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2025
J Occup Environ Med
A French case-control study of 1,230 breast cancer patients and 1,315 controls examined occupational exposure to 49 common workplace chemicals and found elevated breast cancer risk associated with 12 agents. Women with the highest cumulative exposure showed increased risk ranging from 33% to 139% for chemicals including synthetic and natural fibers, plastics, organic dyes, nitrogen oxides, anesthetic gases, and various industrial compounds. The associations were generally stronger in premenopausal women compared to postmenopausal women. These findings suggest certain occupational exposures may play a role in breast cancer development, though larger studies with more detailed exposure assessments are needed to confirm these results.
2025
Environ Health Perspect
An updated analysis of the largest cohort of ethylene oxide (EtO)-exposed workers—7,549 women employed ≥1 year at 13 U.S. facilities followed from 1960-2021 (181 breast cancer deaths)—found that cumulative EtO exposure was strongly associated with elevated breast cancer mortality, with workers accruing 3,650 ppm-days of exposure (equivalent to 10 years at 1 ppm) having over three times the breast cancer death rate compared to unexposed workers (RR = 3.15; 95% CI: 1.78-5.60) using a 20-year lag model. This association remained robust in a subcohort with interview data on breast cancer risk factors after matching on potential confounders (RR = 3.22; 95% CI: 1.52-7.13), with evidence of variation by time since exposure and exposure rate. These findings provide strong evidence that EtO is a human breast carcinogen and support recent emission reduction proposals, raising serious public health concerns given the high prevalence of breast cancer, large numbers of occupationally exposed workers, and potential for widespread environmental exposure from industrial facilities, with elevated risks observed even in low exposure ranges highlighting the need for stringent exposure controls and environmental monitoring.
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
Br J Cancer
This comprehensive meta-analysis of 63 studies found that women who never smoked but were exposed to secondhand smoke had a 24% increased risk of breast cancer, with the risk rising to 45% in some exposure settings. The breast cancer risk increased with greater exposure duration, intensity, and cumulative exposure—women exposed to secondhand smoke for 40 years had a 29% increased risk, while those exposed to the equivalent of 20 cigarettes per day had a 38% increased risk. The analysis showed the strongest associations for home exposure (17% increased risk) and combined home or workplace exposure (24% increased risk), demonstrating clear dose-response relationships where more exposure meant higher breast cancer risk. These findings are particularly important for public health policy because they show that even non-smokers face significant breast cancer risk from breathing others’ tobacco smoke, supporting the need for comprehensive smoke-free laws in homes, workplaces, and public spaces.
2024
Med Lav
A meta-analysis of 23 cohort and case-control studies found that occupational benzene exposure was associated with an 8% increased breast cancer risk overall, with high-level benzene exposure showing a stronger 35% increased risk. The association was consistent for cancer incidence (8% increased risk) though not statistically significant for cancer mortality, and significant heterogeneity was detected across studies based on sex, publication year, study design, quality, and industry of employment. These findings suggest that benzene—a recognized carcinogen primarily studied in relation to leukemia—may also increase breast cancer risk in occupationally exposed workers, though the authors acknowledge that bias, confounding factors, and publication bias limit the strength of causal inference, highlighting the need for high-quality prospective studies with detailed exposure assessment to confirm these associations and inform workplace safety standards for the millions of workers potentially exposed to benzene in petroleum, chemical manufacturing, automotive repair, and other industries.
2024
Environ Res
This large Danish study of over 5,500 breast cancer cases found that daughters whose mothers worked in horticulture (greenhouse and nursery work) before conception or during pregnancy had significantly increased breast cancer risk—79% higher for estrogen receptor-positive tumors and 148% higher for estrogen receptor-negative tumors. The associations were particularly strong for maternal horticulture work compared to paternal work, suggesting that pesticide and chemical exposures during critical windows of fetal development may affect daughters’ breast cancer risk decades later. These findings are concerning because horticultural workers have high exposure to pesticides and other agricultural chemicals, and the study suggests that even preconceptional maternal exposure—before pregnancy begins—may influence a daughter’s future cancer risk, highlighting the potential for intergenerational effects of occupational chemical exposures.
