Research Results
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2025
Environ Int
A large French study following nearly 68,000 women for over 17 years found that dietary intake of polycyclic aromatic hydrocarbons (PAHs)—cancer-causing chemicals formed when meat, fish, and other foods are grilled, smoked, or cooked at high temperatures—was associated with increased breast cancer risk, particularly for hormone receptor-negative (ER-PR-) breast cancer which had a 34% higher risk at the highest exposure levels. The relationship showed a non-linear pattern, with elevated risk observed at moderate PAH intake levels, and similar trends for benzo[a]pyrene, a marker compound for total PAH exposure. These findings suggest that cooking methods that produce PAHs—such as grilling, barbecuing, and smoking foods—may increase breast cancer risk, supporting recommendations to limit charred or heavily grilled foods and use gentler cooking methods like baking, steaming, or stewing, particularly for women at higher risk.
2025
Environ Pollut
A study of 574 breast cancer cases and 2,295 controls from rural Arkansas found that moderate exposure to polycyclic aromatic hydrocarbons (PAHs) and high chromium exposure were associated with statistically significant 32% increased breast cancer risk, with the strongest effects observed among women with a family history of breast cancer. When examining 12 hazardous air pollutants as a mixture, there was a suggested but non-statistically significant 21% increased breast cancer risk, with chromium, propylene dichloride, and PCBs contributing most to the elevated risk. This study is important because it demonstrates that hazardous air pollutants pose breast cancer risks even in rural areas, which are often overlooked in environmental health research despite experiencing different pollution sources and healthcare disparities compared to urban populations.
2024
Cancer Causes Cont
This large Canadian population-based study examined whether long-term residential exposure to polycyclic aromatic hydrocarbons (PAHs)—widespread environmental pollutants from sources like vehicle exhaust and industrial emissions—increases breast cancer risk. Using 20 years of residential history data, researchers found that exposure to fluoranthene (a common PAH) was associated with significantly increased risk of premenopausal breast cancer, with women in moderately high exposure areas showing 59-148% higher risk compared to those in low-exposure areas. The associations with postmenopausal breast cancer were inconsistent, with only one analysis showing a modest increased risk. These findings support the hypothesis that ambient PAH exposure may increase the risk of breast cancer in premenopausal women, though the relationship appears complex and requires further investigation.
2024
Environ Health
This large French cohort study analysed long-term residential exposure trajectories of PCB153 and benzo[a]pyrene (BaP) among more than 10,000 women and estimated associations with breast cancer risk. Women in the highest trajectory class for PCB153 had an OR of ~1.69 (95% CI: 1.08–2.64) compared to the lowest class; associations for BaP were weaker and not consistently statistically significant. The research highlights how evolving environmental exposures over decades may influence hormone-sensitive cancer risk.
2024
Environ Health Perspect
A nationwide study using CDC biomonitoring data found that California’s Proposition 65, which requires warnings about chemicals that cause cancer or reproductive harm, led to reduced exposures to listed chemicals across the entire United States, not just California. While blood and urine concentrations of 37 monitored chemicals generally declined over time, the researchers found evidence of problematic chemical substitution—for example, after bisphenol A (BPA) was listed, its concentrations dropped 15% but levels of the unlisted substitute bisphenol S (BPS) increased 20%. Californians generally had lower levels of harmful chemicals in their bodies compared to residents of other states, suggesting the law had additional protective effects. The findings indicate that transparency laws like Prop 65 can drive manufacturers to reformulate products nationwide, but regulations need to address entire chemical classes rather than individual substances to prevent companies from simply switching to similar but unlisted toxic chemicals.
2024
Environ Pollut
A French study of over 10,000 women found that combined exposure to a mixture of four hormone-disrupting air pollutants (benzo[a]pyrene, cadmium, dioxin, and PCB153) was associated with an approximately 10-11% increased risk of breast cancer. Using advanced statistical methods that account for simultaneous exposure to multiple pollutants rather than examining each separately, researchers found that benzo[a]pyrene, cadmium, and PCB153 showed the strongest individual contributions to increased breast cancer risk within the mixture. This research provides important evidence that the cumulative effect of multiple air pollutants acting together on hormone pathways may be a significant risk factor for breast cancer development.
2023
Environ Res
This case-control study of 5587 women with breast cancer and age-matched controls for which there was data on maternal employment. Maternal occupational exposure to diesel exhaust (OR=1.13, 95%CI,1.01-1.27) and bitumen fumes (OR=1.51., 95%CI,1.00-2.26) was associated with breast cancer. Further, exposures to diesel exhaust (OR=1.23, 95%CI, 1.01-1.50) were more strongly associated with ER- tumors than with ER+ tumors.
