Breast cancer development is a complex process influenced by genetics, lifestyle, and environmental exposures. While inherited gene mutations contribute to some cases, most breast cancers are not directly linked to these genetic predispositions. Understanding non-genetic influences, broadly defined as environmental causes, is important. These factors include dietary choices, lifestyle habits, and exposure to various substances in our surroundings. This article explores scientific findings connecting these external influences to breast cancer risk.
Hormone-Disrupting Chemicals in Consumer Products
Endocrine-disrupting chemicals (EDCs) interfere with the body’s hormonal system. They often mimic natural hormones, especially estrogen, which can promote breast cancer growth. EDCs are common in consumer products, leading to widespread exposure.
Bisphenol A (BPA) is an EDC found in hard plastics, like reusable water bottles, and in the epoxy linings of food and soda cans. It is also present in thermal paper used for cash register receipts. BPA can leach into food and beverages, especially when containers are heated, leading to human exposure. Studies indicate BPA can disrupt the hormone system and may induce breast cancer cell growth.
Phthalates are chemicals used to make plastics flexible and durable. They are also in fragrances, personal care products like shampoos, lotions, and cosmetics. Phthalates can be found in vinyl products, shower curtains, and some food packaging. Research links exposure to certain phthalates, such as DEP and BBP, to an increased breast cancer risk, especially in premenopausal women.
Parabens are preservatives in personal care products, including cosmetics, lotions, and some foods. They mimic estrogen, activating the same receptors as the body’s natural hormones. This estrogenic activity raises concerns about their role in stimulating breast cancer cell growth. Studies have detected parabens in breast tissue samples, suggesting their presence in the body.
Pollutants and Contaminants in the Environment
Environmental substances also contribute to breast cancer risks through inhalation or ingestion. Polycyclic Aromatic Hydrocarbons (PAHs) form when organic materials like coal, wood, or gasoline are incompletely burned. Common sources of PAHs include vehicle exhaust, tobacco smoke, and charred or grilled foods. These chemicals can accumulate in fatty tissues, including breast tissue, and have been detected in breast milk.
Exposure to PAHs from traffic emissions is associated with an increased breast cancer incidence, especially during early life or around a woman’s first menstruation. Indoor PAH sources, like secondhand smoke and indoor stoves or fireplaces, also link to a 30% to 50% increased breast cancer incidence. While research continues, PAHs are considered established human carcinogens that can affect breast tissue.
Pesticides and herbicides, used in agriculture, are another environmental concern. Historically, persistent chemicals like DDT were banned due to environmental and health impacts, including endocrine disruption. Modern agricultural chemicals are still under investigation, with some exhibiting estrogenic activity or inducing mammary tumors in animal models. Exposure can occur through inhalation, skin absorption for those working in or near agricultural fields, or by consuming produce with chemical residues.
Secondhand smoke is a distinct environmental risk factor. It contains over 7,000 chemicals, with at least 69 recognized as carcinogens. Inhaling secondhand smoke increases lung cancer risk in nonsmokers, and some research suggests it may also elevate breast cancer risk. A meta-analysis indicated nonsmoking women exposed to secondhand smoke face a 24% increased breast cancer risk, with higher risks for longer exposure.
Radiation and Workplace Factors
Ionizing radiation, which can damage DNA, is an environmental factor linked to breast cancer. For many individuals, the largest source of exposure comes from medical diagnostic procedures such as X-rays and CT scans. While these procedures offer diagnostic benefits, CT scans are a concern due to higher radiation doses, up to 500 times greater than a standard X-ray.
Repeated low-dose exposures over time may have similar harmful effects as a single high-dose exposure. The Institute of Medicine estimated that a year of medical radiation exposure in the U.S. female population could result in approximately 2,800 future breast cancer cases, with two-thirds from CT scans. Limiting unnecessary medical imaging, especially for younger individuals, is a consideration, although the diagnostic benefits often outweigh the small individual risk.
Workplace environments can present unique exposures influencing breast cancer risk. Occupations involving manufacturing solvents have been studied for their link to breast cancer. Research indicates an association between occupational exposure to organic solvents like styrene, carbon tetrachloride, and formaldehyde and an increased breast cancer risk. A meta-analysis found a pooled increased risk of 18% for breast cancer among workers exposed to organic solvents compared to unexposed individuals.
Emerging research highlights a connection between night shift work and breast cancer, often attributed to circadian rhythm disruption. Light exposure at night can suppress melatonin production, a hormone that regulates sleep and may have tumor-suppressing properties. This melatonin disruption can lead to hormonal imbalances, potentially increasing breast cancer risk, especially for women with long-term or high-intensity night shift exposure.
Minimizing Environmental Risk Factors
Reducing exposure to environmental risk factors involves conscious choices in daily life. To limit exposure to hormone-disrupting chemicals, opt for glass or stainless steel containers instead of plastic for food storage. Choose personal care products and cosmetics labeled “BPA-free,” “paraben-free,” and “phthalate-free” to avoid these substances. Washing produce thoroughly can reduce residues of agricultural chemicals.
Improve home ventilation and avoid secondhand smoke to lower risks from air pollutants. When considering medical imaging, discuss test necessity and explore alternatives like ultrasound or MRI that do not use ionizing radiation. For those in occupations with potential exposures, adhere to workplace safety guidelines and advocate for safer practices to mitigate risks.