Household and occupational exposure to pesticides and risk of breast cancer

Pesticide exposure and increased breast cancer risk in women population studies

Pesticide exposure is emerging as a risk factor for various human diseases. Breast cancer (BC) is a multifactorial disease with known genetic and non-genetic risk factors. Most BC cases are attibutable to non-genetic risk factors, with a history of adverse environmental exposures playing a significant role. Pesticide exposure can occur at higher levels in female populations participating in rural activities such as spraying of pesticides in the field, unprotected handling of pesticides at home, and washing of contaminated clothes. Exposure can also be significant in the drinking water of certain populations. Here, we reviewed the literature on women's exposure to pesticides and the risk of BC. We summarize the main links between pesticide exposure and BC and discuss the role of dose and exposure context, as well as potential mechanisms of toxicity. Overall, reports reviewed here have documented stronger associations between higher levels of exposure and BC risk, including documenting direct and acute pesticide exposure in certain female populations. However, discrepancies among studies regarding dose and mode of exposure may result in misunderstandings about the risks posed by pesticide exposure. Plausible mechanisms linking pesticides to breast cancer risk include their impacts as endocrine disruptors, as well as their roles as genotoxic agents, and modulators of the epigenome. Besides establishing links between pesticide exposure and breast cancer, the literature also highlights the critical need to understand the routes and doses of women's exposure to pesticides and the specific associations and mechanisms that are determinants of disease etiology and prognosis.

Brief research report pesticide occupational exposure leads to significant inflammatory changes in normal mammary breast tissue

Studies have documented the high occurrence of several tumors, including female breast cancer, in populations occupationally exposed to pesticides worldwide. It is believed that in addition to direct DNA damage, other molecular alterations that indicate genomic instability are associated, such as epigenetic modifications and the production of inflammation mediators. The present study characterized the profile of inflammatory changes in the breast tissue of women without cancer occupationally exposed to pesticides. In samples of normal breast tissue collected during biopsy and evaluated as negative for cancer by a pathologist, oxidative stress levels were assessed as inflammatory markers through measurements of lipoperoxides and total antioxidant capacity of the sample (TRAP) by high-sensitivity chemiluminescence, as well as levels of nitric oxide (NOx) metabolites. The levels of inflammation-modulating transcription factors PPAR-γ (peroxisome proliferator-activated receptor gamma) and NF-κB (nuclear factor kappa B) were also quantified, in addition to the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin 12 (IL-12). The levels of lipoperoxides, TRAP, and NOx were significantly lower in the exposed group. On the other hand, PPAR-γ levels were increased in the breast tissue of exposed women, with no variation in NF-κB. There was also a rise of TNF-α in exposed women samples without significant variations in IL-12 levels. These findings suggest an inflammatory signature of the breast tissue associated with pesticide exposure, which may trigger mechanisms related to mutations and breast carcinogenesis.

A salting-out assisted liquid-liquid extraction method for 25 emerging pesticides in follicular fluid

Emerging pesticides of neonicotinoids (NEOs) and "Universal Pesticides" (UPs) are a growing global concern due to their growing commercial importance and potential risks to human health. The currently available analytical methods for these pesticides in biomonitoring were usually tailored for limited number of analytes, or were time consuming and costly. In this study, an efficient and sensitive method for the analysis of 16 NEOs and nine UPs in human follicular fluid (FF) was developed by using a salting-out assisted liquid-liquid extraction (SALLE) method and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Method performance was evaluated by calibration linearity (r > 0.99), sensitivity at limits of quantification (0.01-0.50 ng/mL), accuracy at relative recoveries (81-117%) and precision at relative standard deviations (≤16%). The developed method was further validated by analyzing 21 human FF samples that were collected from a hospital in Guangzhou, China. Among the 25 study analytes, two NEOs and six UPs had their detection rates over 85% and medians at 0.048-0.808 ng/mL in the FF samples. Considering the well-known toxicity of these pesticides and their metabolites, it is urgent to figure out exposure profiles of study pesticides and potential reproductive risk for women. To the best of our knowledge, this study is the first to develop and apply the SALLE method in the extraction of 16 NEOs and nine UPs simultaneously in human FF.

