Urban Environmental Exposures Increase Breast Cancer

A Duke Health study of breast cancer in North Carolina found that the state’s metropolitan counties had higher overall occurrences of the illness than rural counties, particularly in the early stages of diagnosis.

The findings, published in the journal Scientific Reports, serve as a national framework for analyzing the impact of poor environmental quality throughout different phases of breast cancer, which has widely diverse origins and spreading mechanisms. North Carolina is an excellent model since it has a diversified population of 10 million people scattered across 100 rural and urban counties with varying environmental circumstances.

“Individual environmental contaminants have long been associated with breast cancer, but we have a limited understanding of how multiple exposures simultaneously affect this disease,” said senior author Gayathri Devi, Ph.D., a professor in Duke’s departments of Surgery and Pathology and Program Director of the Duke Consortium for Inflammatory Breast Cancer at the Duke Cancer Institute.

“Our study explored the incidence of breast cancer within the context of the Environmental Quality Index (EQI) – a county-by-county assessment of air, water, land, built environment, as well as the sociodemographic environment,” Devi went on to say. “This type of data analysis allows for a high-level look at broader environmental factors and health outcomes.”

Devi and colleagues studied the EQI data alongside breast cancer incidence rates from the North Carolina Central Cancer Registry, including lead author Larisa M. Gearhart-Serna, a Ph.D. candidate at Duke. The researchers also looked at the different phases of breast cancer, including in situ and localized (early stages), regional and distant (late stages), and rural-urban status.

“In an earlier study, we assessed how environmental conditions impact the risk of a breast cancer patient having later stage invasive disease compared to non-invasive carcinoma in-situ,” she stated. “This is a continuation of that work to determine whether environmental quality and an urban environment are related to the development of more advanced tumors in a community and, if so, what stages.”

Total incidence of breast carcinoma was 10.82 incidences per 100,000 people higher in counties with poor overall environmental quality compared to those with good overall environmental quality. This link was strongest for locally advanced breast carcinoma.

The researchers also discovered that community-level environmental exposures were linked to higher rates of overall breast cancer incidence, particularly in counties with poor land quality, particularly in metropolitan areas. Exposures from pesticides and hazardous emissions from industrial, agricultural, and animal operations are included in the land EQI.

Breast carcinoma incidence rates for later stage illness and overall breast carcinoma were significantly higher in counties with a higher Black population. This is significant since Black women have a greater global incidence of severe breast carcinoma.

Higher mammography screening rates were shown to be associated with reduced regional breast cancer incidence rates, which is significant because greater screening is anticipated to reduce diagnoses of later-stage illness.

“Our analyses indicate significant associations between environmental quality and breast cancer incidence, which differ by breast cancer stage and urbanicity, identifying a critical need to assess cumulative environmental exposures in the context of cancer stage,” she added. “This has the potential to develop measures to reduce disease incidence in vulnerable communities.”

The study is the outcome of a long-running cooperation between Duke University’s School of Medicine and the Nicholas School of the Environment.

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