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2025
J Clin Oncol
A large California study of over 58,000 racially and ethnically diverse women found that long-term exposure to fine particulate matter (PM2.5) air pollution was associated with a statistically significant 28% increased risk of breast cancer for each 10 μg/m³ increase in PM2.5 concentration, with the association consistent across African American, Latino, and other ethnic groups. When combined with data from 10 other studies in a meta-analysis, PM2.5 exposure showed a borderline significant 5% increased breast cancer risk, providing strong evidence that air pollution is an important breast cancer risk factor. These findings emphasize that breast cancer prevention strategies should extend beyond individual lifestyle changes to include population-level policies aimed at reducing air pollution, particularly as traditional risk factors explain only half of breast cancer cases and incidence continues to rise globally.
2025
Public Health
In this Mendelian-randomization study of European and East Asian populations, genetic variants linked to daytime/evening Noise and air pollutants (NO₂, NOₓ, PM₂.₅, PM₁₀) were used to assess breast cancer risk. In the European cohort, genetically predicted NO₂ exposure had an OR of 1.94 (95% CI: 1.29–2.92) and PM₁₀ had an OR of 1.42 (95% CI: 1.09–1.85) for breast cancer; in East Asian populations, NO₂ exposure showed OR = 1.14 (95% CI: 1.008–1.287). The findings suggest that both traffic-related air pollutants and Noise may causally contribute to breast cancer risk.
2025
Environ Pollut
A study of 574 breast cancer cases and 2,295 controls from rural Arkansas found that moderate exposure to polycyclic aromatic hydrocarbons (PAHs) and high chromium exposure were associated with statistically significant 32% increased breast cancer risk, with the strongest effects observed among women with a family history of breast cancer. When examining 12 hazardous air pollutants as a mixture, there was a suggested but non-statistically significant 21% increased breast cancer risk, with chromium, propylene dichloride, and PCBs contributing most to the elevated risk. This study is important because it demonstrates that hazardous air pollutants pose breast cancer risks even in rural areas, which are often overlooked in environmental health research despite experiencing different pollution sources and healthcare disparities compared to urban populations.
2025
JAMA Netw Open
In a cross-sectional study involving Black and White women participating in the NCI Maryland Breast Cancer Study, the investigators examined associations between neighborhood-level deprivation, air pollution (PM₂.₅) and presence of breast tissue crown-like structures (CLS-B) plus DNA methylation patterns. Higher PM₂.₅ exposure and greater neighborhood deprivation were associated with increased odds of having CLS-B (OR for PM₂.₅ 2.32, 95% CI: 1.12–4.78). The findings point to how socio-environmental disadvantage and pollution may influence breast adipose inflammation and epigenetic changes linked to cancer risk.
2025
Ecotoxicol Environ Saf
This study analyzed six xenoestrogens (hormone-disrupting chemicals including phthalates, BPA, and alkylphenols) in atmospheric particles at a university campus in China from 2021 to 2023. BPA was the most prevalent xenoestrogen detected, with concentrations of these chemicals being significantly higher in winter than summer, and the overall cancer and non-cancer health risks were below threshold limits for the general population. However, infants and young children showed significantly higher risk values compared to other age groups, indicating they face greater health risks from atmospheric exposure to these endocrine disruptors. The research provides important data for developing policies to reduce health risks from airborne xenoestrogen exposure, particularly for vulnerable populations like children.
2024
Eur J Cancer
A French study of over 5,400 women found a suggested 28% increased risk of breast cancer associated with long-term exposure to fine particulate matter (PM2.5) air pollution for each 10 µg/m³ increase in average concentration, though this association did not reach statistical significance, with weaker trends also observed for PM10 and nitrogen dioxide (NO2). This study uniquely examined air pollution exposure at both residential and workplace locations, finding that residential and workplace pollution levels were highly correlated, suggesting that residential exposure assessments can serve as a reasonable proxy for total pollution exposure. The findings contribute to growing evidence linking air pollution to breast cancer risk and suggest that future research should also consider exposure during commuting to capture complete pollution exposure patterns.
2024
J Natl Cancer Inst
A large US study of nearly 197,000 women found that exposure to fine particulate matter air pollution (PM2.5) during the 1980s—when pollution levels were higher—was associated with an 8% increased risk of breast cancer overall, with each 10 µg/m³ increase in PM2.5 concentration linked to the elevated risk. The association was particularly strong for estrogen receptor-positive breast cancers, showing a 10% increased risk, while no association was found for estrogen receptor-negative tumors. This study provides important evidence that historical air pollution exposure, even decades before diagnosis, may contribute to breast cancer development, particularly for hormone-sensitive tumors, emphasizing the long-term health consequences of air quality and the benefits of pollution reduction efforts.
