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2023
J Epidemiol
A comprehensive systematic review and meta-analysis of 169 observational studies published through January 2020 examined the association between cigarette smoking and breast cancer risk using random-effects models and dose-response analyses. The pooled analysis found that current smokers had 7% increased breast cancer risk, former smokers 8% increased risk, and ever smokers 9% increased risk compared to never smokers, with results consistent across both case-control and cohort studies and across most covariates including genetic mutations (BRCA) and relevant polymorphisms. Importantly, breast cancer risk increased in a linear dose-response manner with both smoking intensity (12% increased risk for 20 cigarettes/day, 26% for 40 cigarettes/day) and duration (5% increased risk for 20 years, 11% for 40 years), demonstrating clear dose-response relationships. This large and comprehensive meta-analysis, which employed innovative search methods, provides strong evidence supporting a causal role of tobacco smoking in breast cancer development, resolving previous controversy on this association and establishing smoking as a modifiable risk factor for breast cancer with risks increasing proportionally to the amount and duration of smoking exposure.
2023
J Natl Cancer Inst
A large cohort study of 451,945 National Institutes of Health-AARP Diet and Health Study participants used EPA Toxics Release Inventory data to estimate historical environmental ethylene oxide (EtO) exposures based on proximity to EtO-emitting facilities, wind patterns, and emission levels from enrollment in 1995-1996. Among 173,670 postmenopausal women, living within 10 km of EtO facilities was associated with statistically significant breast cancer risk for invasive disease (HR = 1.03; 95% CI: 0.97-1.09); women in the highest quartile of the airborne emissions index showed elevated risk of in situ breast cancer at 10 km (HR = 1.25; 95% CI: 1.02-1.53), with no clear patterns for non-Hodgkin lymphoma risk. These findings reveal a novel potential association between environmental EtO exposure and in situ breast cancer—but not invasive breast cancer or lymphohematopoietic cancers—contrasting with occupational studies that found associations with invasive disease. The differential association with in situ versus invasive disease suggests EtO may influence early-stage breast carcinogenesis, though the mechanism remains unclear and warrants further investigation to understand why environmental exposures show different patterns than occupational exposures and why the effect appears limited to pre-invasive lesions.
2023
Environ Sci Pollut Res
A hospital-based case-control study in Petrópolis, Brazil found that women exposed to pesticides for 10 or more years had elevated but non-significant breast cancer risk after adjusting for confounders (OR = 1.40; 95% CI: 0.85-2.49), while higher education and hormone replacement therapy showed significant positive associations, and having 2+ pregnancies was protective. The authors conclude that further research is needed to clarify pesticide exposure’s contribution to breast cancer development given conflicting findings in the literature.
2023
Endocrine
A case-control study in North India found that breast cancer patients had significantly lower serum Vitamin D levels than healthy controls, with women in the highest Vitamin D quartile having 59% lower breast cancer risk than those in the lowest quartile (OR = 2.44; 95% CI: 1.09-5.45); additionally, women with the polymorphic T allele for VDR FokI genotype (CT/TT) had over 4-fold increased breast cancer risk compared to those homozygous for the wild C allele (OR = 4.30; 95% CI: 2.21-8.35). Vitamin D levels were significantly higher in ER+ patients and significantly lower in advanced-stage cancers, suggesting Vitamin D may serve as both a risk factor and prognostic marker. The study concludes that FokI polymorphism of the VDR gene and low circulating Vitamin D levels independently increase breast cancer risk in North Indian women.
2023
Compr Rev Food Sci Food Saf
A systematic review of phthalate contamination in food identified 19 phthalates across multiple food categories, with 57 measurements exceeding legal limits and DEHP showing the highest incidence; risk assessment revealed high probability of exceeding tolerable daily intake for DEHP and DBP in fish, oils/fats, cereals, and dairy for both children and adults, with fats/oils being the most critical category. Migration from food contact materials is positively correlated with temperature, contact time, fat content, and acidity, with contamination occurring throughout the production chain. The widespread contamination exceeding safe exposure limits—particularly for vulnerable populations including children—highlights the urgent need for stricter regulation of phthalates in food packaging and production materials.
2023
Front Oncol
A study of 80 Black and White women with breast cancer at Emory University Hospitals (2008-2017) examined associations between contemporary neighborhood redlining—a structural racism measure derived from Home Mortgage Disclosure Act data—and DNA methylation patterns in breast tumor tissue. Contemporary redlining was significantly associated with aberrant methylation at 5 CpG sites (FDR<0.10) in genes implicated in breast carcinogenesis, inflammation, immune function, and stress response (ANGPT1, PRG4), with additional top sites showing interaction by ER status and association with mortality; redlining was also associated with epigenetic age acceleration (β=5.35; 95% CI: 0.30-10.4 by Hannum metric). These novel findings suggest that structural racism—manifested through discriminatory housing policies leading to inequitable social and environmental exposures—may biologically embed in the breast tumor epigenome through altered DNA methylation patterns, potentially contributing to documented racial disparities in breast cancer outcomes and highlighting the need for further research on epigenetic mechanisms linking neighborhood-level structural racism to cancer prognosis.