Breast cancer and occupational exposures: an integrative review of the literature

Occupational factors can lead to breast cancer, though the relationship between these variables is not well established. The objective of this study was to search the relevant literature for information on the association between breast cancer and exposure to occupational risk factors. For that purpose, electronic databases were searched using the following keywords: breast cancer and occupational exposures. A total of 40 articles published in the 10-year period from 2009 to 2019 were included in this review. Workers exposed to metals such as cadmium, chemical products, radiation and night work were more susceptible to breast cancer. The findings showed significant evidence to support an association between breast cancer and some chemical products, ionizing radiation and night work. However, most studies have difficulty establishing a causal relationship between these variables, pointing to the need for further investigation of these issues.

Pesticides in the urban environment: A potential threat that knocks at the door

Pesticides play a pivotal role in controlling pests and disease infestations not only in urban agriculture but also in non-agricultural settings. Several pesticides like herbicides, insecticides, fungicides, rodenticides, etc. are applied unintentionally at higher concentrations even in small urban areas such as lawns, gardens and impermeable surfaces. Consequent to their indiscriminate use, both extensively and intensively, in the urban areas, contamination of pesticides poses a serious threat to the environment, living organisms and food safety. Although the fate and ecological effects of pesticides and their residues have been thoroughly understood in agricultural soils, information available in the literature on the impact of these contaminants in the urban environment is very limited and fragmentary. In fact, the fate and behaviour of pesticide residues in the urban environment are distinct from those in other ecosystems since the soils in urban areas greatly vary in their physico-chemical properties. Development of sustainable and eco-friendly approaches for remediation of even urban soils contaminated with pesticides is therefore greatly warranted. Thus, the present critical review is the first single source that provides updated knowledge on the sources, nature and extent of pesticide pollution in the urban environment, and the ecological and human health effects of pesticides and their residues. The potential of nano-encapsulation of pesticides for their application in urban settings has also been discussed.

[Impact of endocrine disrupting pesticides on breast cancer]

Of the 800 pesticides used worldwide, about 650 can affect the functioning of the endocrine system: endocrine disrupting pesticides (EDPs). Dietary or environmental exposure to EDPs is a concern, as their presence is currently demonstrated in most biological fluids. Some EDPs are prohibited, classified as carcinogenic, others are "probable" or "possible" carcinogens when there is limited evidence of their tumor effect. The impact of EDPs on breasts is not well known to date. However, since most EDPs have a long half-life and are lipophilic, breasts, composed mainly of adipose tissue, are a suitable site for their concentration. The objective of our review was to analyze the impact of EDPs related to our environmental exposure on breast cancer risk, through an analysis of recent literature, including epidemiological and biological data. Our review showed a positive association between the presence of EDPs and breast cancer, especially among women farmers or EDPs users but also in the general population. Studies on breast tumors have found a higher concentration of EDPs in estrogen-sensitive tumors. As for mortality, studies are contradictory, but confirm the dangerousness of some EDPs. The different series analyzed have several limitations, such as the low number of EDPs evaluated, small numbers and insufficient follow up. The potentiating effect of different EDPs used concomitantly and the window of exposure to these substances are parameters to be assessed.

A case-control study of breast cancer risk and ambient exposure to pesticides

Background:

While the estrogenic properties of certain pesticides have been established, associations between pesticide exposure and risk of breast cancer have been inconsistently observed. We investigated the relation between pesticide exposure and breast cancer risk using methods capable of objectively assessing exposure to specific pesticides occurring decades before diagnosis.

Methods:

A case–control study was conducted to evaluate the risk of postmenopausal breast cancer associated with historic pesticide exposure in California’s Central Valley, the most agriculturally productive region in the United States where pesticide drift poses a major source of nonoccupational exposure. Residential and occupational histories were linked to commercial pesticide reports and land use data to determine exposure to specific chemicals. Cases (N = 155) were recruited from a population-based cancer registry, and controls (N = 150) were obtained from tax assessor and Medicare list mailings.