2021
Scand J Work Environ Health
This large Danish study of over 38,000 women with breast cancer found that occupational exposure to diesel exhaust was associated with a modestly increased risk of estrogen receptor-negative breast tumors in women under age 50, with the risk increasing with longer duration and higher levels of exposure. No significant associations were found for overall breast cancer risk or for exposure to polycyclic aromatic hydrocarbons (PAHs). These findings suggest that workplace diesel exhaust exposure may be particularly relevant for early-onset, harder-to-treat forms of breast cancer, highlighting the importance of protecting workers from diesel fumes.
2021
Environ Int
Long-term exposure to benzo[a]pyrene (BaP), a toxic air pollutant from gas and diesel vehicle exhaust, was associated with a 15% increased risk of breast cancer in a large French study of over 10,000 women. The risk was particularly elevated in women transitioning through menopause and for hormone receptor-positive breast cancers, with each increase in BaP exposure levels raising breast cancer odds by 15-20%. This study provides important real-world evidence that BaP air pollution may contribute to breast cancer development, especially affecting hormone-sensitive tumors.
2019
Occ Environ Med
This Canadian study of over 2,200 women found that occupational exposure to polycyclic aromatic hydrocarbons (PAHs)—chemicals released from burning materials like coal, oil, and gasoline—increased breast cancer risk by 32%, with higher risks seen in women exposed to high levels for more than 7 years. The association was particularly strong among women with a family history of breast cancer, where prolonged high exposure nearly tripled the risk. These findings suggest that workplace PAH exposure may be an important and preventable breast cancer risk factor, especially for women with genetic susceptibility to the disease.
2000
Am J Indust Med
This Danish nationwide study of 230 male breast cancer cases found that men occupationally exposed to gasoline and its combustion products had a 2.5 times higher risk of breast cancer, with the risk rising to 5.4 times higher among men first exposed before age 40. Gasoline contains several known carcinogens including benzene and produces cancer-causing combustion products, which may explain this elevated risk. Since male breast cancer is rare but shares similar biology with female breast cancer, these findings suggest that gasoline exposure may also increase breast cancer risk in women and warrant further investigation in female workers.
2024
Breast Cancer Res
A nested case-control study within the French E3N-Generations cohort examined 523 breast cancer cases and 523 matched controls to investigate whether thirteen metabolic health biomarkers mediate the relationship between exposure to three air pollutants (nitrogen dioxide, PCB153, and benzo[a]pyrene) and breast cancer risk. The study found that benzo[a]pyrene exposure was associated with a significant 2.32-fold increased breast cancer risk (highest vs. lowest quartile), PCB153 showed inconsistent positive associations, and nitrogen dioxide showed no association; among biomarkers, estradiol was associated with increased breast cancer risk (OR = 1.22 per SD). Four-way decomposition mediation analysis revealed suggestive evidence that albumin, HDL and LDL cholesterol, parathormone, and estradiol may partially mediate the associations between all three pollutants and breast cancer risk, though findings were limited by statistical power. These results provide preliminary mechanistic insights suggesting that air pollutants may influence breast cancer risk through alterations in metabolic biomarkers—particularly lipid metabolism and hormone regulation—though larger studies are needed to confirm these pathways and establish the clinical significance of these mediating effects in the relationship between environmental exposures and breast cancer development.
2023
Environ Sci Technol
The following study discusses a strategic framework to improve how chemicals are managed in North America. The Essential-Use Approach is a policy that prioritizes restricting the use of chemicals based on necessity and safety. It proposes three guiding questions: Is the chemical essential to the product’s function? Is it the safest option? Is it necessary for health and safety? They also prioritize speed of assesments so that chemicals can be quickly phased out if evidence suggests danger to human health. This study is a call for change and aims to become a tool to simplify decision-making for regulating organizations, help businesses avoid liability related to harmful chemicals, and ultimately improve public health by ensuring only the safest substances are used in consumer products.
2021
BMC Complement Med Ther
This study focused on the effect that tartrazine (E102), a common yellow food dye, had on the progression of breast cancer in rats that were exposed to 7,12-Dimethylbenz(a)anthracene (DMBA), a polycyclic aromatic hydrocarbons (PAH) that is widely known for its carcinogenicity. The researchers discovered that tartrazine accelerated the development and growth of tumors in the rats with 100% of rats having early incidents of breast cancer when exposed to both DMBA and tartrazin, and only 80% having early incidence when exposed to DMBA alone. The authors also hypothesized that tartrazine could cause oxidative stress, leading to DNA damage by producing Reactive Oxygen Species. These results may apply to humans as well, and raise concerns about the safety of prolonged or high-dose exposure to synthetic food dyes like tartrazine, especially in individuals who may already have other risk factors for cancer.