2023
Cancer Causes Control
A review examining how low socioeconomic status (SES) contributes to early chronic disease onset and reduced life expectancy found that neighborhood-level factors—including environmental pollutants, deprivation, social isolation, structural racism, and discrimination—create chronic life stress that affects molecular processes like DNA methylation, inflammation, and immune response, contributing to more aggressive tumor biology, particularly in Black Americans. Despite decades of research showing associations between neighborhood factors and cancer outcomes in marginalized communities, the biological mechanisms linking SES to cancer disparities remain poorly understood, though emerging evidence suggests chronic stress pathways may play a central role. The authors summarize current methods for measuring neighborhood-level deprivation, discrimination, and structural racism in cancer disparities research and recommend adopting a multi-faceted intersectional approach to reduce cancer health inequities and develop effective interventions promoting health equity.
2023
Environ Pollut
A study analyzing breast milk from 50 U.S. mothers ten years after the PBDE phaseout detected 25 brominated flame retardants including 9 PBDEs (found in 100% of samples), 8 bromophenols (88% of samples), and 8 other BFRs, with PBDE concentrations showing a significant 70% decline since 2002 (median 15.0 ng/g lipid, halving time 12.2 years) but bromophenols and replacement flame retardants reaching concentrations up to 71.1 and 278 ng/g lipid respectively. This represents the first measurement of bromophenols and replacement flame retardants in U.S. breast milk, revealing that while legacy PBDE levels have declined substantially following regulatory action, current-use flame retardants are now contaminating breast milk at concerning levels. The persistent presence of phased-out PBDEs alongside emerging bromophenols and replacement BFRs—many of which are persistent, toxic, and bioaccumulative—indicates ongoing prenatal exposure through breastfeeding and increased risk for adverse impacts on infant neurodevelopment; however, it’s important to note that breastfeeding remains recommended and is still considered safer and more beneficial than formula feeding despite the presence of these contaminants, highlighting the urgent need for policies to reduce flame retardant contamination at the source rather than discouraging breastfeeding.
2023
Nutrients
A case-control study of 42 newly diagnosed, treatment-naïve breast cancer patients and 44 age-matched cancer-free controls at Oregon Health & Science University (2020-2021) found reduced gut microbial diversity in breast cancer patients and enrichment of three specific bacterial genera—Acidaminococcus, Tyzzerella, and Hungatella—in fecal samples from cases, with these genera associated with distinct dietary patterns including vegetables and dairy (Hungatella) and whole fruits (Acidaminococcus). Breast cancer patients also had significantly higher BMI and lower physical activity levels, and microbiome analysis revealed significant differences in composition between cases and controls using 16S rRNA sequencing. These findings highlight complex interactions between the gut microbiome, dietary habits (assessed via National Cancer Institute Diet History Questionnaire), lifestyle factors like weight management and physical activity, and breast cancer risk, suggesting the gut microbiome may serve as a source of biomarkers for breast cancer risk assessment, though larger studies are needed to establish causal relationships and validate these microbial signatures.
2023
Microbiol Spectr
A study of 117 postmenopausal African women found significant links between blood levels of estrogens (hormones associated with breast cancer risk) and the composition of bacteria in both the gut and mouth. Higher levels of certain estrogens were associated with greater diversity of gut bacteria, while specific estrogen byproducts were linked to differences in oral bacteria composition, including bacterial families known to help metabolize estrogens. These findings suggest that gut and oral bacteria may influence breast cancer risk by affecting how the body processes estrogens, though larger studies are needed to confirm how these relationships develop over time.
2023
Gut Microbes
A mouse study revealed that Vitamin D receptor (VDR) deficiency in the gut lining leads to bacterial imbalance (dysbiosis), increased intestinal permeability (“leaky gut”), and bacterial migration to breast tissue, significantly increasing breast tumor formation. Mice lacking intestinal VDR developed larger and more numerous breast tumors, with harmful bacteria like Streptococcus found in the tumor tissue, while beneficial bacteria that normally protect against cancer were depleted. However, treatment with butyrate (a beneficial bacterial byproduct) or the probiotic Lactobacillus plantarum reduced breast tumors by restoring gut barrier function and reducing inflammation, demonstrating a direct gut-breast axis. These findings suggest that maintaining gut health through adequate Vitamin D, beneficial bacteria, and a healthy microbiome may be a promising strategy for breast cancer prevention, though human studies are needed to confirm these results.
2023
Reprod Toxicol
A review of epidemiologic literature examining environmental chemical exposures during pregnancy and three maternal health outcomes (preeclampsia, gestational diabetes, and breast cancer) found that pregnancy represents a unique critical period when biological changes can heighten women’s susceptibility to chemicals from air, food, water, and consumer products—including flame retardants, plasticizers, pesticides, and lead—though research has disproportionately focused on fetal outcomes rather than maternal health risks, which remain poorly characterized for most chemicals. While evidence shows that lead exposure increases risk of pregnancy-induced hypertensive disorders and pregnancy can amplify women’s vulnerability to environmental chemicals, variations in study design, exposure assessment methods, and inconsistent adjustment for confounders limited comparability across studies. The authors emphasize that future research must recognize pregnancy as a critical window for women’s lifelong health, calling for incorporation of biomarkers of exposure and effect, deliberate timing and methods of measurement, and consistent confounder adjustment to strengthen understanding of the pregnancy exposome and its impacts on maternal health outcomes beyond the immediate postpartum period.