Results:

There was no association between breast cancer and exposure to a selected group of organochlorine pesticides thought to have synergistic endocrine-disrupting potential; however, breast cancer was three times as likely to occur among women exposed to chlorpyrifos compared with those not exposed, after adjusting for exposure to other pesticides including organochlorines (OR = 3.22; 95% CI = 1.38, 7.53).

Conclusions:

Organophosphate pesticides, such as chlorpyrifos, have rarely been evaluated in studies of breast cancer risk. Additional research is needed to confirm these findings and to better understand the underlying mechanisms given that chlorpyrifos has been detected in local air monitoring at levels of concern for residents living in the agricultural regions where it is used.

Self-reported residential pesticide use and survival after breast cancer

INTRODUCTION

Previous investigations found elevated mortality after breast cancer in association with biomarkers of persistent organochlorine pesticides in non-occupationally exposed women. We hypothesized that lifetime residential pesticide use, which includes persistent and non-persistent pesticides, would also be associated with increased mortality after breast cancer.

METHODS

A population-based cohort of 1505 women with invasive or in situ breast cancer was interviewed in 1996-1997, shortly after diagnosis, about pre-diagnostic lifetime residential pesticide use. Participants were followed for mortality through 2014 (595 deaths from any cause and 236 from breast cancer, after 17.6 years of follow-up). Pesticides were examined as 15 individual categories; a group of seven used for lawn and garden purposes; a group of eight used for nuisance-pest purposes; and all combined. Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause and breast cancer-specific mortality. Modification by estrogen receptor (ER) status, body mass index, and long-term residence was examined.

RESULTS

Ever use (HR = 0.77, 95%CI = 0.63-0.95) and higher lifetime applications (4th quartile: HR = 0.62, 95%CI = 0.47-0.81, ptrend = 0.3) of the lawn and garden group of pesticides were inversely associated with all-cause mortality, compared to never use. The inverse association for lawn and garden pesticide use was limited to ER positive (vs. negative) tumors (pinteraction = 0.05). Nuisance-pest pesticides, and all groups combined, were not associated with all-cause or breast cancer-specific mortality.

CONCLUSIONS

Contrary to our hypothesis, lifetime residential use of lawn and garden pesticides, but not all combined or nuisance-pest pesticides, was inversely associated with all-cause mortality after breast cancer.

Respiratory and Dermal Symptoms and Raised Serum Concentrations of Biomarkers of Oxidative Stress among Pesticide Retailers

BACKGROUND

Recently concern has been raised regarding possible health effects resulting from exposure of a group of pesticide retailers to chemicals they handle.

OBJECTIVE

To investigate the prevalence of respiratory and dermal symptoms, as well as biomarkers of oxidative stress, among pesticide retailers and to compare them with those of an unexposed comparison group.

METHODS

70 male pesticide retailers and 64 male construction workers (served as the comparison group) were investigated. Blood samples were taken from all participants to assess the biomarkers of oxidative stress. A data sheet and the European Community Respiratory Health Survey II questionnaire were used to determine the prevalence of dermal and respiratory disorders, respectively.

RESULTS

After adjusting for age, weight, height, education level, job tenure, average daily work, presence of family history of respiratory diseases, marital status, smoking status, and number of cigarettes smoked per day, we found that wheezing (OR 4.07, 95% CI 1.17 to 14.17), cough (OR 3.38, 95% CI 1.15 to 9.98), and mucus hypersecretion (OR 3.66, 95% CI 1.45 to 9.05) were significantly more prevalent among pesticide retailers compared with the comparison group. The prevalence of tingling and dryness of skin exposed individuals was significantly higher than unexposed participants. The mean serum concentrations of glutathione and malondialdehyde in the exposed group were significantly higher than those in the comparison group.

CONCLUSION

Occupational exposure to low doses of a mixture of pesticides by retailers was associated with increased prevalence of dermal and respiratory symptoms as well as raised concentrations of biomarkers of oxidative stress.

