Occupations and breast cancer risk among Chinese women in urban Shanghai

Employment and risk of female breast cancer in Denmark

BACKGROUND

Occupational exposures may play a role in breast cancer etiology, and research focusing on identifying high-risk workplaces is important to advance the understanding and prevention of breast cancer.

METHODS

We undertook a population-based nested case-control study among women who were less than 70 years of age and born in Denmark, based on registry data including 38,375 breast cancer cases and 191,875 controls matched on year of birth, with information on lifetime work history. Odds ratios for women ever employed in a job branch were adjusted for socioeconomic status and reproductive variables.

RESULTS

Adjusted odds ratios of less than 0.75 were observed for several occupations in agriculture, hunting, forestry, and fishing, while increased risk patterns (odds ratios greater than 1.50) were noted for a number of production occupations, including employment in graphics and printing, and metal and machinery production. In services, several military professions were also associated with a high increased breast cancer risk.

CONCLUSIONS

The study shows a variation in the risk of female breast cancer by employment in different industrial and occupational sectors, and suggests that certain occupational exposures, for example, outdoor work, organic solvents, polycyclic aromatic hydrocarbons (PAHs), and night-shift work may play a role in the risk of breast cancer. Further hypothesis-testing studies focusing on these employments with a detailed assessment of specific occupational exposures are warranted.

Occupational exposure to organic solvents and breast cancer risk: a systematic review and meta-analysis

Breast cancer is the most common cancer worldwide. Recent studies suggest that organic solvent exposure could be closely related to breast cancer, although the evidence remains controversial. Thus, we evaluated existing epidemiological evidence for the association between occupational solvent exposure and breast cancer. PubMed, Embase, and Cochrane Library were searched to identify published case-control and cohort studies that addressed occupational exposure to organic solvents and breast cancer, up to April, 2021. Meta-analyses using random-effects models were conducted to obtain the pooled odds ratios (OR) and 95% confidence intervals (CI) on the incidence of breast cancer in relation to occupational exposure. The pooled OR of breast cancer among workers exposed to organic solvents overall was 1.18 (95%CI, 1.11 ~ 1.25; I² = 76.3%; 24 studies), compared to those with no exposure. After stratification by menopause and study location, it was revealed that the association between occupational exposure to organic solvents and the risk of breast cancer in postmenopausal women (OR, 1.35; 95% CI, 1.09 ~ 1.67; I² = 73.4%; 7 studies) was significant, and there was also a clear association in workers in Europe (OR, 1.21; 95% CI, 1.12 ~ 1.32; I² = 82.9%; 13 studies). We observed a significant association between occupational exposure to organic solvents and breast cancer in both cohort and case-control studies.

Menopause and Sustainable Career Outcomes: A Science Mapping Approach

This paper provides a systematic review of the phenomenon of menopause at the workplace from a sustainable career perspective, by highlighting its major themes along with the evolution and tendencies observed in this field. A conceptual science mapping analysis based on co-word bibliographic networks was developed, using the SciMAT tool. From 1992 to 2020, 185 documents were retrieved from the Web of Science. In the first analyzed time span (1992-2002), postmenopausal women, health, and risk factors appeared to be the motor themes (well-developed and important for the structure of the discipline under focus), and disorder was an emerging or disappearing theme in the phenomenon under research. In the second studied period (2003-2013), risk and health were motor themes, menopausal symptoms was a basic or transversal theme (important for the discipline but not well-developed), coronary heart disease was a specialized theme (well-developed but less important for the structure of the research field), and postmenopausal women was an emerging or disappearing theme (both weakly developed and marginal to the field). In the third studied period (2014-2020), menopause, breast cancer, and menopausal symptoms were motor themes, Anxiety was a specialized theme and risk and body mass index were emerging or disappearing themes. Sustainability of women's careers in the second half of life is of increasing importance given the increasing equal representation of men and women in working organizations, and the impact of the changing nature of work in the 21st century on older workers.

Associations of age at natural menopause and occupations in Chinese female workers: A cross-sectional study

AIMS

To investigate the impact of occupation types on age at natural menopause.