2023
Endocrinol Metab Clin North Am
Multiple social and structural determinants of health undoubtedly contribute to the marked racial/ethnic-, gender-, and socioeconomic-based disparities in endocrine health; however, the contribution of environmental injustice is vastly underappreciated. Indeed, those groups disproportionately burdened by endocrine disorders are often exposed to higher levels of various EDCs, including PCBs, phthalates, bisphenols, OC pesticides, air pollutants, PFASs, toxic metals/metalloids, and BFRs. These chemicals threaten our reproductive and metabolic health, contributing to diabetes prevalences, obesity, and disorders related to hormonal regulation. This review increases awareness of these disparities and encouraged equitable healthcare for those who are disadvantaged.
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.
2023
Toxicol Sci
A high-throughput transcriptomic study using MCF-7 breast cancer cells exposed to BPA and 15 alternative chemicals (0.0005-100 µM for 48 hours) found that 8 alternative chemicals activated estrogen receptor alpha (ERα), with bisphenol AF identified as the most potent, followed by BPA and bisphenol C, and benchmark concentration analysis revealing that BPA and transcriptionally active alternatives enriched similar gene sets associated with increased cell division and cancer-related processes at comparable concentrations. Global transcriptomic and ERα-specific points of departure produced highly consistent potency rankings, and pathway analysis showed that active alternatives induced hazards similar to BPA through shared molecular mechanisms. These findings reveal that many BPA replacement chemicals used since initial 2010 Canadian regulatory action are not safer alternatives and may pose similar or greater hazards at comparable exposure levels despite being data-poor compounds with limited toxicological assessment, supporting the use of transcriptomic profiling for read-across risk assessment of structurally related chemicals and raising concerns about regrettable substitution in which one harmful chemical is simply replaced with equally harmful alternatives.
2023
Nutrient
A meta-analysis of 7 cohort studies and 17 case-control studies examining dietary isoflavone intake and breast cancer risk found a 29% reduced risk when comparing highest to lowest intake (OR=0.71; 95% CI: 0.72-0.81), with dose-response analysis showing that each 10 mg/day increase in isoflavone intake reduced breast cancer risk by 6.8% (cohort studies, OR=0.932; 95% CI: 0.90-0.96) and 11.7% (case-control studies), though no protective effects were detected at doses below 10 mg/day. The inverse association was independent of menopausal status and estrogen receptor status but varied by study design, being significant in case-control studies but not reaching significance in cohort studies alone. These findings provide evidence that dietary isoflavone intake—particularly from soy foods consumed in Asian populations—may reduce breast cancer risk in a dose-dependent manner starting at intake levels above 10 mg/day, supporting recommendations for dietary isoflavone consumption for breast cancer prevention.
2023
Adv Nutr
A systematic review and meta-analysis of 31 studies (29 included in quantitative analysis) following Cochrane methodology examined associations between healthy lifestyle indices (incorporating factors like healthy body weight, diet, physical activity) and breast cancer risk. Comparing the highest versus lowest adherence categories, the analysis found a 20% breast cancer risk reduction in prospective studies (HR=0.80; 95% CI: 0.78-0.83) and 26% reduction in retrospective studies (OR=0.74; 95% CI: 0.63-0.86), with inverse associations remaining significant when stratified by menopausal status (except for premenopausal BC in prospective studies) and across molecular subtypes: ER+/PR+ (HR=0.68; 95% CI: 0.63-0.73), ER+/PR- (HR=0.78; 95% CI: 0.67-0.90), and ER-/PR- (HR=0.77; 95% CI: 0.64-0.92). These findings—with most studies scoring low risk of bias and moderate certainty of evidence—demonstrate that adherence to healthy lifestyles reduces breast cancer risk by approximately 20-30% regardless of molecular subtype or menopausal status, supporting the prioritization of lifestyle-based recommendations for population-level breast cancer prevention as a key modifiable approach to reducing the substantial disease burden.
Low Vitamin D level increases women’s breast cancer risks, Sulaimaniyah, Iraq: A case-control study.
2023
Cell Mol Biol
A case-control study of 130 women (65 breast cancer patients, 65 healthy controls) aged 20-60 at Shar Hospital in Sulaimaniyah, Iraq found that 66.1% of breast cancer patients had vitamin D deficiency (<20 ng/L) compared to 43.1% of controls, with significantly lower mean vitamin D levels in cases (17.8±8.6) versus controls (20.2±8.7), and vitamin D levels below 20 ng/L associated with 2.59-fold increased breast cancer risk (OR=2.59; 95% CI: 1.24-5.38). After adjusting for age and BMI, vitamin D insufficiency remained a significant breast cancer risk factor (AOR=2.30; 95% CI: 1.1-4.86 for patients; AOR=3.67; 95% CI: 1.55-8.7 for controls). These findings indicate that vitamin D insufficiency substantially increases breast cancer risk among Iraqi women, supporting the role of vitamin D in breast cancer prevention and highlighting the importance of maintaining adequate vitamin D levels, particularly in populations with high deficiency rates.