2023
Asian Pac J Cancer Prev
A study of 360 participants found that agricultural workers exposed to pesticides who carry genetic variations that impair their body’s ability to detoxify chemicals (null mutations in GSTT1 and GSTM1 genes) had substantially increased cancer risk, with 4-7 times higher odds of developing lymphoma or breast cancer compared to those with normal detoxification genes. The study also found elevated markers of oxidative stress (cellular damage) in farm workers with these genetic variants who developed leukemia, suggesting that pesticide exposure combined with impaired detoxification capacity triggers cancer development. These findings indicate that certain genetic profiles make agricultural workers particularly vulnerable to pesticide-related cancers, highlighting the importance of protective measures for farm workers and potential genetic screening to identify high-risk individuals.
2023
Environ Int
This cohort study examined associations of metals to multiple cancer sites. Participants were from a cohort study of worker from the French national energy company who lived in semi-urban or rural locations. The researchers estimated metal exposures from moss biomonitoring (part of a larger effort to measure air pollution). Estimated exposures to metals were associated any cancer (bladder, lung, breast or prostate), but no estimated exposures were associated with breast cancer alone. Some estimates appraoched HR >1 for breast cancer.
2022
Environ Sci Poll Res
This meta-analysis of 24 studies found that women occupationally exposed to organic solvents (chemicals used in manufacturing, cleaning, and industrial processes) had an 18% increased risk of breast cancer compared to unexposed workers, with the association being particularly strong in postmenopausal women (35% increased risk) and European workers. Organic solvents are commonly found in workplaces involving paint, adhesives, dry cleaning, and manufacturing, and the increased risk was consistent across both large cohort studies and case-control studies. These findings suggest that workplace exposure to organic solvents is an important and preventable occupational health hazard that contributes to breast cancer risk, especially for women working in industries that regularly use these chemicals.
2022
Environ Res
A study of 6,247 greenspace workers (landscapers, gardeners, groundskeepers) from the French AGRICAN cohort found significantly elevated cancer risks compared to farmers and non-agricultural workers. Male greenspace workers showed 15% higher overall cancer incidence, with particularly elevated risks for prostate cancer (21% increase), thyroid cancer (184% increase), testicular cancer (298% increase), and skin melanoma (115% increase), while female greenspace workers had a 71% increased risk of breast cancer. The study also found that greenspace workers reported more allergic diseases and, among males, more depression compared to other occupational groups. These findings highlight that greenspace workers face distinct occupational health risks, likely related to pesticide exposure and other workplace hazards, and should be studied separately from agricultural workers rather than being grouped together in research.
2021
Cancer Epidemiol Biomarkers Prev
A Spanish case-control study of 1,738 breast cancer cases and 1,910 controls found that occupational heat exposure was associated with a 22% increased risk of breast cancer among women who had ever been exposed. The study found significant dose-response relationships, with risk increasing with both cumulative heat exposure and duration of exposure, and particularly strong associations for hormone receptor-positive breast cancer (38% increased risk). The associations were strongest when not adjusted for detergent exposure, suggesting potential confounding or interaction between these workplace exposures. These findings suggest that chronic workplace heat stress may be a previously underrecognized occupational risk factor for breast cancer, though further research is needed to confirm these results and understand potential interactions with other workplace exposures.
2021
Scand J Work Environ Health
This large Danish study of over 38,000 women with breast cancer found that occupational exposure to diesel exhaust was associated with a modestly increased risk of estrogen receptor-negative breast tumors in women under age 50, with the risk increasing with longer duration and higher levels of exposure. No significant associations were found for overall breast cancer risk or for exposure to polycyclic aromatic hydrocarbons (PAHs). These findings suggest that workplace diesel exhaust exposure may be particularly relevant for early-onset, harder-to-treat forms of breast cancer, highlighting the importance of protecting workers from diesel fumes.
2020
Int Arch Occup Environ Health
This Swedish study of 2,400 postmenopausal women found that those exposed to chemicals in the workplace had a 59% increased risk of breast cancer, with the risk increasing with longer duration of exposure. Women exposed to chlorinated hydrocarbon solvents or oil mist for more than 10 years had approximately triple the breast cancer risk compared to unexposed women. The study used individualized exposure assessments based on specific work tasks rather than just job titles, providing stronger evidence that workplace chemical exposures—particularly to organic solvents and oil mist commonly found in manufacturing and industrial settings—may be important contributors to breast cancer risk.
