Scientists at Columbia University are working with community groups in Upper Manhattan and the South Bronx to investigate how exposure to polycyclic aromatic hydrocarbons (PAHs)—a component of combustion-related air pollution—affects breast cancer risk. The Columbia study is one of six projects, including the ELLA study, funded through the Breast Cancer and Environment Research Program (BCERP)—a joint effort co-funded by the National Institute of Environmental Health Sciences (NIEHS) and the National Cancer Institute (NCI).

PAHs are widespread in the environment. They are found in vehicle exhaust, cigarette smoke, certain industrial emissions, as well as smoked or grilled foods. Both the International Agency for Research on Cancer (IARC) and the U.S. Environmental Protection Agency (EPA) have classified PAHs as probable human carcinogens. While the relationship between air pollution and adverse respiratory effects, such as asthma, has been studied, in more recent years scientists have become newly concerned about the effects of air pollution on other complex diseases and health outcomes such as breast cancer, neurocognitive issues, and obesity.

The Long Island Breast Cancer Study Project, one of the largest population-based studies on breast cancer, previously found that exposure to PAHs may influence the development of breast cancer. However, a clear and consistent link was likely obscured because the study did not focus on individuals or life stages that might be particularly susceptible to breast carcinogens.  To further elucidate this link, the team at Columbia is focusing on times when an individual might be most vulnerable to exposures, for instance in the womb and during pregnancy, and how a person’s risk varies based on interactions between their genes and their environment.

The study participants are comprised exclusively of African American and Hispanic-Dominican women. Compared to non-Black women, African American women are more likely to be diagnosed with more aggressive forms of breast cancer and experience higher mortality rates. Breast cancer rates are also increasing rapidly among young African American women, making this an important study for addressing widespread health disparities. What’s more, local figures show that the communities in New York City participating in the study have higher numbers of early-onset cancers and higher exposures to environmental pollutants than much of the rest of the country.

The study cohort will ultimately include close to 200 mother-daughter pairs. Mothers were originally recruited during pregnancy by the Center for Children’s Environmental Health at Columbia; their daughters now range in age from 10 to 18 years. “It’s critical to focus on cancer prevention within families,” says principal co-investigator Dr. Mary Beth Terry. “Because the risk of developing cancer much later in life can be influenced by exposures early in on.”

The Columbia team hypothesizes that changes in breast tissue characteristics will be greater for girls and women exposed to PAHs during key windows of breast susceptibility (i.e., during the prenatal and pregnancy periods). These are vulnerable periods during which the breast undergoes rapid changes in structure and function. Like the ELLA study, the researchers at Columbia are also looking at the impacts of environmental exposures on breast density as a possible intermediate risk marker for breast cancer. Breast tissue characteristics are being measured at Columbia using a light-based technique called optical spectroscopy.  In addition, the researchers are collecting blood and urine samples from both mothers and daughters. To assess individual exposures, for two-days during their pregnancy, the mothers wore a small backpack containing a monitor that measured air pollutants levels.

In addition to the mother-daughter study, the Columbia project also includes experiments in mice to investigate the influence of PAHs during gestation on mammary gland tissue and gene expression in mothers, their offspring, and their grand-offspring. The mouse study will assess the impacts of PAH exposure across multiple generations. “If what we are exposed to in life affects our children, as well as our children’s children, then it’s important to know that so we can do something about it,” Dr. Rachel Miller, who is co-leading the project with Dr. Terry. “In terms of challenges of the 21st century, multigenerational effects is one of them.”

The research team has partnered with West Harlem Environmental Action (WE ACT) for Environmental Justice to educate local communities about environmental exposures and breast cancer prevention, and to ensure the study’s findings support policy interventions that reduce urban air pollution. WE ACT has been instrumental in pushing forward policy initiatives in New York City, such as reducing bus idling at school bus stops. Other project partners include the Ohio State University Wexner Medical Center, University Health Network, Lovelace Respiratory Research Institute, and Mt. Sinai Hospital.

The Columbia Mailman School and Columbia University Medical Center site is led by Mary Beth Terry, PhD, professor of epidemiology, and Rachel Miller, MD, professor of medicine, pediatrics and environmental health sciences.

Assessing the links between air pollution and breast cancer risk

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