing body of evidence suggests that the environment, including air pollution and chemicals found in everyday products, might play a role. Even more provocatively, so might racism and other social stressors.
White women have the highest breast cancer rates, but a recent study shows that diagnosis rates are rising in Black and Asian women.
Efforts to investigate these connections in a rigorous way began in the 1990s, when women with breast cancer in places that had unusually high rates of the disease — like Long Island, New York; Cape Cod, Massachusetts; and Marin County, California — founded nonprofits to push federal institutions to research environmental risk factors. Tired of waiting for federal funding, some of these activists formed groups like Silent Spring Institute to conduct their own research. Since then, interest in the field has increased. A Google Scholar search of “breast cancer environmental factors” turns up nearly 41,000 papers published in 2012 — a number that has since climbed to around 156,000 as of early July.
New cases of female breast cancer in the U.S. have increased 242 percent from 1970 to 2014; more than 40,000 women will die of the disease this year. “Rates are stabilized for white women, but it’s still such a common disease, and there’s a lot of frustration with that,” says Julia Brody, executive director and senior scientist of Silent Spring Institute. “There’s a desire to look for preventable causes because the treatments are very stressful and debilitating. Too many women are still dying of it.”
Now, some researchers are treating the disease as a public health problem, not just a biomedical one. They emphasize not only treatment but also prevention through policy changes to limit environmental exposures, shifting the burden from women to society. “The historical focus on lifestyle and other known risk factors implies that it’s women’s job to prevent breast cancer,” says Karuna Jaggar, executive director of Breast Cancer Action, an educational and activist organization. “We are told that if we exercise, breast-feed … we can prevent our own breast cancer.”
Some in the field are also taking a public health approach to racial disparities. White women have the highest breast cancer rates, but a recent study shows that incidence rates are rising in Black and Asian/Pacific Islander women. Black women are also the most likely to die of the disease. Instead of focusing exclusively on genetic differences, some researchers are looking at differences in environmental exposures. For instance, hazardous waste sites are often located in poor communities of color.
Following multiple studies that show increased breast cancer incidence in industrialized and urban areas, some researchers are examining whether air pollution plays a role. A recent study found a potential association between exposure to polycyclic aromatic hydrocarbons — air pollutants found in car exhaust and soot, for instance — and female breast cancer incidence in the northeastern and southeastern U.S., based on data that spans from 2000 to 2012. The more industrialized Northeast had significantly higher rates of breast cancer incidence.
Researchers are investigating other chemicals as well. Rachel Morello-Frosch of the UC Berkeley School of Public Health is leading a study that compares blood and urine samples from female firefighters and women working in other sectors, focusing not only on PAHs but also per- and polyfluoroalkyl substances found in firefighting foam and flame retardants, which animal studies have linked to breast cancer. A University of Southern California study is looking at Vietnamese-American nail salon workers, who are exposed to chemicals that could disrupt the endocrine system, which is suspected to raise breast cancer risk.
As for racism and other psychological stressors in the environment, a study published online in Cancer Causes & Control last December showed an association between being born in a state that had enacted pro-segregation Jim Crow laws and increased odds of estrogen receptor–negative breast cancer in Black, but not white, women. Meanwhile, preliminary results from a Medical College of Wisconsin research project found that racial bias in mortgage lending is associated with higher incidences of harder-to-treat forms of breast cancer, including triple-negative breast cancer.
To be sure, we’re all exposed to a complex matrix of stressors, which makes it difficult to disentangle the ones that may influence breast cancer. Identifying the biological markers of damage from chemicals in humans is also challenging, says Silent Spring Institute’s Brody. Plus, most research, some funded by drug companies, is aimed at developing treatments, not prevention. As of July 3, out of 1,007 independent research projects on breast cancer in the International Cancer Research Partnership database, 441 focus on treatment and just 43 on exogenous, or external, factors in the origin and cause of the disease.
Venticinque feels “grim” about the future of research on environmental risk factors, especially since one of President Donald Trump’s campaign promises was to dismantle the Environmental Protection Agency. Still, she feels compelled to continue her advocacy work. Cathie Ragovin, 72, a psychiatrist who was diagnosed and treated for breast cancer 30 years ago and was part of the founding of Silent Spring, notes that medical research is oriented mainly toward diagnosis and treatment, but that prevention should be a priority too. In 2010, the National Institutes of Health estimated that medical costs associated with breast cancer would hit $16.5 billion by 2020. “The cost to families, children and the economy in general is unsustainable,” Ragovin says. “I think once that becomes clear, there will have to be a focus on what is in the environment.”
* Correction: Karuna Jaggar’s quote has been adjusted upon request for clarity.