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2019
Int J Mol Sci
This case-control study of 509 breast cancer patients and 1,170 controls in examined whether cadmium exposure—a metalloestrogen that mimics estrogen—is associated with specific breast cancer subtypes based on urinary cadmium levels. Women with the highest cadmium levels (>0.33 μg/g creatinine) had 53% increased odds of ductal breast cancer (OR=1.53, 95% CI: 1.15-2.04) compared to those with the lowest levels, with the strongest associations observed for hormone receptor-positive tumors: 34% increased odds for ER+ cancers (OR=1.34, 95% CI: 1.14-1.59), 33% for PR+ cancers (OR=1.33, 95% CI: 1.09-1.61), and 35% for ER+/PR+ cancers (OR=1.35, 95% CI: 1.11-1.65). The study found significant associations with HER2-negative cancers, with the strongest link for ER+/PR+/HER2- breast cancers, supporting the hypothesis that cadmium acts as an endocrine disruptor. These findings provide evidence that cadmium exposure is specifically associated with hormone receptor-positive and HER2-negative breast cancer risk, independent of tumor type, suggesting cadmium’s estrogenic properties may contribute to hormone-driven breast cancers.
2019
Cancer Epidemiol
A 22-year Italian study following nearly 9,000 women found that those with the highest dietary cadmium intake (a toxic metal found in foods like grains, vegetables, and shellfish) had a 54% increased breast cancer risk compared to those with the lowest intake, with even stronger associations in premenopausal women (73% increased risk). Cadmium—classified as a proven human carcinogen—enters the food supply primarily through contaminated soil and water, with diet being the main exposure source for non-smokers at an average intake of about 8 micrograms per day in this population. The increased risk was consistent across all breast cancer subtypes regardless of hormone receptor status, supporting cadmium as a dietary risk factor for breast cancer and highlighting the need for strategies to reduce cadmium levels in the food supply through soil remediation and crop selection.
2019
Int J Cancer
A large prospective study of 182,145 women in the Nurses’ Health Study found that higher fruit and vegetable consumption was associated with an 11% lower risk of invasive breast cancer, with the strongest benefits from cruciferous vegetables (like broccoli and cabbage) and yellow/orange vegetables (like carrots and squash). Women consuming more than 5.5 servings per day had significantly lower breast cancer risk compared to those eating 2.5 servings or less, with particularly strong protective effects against aggressive tumor types including estrogen receptor-negative (16% risk reduction per 2 additional servings/day), HER2-enriched (21% reduction), and basal-like (16% reduction) breast cancers. The protective associations were most pronounced for tumor subtypes that tend to be more aggressive and harder to treat. These findings suggest that a diet rich in fruits and vegetables, especially cruciferous and yellow/orange varieties, may help prevent breast cancer and particularly reduce the risk of developing more aggressive forms of the disease.
2019
J Work Environ Health
A prospective study of 16,084 Swedish women found that occupational exposure to chemicals was associated with a 26% increased risk of postmenopausal breast cancer, with risk increasing based on duration of exposure. Women exposed to diesel exhaust for more than 10 years showed a 69% increased risk, while exposure to organic solvents showed a non-significant elevated risk. The researchers estimated that occupational chemical exposures accounted for 2% of all breast cancer cases in this population, highlighting workplace chemical exposure as a potentially important but often overlooked risk factor for breast cancer.
2019
Am J Clin Nutr
A large French cohort study of 76,442 women over age 50 followed for 11 years found that current soy supplement use was associated with a 22% reduced risk of estrogen receptor-positive (ER+) breast cancer but a 101% increased risk of ER-negative breast cancer compared to never users. The risk profile varied significantly by personal characteristics: women with a family history of breast cancer showed a 36% increased risk with soy supplement use, while those without family history showed an 18% reduced risk; premenopausal or recently postmenopausal women showed a 50% risk reduction, while women more than 5 years past menopause showed a 6% increased risk. These findings suggest that soy supplements—often marketed as natural alternatives to hormone therapy—may have complex and opposing effects on breast cancer risk depending on tumor biology and individual characteristics, cautioning against their use particularly in women with breast cancer family history.