2020
Food Chem Tox
This article discusses the harmful impacts of polycyclic aromatic hydrocarbons (PAHs) found in deep-fried foods. It highlights their endocrine-disrupting, genotoxic, and carcinogenic abilities when oils used for deep frying are heated repeatedly or at high temperatures. PAHs disrupt steroidogenic pathways which can lead to hormonal imbalances of estrogen and testosterone causing lower sperm quality, estrogenic effects, and endocrine related disorders. Furthermore, PAHs are linked to increased cancer risks through genotoxicity which can cause mutations in the cell. Organ sites that can be affected by this cancer risk are the breast, prostate, colorectal, renal, and pancreas.
2020
Environ Res
A systematic review of 100 publications across 56 epidemiologic studies found that research enriched with women at higher baseline breast cancer risk—through family history, early-onset disease, or genetic susceptibility—consistently showed stronger and more frequent associations between environmental chemical exposures and breast cancer compared to average-risk populations. Specifically, 80% of studies enriched with family history or early-onset cases showed significant associations with exposures including PAHs, air pollution, DDT, PCBs, PFAS, metals, personal care products, and occupational chemicals, while 74% of studies examining genetic susceptibility found significant gene-environment interactions for various pollutants in women with variants affecting carcinogen metabolism, DNA repair, and oxidative stress. These findings suggest that the inconsistent evidence for environmental chemicals and breast cancer in the literature may partly stem from studying predominantly average-risk populations who may be less susceptible to environmental carcinogens, highlighting the critical need for future research to focus on high-risk populations and measure exposures during key windows of susceptibility (puberty, pregnancy, menopause) to more accurately capture the role of environmental chemicals in breast cancer development.
2018
Environ Res
A systematic review of 158 studies examining environmental chemicals and breast cancer found the strongest evidence for increased risk from exposures during critical developmental periods (in utero, adolescence, pregnancy) to DDT, dioxins, PFOSA, air pollution, and occupational solvents, with risk estimates ranging from 1.4 to 5 times higher. A landmark 50-year study that captured DDT exposure during windows of breast development showed particularly elevated risks, while research on genetic variations found that women with certain DNA repair gene variants had higher breast cancer risk from PAH (polycyclic aromatic hydrocarbon) exposure. However, most studies failed to assess exposure timing during biologically relevant windows of susceptibility, and many current-use chemicals in consumer products remain inadequately studied, with major challenges including reconstructing decades-old exposures and measuring rapidly metabolized chemicals in complex real-world mixtures.
2014
Environ Health Perspect
This review of exposure biomarkers for chemicals potentially linked to breast cancer identified methods for 102 chemicals causing mammary tumors in rodents, finding biomarkers for nearly 75% of them, with human exposure biomarkers existing for 62 chemicals (45 measured in non-occupationally exposed populations) and the CDC tracking 23 of them. Among rodent mammary carcinogens with >50% population detection frequency were PAHs (98%), methyleugenol (98%), PFOA (>50%), chlordane (>50%), acrylamide (>50%), and benzene (>50%), indicating near-universal exposure to multiple mammary carcinogens, with several additional chemicals showing >50% detection of urinary metabolites including ethylene oxide, acrylonitrile, fenvalerate, and vinyl chloride (71-75%). The study found consistent carcinogenicity between humans and rodents for many chemicals, though limited data exists for direct effects in humans, and emphasizes the availability of biomonitoring tools and resources to advance breast cancer prevention efforts. The findings underscore that populations are ubiquitously exposed to multiple known mammary carcinogens simultaneously, highlighting the urgent need for biomonitoring programs to assess mixed exposures and inform prevention strategies targeting modifiable environmental risk factors for breast cancer.
2007
Cancer
A comprehensive review found that while laboratory studies have identified numerous environmental chemicals that cause breast tumors in animals or mimic estrogen, human epidemiological evidence is strongest for PAHs (found in air pollution and grilled foods) and PCBs (banned industrial chemicals), particularly in women with certain genetic variations affecting how their bodies process these chemicals and hormones. Evidence linking dioxins and organic solvents to breast cancer is limited but suggestive, while many chemicals identified as mammary carcinogens in animal studies have never been investigated in human populations due to challenges in measuring past exposures and the decades-long delay between exposure and cancer diagnosis. The review argues that given these methodological limitations in human studies, policymakers should rely more heavily on animal and laboratory evidence to develop regulations that reduce chemical exposures, as waiting for definitive human proof may unnecessarily delay prevention strategies that could reduce breast cancer rates.