METHODS

This is a nation-wide cross-sectional study based on 17,948 female workers aged over 40, who come from different industries or organizations. A face-to-face standardized questionnaire was conducted in all participants with the help of occupational hygienists. Occupational titles were coded according to the International Standard Classification of Occupations (2008) (ISCO08). Cox regression model was used to assess the association between each independent occupation and menopausal timing. Models were adjusted for marriage, education, average annual family income, parity, cigarette smoking, alcohol consumption.

RESULTS

Higher risks of earlier age at natural menopause was found among legislators and senior officials (ISCO Minor group:111, HR = 2.328, P < 0.001), among other health associated professionals (ISCO Minor group: 325, HR = 1.477, P = 0.003), the workers involved in mining and mineral processing (ISCO Minor group: 811, HR = 1.515, P = 0.048) and metal processing and finishing (ISCO Minor group: 812, HR = 1.722, P < 0.001). Reduced risks of earlier age at natural menopause, including: finance professionals (ISCO Minor group: 241, HR = 0.751, P = 0.021), manufacturing and construction supervisors (ISCO Minor group: 312, HR = 0.477, P = 0.002), administrative and specialized secretaries (ISCO Minor group: 334, HR = 0.788, P = 0.045), cleaners and helpers (ISCO Minor group: 911, HR = 0.633, P = 0.01).

CONCLUSIONS

This is the first study to address the influence of occupation types on reproductive aging, showing some specific occupations could be associated with age at natural menopause. Further investigations are necessary to clarify whether it is chance finding or a true association.

Occupation and risk of female breast cancer: A case-control study in Morocco

BACKGROUND

Breast cancer is the most frequent cancer among Moroccan women. Environmental and occupational factors may play a role in breast cancer etiology. This study aimed to investigate the association between occupation, industry, and breast cancer risk among Moroccan women.

METHODS

A total of 300 breast cancer cases and 300 controls (matched by age and area of residence) were included in this study. Full occupational history was collected, with a detailed description of each job held for at least 6 months. Occupations were coded according to the International Standard Classification of Occupations (ISCO 08) and the Moroccan Analytical Classification of Professions (2001). Industries were coded according to the Statistical Classification of Economic Activities in the European Community (2008). Odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for potential confounders were estimated by using conditional logistic regression.

RESULTS

An overall decreased risk of breast cancer was observed among women doing only household work (OR = 0.32; 95% CI = 0.18-0.55). An increased risk of breast cancer was observed among women in agricultural occupations, particularly those employed as agricultural laborers (ISCO 08 code: 921; OR = 2.91; 95% CI = 1.51-5.60) and the risk increased with duration of employment (P trend = .01). Analyses by industry corroborated these findings.

CONCLUSIONS

Our findings suggest that occupational exposures may be associated with increased risk of breast cancer among female agricultural workers in this population. Further investigations, with advanced methods of occupational exposure assessment, are warranted to clarify the role of chemicals involved in this high-risk occupation and to suggest preventive actions and screening.

Work and Female Breast Cancer: The State of the Evidence, 2002-2017

The authors undertook a scoping review to assess the literature from 2002 to 2017 on the relationship between occupation and female breast cancer. Case-control, cohort, and meta-analytic studies suggest that women working as flight attendants, in medical professions, some production positions, sales and retail, and scientific technical staff are likely to have elevated risk of breast cancer. In addition, occupational exposures to night-shift work, ionizing radiation, some chemicals, job stress, and sedentary work may increase risk of breast cancer. Occupational physical activity appears to decrease risk. Workplace exposures to passive smoke and occupational exposure to nonionizing radiation do not appear to affect breast cancer risk. Some studies of occupational categories and workplace exposures indicate that risk may be modified by duration of exposure, timing of exposure, dose, hormone-receptor subtypes, and menopausal status at diagnosis. The compelling data from this review reveal a substantial need for further research on occupation and breast cancer.

Breast cancer risk by occupation and industry in women and men: Results from the Occupational Disease Surveillance System (ODSS)

BACKGROUND

The recently established Occupational Disease Surveillance System (ODSS) was used to examine breast cancer risk in women and men by occupation and industry.

