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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
Environ Res
This case-control study of 5587 women with breast cancer and age-matched controls for which there was data on maternal employment. Maternal occupational exposure to diesel exhaust (OR=1.13, 95%CI,1.01-1.27) and bitumen fumes (OR=1.51., 95%CI,1.00-2.26) was associated with breast cancer. Further, exposures to diesel exhaust (OR=1.23, 95%CI, 1.01-1.50) were more strongly associated with ER- tumors than with ER+ tumors.
2021
Cancer Epi
This study of nearly 48,000 women found that frequent use of chemical hair straighteners and perms during adolescence (ages 10-13) was associated with more than double the risk of premenopausal breast cancer, though no increased risk was seen for postmenopausal breast cancer. Black women who used permanent hair dye during adolescence had a 77% increased breast cancer risk, though permanent dye use was uncommon overall in the study population. The findings are particularly concerning because adolescence is a critical developmental window when breast tissue may be more vulnerable to chemical exposures, and these hair products contain hormonally active and potentially carcinogenic compounds that may have long-lasting effects on breast cancer risk decades later.
2019
J Natl Cancer Inst
This study of over 700 women found that DDT exposure was associated with increased breast cancer risk through age 54, but the timing of first exposure mattered critically: women first exposed to DDT after infancy had nearly triple the risk of early postmenopausal breast cancer (ages 50-54), while women first exposed during infancy through puberty had nearly four times the risk of premenopausal breast cancer (before age 50). These findings suggest there are specific windows of vulnerability when DDT exposure has the strongest impact on future breast cancer risk, with effects that can persist for decades. The results support the idea that DDT acts as an endocrine disruptor affecting breast tissue throughout a woman’s life—from before birth through menopause—even though DDT was banned in the U.S. in 1972, highlighting the long-term health consequences of early-life chemical exposures.
2024
Cancer Epidemiol
A large collaborative study of 609,880 women from 16 prospective studies, including 9,956 breast cancer cases before age 55, examined when the relationship between body mass index (BMI) and breast cancer risk transitions from protective (before menopause) to harmful (after menopause). During the critical age window of 45-55 years, the study found that a five-unit BMI increment remained associated with reduced or neutral breast cancer risk across all menopausal status groups: HR=0.87 for premenopausal women, HR=1.00 for women after natural menopause, HR=0.99 after interventional loss of ovarian function, and HR=0.88 after hysterectomy without bilateral oophorectomy. The findings indicate that the well-documented reversal from BMI being protective to being a risk factor for breast cancer occurs after age 55, later than previously thought, suggesting that the transition to increased risk with higher BMI is not directly tied to the menopausal transition itself but occurs in the years following menopause. This timing provides important insight into how adiposity influences breast cancer risk across the lifespan and suggests that the hormonal and metabolic changes associated with higher BMI have different effects on breast tissue depending on age and years since menopause.
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.
2020
Repro Toxicol
A 54-year follow-up study of 102 breast cancer cases and 310 matched controls among 9,300 daughters born 1959-1967 in the Child Health and Development Studies cohort found that high maternal perinatal levels of N-ethyl-perfluorooctane sulfonamido acetic acid (EtFOSAA, a precursor to PFOS) combined with high maternal cholesterol predicted a 3.6-fold increased breast cancer risk in daughters by age 52 (95% CI: 1.1-11.6), while maternal PFOS alone was paradoxically associated with decreased risk. These robust findings—consistent across alternative modeling approaches and independent of other maternal factors—demonstrate that prenatal exposure to specific PFAS compounds during critical developmental windows can influence breast cancer risk decades later, revealing multigenerational health consequences of persistent environmental chemicals. The results emphasize the critical importance of studying internal PFAS doses and chemical mixture exposures during vulnerable early-life periods for breast cancer prevention, particularly as current and future generations face continued ubiquitous exposure to these persistent compounds, though experimental validation and replication in additional epidemiological cohorts are needed to confirm causality and inform prevention strategies.