2019
Environ Int
A population-based study of 711 breast cancer cases and 598 controls from the Long Island Breast Cancer Study Project measured seven urinary phenol biomarkers (environmental endocrine disruptors from personal care and consumer products) in spot urine samples collected within three months of diagnosis, with 17.6-year median follow-up identifying 271 deaths including 98 from breast cancer. The highest versus lowest quintiles of methylparaben, propylparaben, and sum of parabens (Σparabens) were associated with 31-50% increased breast cancer risk (ORs: 1.31-1.50) but paradoxically with 23-32% reduced all-cause mortality after diagnosis (HRs: 0.68-0.77), with associations for incidence stronger among women with BMI <25 kg/m² and associations for mortality stronger among women with BMI ≥25 kg/m². These findings—the first to examine phenol biomarkers in relation to both breast cancer incidence and subsequent mortality—reveal complex differential associations suggesting that select parabens may increase risk of developing breast cancer but be associated with better survival outcomes, though the mechanisms underlying these paradoxical associations remain unclear and may relate to BMI-dependent metabolic or hormonal factors, reverse causation, or unmeasured confounding.
2018
Eur J Epidemiol
This large international study pooling data from over 13,000 women across five countries found that night shift work increased breast cancer risk by 26% in pre-menopausal women, with the risk rising substantially for those working longer shifts (≥10 hours), more frequent nights (≥3 nights per week), or longer durations (≥10 years). Pre-menopausal women working both long durations and high frequency had a 2.5 times higher breast cancer risk, with current or recent night workers at higher risk than those who had stopped more than two years ago. Notably, no increased risk was found in post-menopausal women, and the elevated risk was primarily for estrogen receptor-positive tumors, particularly those that were also HER2-positive, suggesting that disruption of hormones and circadian rhythms during reproductive years may be key factors in how night work affects breast cancer risk.
2018
Scand J Work Environ Health
A European multicenter case-control study of 104 male breast cancer cases and 1,901 controls found that high cumulative lifetime exposure to trichloroethylene (>23.9 ppm-years) was associated with a 110% increased male breast cancer risk compared to non-exposure, with the association persisting when only exposures occurring 10 or more years before diagnosis were considered, indicating a true latency effect. The study also suggested possible roles for benzene and ethylene glycol in male breast cancer risk, though no clear dose-response relationships were observed for these chemicals. These findings are particularly important given that male breast cancer is rare, often diagnosed at later stages, and has worse prognosis than female breast cancer, and they add to evidence that occupational solvent exposures—particularly trichloroethylene used in metal degreasing, dry cleaning, and industrial cleaning—may be underrecognized risk factors for breast cancer in both men and women, warranting stricter workplace exposure limits and enhanced surveillance of workers in high-exposure industries.
2018
Cancer Epidemiol Biomarkers Prev
This study examined how exposure to endocrine-disrupting chemicals (EDCs) during puberty affects breast tissue development in 200 Chilean girls by measuring urinary concentrations of phenols and phthalates at two stages of breast development and assessing breast density. The researchers found that certain phthalate metabolites were associated with increased breast density measures – specifically, higher levels of monocarboxyisooctyl phthalate were linked to 7% higher percent dense breast tissue, and monoethyl phthalate was associated with increased fibroglandular volume. Bisphenol A showed a U-shaped relationship with fibroglandular volume, where girls with middle-level exposures had at least 10% lower fibroglandular volume compared to those with low or high exposures. The findings suggest that developing breast tissue is vulnerable to certain EDCs during childhood and adolescence, which may have implications for future breast cancer risk since breast density is a known risk factor.
2018
Breast Cancer Res
A nationwide study of 22,466 Danish female nurses found that long-term exposure to road traffic Noise was associated with increased breast cancer risk, particularly for hormone receptor-positive tumors. For every 10-decibel increase in 24-year average Noise levels at their residence, women showed a 23% increased risk of estrogen receptor-positive (ER+) breast cancer and a 21% increased risk of progesterone receptor-positive (PR+) breast cancer, with no significant association for hormone receptor-negative tumors. The association was especially strong among nurses who worked night shifts, showing a 236% increased risk of ER+ breast cancer compared to a 21% increase in those not working nights. These findings suggest that chronic traffic Noise exposure may contribute to breast cancer development, potentially through stress-related hormonal pathways, with night shift work potentially amplifying this risk.
2018
Int J Psychiatry Med
A hospital-based study of 250 breast cancer patients and 250 controls in Turkey found that recent major stressors—particularly those occurring within the last five years—were associated with a 372% increased risk of breast cancer (the strongest factor identified). Other significant risk factors included inadequate social support (83% increased risk), loss of a father during childhood (168% increased risk), family history of cancer (55% increased risk), and history of psychiatric disorders (95% increased risk), suggesting that psychological trauma and social factors may play substantial roles in breast cancer development alongside genetic predisposition.