METHODS

Ontario workers in the ODSS cohort (1983-2016) were followed up for breast cancer diagnosis through the Ontario Cancer Registry. Cox-proportional hazard models were used to calculate age-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

A total of 17 865 and 492 cases were identified in working women (W) and men (M), respectively. Elevated risks were observed in management (W: HR = 1.54, 95% CI = 1.40-1.70; M: HR = 2.79, 95% CI = 1.44-5.39), administrative/clerical (W: HR = 1.16, 95% CI = 1.11-1.21; M: HR = 1.45, 95% CI = 1.06-1.99), and teaching (W: HR = 1.54, 95% CI = 1.44-1.63; M: HR = 3.00, 95% CI = 1.49-6.03). Other elevated risks were observed in nursing/health, social sciences, and janitor/cleaning services for both genders.

CONCLUSIONS

Common occupational associations in both genders warrant investigation into job-related risk factors, such as sedentary behavior, shift work, ionizing radiation, and chemical exposures.

Exposure to Benzene and Risk of Breast Cancer among Shoe Factory Workers in Italy

Aims and background

Evidence of the association between leukemia and benzene exposure has been provided by several epidemiological studies. An increased risk of breast cancer among women exposed to benzene has also been suggested. The aim of this study was to analyze breast cancer risk in a cohort of 1,002 women exposed to benzene in a shoe factory in Florence, Italy, where an excess of leukemia in men was reported.

Methods

The cohort of women at work on January 1st, 1950, was followed from 1950 to 2003 for mortality and from 1985 to 2000 for incidence of breast cancer. For a sub-cohort of 797 women, cumulative exposure to benzene was available.

Results

Standardized mortality ratios were obtained for the 797 women for whom information on cumulative exposure was available. For those with <30 years of latency the standardized mortality ratio was 58.5 (95% CI, 18.9–181.2, based on 3 deaths) and 151.1 (95% CI, 78.6–290.3, based on 9 deaths) for ≥30 years of latency. In the >40 ppm-year and ≥30 year latency period category, the standardized mortality ratio was 166.0 (95% CI, 62.3–442.2, based on 4 deaths). The standardized incidence ratio for women with a latency period <30 years was 140.9 (95% CI, 75.8–261.9, based on 10 cases) and 108.2 (95% CI, 64.1–182.7) for a latency period ≥30 years. For cumulative exposure >40 ppm-years and a latency period <30 years, the standardized incidence ratio was 211.9 (95% CI, 29.9–1504.1, based on 1 case).

Conclusions

The study moderately supports the hypothesis that benzene represents a risk factor for breast cancer.

Occupational exposure to magnetic fields and breast cancer among Canadian men

Occupational magnetic field (MF) exposure has been suggested as a risk factor for breast cancer in both men and women. Due to the rarity of this disease in men, most epidemiologic studies investigating this relationship have been limited by small sample sizes. Herein, associations of several measures of occupational MF exposure with breast cancer in men were investigated using data from the population-based case-control component of the Canadian National Enhanced Cancer Surveillance System. Lifetime job histories were provided by 115 cases and 570 controls. Average MF exposure of individual jobs was classified into three categories (<0.3, 0.3 to <0.6, or ≥0.6 μT) through expert blinded review of participant's lifetime occupational histories. The impact of highest average and cumulative MF exposure, as well as exposure duration and specific exposure-time windows, on cancer risk was examined using logistic regression. The proportion of cases (25%) with a highest average exposure of ≥0.3 μT was higher than among controls (22%). We found an elevated risk of breast cancer in men who were exposed to ≥0.6 μT (odds ratio [OR] = 1.80, 95% CI = 0.82-3.95) when compared to those with exposures <0.3 μT. Those exposed to occupational MF fields for at least 30 years had a nearly threefold increase in risk of breast cancer (OR = 2.77, 95% CI = 0.98-7.82) when compared to those with background levels of exposure. Findings for the other time-related MF variables were inconsistent. Our analysis, in one of the largest case-control studies of breast cancer in men conducted to date, provides limited support for the hypothesis that exposure to MF increases the risk breast cancer in men.