2022
Endocrinology
A review examining PFAS (found in nonstick cookware, food packaging, and stain-resistant fabrics) and parabens (used in personal care products) found that exposure to these endocrine-disrupting chemicals is linked to breast cancer development, with marginalized and socially disadvantaged communities facing disproportionately higher exposures due to structural racism and inequitable environmental conditions. These disparities in chemical exposure may contribute to poorer breast cancer outcomes in these populations, yet breast cancer research continues to underrepresent these communities, limiting our ability to address treatment disparities and improve survival rates. The authors emphasize the urgent need to both reduce EDC exposures in vulnerable communities and increase research inclusion of diverse populations to understand how environmental injustices intersect with breast cancer risk and develop interventions that address these health inequities.
2022
Biomedicines
This study investigates the effects of di-(2-ethylhexyl) phthalate (DEHP), a common plasticizer, on female rats. It found that exposure to DEHP, even at realistic environmental doses, led to significant disruptions in the rats’ reproductive and thyroid systems. More specifically it found that even low exposure to DEHP over a period of 21 days resulted in a significant decrease in the levels of estrogen and progesterone, which correlated with damage to ovarian follicles. Additionally, the thyroid showed signs of damage, including alterations in hormone regulation. The data in this study suggests that DEHP can potentially lead reproductive issues and impaired ovarian and thyroid gland function.
2022
J Expo Sci Environ Epidemiol
A comprehensive analysis of 6,793 chemicals in commercial use identified 50 high-priority understudied chemicals that frequently co-occur with known breast cancer-associated chemicals in everyday exposure sources like food, consumer products, and personal care items. Using chemical databases and structural similarity analyses, researchers found these understudied chemicals share physicochemical properties with established mammary carcinogens and potential endocrine disruptors, yet have not been adequately evaluated for breast cancer risk. The findings highlight that real-world chemical exposures occur as mixtures rather than isolated compounds, and that focusing solely on individual well-known chemicals may miss important combination effects—underscoring the urgent need for mixtures-based research in clinical, epidemiological, and toxicological studies to better understand and prevent environmentally-driven breast cancer.
2022
Crit Rev Food Sci Nutr
This systematic review of 131 epidemiological studies evaluated the association between various endocrine-disrupting chemicals, including phthalates and hormonal exposures like contraceptive pills, and the risk of breast cancer. It found that several EDCs, particularly phthalates and oral contraceptive use, were consistently associated with increased breast cancer risk across multiple studies.
2022
Eur J Epidemiol
A comprehensive study combining meta-analysis of observational data with genetic (Mendelian randomization) analysis found that each 10 grams per day increase in alcohol consumption was associated with a 4% increased breast cancer risk, and importantly, genetic predisposition to problematic alcohol use showed a 76% increased risk even after accounting for alcohol quantity consumed. The study identified four specific DNA methylation sites (epigenetic modifications) affected by alcohol—near the CDC7, ZNF318, RIN3, and RP11-867G23.13 genes—where alcohol-induced changes were causally linked to increased breast cancer risk, providing mechanistic insight into how alcohol drives carcinogenesis. These findings confirm that even low-dose alcohol consumption increases breast cancer risk and suggest that the harm stems not just from the amount consumed but from pathological drinking patterns and specific epigenetic changes that could serve as targets for prevention strategies.
2022
Clin Breast Cancer
A case-control study of 150 Iranian women with newly diagnosed breast cancer matched with 150 controls found that women consuming the most pro-inflammatory diets (highest quartile of food-based dietary inflammatory index) had a 138% increased breast cancer risk compared to those with the least inflammatory diets, with the association remaining significant (180% increased risk) after adjusting for confounding factors. The food-based empirical dietary inflammatory index (FDII), which scores dietary patterns based on 27 pre-defined food groups according to their inflammatory potential, showed a clear dose-response relationship with breast cancer risk across quartiles. These findings from a Middle Eastern population reinforce that dietary patterns promoting systemic inflammation substantially increase breast cancer risk, and suggest that practical, food-based dietary modifications—emphasizing anti-inflammatory whole foods like fruits, vegetables, whole grains, legumes, nuts, and fish while limiting pro-inflammatory processed foods, red meat, and refined carbohydrates—could be an effective and culturally adaptable breast cancer prevention strategy.
2022
J Occup Environ Med
A systematic review and meta-analysis of 9 studies found that female flight attendants had a 43% increased breast cancer incidence compared to the general population, but surprisingly, neither cosmic radiation exposure nor circadian rhythm disruption—the two primary occupational hazards hypothesized to drive this excess risk—showed clear associations with breast cancer in the available studies. Three studies suggested a possible link with cosmic radiation while none found associations with circadian disruption, leaving the underlying cause of the elevated breast cancer risk among flight attendants unexplained. These findings highlight a critical gap in occupational health research: while flight attendants clearly face elevated breast cancer risk, the mechanisms remain unclear, potentially involving unmeasured factors such as reproductive patterns (delayed childbearing, fewer children), lifestyle factors associated with the profession, cumulative effects of multiple low-level exposures, or limitations in exposure assessment methods—underscoring the urgent need for studies with detailed individual-level data on occupational exposures, work schedules, and lifestyle factors to identify modifiable risk factors for this vulnerable workforce.