2018
Am J Epidemiol
A cohort study of 4,503 female autoworkers in Michigan exposed to metalworking fluids (MWFs)—oil and chemical mixtures used in metal manufacturing—found that increased exposure to straight mineral oil MWFs was associated with a 13% increased breast cancer risk per interquartile range increase in cumulative exposure. Among younger women who developed premenopausal breast cancer, exposure to synthetic MWFs (chemical lubricants without oil) showed elevated risk, suggesting potentially different carcinogenic mechanisms in younger versus older women. This occupational study addresses a critical gap in breast cancer research by providing quantitative exposure-response data for a specific chemical mixture affecting a large workforce, offering one of the few leads on modifiable environmental risk factors for breast cancer.
2018
Discov Oncol
This systematic review examined the relation of 4 neighborhood factors on breast cancer incidence and prognosis among African-American women: neighborhood socioeconomic status (nSES), residential segregation, spatial access to mammography, and residential pollution. The authors found that nSES, residential segregation and access to mammography were all related to stage at diagnosis, and nSES and living in more segregated areas were both associated with mortality. Residential pollution was not associated with increased risk of breast cancer in the studies reviewed.
2018
Environ Health
This longitudinal study examined how exposure to endocrine disrupting chemicals (EDCs) affects the timing of menarche in Chilean girls by measuring 26 phenol and phthalate compounds in urine samples collected before breast development and during adolescence. The researchers found that different chemicals had varying effects depending on when exposure was measured: higher early exposure to DEHP was associated with later menarche, while early exposure to certain phenols and later exposure to some phthalates were linked to earlier menarche. The study also revealed that body weight influenced these effects, with overweight or obese girls showing earlier menarche when exposed to higher levels of certain chemicals like triclosan, while normal-weight girls did not show this association. These findings demonstrate that specific EDCs can disrupt normal sexual development in girls, with timing of exposure and body weight being important factors.
2018
Environ Res
A Chinese case-control study of 209 breast cancer patients and 165 controls found that women with the highest levels of PBDE flame retardants in their adipose tissue had dramatically elevated breast cancer risk, with some congeners showing 447% to 545% increased risk in the highest exposure groups compared to the lowest. Most individual PBDE congeners—including BDE-47, BDE-99, BDE-100, BDE-209, and total PBDEs—were significantly higher in breast cancer cases than controls (median 95.0 vs 73.7 ng/g lipid) and showed strong dose-response relationships with increasing exposure levels. The associations remained robust for estrogen receptor-positive breast cancers and in multivariate models adjusting for age and reproductive factors, providing compelling evidence that PBDE exposure may play an important role in breast cancer development, particularly in populations with high environmental exposures to these persistent flame retardant chemicals.
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.
Cancer Epidemiol
A study of 46,709 women in the Sister Study found that use of permanent hair dye and chemical straighteners was associated with increased breast cancer risk, with particularly strong associations among Black women. Permanent hair dye use was linked to a 45% increased risk in Black women, while chemical straightener use showed an 18% increased risk overall, with higher risks associated with more frequent use. Women who applied semipermanent dyes to others showed a 28% increased risk. These findings suggest that endocrine-disrupting chemicals and carcinogens in hair products, which are often present at higher concentrations in products marketed to Black women, may contribute to breast cancer development.
2025
Epidemiol
A prospective study of 46,150 Sister Study participants followed for a median 13.4 years (4,155 breast cancer cases) used EPA Toxics Release Inventory data to quantify residential air emissions of 28 industrial compounds—many carcinogenic or endocrine-disrupting—during the 10 years before enrollment (2003-2006). Emissions within 3 km of residences showed non-significant associations with breast cancer for nickel compounds (HR = 1.3; 95% CI: 1.0-1.6 for highest vs. no exposure) and trichloroethylene (HR = 1.3; 95% CI: 1.0-1.6), while exposure continuum mapping identified 25 mixture profiles explaining 72% of emissions variance, with the joint-exposure response function suggesting higher breast cancer incidence among individuals with rare, high-emission profiles, though the overall mixture trend was not statistically significant (p = 0.09). These findings indicate that residential proximity to industrial air emissions of certain carcinogens—particularly nickel compounds and trichloroethylene—may be associated with increased breast cancer risk, though the lack of overall mixture association may reflect that individual compounds or specific emission sources are more important than cumulative exposure profiles, or that most participants experienced relatively low emissions with elevated risks concentrated among small subgroups with high exposure to specific pollutants.
2025
Int J Environ Sci
This study investigated how DEHP (a common plastic additive) affects triple-negative breast cancer (TNBC), the most aggressive form of breast cancer. The researchers found that prolonged DEHP exposure enhanced cancer cell migration and invasion both in laboratory cultures and in animal models by activating a specific protein pathway involving MSI2, which promotes cancer spread and stem cell-like properties. DEHP exposure also reduced levels of a protective microRNA (miR-155-5p), while increasing MSI2 expression, suggesting these molecules work in opposition to each other. The findings identify MSI2 as a potential therapeutic target and prognostic marker for TNBC patients, providing new insights into how plastic additives may contribute to cancer metastasis.