Household and occupational exposure to pesticides and risk of breast cancer

The association between breast cancer in women and the use of household or occupational pesticides was examined in a population-based case-control study. This study was conducted in Western Australia in 2009-2011 and included 1,789 controls and 1,205 cases. Information on household pesticide exposure was collected from questionnaires. For occupational pesticide exposure, job-specific modules (JSMs) were used. To evaluate potential recall bias, we stratified the analysis by belief about whether pesticides contribute to breast cancer. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Women's exposures to pesticides in households and workplaces were not related to increased risk of breast cancer (OR = 1.10; CI: 0.86-1.37) and (OR = 0.77; CI: 0.45-1.32), respectively. The prevalence of occupational exposure to pesticides among women in our study was low. In the stratified analyses, the odd ratios associated with household pesticide use were similar among participants who believed pesticides increased breast cancer risk and those who did not. The results of our study did not show associations between breast cancer and household or occupational exposure to pesticides.

Breast cancer risk in relation to occupations with exposure to carcinogens and endocrine disruptors: a Canadian case-control study

BACKGROUND

Endocrine disrupting chemicals and carcinogens, some of which may not yet have been classified as such, are present in many occupational environments and could increase breast cancer risk. Prior research has identified associations with breast cancer and work in agricultural and industrial settings. The purpose of this study was to further characterize possible links between breast cancer risk and occupation, particularly in farming and manufacturing, as well as to examine the impacts of early agricultural exposures, and exposure effects that are specific to the endocrine receptor status of tumours.

METHODS

1005 breast cancer cases referred by a regional cancer center and 1146 randomly-selected community controls provided detailed data including occupational and reproductive histories. All reported jobs were industry- and occupation-coded for the construction of cumulative exposure metrics representing likely exposure to carcinogens and endocrine disruptors. In a frequency-matched case-control design, exposure effects were estimated using conditional logistic regression.

RESULTS

Across all sectors, women in jobs with potentially high exposures to carcinogens and endocrine disruptors had elevated breast cancer risk (OR = 1.42; 95% CI, 1.18-1.73, for 10 years exposure duration). Specific sectors with elevated risk included: agriculture (OR = 1.36; 95% CI, 1.01-1.82); bars-gambling (OR = 2.28; 95% CI, 0.94-5.53); automotive plastics manufacturing (OR = 2.68; 95% CI, 1.47-4.88), food canning (OR = 2.35; 95% CI, 1.00-5.53), and metalworking (OR = 1.73; 95% CI, 1.02-2.92). Estrogen receptor status of tumors with elevated risk differed by occupational grouping. Premenopausal breast cancer risk was highest for automotive plastics (OR = 4.76; 95% CI, 1.58-14.4) and food canning (OR = 5.70; 95% CI, 1.03-31.5).

CONCLUSIONS

These observations support hypotheses linking breast cancer risk and exposures likely to include carcinogens and endocrine disruptors, and demonstrate the value of detailed work histories in environmental and occupational epidemiology.

Breast cancer risk by occupation and industry: analysis of the CECILE study, a population-based case-control study in France

BACKGROUND

It has been suggested that certain occupational exposures may play a role in breast cancer etiology. The recognition of high-risk occupations may give clues about potential mammary carcinogens in the work place.

METHODS

We conducted a population-based case-control study in France including 1,230 breast cancer cases and 1,315 population controls with detailed information on lifetime work history. Odds ratios for women ever employed in an occupation or industry were adjusted for well-established risk factors for breast cancer.

RESULTS

Adjusted odds ratios were marginally increased in some white-collar occupations, as well as in textile workers (2.4; 95% CI [0.9-6.0]), rubber and plastics product makers (1.8; 95% CI [0.9-3.5]), and in women employed for more than 10 years as nurses (1.4; 95% CI [0.9-2.1]) and as tailors/dressmakers (1.5; 95% CI [0.9-2.6]). The incidence of breast cancer was increased among women employed in the manufacture of chemicals, of non-metallic mineral products, and decreased among women in agriculture.