2019
Occ Environ Med
This Canadian study of over 2,200 women found that occupational exposure to polycyclic aromatic hydrocarbons (PAHs)—chemicals released from burning materials like coal, oil, and gasoline—increased breast cancer risk by 32%, with higher risks seen in women exposed to high levels for more than 7 years. The association was particularly strong among women with a family history of breast cancer, where prolonged high exposure nearly tripled the risk. These findings suggest that workplace PAH exposure may be an important and preventable breast cancer risk factor, especially for women with genetic susceptibility to the disease.
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.
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
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.
2000
Am J Indust Med
This Danish nationwide study of 230 male breast cancer cases found that men occupationally exposed to gasoline and its combustion products had a 2.5 times higher risk of breast cancer, with the risk rising to 5.4 times higher among men first exposed before age 40. Gasoline contains several known carcinogens including benzene and produces cancer-causing combustion products, which may explain this elevated risk. Since male breast cancer is rare but shares similar biology with female breast cancer, these findings suggest that gasoline exposure may also increase breast cancer risk in women and warrant further investigation in female workers.
2024
Ecotoxicol Public Health
A case-control study of 758 women in southwestern Paraná, Brazil—a region with intensive pesticide use and 41% higher breast cancer rates than the national average—found that even women not working in fields but handling contaminated equipment and laundry tested positive for Glyphosate, atrazine, and 2,4-D. While the overall breast cancer risk association with pesticide exposure was non-significant after adjustment (OR = 1.30), exposed women had significantly higher risk of lymph node metastasis (OR = 2.19; 95% CI: 1.31-3.72), indicating more aggressive disease. These findings suggest pesticide exposure in agricultural communities may be associated with development of more aggressive breast cancer, highlighting the need for monitoring both occupational and household pesticide exposure in rural populations.
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.
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
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
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.
2021
BMC Women's Health
A meta-analysis of 26 studies including over 1.3 million participants found that short-term night-shift work (<10 years) was associated with a 13% increased breast cancer risk, but surprisingly, long-term night-shift work (≥10 years) showed no statistically significant increased risk (8% increase, not significant). Flight attendants with long overnight flights showed elevated breast cancer risk, though unmeasured confounders may have influenced these results, and the increased risk in short-term workers was most robust in case-control studies that adjusted for reproductive factors and family history. The paradoxical finding that short-term but not long-term night-shift work showed significant associations contradicts the expected dose-response relationship and may reflect healthy worker bias (where women susceptible to night-shift effects leave such work before reaching 10 years), methodological limitations in measuring long-term exposures, or unmeasured confounding factors that accumulate differently over time.
2021
Int J Environ Res Pubilc Health
A case-control study of 494 breast cancer cases and 515 healthy controls in Poland’s Lodz region (2015-2019) found that night shift work was the third most important breast cancer risk factor after high BMI and short/no breastfeeding, ranking before early menstruation, late menopause, nulliparity, and smoking. Night work increased breast cancer risk 2.34-fold, with high-intensity night work showing an even greater 2.66-fold increase, and the harmful effects were influenced by intensity, frequency, rotation patterns, and cumulative years of night shift exposure. The findings support the IARC’s 2019 classification of night shift work as probably carcinogenic (Group 2A) and emphasize the need for ergonomic recommendations to minimize breast cancer risk among night shift workers through optimized scheduling practices.
2020
Int J Environ Res Public Health
A case-control study of 494 breast cancer patients and 515 healthy women in Poland found that night-shift work was associated with a 161% increased breast cancer risk, even after adjusting for other cancer risk factors including BMI, smoking, reproductive history, age, location, and education. While 51.9% of breast cancer cases had a history of shift work compared to 34.1% of controls (108% increased risk overall), further analysis revealed that only night shifts—not other shift patterns—significantly increased risk, showing a 120% increased risk after adjustment for confounders. Given that Poland has a high percentage of night-shift workers and the dramatically elevated cancer risk observed, the authors call for government action on prophylactic measures and workplace policies to protect this vulnerable population from occupational cancer hazards.