2020
Env Health Persp
A systematic review and meta-analysis of 14 studies found that spending one or more hours per day in the sun during summer months was associated with a 16% reduced breast cancer risk compared to less than one hour daily, with similar protective effects observed for both 1-2 hours and more than 2 hours of sun exposure. Sun exposure during adolescence appeared particularly protective (17% risk reduction), while exposure after age 45 showed no significant benefit, and interestingly, ambient UV radiation levels alone were not associated with breast cancer risk. These findings suggest that active sun exposure—likely through Vitamin D production—may offer modest breast cancer protection when obtained regularly during youth and early adulthood, though the results should be balanced against known skin cancer risks from excessive UV exposure.
2020
Mol Cell Endocrinol
A review of EPA pesticide registration documents found that 28 pesticides cause mammary tumors in animals and five alter mammary gland development, yet the agency’s risk assessments often dismiss these findings or don’t evaluate their implications for breast cancer risk. Many of these pesticides work through hormone-disrupting pathways that could affect breast tissue, including common chemicals like malathion, atrazine, and triclopyr. The authors argue that current testing guidelines don’t adequately assess effects on the mammary gland and call for re-evaluation of several widely-used pesticides based on stronger standards informed by breast cancer biology.
2019
Int J Env Res Public Health
A French population-based case-control study (CECILE study) of 695 breast cancer cases and 1,055 controls measured plasma levels of organochlorine compounds (OCs)—p,p’-DDE and PCB153—at the time of diagnosis and used a physiologically-based pharmacokinetic (PBPK) model to estimate PCB153 exposure levels during adolescence (ages 11-20), when breast tissue may be particularly susceptible to hormonal disruption. The study found no clear association between measured OC levels at diagnosis and breast cancer risk overall, though there was a trend toward decreasing breast cancer odds ratios with increasing OC levels in women aged 50 and over; similarly, negative associations were observed between breast cancer and estimated adolescent PCB153 exposure levels. The PBPK modeling revealed that women born after 1960 had the highest estimated PCB153 exposures during adolescence (coinciding with peak environmental contamination), while older women had very low adolescent exposures, yet the unexpected negative associations between OC levels and breast cancer risk remained unexplained and may represent study artifacts. Despite these puzzling findings, the study demonstrates that PBPK models can be valuable tools in epidemiological research for back-estimating exposures during critical developmental windows, which could help address important questions about how early-life environmental exposures influence cancer risk decades later.
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.
2018
Environ Res
A systematic review of 158 studies examining environmental chemicals and breast cancer found the strongest evidence for increased risk from exposures during critical developmental periods (in utero, adolescence, pregnancy) to DDT, dioxins, PFOSA, air pollution, and occupational solvents, with risk estimates ranging from 1.4 to 5 times higher. A landmark 50-year study that captured DDT exposure during windows of breast development showed particularly elevated risks, while research on genetic variations found that women with certain DNA repair gene variants had higher breast cancer risk from PAH (polycyclic aromatic hydrocarbon) exposure. However, most studies failed to assess exposure timing during biologically relevant windows of susceptibility, and many current-use chemicals in consumer products remain inadequately studied, with major challenges including reconstructing decades-old exposures and measuring rapidly metabolized chemicals in complex real-world mixtures.
2014
Aging Dis
The following review article described how exposure to EDCs during early development can lead to adverse health outcomes later in life through epigenetic mechanisms based on existing studies. The article emphasizes that exposure to EDCs during critical developmental periods such as in utero and early childhood, can have lasting effects on health since, during these periods, the body’s systems are particularly vulnerable to exposures. Additionally, the article finds a link between early-life exposure to EDCs and increased risk of various health issues later on in life, including metabolic disorders and cancers. The suspected mechanism by which these chemicals do this is thought to be mediated by epigenetic changes, which are changes to gene expression without altering the DNA. Therefore, the article emphasizes understanding how exposure during such sensitive periods in development can pose such drastic problems later on in life.