CONCLUSIONS

These findings suggest a possible role of occupational exposures in breast cancer, including night-shift work, solvents and endocrine disrupting chemicals and require further studies with detailed assessment of occupational exposures.

Risk factors for breast cancer, including occupational exposures

The knowledge on the etiology of breast cancer has advanced substantially in recent years, and several etiological factors are now firmly established. However, very few new discoveries have been made in relation to occupational risk factors. The International Agency for Research on Cancer has evaluated over 900 different exposures or agents to-date to determine whether they are carcinogenic to humans. These evaluations are published as a series of Monographs (www.iarc.fr). For breast cancer the following substances have been classified as "carcinogenic to humans" (Group 1): alcoholic beverages, exposure to diethylstilbestrol, estrogen-progestogen contraceptives, estrogen-progestogen hormone replacement therapy and exposure to X-radiation and gamma-radiation (in special populations such as atomic bomb survivors, medical patients, and in-utero exposure). Ethylene oxide is also classified as a Group 1 carcinogen, although the evidence for carcinogenicity in epidemiologic studies, and specifically for the human breast, is limited. The classification "probably carcinogenic to humans" (Group 2A) includes estrogen hormone replacement therapy, tobacco smoking, and shift work involving circadian disruption, including work as a flight attendant. If the association between shift work and breast cancer, the most common female cancer, is confirmed, shift work could become the leading cause of occupational cancer in women.

Occupational exposure to organic solvents and breast cancer in women

BACKGROUND

Although studies in rodents suggest possible associations between exposure to organic solvents and breast cancer, the evidence in humans is limited.

METHODS

We evaluated job histories of 2383 incident breast cancer cases diagnosed during 2000-2003, and 2502 controls who participated in a large population-based case-control study in Poland. Industrial hygienists reviewed occupational histories and developed exposure metrics for total organic solvents and benzene. Unconditional logistic regression analyses estimated ORs and 95% CIs as the measure of association with breast cancer, controlling for breast cancer risk factors. Stratified analyses examined the potential modification by known breast cancer risk factors. Associations were also evaluated by oestrogen and progesterone receptor status and by other clinical characteristics of the tumours using polytomous regression analyses.

RESULTS

Women who ever worked at jobs with organic solvents exposure had a small, non-significant increase in breast cancer risk (OR=1.16; 95% CI 0.99 to 1.4). A significant association was present for oestrogen receptor- and progesterone receptor-negative tumours (OR 1.40; 95% CI 1.1 to 1.8), but there was no association with tumours with both positive receptors (OR 0.97; 95% CI 0.8 to 1.2 (p heterogeneity: 0.008)). We did not observe trends with increasing level of exposure. Known breast cancer risk factors did not modify the association between organic solvents and breast cancer risk. No association with breast cancer was found for benzene exposure (OR 1.00; 95% CI 0.8 to 1.3).

CONCLUSION

Our study provides weak evidence for a possible association between occupational exposure to organic solvents as a class and breast cancer risk. The association might be limited to hormone receptor-negative tumours.

Family history of malignancies and risk of breast cancer: prospective data from the Shanghai women's health study

A population-based cohort study was conducted in Shanghai, China, to investigate the relationship between family cancer history in first-degree relatives and risk of breast cancer. A total of 570 newly diagnosed breast cancer patients were identified from the cohort of 73,222 women during the follow-up period. Breast cancer risk was elevated (RR = 1.74, 95% CI: 1.10-2.73) for those with a family history of breast cancer and the risk was stronger for women who were younger than 55 years (RR = 2.07, 95% CI: 1.17-3.64). In addition, a significantly increased risk was observed for women with a family history of leukemia (RR = 2.06; 95% CI: 1.02-4.15) and among younger women, those who reported having a family history of any cancer (RR = 1.41, 95% CI: 1.10-1.82), lung cancer (RR = 1.72, 95% CI: 1.12-2.65), and esophageal cancer (RR = 2.99, 95% CI: 1.62-5.51). This cohort study suggests that, as previously observed in high risk populations, family history plays an important role in breast cancer also in a low risk population. The link between breast cancer risk and family history of cancers of the lung and esophagus, as well as leukemia, warrants further investigation.