2025
Environ Pollut
This study examined the combined toxic effects of nanoplastic particles (NPs) and DEHP plasticizer on mouse mammary epithelial cells, finding that co-exposure caused severe cell death (pyroptosis), inflammation, and oxidative stress. The researchers discovered that the combination damaged mitochondria and increased endoplasmic reticulum stress, leading to disrupted cellular energy production and membrane integrity. Notably, co-exposure enhanced communication between cellular organelles (ER-mitochondria crosstalk), involving increased calcium levels and expanded contact areas between these structures. The findings reveal new molecular mechanisms by which plastic particles and plasticizers can work together to damage mammary gland tissue, providing insights into potential breast health risks from environmental plastic pollution.
2025
Sci Rep
A large U.S. study of 4,455 people found that exposure to triclosan (TRS)—an antibacterial chemical commonly found in soaps, toothpaste, and personal care products—was associated with more than double the risk of breast cancer at moderate exposure levels, with the relationship following an inverted U-shape pattern. The association was strongest among overweight individuals, people under 60 years old, and white participants, while other tested chemicals (including bisphenol A, benzophenone-3, and parabens) showed no significant link to breast cancer risk. These findings suggest that triclosan exposure may be an important modifiable risk factor for breast cancer, particularly for certain population groups, though more research is needed to understand the underlying mechanisms and confirm causality.
2025
Saudi Med J
A systematic review and meta-analysis of 15 studies including 92,555 women found no evidence that hormonal fertility medications increase breast cancer risk, with pooled risk ratio analysis showing no association (RR=1.00, 95% CI: 0.97-1.02) and hazard ratio analysis initially suggesting a protective effect that became non-significant after accounting for study heterogeneity. The analysis revealed low heterogeneity in risk ratio studies but substantial heterogeneity in hazard ratio studies, which the authors attributed to methodological differences between studies rather than true variation in effects. These findings provide reassuring evidence for women considering or undergoing fertility treatment, though the authors caution that results should be interpreted carefully given the study heterogeneity and note that longer-term follow-up studies with standardized methodologies are needed to definitively establish the safety profile of hormonal fertility medications with respect to breast cancer risk, particularly for specific medication types, dosages, and treatment durations.
2025
Global Health Res Pol
A meta-analysis of 17 observational studies found that the highest consumption of fast foods and ultra-processed foods (FFs/UPFs) was associated with a 25% increased breast cancer risk compared to the lowest consumption levels. The association was particularly strong in case-control studies and in Latin American populations, and remained significant regardless of sample size or BMI adjustment, though no association was found in cohort studies or when stratified by menopausal status. These findings suggest that diets high in ultra-processed foods—which often contain carcinogenic compounds formed during processing, additives, packaging contaminants, and unhealthy nutrient profiles—may contribute to breast cancer development, highlighting the urgent need for public health strategies and regulatory policies targeting food processing standards, marketing restrictions, improved labeling, and reduced accessibility of ultra-processed foods to reduce cancer risk, particularly as global consumption of these products continues to rise.
2025
Ecotoxicol Env Saf
A Mendelian randomization study using genetic data from European populations found that specific endocrine-disrupting chemicals (EDCs) were causally associated with different breast cancer subtypes: n-butyl paraben (n-BuP) increased Luminal A risk, mono-methyl phthalate decreased Luminal B risk, and mono-iso-butyl phthalate (MiBP) increased triple-negative breast cancer risk. Mediation analysis revealed that blood metabolites—including caffeic acid sulfate and caffeine metabolism ratios—partially explained the n-BuP effect on Luminal A, while methylsuccinate mediated the MiBP effect on triple-negative cancer, and epigenetic analysis identified specific DNA methylation sites associated with EDC exposure and breast cancer risk. These findings provide the first genetic evidence suggesting causal relationships between specific EDC exposures and breast cancer subtypes through distinct metabolic and epigenetic pathways, identifying potential biomarkers for early detection and highlighting the heterogeneous effects of different EDCs on breast cancer biology—underscoring the need for chemical-specific and subtype-specific prevention strategies rather than treating all EDCs or breast cancers as uniform entities.