2020
Medicina
A systematic review of 12 studies examining nurses and shift work found that most studies showed an association between breast cancer and consecutive rotating night shifts prolonged over time, with risk increasing particularly during early adulthood and after 5 or more years of working 6 or more consecutive night shifts. The review identified disruption of circadian rhythm and alterations in peripheral clock genes and reproductive hormones as key mechanisms linking night shift work to breast cancer development, with potential roles for melatonin suppression and epigenetic changes including telomere alterations. These findings are particularly concerning given that nursing is a predominantly female profession requiring 24-hour staffing, suggesting the need for workplace policies that limit consecutive night shifts and total years of night work exposure, along with further research to establish definitive causal mechanisms and identify protective strategies for the millions of women working night shifts globally.
2019
J Occup Environ Med
This case control study was conducted among Hispanic women agricultural workers who are exposed to pesticides. Chemicals associated with BC risk included organophosphates, organochlorines, and a phthalimide, Captan. The study concluded that agricultural work may be associated with increased BC risk in female Hispanic farm workers.
2019
Int Arch Occup Environ Health
A systematic review and meta-analysis of 30 studies (with meta-analyses conducted on 13 studies) examined the association between occupational ethylene oxide (EO) exposure and risk of lympho-hematopoietic cancers (LHC) and breast cancer. The overall pooled meta-relative risk was 1.48 (95% CI: 1.07-2.05) for LHC and 0.97 (95% CI: 0.80-1.18) for breast cancer, with meta-RRs for LHC among EO production workers at 1.46 and sterilization workers at 1.07, neither reaching statistical significance. Notably, a clear temporal trend emerged showing substantially higher LHC risk estimates in earlier studies from the 1980s (meta-RR = 3.87) that progressively declined in more recent decades, with studies from the 2000s and 2010s showing meta-RRs of 1.05 and 1.19 respectively, neither statistically significant. The authors conclude that the most informative and methodologically rigorous epidemiological studies published in recent decades do not support an association between occupational ethylene oxide exposure and increased risk of either lympho-hematopoietic cancers or breast cancer, suggesting that earlier positive findings may have been influenced by methodological limitations, exposure misclassification, or confounding factors that have been better controlled in more recent research.
2018
Environ Int
A study of 54 female cashiers in South Korea found that handling thermal paper receipts without gloves doubled their urinary BPA levels during work shifts, but wearing gloves completely prevented this increase in exposure. Higher BPA levels were associated with elevated fasting insulin and insulin resistance, markers of metabolic dysfunction that can lead to diabetes and cardiovascular disease. The findings demonstrate that cashiers face significant occupational BPA exposure from receipt handling and that simple protective measures like wearing gloves can effectively eliminate this exposure route, offering an immediate and practical intervention to protect workers’ health.
2011
J Steroid Biochem Mol Biol
Bisphenol A (BPA) is a widely produced chemical used in plastics and food container linings, with frequent human exposure due to its leaching into food and beverages. BPA, a known endocrine disruptor, was initially deemed a weak estrogen but has shown potency comparable to estradiol, a form of estrogen, shown to affect multiple hormonal pathways. Studies on rodents reveal adverse effects at levels below and at the current acceptable daily intake, raising concerns about human health impacts about concentration. BPA’s estrogenic effects highlight the importance of investigating BPA’s complex, widespread impacts on health.
2020
Epidemiol
This study of Norwegian offshore petroleum workers found that both male and female workers had increased overall cancer risk (7% and 13% increased risk, respectively), with particularly notable elevations for specific cancers. Male workers showed more than double the risk of pleural cancer (138% increase) and male breast cancer (118% increase), plus a 20% increased risk of prostate cancer, while female workers had 62% increased risk of melanoma and nearly quadruple the risk of acute myeloid leukemia (276% increase). These findings suggest that occupational exposures in the offshore petroleum industry—including potential exposure to chemicals, radiation, shift work, and other workplace hazards—may contribute to elevated cancer risks across multiple organ sites in both men and women.