Activation of estrogen receptor-alpha by the anion nitrite

In this study, the ability of nitrite and nitrate to mimic the effects of estradiol on growth and gene expression was measured in the human breast cancer cell line MCF-7. Similar to estradiol, treatment of MCF-7 cells with either 1 mumol/L nitrite or 1 mumol/L nitrate resulted in approximately 4-fold increase in cell growth and 2.3-fold to 3-fold increase in progesterone receptor (PgR), pS2, and cathepsin D mRNAs that were blocked by the antiestrogen ICI 182,780. The anions also recruited estrogen receptor-alpha (ERalpha) to the pS2 promoter and activated exogenously expressed ERalpha when tested in transient cotransfection assays. To determine whether nitrite or nitrate was the active anion, diphenyleneiodonium was used to inhibit oxidation/reduction reactions in the cell. The ability of diphenyleneiodonium to block the effects of nitrate, but not nitrite, on the induction of PgR mRNA and the activation of exogenously expressed ERalpha suggests that nitrite is the active anion. Concentrations of nitrite, as low as 100 nmol/L, induced a significant increase in PgR mRNA, suggesting that physiologically and environmentally relevant doses of the anion activate ERalpha. Nitrite activated the chimeric receptor Gal-ER containing the DNA-binding domain of GAL-4 and the ligand-binding domain of ERalpha and blocked the binding of estradiol to the receptor, suggesting that the anion activates ERalpha through the ligand-binding domain. Mutational analysis identified the amino acids Cys381, His516, Lys520, Lys529, Asn532, and His547 as important for nitrite activation of the receptor.

Review of the etiology of breast cancer with special attention to organochlorines as potential endocrine disruptors

Breast cancer is the most frequently diagnosed cancer among Canadian women, accounting for about 30% of all new cancer cases each year. Although the incidence of breast cancer has increased over the past 50 years, the cause of this rise is unknown. Risk factors for breast cancer may be classified into four broad categories: (1) genetic/familial, (2) reproductive/hormonal, (3) lifestyle, and (4) environmental. Established risk factors for breast cancer include older age, later age at first full-term pregnancy, no full-term pregnancies, postmenopausal obesity, and genetic factors. However, these known risk factors cannot account for the majority of cases. In the early 1990s, it was suggested that exposure to some environmental chemicals such as organochlorine compounds may play a causal role in the etiology of breast cancer through estrogen-related pathways. The relationship between organochlorines and breast cancer risk has been studied extensively in the past decade and more, and at this point there is no clear evidence to support a causal role of most organochlorine pesticides in the etiology of human breast cancer, but more evidence is needed to assess risk associated with polychlorinated biphenyls (PCBs). Future studies need to consider the combined effects of exposures, concentrate on vulnerable groups such as those with higher levels of exposure, only consider exposures occurring during the most etiologically relevant time periods, and more thoroughly consider gene-environment interactions.

Occupation and breast cancer risk among Shanghai women in a population-based cohort study

INTRODUCTION

A total of 74,942 female subjects were recruited in a population-based cohort study in Shanghai, China between 1997 and 2000. We examined the relationship between occupation and breast cancer risk.

METHODS

Cases were 586 women previously diagnosed with breast cancer at baseline and 438 women newly diagnosed with breast cancer during follow-up through December 2004. Eight controls were randomly selected for each case from cancer-free cohort members and frequency-matched to the cases by year of birth and age at diagnosis. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of breast cancer risk associated with occupations, adjusting for established breast cancer risk factors.