2024
Environ Int
A comprehensive French study of over 10,000 women examined exposure to eight different air pollutants simultaneously and identified that women exposed to high levels of nitrogen dioxide (NO₂), particulate matter, and PCB153 had a 38-61% increased risk of breast cancer compared to women with low pollution exposure. Using advanced statistical modeling that groups women by their combined pollution exposure patterns rather than examining pollutants individually, researchers found that specific combinations of high pollutant exposures were strongly associated with elevated breast cancer risk. This study provides important evidence that the combined “cocktail effect” of multiple air pollutants, particularly traffic-related pollution (NO₂) and industrial chemicals (PCB153), may significantly increase breast cancer risk beyond what individual pollutants cause alone.
2024
Int J Hyg Environ Health
A study of 48,665 California women in the Multiethnic Cohort found that exposure to specific ambient air toxics at residential addresses was associated with increased breast cancer risk over a 10-year follow-up period. Industrial chemicals showed the strongest associations, with 1,1,2,2-tetrachloroethane linked to a 322% increased risk, ethylene dichloride to a 181% increased risk, and vinyl chloride to a 127% increased risk. Gasoline-related pollutants also showed elevated risks, including benzene (32% increase), acrolein (126% increase), and toluene (29% increase), with generally stronger associations observed among African American and White women. These findings suggest that toxic air pollutants, particularly from industrial sources and vehicle emissions, may contribute to breast cancer development, which is especially concerning for populations living in high-pollution areas like Los Angeles.
2024
Cancer Epidemiol
A Canadian case-control study of 465 young women (ages 18-45) with breast cancer and 242 controls found that residential exposure to air pollution was strongly associated with increased breast cancer risk. For each interquartile range increase in nitrogen dioxide (NO₂) exposure—a traffic-related pollutant—women had a 133% increased risk of breast cancer at their current residence and a 116% increased risk based on exposure five years earlier. The findings suggest that traffic-related air pollution may be a particularly important and underrecognized breast cancer risk factor in younger women.
2024
Environ Pollut
A French study of over 10,000 women found that combined exposure to a mixture of four hormone-disrupting air pollutants (benzo[a]pyrene, cadmium, dioxin, and PCB153) was associated with an approximately 10-11% increased risk of breast cancer. Using advanced statistical methods that account for simultaneous exposure to multiple pollutants rather than examining each separately, researchers found that benzo[a]pyrene, cadmium, and PCB153 showed the strongest individual contributions to increased breast cancer risk within the mixture. This research provides important evidence that the cumulative effect of multiple air pollutants acting together on hormone pathways may be a significant risk factor for breast cancer development.
2024
Environ Health
This large French cohort study analysed long-term residential exposure trajectories of PCB153 and benzo[a]pyrene (BaP) among more than 10,000 women and estimated associations with breast cancer risk. Women in the highest trajectory class for PCB153 had an OR of ~1.69 (95% CI: 1.08–2.64) compared to the lowest class; associations for BaP were weaker and not consistently statistically significant. The research highlights how evolving environmental exposures over decades may influence hormone-sensitive cancer risk.
2021
Environ Int
Long-term exposure to benzo[a]pyrene (BaP), a toxic air pollutant from gas and diesel vehicle exhaust, was associated with a 15% increased risk of breast cancer in a large French study of over 10,000 women. The risk was particularly elevated in women transitioning through menopause and for hormone receptor-positive breast cancers, with each increase in BaP exposure levels raising breast cancer odds by 15-20%. This study provides important real-world evidence that BaP air pollution may contribute to breast cancer development, especially affecting hormone-sensitive tumors.
2021
Environ Res
A French study of over 10,000 women found that long-term atmospheric exposure to PCB153, a widespread environmental pollutant with estrogen-like properties, was associated with a 19% increased risk of breast cancer for each standard deviation increase in cumulative exposure. The association was particularly strong for women who became postmenopausal during the study period (23% increased risk) and for estrogen receptor-positive breast cancers (18% increased risk), while no association was found for estrogen receptor-negative tumors. This is the first study to link airborne PCB exposure to breast cancer risk, providing evidence that these persistent environmental pollutants may contribute to hormone-sensitive breast cancer development even decades after their use was banned.
Chronic long-term exposure to cadmium air pollution and breast cancer risk in the French E3N cohort.