2025
JAMA Netw Open
A cross-sectional study of 121 Black and White women with breast cancer found that chronic stressors—including perceived stress, inadequate social support, discrimination, and neighborhood deprivation—were associated with harmful immune and tumor changes, with particularly pronounced effects in Black women who also lived in significantly more socioeconomically deprived neighborhoods. Higher stress, discrimination, and neighborhood deprivation were linked to increased systemic inflammation, immune-suppressive tumor environments (including tumor-promoting M2 macrophages), and elevated tumor mutational burden, while greater social support was associated with beneficial immune-stimulatory changes including increased natural killer cells in breast tissue. Black women showed distinct stress-related immunologic signatures including enhanced chemotaxis, immune suppression at the systemic level, and increased tumor-associated myeloid cells, suggesting that chronic psychosocial and environmental stressors may biologically contribute to breast cancer disparities by creating a pro-tumorigenic immune environment—findings that underscore the urgent need for interventions addressing social determinants of health as cancer prevention strategies.
2025
Int J Environ Res Public Health
A prospective study of 10,305 women in Nova Scotia found that frequent sleep trouble (“all of the time”) was associated with a 141% increased breast cancer risk, while high physical activity was associated with a 42% reduced risk. Interestingly, sleep duration itself showed no association with breast cancer risk, suggesting that sleep quality—rather than quantity—may be the more important factor. These findings add sleep disturbances to the list of modifiable lifestyle risk factors for breast cancer and reinforce the protective benefits of physical activity, though the authors note that further research is needed to understand the biological mechanisms linking poor sleep quality to increased cancer risk.
2025
Nutr J
A prospective cohort study of 13,567 Chinese women followed for nearly 15 years found that consuming one or more servings of sugar-sweetened beverages (SSBs) per week was associated with a 58% increased breast cancer risk compared to consuming less than one serving weekly. The association was partly mediated by body mass index (4.2%) and uric acid (18.8%), with genetic analyses identifying additional metabolic mediators including cholesterol and fatty acid ratios accounting for small portions of the effect. Interestingly, higher soy milk consumption (3-6 portions weekly) was associated with a 69% reduced breast cancer risk, while dairy milk showed a non-significant trend toward increased risk, and no associations were found for juice, coffee, tea, or alcohol, suggesting that reducing SSB consumption and addressing the associated metabolic disruptions could be effective breast cancer prevention strategies.
2025
J Hazard Mater
This study investigated whether DEHCH, a newly developed alternative plasticizer, has safer endocrine-disrupting effects compared to conventional phthalates and other alternative plasticizers using computer modeling, cell studies, and zebrafish testing. The researchers found that DEHCH showed lower binding affinity to hormone receptors and did not affect hormone-related gene expression or neurosteroid levels in zebrafish, unlike the other tested plasticizers. In contrast, conventional phthalates (DEHP, DINP) and previously proposed alternatives (DINCH, DEHTP) caused hyperactivity in zebrafish and altered hormone-related gene expression and neurosteroid concentrations. The results suggest that DEHCH may be a safer alternative to both conventional phthalates and previously proposed substitutes in terms of endocrine disruption and neurological effects.
2025
J Hazard Mater
This study used advanced computer modeling to assess the combined reproductive health risks of phthalates (PAEs) and organophosphates (OPEs) found in atmospheric particles, focusing on their ability to disrupt hormone receptors. The researchers found that the mixed toxicity of these compounds was lower than expected from individual effects, suggesting they may interfere with each other’s toxic actions through antagonistic effects. Using network analysis and molecular modeling, they identified 590 potential targets and 50 core targets (including hormone receptors) affected by these pollutants, with DEHP, TPHP, and MEHP being key disruptors of hormone signaling pathways. The study also identified two previously overlooked targets (AKT1 and HSP90AA1) that may be important for reproductive toxicity, providing new insights into how these atmospheric pollutants may affect human reproductive health.
2025
Sci Totl Environ
This study investigated the effects of three common plastic additives (DEHP, BPA, and benzotriazoles) on Atlantic cod liver tissue using precision-cut liver slices exposed to various concentrations of these chemicals individually and in mixtures. The researchers found that BPA and chemical mixtures caused estrogenic effects, significantly increasing vitellogenin (a female egg protein) production and related gene expression in male juvenile cod. The study also observed changes in liver metabolism genes, with mixture exposures showing potentially different effects than individual chemical exposures. The results suggest these plastic additives can disrupt hormone systems in fish, with BPA being the primary driver of estrogenic effects, though the interaction effects between chemicals require further investigation.
2025
Front Toxicol
The study examined the estrogenic and anti-estrogenic effects of three endocrine disruptors: Bisphenol A (BPA), which mimics estrogen, 17 -Estradiol (E2), the endogenous nuclear estrogen receptor ligand, and Fulvestrant (FUL), a drug that interferes with proper estrogen function. The experiment measured the influence of the endocrine disruptors in vitro using 2D and 3D T47D and MCF7 cells, which are estrogen receptor-positive human breast cancer cells. The study results concluded that E2 and BPA increased the expression of the estrogen-regulated marker pS2 and decreased TGF 3. Meanwhile, FUL inhibited E2 and BPA’s expression of the estrogen-regulated markers, meaning FUL reversed the effects of the other two endocrine disruptors.