2022
Environ Res
A case-control study of 499 breast cancer patients and 499 controls in Northern Mexico found that women with breast cancer had distinct patterns of urinary metal exposure, with higher concentrations of tin and lower concentrations of vanadium, cobalt, and molybdenum compared to controls. Using principal component analysis to identify metal mixtures, researchers discovered two distinct exposure patterns with opposite breast cancer associations: a mixture containing chromium, nickel, antimony, aluminum, lead, and tin showed a 15% increased risk, while a mixture of molybdenum and cobalt showed a 44% reduced risk. This is the first study to identify specific urinary metal mixture profiles associated with breast cancer, highlighting that metals may interact synergistically or antagonistically rather than acting independently, and underscoring the critical need for mixture-based approaches in environmental health research—since real-world exposures involve multiple simultaneous contaminants whose combined effects may differ substantially from predictions based on individual metals alone—along with mechanistic studies to understand how metal interactions influence breast carcinogenesis.
2022
Int Arch Occup Environ Health
A nationwide retrospective cohort study of over 4.7 million Taiwanese workers found that occupational exposure to specific hazardous chemicals was associated with significantly elevated breast cancer risk among female workers, with asbestos showing the highest increase (107% increased incidence, 80% increased risk after adjusting for age and exposure duration). Other notable associations included 1,1,2,2-tetrachloroethane (74% increased incidence, 52% adjusted risk increase), trichloroethylene/tetrachloroethylene (47% increased incidence, 42% adjusted risk increase), benzene (40% increased incidence, 38% adjusted risk increase), and lead (27% increased incidence, 31% adjusted risk increase), with associations remaining robust even after accounting for 2- or 5-year latency periods. These findings from 3,248 breast cancer cases among exposed workers provide compelling evidence that occupational chemical exposures substantially increase breast cancer risk, highlighting the urgent need for enhanced workplace protections, regular breast cancer screening programs for exposed workers, substitution of safer alternatives where possible, and recognition of breast cancer as an occupational disease for workers with documented exposure to these carcinogens.
2022
Nutr Cancer
An updated meta-analysis of 21 studies including over 346,000 participants found that the most pro-inflammatory diets were associated with a 16% increased breast cancer risk overall, with particularly strong associations among postmenopausal women (13% increased risk), obese women with BMI ≥30 kg/m² (35% increased risk), and populations in developing countries (79% increased risk). The analysis revealed important methodological influences on effect estimates, with stronger associations observed in case-control studies (50% increased risk), studies using hospital-based controls (111% increased risk), and cohort studies with prolonged follow-up (13% increased risk). These findings not only confirm that pro-inflammatory dietary patterns increase breast cancer risk but also demonstrate that the magnitude of association varies substantially by population characteristics and study design, with obesity and postmenopausal status appearing to amplify the carcinogenic effects of inflammatory diets—suggesting that anti-inflammatory dietary interventions may be particularly beneficial for overweight/obese postmenopausal women and populations in developing countries where rapid dietary transitions toward processed, inflammatory foods are occurring.
2022
Int J Epidemiol
A large European prospective study of 150,257 women followed for 14 years found that weight gain of more than 10 kg from age 20 to middle adulthood was associated with a 42% increased postmenopausal breast cancer risk among women who were lean at age 20, with the association present in both HRT users (23% increased risk) and non-users (40% increased risk) and particularly strong for ER+/PR+ breast cancers (46% increased risk). The findings indicate that maintaining stable weight from young adulthood is especially important for women who start out lean, as weight gain appears to negate the protective effect of lower early-life body weight. These results highlight a critical window for breast cancer prevention: while being lean in early adulthood is protective, this benefit is substantially diminished by subsequent weight gain, suggesting that weight management efforts should focus not just on current weight but on preventing long-term weight accumulation from young adulthood through menopause.
2022
Asian Pac J Cancer Prev
A matched case-control study of 187 breast cancer patients and 187 controls in Asia found that irregular sleep patterns and severe stress were the strongest modifiable risk factors, with irregular sleep associated with a staggering 3,311% increased breast cancer risk and severe stress showing a 574% increased risk. Poor sleep quality showed an even more dramatic 1,029% increased risk, while regular multivitamin use was associated with a 238% increased risk—a surprising finding requiring further investigation—and having a first child before age 30 was protective with a 56% risk reduction. Notably, none of the traditional non-modifiable risk factors (such as family history) showed significant associations in this study, suggesting that modifiable lifestyle factors—particularly sleep quality and stress management—may be critically important targets for breast cancer prevention in Asian populations experiencing rapidly rising breast cancer rates.
2022
Sleep Breath
A comprehensive meta-analysis of 31 prospective cohort studies including 9.3 million participants found that night-shift work was associated with a modest but statistically significant 2.9% increased breast cancer risk overall, with risk escalating to 8.6% for women working night shifts for more than 10 years and 5.3% for rotating night-shift work specifically. Night-shift workers also showed a 3.1% increased risk of cardiovascular mortality compared to day workers, highlighting broader health impacts beyond cancer. These findings provide strong epidemiological evidence that chronic circadian disruption from night-shift work increases breast cancer risk in a dose-dependent manner, with implications for the millions of women worldwide working non-standard hours in healthcare, manufacturing, transportation, and service industries—suggesting the need for policy interventions to limit long-term night-shift exposure and provide enhanced health monitoring for affected workers.