2020
Cancer Epiemiol
A French study of over 8,000 women found no overall association between long-term airborne cadmium exposure and breast cancer risk, but unexpectedly discovered that higher cadmium exposure was associated with a 32-38% decreased risk of estrogen receptor-negative (ER-) breast cancers. This finding contradicts the hypothesis that cadmium increases breast cancer risk through its estrogen-like effects, and instead suggests cadmium may have different biological effects depending on the hormone receptor status of tumors. These surprising results indicate that cadmium’s relationship with breast cancer is more complex than previously thought and may involve mechanisms beyond its known estrogen-mimicking properties, requiring further research to understand why it might protect against hormone receptor-negative tumors.
2019
Epidemiol
A large US study of nearly 51,000 women found that exposure to airborne toxic metals, particularly mercury, cadmium, and lead, was associated with increased postmenopausal breast cancer risk, with mercury showing the strongest effect at 30% increased risk for the highest exposure levels. When examining the combined effect of 10 different airborne metals together, the mixture was associated with elevated postmenopausal breast cancer risk, with mercury, lead, and cadmium contributing most to this increased risk. These findings suggest that environmental exposure to toxic metals through air pollution may be an important and underrecognized risk factor specifically for breast cancer in postmenopausal women.
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
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.
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
Breast Cancer Res
A nested case-control study within the French E3N-Generations cohort examined 523 breast cancer cases and 523 matched controls to investigate whether thirteen metabolic health biomarkers mediate the relationship between exposure to three air pollutants (nitrogen dioxide, PCB153, and benzo[a]pyrene) and breast cancer risk. The study found that benzo[a]pyrene exposure was associated with a significant 2.32-fold increased breast cancer risk (highest vs. lowest quartile), PCB153 showed inconsistent positive associations, and nitrogen dioxide showed no association; among biomarkers, estradiol was associated with increased breast cancer risk (OR = 1.22 per SD). Four-way decomposition mediation analysis revealed suggestive evidence that albumin, HDL and LDL cholesterol, parathormone, and estradiol may partially mediate the associations between all three pollutants and breast cancer risk, though findings were limited by statistical power. These results provide preliminary mechanistic insights suggesting that air pollutants may influence breast cancer risk through alterations in metabolic biomarkers—particularly lipid metabolism and hormone regulation—though larger studies are needed to confirm these pathways and establish the clinical significance of these mediating effects in the relationship between environmental exposures and breast cancer development.
2023
Cancer Epidemiol Biomark Prev
A pooled analysis of six European cohorts including 199,719 women followed for 3.6 million person-years found that long-term exposure to fine particulate matter (PM₂.₅) was associated with a 6% increased breast cancer risk per 5 μg/m³ increase. The association was strongest among middle-aged women (ages 50-54) and never-smokers, and notably, the cohorts studied represented the lower range of air pollution concentrations in Europe, suggesting that even relatively low levels of air pollution may contribute to breast cancer risk. These findings add to mounting evidence that air pollution—particularly fine particulate matter from traffic, industry, and combustion sources—is an environmental breast cancer risk factor operating independently of established risk factors, with important implications for public health policy, urban planning, and air quality regulations aimed at reducing population-level cancer burden, especially given that air pollution exposure is largely involuntary and affects entire populations.
2023
Environ Res
A nationwide Danish study of 55,745 breast cancer cases matched with controls found that each 10 μg/m³ increase in fine particulate matter (PM₂.₅) air pollution exposure over 20 years was associated with a 21% increased breast cancer risk, with the association particularly strong (32% increased risk) among women diagnosed before age 55. While elemental carbon and nitrogen dioxide also showed modest associations initially, these disappeared in multi-pollutant models, suggesting PM₂.₅ is the primary air pollutant linked to breast cancer risk. These findings add breast cancer to the growing list of cancers associated with air pollution exposure and suggest that younger women may be especially vulnerable, though the authors caution that unmeasured confounding factors may influence the results.
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.
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.
2021
Sci Rep
A nested case-control study of 4,401 breast cancer cases and 4,401 matched controls from the French E3N cohort found no overall association between long-term airborne cadmium exposure and breast cancer stage or tumor grade, but identified a striking 240% increased risk of invasive tubular carcinoma (ITC)—a specific breast cancer subtype—among women in the highest versus lowest quintile of cadmium exposure. The dose-response analysis suggested a linear relationship between cadmium exposure and ITC risk specifically, though no associations were found for other histological subtypes or more advanced disease. These findings suggest that cadmium’s estrogenic properties may selectively promote certain breast cancer subtypes rather than broadly increasing all breast cancer risk, highlighting the importance of examining cancer heterogeneity in environmental exposure studies and raising concerns about air pollution from industrial sources, waste incineration, and fossil fuel combustion that release cadmium into the environment.