Environmental chemicals and breast cancer: An updated review of epidemiological literature informed by biological mechanisms

BACKGROUND

Many common environmental chemicals are mammary gland carcinogens in animal studies, activate relevant hormonal pathways, or enhance mammary gland susceptibility to carcinogenesis. Breast cancer's long latency and multifactorial etiology make evaluation of these chemicals in humans challenging.

OBJECTIVE

For chemicals previously identified as mammary gland toxicants, we evaluated epidemiologic studies published since our 2007 review. We assessed whether study designs captured relevant exposures and disease features suggested by toxicological and biological evidence of genotoxicity, endocrine disruption, tumor promotion, or disruption of mammary gland development.

METHODS

We systematically searched the PubMed database for articles with breast cancer outcomes published in 2006-2016 using terms for 134 environmental chemicals, sources, or biomarkers of exposure. We critically reviewed the articles.

RESULTS

We identified 158 articles. Consistent with experimental evidence, a few key studies suggested higher risk for exposures during breast development to dichlorodiphenyltrichloroethane (DDT), dioxins, perfluorooctane-sulfonamide (PFOSA), and air pollution (risk estimates ranged from 2.14 to 5.0), and for occupational exposure to solvents and other mammary carcinogens, such as gasoline components (risk estimates ranged from 1.42 to 3.31). Notably, one 50-year cohort study captured exposure to DDT during several critical windows for breast development (in utero, adolescence, pregnancy) and when this chemical was still in use. Most other studies did not assess exposure during a biologically relevant window or specify the timing of exposure. Few studies considered genetic variation, but the Long Island Breast Cancer Study Project reported higher breast cancer risk for polycyclic aromatic hydrocarbons (PAHs) in women with certain genetic variations, especially in DNA repair genes.

CONCLUSIONS

New studies that targeted toxicologically relevant chemicals and captured biological hypotheses about genetic variants or windows of breast susceptibility added to evidence of links between environmental chemicals and breast cancer. However, many biologically relevant chemicals, including current-use consumer product chemicals, have not been adequately studied in humans. Studies are challenged to reconstruct exposures that occurred decades before diagnosis or access biological samples stored that long. Other problems include measuring rapidly metabolized chemicals and evaluating exposure to mixtures.

Insecticide Use and Breast Cancer Risk among Farmers' Wives in the Agricultural Health Study

BACKGROUND

Some epidemiologic and laboratory studies suggest that insecticides are related to increased breast cancer risk, but the evidence is inconsistent. Women engaged in agricultural work or who reside in agricultural areas may experience appreciable exposures to a wide range of insecticides.

OBJECTIVE

We examined associations between insecticide use and breast cancer incidence among wives of pesticide applicators (farmers) in the prospective Agricultural Health Study.

METHODS

Farmers and their wives provided information on insecticide use, demographics, and reproductive history at enrollment in 1993-1997 and in 5-y follow-up interviews. Cancer incidence was determined via cancer registries. Among 30,594 wives with no history of breast cancer before enrollment, we examined breast cancer risk in relation to the women's and their husbands' insecticide use using Cox proportional hazards regression to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

During an average 14.7-y follow-up, 39% of the women reported ever using insecticides, and 1,081 were diagnosed with breast cancer. Although ever use of insecticides overall was not associated with breast cancer risk, risk was elevated among women who had ever used the organophosphates chlorpyrifos [HR=1.4 (95% CI: 1.0, 2.0)] or terbufos [HR=1.5 (95% CI: 1.0, 2.1)], with nonsignificantly increased risks for coumaphos [HR=1.5 (95% CI: 0.9, 2.5)] and heptachlor [HR=1.5 (95% CI: 0.7, 2.9)]. Risk in relation to the wives' use was associated primarily with premenopausal breast cancer. We found little evidence of differential risk by tumor estrogen receptor status. Among women who did not apply pesticides, the husband's use of fonofos was associated with elevated risk, although no exposure-response trend was observed.

CONCLUSION

Use of several organophosphate insecticides was associated with elevated breast cancer risk. However, associations for the women's and husbands' use of these insecticides showed limited concordance. Ongoing cohort follow-up may help clarify the relationship, if any, between individual insecticide exposures and breast cancer risk. https://doi.org/10.1289/EHP1295.