2025
J Exp Sci Environ Epidemiol
A nationwide US study analyzing drinking water contamination and cancer incidence (2016-2021) found that PFAS (“forever chemicals”) in public water systems were associated with increased rates of multiple cancers, with incidence rate increases ranging from 2% to 33% across different cancer types. The strongest association was a 33% increased rate of oral cavity and pharyngeal cancers linked to PFBS exposure, with other significant associations found for digestive, respiratory, endocrine, thyroid, urinary, brain, and soft tissue cancers, showing notable sex-based differences in cancer patterns. Researchers estimate that PFAS contamination in US drinking water may contribute to approximately 4,600-6,900 new cancer cases annually, underscoring the urgent public health need for stricter water quality standards and expanded monitoring of these persistent environmental pollutants.
2025
Sci Rep
A secondary analysis of 15,536 post-menopausal women from the Alberta Tomorrow Project cohort examined whether exposure to traffic-related air pollution (TRAP), measured using nitrogen dioxide (NO₂) levels, was associated with breast cancer risk over 12.6 years of follow-up during which 523 breast cancer cases were diagnosed. After adjusting for confounders including age, education, births, diet, income, physical activity, BMI, and smoking, the study found no significant association between NO₂ exposure and post-menopausal breast cancer risk (HR = 1.10 per 10-ppb increase in NO₂; 95% CI = 0.90, 1.34). The authors suggest that while the magnitude of risk observed was similar to other studies, the lack of statistical significance may be due to the study’s sample size limitations and the fact that NO₂ levels in Alberta are lower than in many other regions globally where associations have been found. These findings indicate that traffic-related air pollution may not significantly impact post-menopausal breast cancer risk in regions with relatively low pollution levels, though larger studies in more polluted areas may be needed to fully assess this relationship.
2025
Sci Rep
A study of 50 breast cancer patients and 50 healthy women found that 60% of breast cancer patients had metabolic syndrome (a cluster of conditions including high blood pressure, blood sugar, and cholesterol) compared to 40% of healthy controls, and breast cancer patients had significantly lower levels of beneficial gut bacteria—specifically Lactobacillus and Bifidobacterium. These beneficial bacteria normally help protect against disease and regulate the immune system, suggesting their depletion may play a role in breast cancer development. The findings support a connection between metabolic health, gut bacteria composition, and breast cancer risk, pointing to potential new avenues for cancer prevention through dietary or probiotic interventions, though more research is needed.
2025
Breast Cancer
A meta-analysis of 10 studies involving 1,730 women found that breast cancer patients had significantly lower gut bacterial diversity compared to healthy controls, with particularly pronounced differences in premenopausal women and women with normal body weight. The reduction in gut microbiome diversity—a marker of gut health—was not seen in overweight or obese women, suggesting body weight may influence the relationship between gut bacteria and breast cancer. These findings support the hypothesis that gut bacteria may play a role in breast cancer development, possibly through their influence on estrogen levels, though more research is needed to understand the underlying mechanisms and whether improving gut health could help prevent breast cancer.
2025
Clin Transl Oncol
A review of 29 studies found that breast cancer patients have distinct imbalances in their gut and breast tissue bacteria that vary based on cancer type, stage, menopause status, body weight, and physical activity, though no single bacterial profile has yet emerged as a reliable biomarker. The research suggests that gut microbiome composition may influence how well breast cancer treatments work, with some beneficial bacteria and their metabolites potentially improving therapy effectiveness or slowing tumor growth. These findings highlight the microbiome as a promising new area for developing personalized breast cancer treatments and improving outcomes, though more research is needed to identify specific bacterial targets and understand the underlying mechanisms.
2025
Food Chem Toxicol
An in vitro study examining the effects of Roundup® (a Glyphosate-based herbicide) on non-tumorigenic (MCF10A) and tumorigenic (MCF7 and MDA-MB-231) breast cell lines found that the herbicide affects cells through a non-estrogenic mechanism, impacting both hormone-dependent and -independent cells with dose- and time-dependent toxic and proliferative effects, and altered expression of key breast cancer genes (BRCA1 and BRCA2) even at low doses. Treatment with epigenetic modulators (epidrugs) was able to reverse some Roundup®-induced changes, suggesting the herbicide causes epigenetic modifications that may contribute to breast cancer development. These findings highlight that Glyphosate-based herbicides—widely used in agriculture and recognized as potential carcinogens and endocrine disruptors—may induce epigenetic changes linked to breast cancer risk through mechanisms distinct from estrogenic pathways, underscoring the importance of understanding these mechanisms to develop personalized prevention strategies for populations exposed to agricultural herbicides.