2022
Cancers
A meta-analysis of 19 case-control studies found that oral contraceptive (OC) use had markedly different effects on breast cancer risk depending on tumor receptor status: OC use was associated with a 37% increased risk of triple-negative breast cancer and a 20% increased risk of ER-negative breast cancer, while showing an 8% reduced risk of ER-positive breast cancer and a non-significant 5% reduced risk of HER2-positive breast cancer. These contrasting associations suggest that oral contraceptives may influence breast cancer development through different biological mechanisms depending on tumor subtype, with particularly concerning implications for triple-negative breast cancer—the most aggressive subtype with limited treatment options. The findings highlight the importance of considering breast cancer heterogeneity when evaluating hormonal contraceptive risks and suggest that women at high risk for triple-negative or ER-negative breast cancer may need alternative contraceptive counseling.
2022
Carcinogen
A meta-analysis of 12 breast cancer studies and 8 ovarian cancer studies in women with BRCA1 or BRCA2 mutations found that oral contraceptive (OC) use was associated with a 24% increased breast cancer risk but a 47% decreased ovarian cancer risk. The increased breast cancer risk was observed only with long-term OC use (>5 years), while the ovarian cancer protection occurred regardless of duration, and these patterns were consistent when BRCA1 and BRCA2 carriers were analyzed separately. These findings present a complex risk-benefit trade-off for BRCA mutation carriers considering oral contraceptives, suggesting that while OCs provide substantial protection against ovarian cancer—a particularly deadly cancer in this high-risk population—they also modestly increase breast cancer risk with prolonged use, requiring careful individualized counseling about contraceptive choices and cancer prevention strategies.
Risk of breast cancer in Danish women occupationally exposed to organic solvents, including ethanol.
2022
Am J Indust Med
A Danish nested case-control study of 845 breast cancer patients and 1,500 matched controls found that occupational exposure to organic solvents was associated with a 220% increased breast cancer risk among ever-exposed women compared to never-exposed women. The elevated risk was observed across all breast cancer subtypes—both estrogen receptor-positive and negative tumors—and in both pre- and postmenopausal women, though surprisingly, no dose-response relationship was detected with duration or cumulative exposure levels. Occupational ethanol exposure showed no association with breast cancer, suggesting that specific properties of other organic solvents may drive the carcinogenic effect, and highlighting the need for workplace protections and further research to identify which solvent types pose the greatest risk.
2022
Molec Carcinogen
A case-control study of 708 breast cancer patients and 598 controls from Long Island found that paraben exposure—particularly methylparaben—was associated with significantly increased breast cancer risk among women with hypomethylated (undermethylated) DNA, showing a 46% increased risk in the highest versus lowest exposure group and a 32% increased risk per one-quantile increase in combined paraben exposure. Importantly, paraben exposure was specifically associated with breast tumors characterized by hypomethylation of the CCND2 gene promoter, with methylparaben showing a 25% increased risk and combined parabens showing a 55% increased risk for this tumor subtype. These findings suggest that parabens—ubiquitous preservatives in personal care products—may contribute to breast cancer development through epigenetic mechanisms, particularly in women with pre-existing DNA methylation abnormalities, identifying a potentially vulnerable subpopulation and a specific molecular pathway through which these chemicals may promote carcinogenesis.
2022
BMP Nutr Prev Health
A recent study found that ultra-processed food intake is associated with an increased risk of breast cancer in young women across Latin American countries. The study, involving 525 cases and 525 controls, revealed that major contributors to ultra-processed food intake included ready-to-eat meals, sugary beverages, processed meats, and packaged snacks. Ultra-processed foods are rich in unhealthy fats, sugars, and additives that may drive cancer risk. This highlights the need to reduce ultra-processed food consumption and promote healthier, whole-food diets as a preventative measure, especially among young women in Latin America.
2022
Sci Rep
A study of drinking water found widespread contamination with phthalates (plastic chemicals) and bisphenol-A, with DEHP—the most common phthalate detected—exceeding safety limits in concentrations up to 8,351 µg/L in winter and 410 µg/L in summer, posing potential health risks to consumers. The research revealed significant seasonal variations with higher contamination in winter than summer, and health risk assessment showed that DEHP exposure from drinking water alone exceeded safe levels (hazard quotient >1), raising concerns about hormone disruption and potential breast cancer risk. These findings highlight an urgent need for water treatment plants to implement better technologies to remove these endocrine-disrupting chemicals and ensure safe drinking water, as current contamination levels may threaten both human and environmental health.
2022
J Hazard Mater
This study investigates human exposure to bisphenol A (BPA) and bisphenol S (BPS) by handling thermal paper receipts. The study analyzed the BPS and BPA concentrations from the fingerprints of individuals who handled thermal paper receipts and compared them to those of people who didn’t handle thermal paper receipts. The results found that 20–40 μg of BPS or BPA is transferred to human skin as seen through the fingerprint after contact with thermal papers containing 100–300 μg. Additionally, the transfer of BPA was 2.9–5.2 times higher than BPS, which is consistent with higher concentrations in receipts. However, washing hands significantly reduced the transfer of both BPS and BPA. This is important because the study also determined lipid metabolism was affected at concentrations greater than 10 mg/L. Additionally, it had adverse effects on the growth of water flees, indicating that it may potentially have some effect on human development as well.