2025
Int J Hyg Environ Health
New research highlights the link between endocrine-disrupting chemicals (EDCs) and earlier breast development in girls. A systematic review of 68 studies found that 10 out of 14 high-quality studies linked prenatal and postnatal exposure to EDCs like organohalogenated compounds and phthalates to earlier thelarche. With thelarche now occurring nearly three months earlier per decade, these findings raise serious concerns about long-term health risks, including breast cancer. Reducing exposure to harmful chemicals in everyday products is crucial to protecting hormonal health and preventing early puberty.
2024
Int J Env Res Pub Health
This study surveyed 746 Kenyan women about their hair product use and found that nearly 60% had used chemical relaxers and one-third had used hair dyes, despite many expressing concerns about health risks including breast cancer. Older women and those working in sales and service industries were more likely to use these products, which may contain endocrine-disrupting chemicals linked to breast cancer. Surprisingly, women’s awareness of potential health risks did not consistently lead to reduced use of these products, suggesting that concern alone may not be enough to change behavior. These findings are particularly important for Kenya, where breast cancer rates are rising, and highlight the need for better education about chemical exposures in hair products and strategies to reduce potentially harmful exposures.
2024
Environ Sci Technol
A study of 751 reproductive-aged Black women found that the relationship between personal care product (PCP) use and exposure to endocrine-disrupting chemicals (EDCs) varied significantly by socioeconomic status (SES), with different patterns of chemical exposure from the same products depending on women’s education, income, and employment. For example, vaginal powder use was associated with higher phenol exposure (a class of EDCs) among lower SES women but showed no such association in higher SES women, suggesting that product formulations, brands, or usage patterns may differ across SES groups. These findings highlight that Black women face inequitable EDC exposures that are influenced by both race and socioeconomic factors, underscoring the need for targeted public health interventions that address these intersecting disparities in chemical exposures from everyday products
2024
PNAS
This study examined the health impacts of three major plastic-associated chemicals—BPA, DEHP, and PBDEs—across 38 countries representing one-third of the global population. The researchers found that in 2015, these chemicals were linked to approximately 5.4 million cases of heart disease, 346,000 strokes, 164,000 deaths among older adults, and 11.7 million lost IQ points in children due to prenatal exposure. The total economic cost of these health impacts was estimated at $1.5 trillion. The study suggests that if exposure levels had been reduced earlier, hundreds of thousands of deaths and millions of IQ points could have been prevented.
2024
Int J Environ Res Public Health
A systematic review of 25 epidemiological studies (2013-2022) found that seven out of eight investigated outdoor air pollutants showed significant associations with increased breast cancer risk, with benzo[a]pyrene showing the strongest relationship. The review found that 100% of studies examining nitrogen oxides (NOₓ), 83% of PM₂.₅ studies, 69% of nitrogen dioxide (NO₂) studies, and 43% of PM₁₀ studies demonstrated positive associations with breast cancer risk, with hazard ratios ranging from 1.05-1.56 and odds ratios from 1.03-1.86, while ozone and cadmium showed negative or no associations. These findings strengthen the evidence that outdoor air pollution—particularly traffic-related pollutants and fine particulate matter—contributes to breast cancer development, though the authors note that further research is needed to establish causal mechanisms, particularly through epigenetic pathways, and acknowledge that the review’s focus on English-language articles from developed countries may limit generalizability.
2024
Toxicol Lett
A meta-analysis of 15 studies including 3,468 cancer cases and 4,187 controls found that brominated flame retardant (BFR) exposure in adipose tissue was significantly associated with increased breast cancer risk, though no association was observed for thyroid cancer. The analysis revealed that BFR exposure generally elevates the risk of endocrine-related cancers, with BDE-28—a lower-brominated congener—showing particularly strong associations with increased cancer risk. These findings identify BFRs as a significant environmental risk factor for breast cancer and suggest that certain BFR congeners may be more carcinogenic than others, though the authors emphasize the need for further research to establish causal mechanisms and clarify how these ubiquitous flame retardant chemicals disrupt endocrine function to promote cancer development.
2024
Cancer Causes Control
A population-based study using Kentucky cancer registry data (77,637 breast cancer and 56,598 colorectal cancer cases) found that higher ambient air concentrations of carcinogenic metals—cadmium, arsenic, nickel, and chromium(VI)—were associated with increased odds of residing in breast and colorectal cancer hotspots, independent of individual risk factors including age, race, smoking, and neighborhood socioeconomic characteristics. Cancer hotspot populations were disproportionately Black and exhibited markers of lower socioeconomic status, and importantly, the metal-cancer associations persisted even after adjusting for these factors, suggesting environmental metal exposure is an independent contributor to geographic cancer clustering. These findings provide evidence that historically marginalized communities face disproportionate exposure to carcinogenic metals through environmental pollution, likely contributing to cancer disparities, and underscore the urgent need for environmental justice interventions including stricter air quality regulations, cleanup of contaminated sites, and individual-level exposure assessments to fully understand how metal exposures drive cancer inequities in vulnerable populations.
2024
Sci Tot Environ
A comprehensive systematic review and meta-analysis of 28 studies including over 2.5 million individuals found that higher levels of outdoor artificial light at night (ALAN) were associated with a 12% increased breast cancer risk, though indoor ALAN showed a non-significant 7% increased risk, with no differences by menopausal status. For prostate cancer, the analysis suggested a 43% increased risk with outdoor ALAN exposure, though this was not statistically significant, and qualitative synthesis revealed positive associations with non-Hodgkin lymphoma, colorectal, pancreatic, and thyroid cancers. The authors note a critical limitation: most studies relied on low-resolution satellite imagery (1-5 km resolution from the Defense Meteorological Program) without information on light color or spectral composition, which may have led to exposure misclassification and underestimation of true effects, highlighting the urgent need for studies using higher-resolution exposure assessment methods and investigation of light pollution effects on cancers beyond breast cancer.
2024
Breast Cancer Res Treat
A meta-analysis of 10 randomized controlled trials including 14,282 participants and 591 breast cancers found that estrogen-alone hormone therapy was associated with a significant 23% reduction in breast cancer incidence (3.6% vs 4.7% in estrogen vs placebo groups, RR 0.77, 95% CI 0.65-0.91, P=0.002). This finding was driven primarily by the large Women’s Health Initiative trial but was supported by nine smaller trials showing similar directional effects, with estradiol formulations showing a 37% non-significant risk reduction. These results from randomized trials contradict findings from observational cohort studies and challenge conventional wisdom about hormone therapy and breast cancer, suggesting that estrogen-alone therapy (in women without a uterus) may actually protect against breast cancer rather than increase risk—a finding with important implications for counseling postmenopausal women about menopausal hormone therapy decisions.
2024
Breast Cancer Res Treat
A large prospective study of 187,278 nurses followed for up to 31 years found that high levels of recreational physical activity (≥27 vs <3 MET-hours/week, roughly equivalent to ≥9 hours/week of brisk walking) were associated with 17% reduced breast cancer risk in both premenopausal and postmenopausal women. The protective effect was strongest for hormone receptor-positive (ER+/PR+) tumors in both groups, with no significant associations observed for hormone receptor-negative cancers, and while the benefit in postmenopausal women was partly explained by lower body weight, the association in premenopausal women remained independent of BMI. These findings provide strong evidence that regular recreational physical activity is a modifiable risk factor that reduces breast cancer risk across the lifespan, regardless of menopausal status, supporting public health recommendations for regular exercise as an accessible breast cancer prevention strategy for all women.
2024
BMC Pub Health
This study used NHANES 2011–2018 data (n = 6,147) to evaluate the association between DEHP exposure and cancer risk. After adjusting for confounders, DEHP and its metabolites were significantly associated with increased risk of overall cancer prevalence, especially female reproductive system cancers (OR > 1.0, p < 0.05).
2024
J Clin Oncol
The aim of this pooled analysis (taking data from 19 cohort studies from around the world) was to determine the effect (if any) of leisure-time physical activity on the premenopausal risk of breast cancer. Leisure time physical activity is defind as physical activity occuring during free time (so, not related to work). This analysis took data from a little over half a million women, where the incidence of breast cancer was about 10,000 across the studies. Hazard ratios (how often breast cancer occured in groups w/ high activity versus low activity) was used to asses relative risk. High levels of leisure time activity were associated with an approximately 10% reduction in breast cancer risk after adjusting for BMI. This association was found to be particuarily strong for human epidermal growth factor receptor 2–enriched breast cancer, with a 16-61% reduction in risk.
2024
Environ Int
A study in mice found that exposure to DEHP—a common chemical used to make plastics flexible—disrupts the gut-mammary connection, causing changes in gut bacteria, intestinal inflammation, and direct damage to mammary (breast) tissue that could impair milk production. DEHP altered gut microbiome composition (increasing some bacteria while decreasing others), changed blood metabolite levels, and its breakdown product (MEHP) triggered cell death in mammary tissue through multiple pathways. These findings raise concerns about DEHP exposure from plastics affecting both human breast health and dairy production in livestock, while identifying potential therapeutic targets to counteract the chemical’s harmful effects on the gut-breast axis.