2022
Talanta Open
This study developed a sensitive analytical method to detect steroid hormones (progestins, estrogens, androgens, and glucocorticoids) in fruits and vegetables, using strawberry, carrot, and spinach as test samples. The optimized extraction procedure uses ultrasonic extraction with minimal methanol, followed by clean-up and analysis via HPLC-ESI-MS/MS, achieving good recoveries at concentrations of 10-50 ng/g. The method was successfully applied to additional produce (raspberry, radish, arugula) and used to analyze market-purchased samples, where some steroids were detected at low ng/g levels. These findings are consistent with existing literature on steroid hormone accumulation in edible plants as emerging environmental pollutants.
2022
BMJ
Ultra-processed foods (UPFs), commonly found in ready-to-eat items like packaged snacks, frozen meals, and sodas, are filled with added sugars, unhealthy fats, and harmful chemicals like preservatives and flavor enhancers. These foods are increasingly linked to serious health issues, including obesity and cancer. Studies show that replacing UPFs with whole, unprocessed foods can reduce the risk of disease and improve overall health. The harmful ingredients in these products, such as phthalates and bisphenols, can also disrupt the endocrine system, further increasing the risk of developing serious health problems, including cancer.
2022
Chemosphere
A study analyzing 12 commercial bottled water brands found that all tested products contained 2-6 different phthalate chemicals at concentrations ranging from 6.3 to 112.2 ng/mL, with di-n-butyl phthalate (DnBP) showing the highest levels followed by DEHP, DiBP, DMP, DEP, and DiPP. Using an optimized solid-phase microextraction method combined with tandem mass spectrometry, researchers detected these endocrine-disrupting chemicals—which leach from plastic bottles into drinking water—at levels detectable with limits as low as 0.3-2.6 ng/mL. These findings raise significant public health concerns given that phthalates are recognized endocrine disruptors with estrogenic properties that have been linked to breast cancer and other hormone-related health effects, and that billions of people worldwide consume bottled water daily with cumulative lifetime exposures potentially reaching harmful levels, highlighting the urgent need for regulatory limits on phthalates in bottled water and increased adoption of alternative packaging materials that don’t leach endocrine-disrupting chemicals.
2022
Food Chem
A study analyzing 27 vegetable oils using advanced two-dimensional gas chromatography found phthalates—endocrine-disrupting chemicals used as plasticizers that have been linked to cancer—in vegetable oil products, though specific concentration ranges and detection frequencies were not provided in the abstract. The researchers developed a simple, direct analytical method requiring only dilution with solvent (no complex sample preparation) that achieved good repeatability, low detection limits (0.06-2.10 mg/kg), and high accuracy (-9.2% to 10.4%), making it suitable for routine monitoring of phthalate contamination in edible oils. These findings raise concerns about dietary phthalate exposure through cooking oils—a staple food ingredient consumed daily by billions—particularly since phthalates can migrate into oils from plastic packaging, processing equipment, or storage containers, and given their known endocrine-disrupting properties and associations with hormone-related cancers including breast cancer, highlighting the need for stricter regulations on phthalate use in food contact materials and routine monitoring of edible oils for these contaminants.
2022
Environ Sci Pollut Res
The following study explores the presence of endocrine disruptors such as phthalates (specifically mono-2-ethyl phthalate and mono-n-butyl phthalate), bisphenol A (BPA), and 1-hydroxypyrene in the urine samples of marginalized Indigenous populations. The study found that 100% of the women sampled showed exposure to these harmful chemicals, with higher concentrations than observed in similar studies from other communities. This increased exposure is linked to environmental and cultural factors, such as the common use of plastic containers and practices such as burning garbage. The women sampled were found to have especially high levels of mono-2-ethyl phthalate, which suggests significant exposure to di(2-ethylhexyl) phthalate. These findings highlight the vulnerability of indigenous communities to pollution due to a lack of awareness, limited healthcare access, and inadequate regulatory measures.
2022
Int J Cancer
A study of 881 Ghanaian women found that lower diversity of bacteria in the mouth was associated with increased risk of both breast cancer and nonmalignant breast disease, with specific bacterial types like Porphyromonas and Fusobacterium being less common in breast cancer patients. The research also revealed that among women with breast cancer, the composition of oral bacteria was strongly linked to their gut bacteria composition, while this connection was weak in healthy women. These findings suggest that the oral microbiome—the community of bacteria living in the mouth—may play a role in breast cancer risk and could potentially serve as a marker for disease, though more research is needed to understand how these bacteria might influence cancer development.
2022
Food Chem
This study introduced a novel material, UVM-7 mesoporous silica modified with cyclodextrins, for extracting endocrine-disrupting chemicals (EDCs) from apple juice. The cyclodextrin units enhance selectivity, allowing for precise detection of EDCs like bisphenols and parabens in low ng/L concentrations, meeting regulatory limits. When compared with conventional methods, the UVM-7-based extraction shows high recovery rates (94-100%) and low deviation, making it a promising, sensitive tool for identifying harmful chemicals leaching from packaging.
2022
Front Endocrinol
A meta-analysis of 8 studies (5 cohort and 3 case-control studies) examined whether fertility treatments increase breast cancer risk in genetically susceptible women, including those with a family history of breast cancer or BRCA mutations. The analysis found no significant increase in breast cancer risk associated with fertility treatments in genetically susceptible women overall (OR 1.18), women with a family history of breast cancer (OR 1.35), or BRCA mutation carriers (OR 1.02), with similarly reassuring results across subgroups including BRCA1 carriers, BRCA2 carriers, and women treated with specific fertility medications like in vitro fertilization, clomiphene citrate, or gonadotropins. This first meta-analysis on this topic provides reassuring evidence that fertility treatments do not significantly increase breast cancer risk even in women with hereditary susceptibility, though the authors note that larger prospective studies with more detailed information are needed to fully understand potential risks. Future research should examine whether risks vary by breast cancer subtype, explore the genetic mechanisms underlying hormone-related breast cancer, and investigate the relationship between BRCA mutations and hormone receptor-positive breast cancer specifically.
2022
Cancer Epidemiol Biomark Prev
A study of 102,572 women aged 40-69 years with normal BMI (18.5-<25 kg/m²) from the UK Biobank examined whether a healthy lifestyle index (HLI)—a composite score based on diet quality, low alcohol consumption, no smoking, moderate-to-high physical activity, and waist circumference <80 cm—was associated with breast cancer risk. Postmenopausal women with the highest HLI scores (3rd tertile) had a 24% reduced risk of breast cancer compared to those with the lowest scores (HR = 0.76; 95% CI: 0.64-0.91), while premenopausal women showed similar but non-significant trends, except when smoking was excluded from the score (HR = 0.71; 95% CI: 0.56-0.90). These findings demonstrate that even among women with normal BMI—a group traditionally considered at lower risk—adhering to multiple healthy lifestyle behaviors is associated with reduced breast cancer risk in postmenopausal women. The results suggest that maintaining a healthy lifestyle through diet, physical activity, limited alcohol, healthy waist circumference, and not smoking may provide breast cancer protection beyond weight management alone, particularly for postmenopausal women.
2022
Int J Env Res Public Health
A large population-based retrospective case-control study in Taiwan examined 103,047 female workers with breast cancer diagnosed between 2008-2017 and matched controls (1:4 ratio) using lifetime labor enrollment records from 1950-2017 to investigate the association between occupational industries and breast cancer risk. The study identified slightly elevated breast cancer risk across nine major occupational classifications, with the highest risks observed in education (OR: 1.199), professional/scientific/technical activities (OR: 1.118), human health and social work (OR: 1.125), and financial/insurance activities (OR: 1.109), while manufacturing, wholesale/retail trade, information/communication, real estate, and public administration sectors showed smaller but statistically significant increases (ORs ranging from 1.027-1.074). The findings suggest that women employed in certain white-collar professions (education, healthcare, finance, professional services) and some industrial sectors (manufacturing, retail) have modestly increased breast cancer risk compared to other Occupations. The authors recommend further investigation into specific risk factors within these industries—such as work schedules, occupational exposures, socioeconomic factors, or lifestyle patterns associated with these professions—that might explain the slightly elevated breast cancer incidence among female workers in these sectors.
2022
Int J Obesity
A large retrospective cohort study using South Korea’s National Health Insurance Service database followed 691,253 premenopausal and 1,519,211 postmenopausal women aged ≥40 who underwent three consecutive biennial breast cancer screenings between 2009-2014 and were followed until 2020, identifying 9,485 and 12,553 breast cancer cases respectively over a median 6.9 years. In postmenopausal women, consecutive weight gains increased breast cancer risk by 11% while consecutive weight losses decreased risk by 16%; similarly, continuous increases in waist circumference raised risk by 13% while continuous decreases lowered risk by 16%, demonstrating a dose-response relationship. In premenopausal women, a single weight gain was associated with 7% increased breast cancer risk. These findings indicate that longitudinal changes in weight and waist circumference—not just baseline measurements—are important predictors of breast cancer risk in a dose-response manner, with the direction and consistency of changes over time being particularly significant for postmenopausal women, suggesting that sustained weight loss and waist reduction may be effective breast cancer prevention strategies even in midlife and beyond.
2022
Environ Int
A large prospective study within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort examined 318,607 women from nine European countries over a median 14.9 years of follow-up, identifying 13,241 incident invasive breast cancer cases, to assess whether dietary intake of 17 dioxins and 35 polychlorobiphenyls (PCBs)—persistent organic pollutants with endocrine-disrupting and carcinogenic properties—was associated with breast cancer risk. Dietary exposures to dioxins, dioxin-like PCBs (DL-PCBs), non-dioxin-like PCBs (NDL-PCBs), and combined dioxins + DL-PCBs showed no associations with breast cancer incidence (all HRs approximately 1.00-1.01 per 1 SD increase), with results remaining consistent when analyzed by quintile groups, by country, by estrogen receptor status, or after adjusting for contributing food groups and nutritional factors. These findings from one of the largest prospective studies on this topic do not support an association between dietary intake of dioxins and PCBs—the main exposure route for these chemicals in the general population—and breast cancer risk. Despite the established endocrine-disrupting properties of these pollutants and some previous suggestions of positive associations, this comprehensive European study provides reassuring evidence that typical dietary exposures to dioxins and PCBs are not linked to increased breast cancer incidence.