RESULTS

In the prevalent breast cancer data analysis, increased risks of breast cancer were associated with technicians in engineering/agriculture/forestry (OR = 1.6, CI: 1.0-2.4), teaching personnel (OR = 1.5, CI:1.1-2.0), tailoring/sewing workers (OR = 1.6, CI:1.0-2.7), and examiners/measurers/testers (OR = 1.5, CI:1.1-2.1) among those who started the jobs at least 20 years ago. Among incident breast cancer cases, significantly increased risks were associated with medical/health care workers (OR = 1.4, CI:1.0-2.0), administrative clerical workers (OR = 1.5, CI:1.0-2.4), postal/telecommunication workers (OR = 2.2, CI:1.0-5.5), and odd-job workers (OR = 1.7, CI:1.1-2.8) among those who started the jobs at least 20 years ago. The excess risks were found in both prevalent and incident cases for postal/telecommunication workers and purchasing/marketing personnel, although ORs reached only marginal significance.

CONCLUSIONS

This study suggests that white-collar professionals and several production occupations may be associated with an increased risk of breast cancer.

Environmental pollutants and breast cancer: epidemiologic studies

Laboratory research has shown that numerous environmental pollutants cause mammary gland tumors in animals; are hormonally active, specifically mimicking estrogen, which is a breast cancer risk factor; or affect susceptibility of the mammary gland to carcinogenesis. An assessment of epidemiologic research on these pollutants identified in toxicologic studies can guide future research and exposure reduction aimed at prevention. The PubMed database was searched for relevant literature and systematic critical reviews were entered in a database available at URL: www.silentspring.org/sciencereview and URL: www.komen.org/environment (accessed April 10, 2007). Based on a relatively small number of studies, the evidence to date generally supports an association between breast cancer and polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in conjunction with certain genetic polymorphisms involved in carcinogen activation and steroid hormone metabolism. Evidence regarding dioxins and organic solvents is sparse and methodologically limited but suggestive of an association. Methodologic problems include inadequate exposure assessment, a lack of access to highly exposed and unexposed populations, and a lack of preclinical markers to identify associations that may be obscured by disease latency. Among chemicals identified in toxicologic research as relevant to breast cancer, many have not been investigated in humans. The development of better exposure assessment methods is needed to fill this gap. In the interim, weaknesses in the epidemiologic literature argue for greater reliance on toxicologic studies to develop national policies to reduce chemical exposures that may be associated with breast cancer. Substantial research progress in the last 5 years suggests that the investigation of environmental pollutants will lead to strategies to reduce breast cancer risk.

Occupational Exposures and Breast Cancer Among Women Textile Workers in Shanghai

BACKGROUND

Breast cancer incidence rates have been increasing in China over the past 2 decades. Most studies have focused on reproductive, dietary, and genetic risk factors. Little is known about the contribution of occupational exposures.

METHODS

We conducted a case-cohort study within a cohort of female textile workers who had participated in a randomized trial of breast self-examination in Shanghai, China. We compared 1709 incident breast cancer cases with an age-stratified reference subcohort (n = 3155 noncases). Cox proportional hazards modeling, adapted for the case-cohort design, was used to estimate hazard ratios for breast cancer in relation to duration of employment in various job processes and duration of exposure to several agents. We also evaluated the associations of cotton dust and endotoxin with breast cancer.

RESULTS

Cumulative exposures to cotton dust and endotoxin demonstrated strong inverse gradients with breast cancer risk when exposures were lagged by 20 years (trend P-values <0.001). We did not observe consistent associations with exposures to electromagnetic fields, solvents, or other chemicals.

CONCLUSION

Endotoxin or other components of cotton dust exposures may have reduced risks for breast cancer in this cohort, perhaps acting at early stages of carcinogenesis. Replication of these findings in other occupational settings with similar exposures will be needed to confirm or refute any hypothesis regarding protection against breast cancer.

Occupation and breast cancer risk in Polish women: a population-based case-control study

BACKGROUND

The etiology of breast cancer is not well understood and the role of occupational exposures in breast carcinogenesis is still uncertain.

METHODS

The population-based case-control study included 2,386 incident breast cancer cases diagnosed in 2000-2003, and 2,502 controls. Lifetime occupational histories and information on other potential breast cancer risk factors were obtained through personal interviews. Conditional logistic regression analyses calculated odds ratios (ORs) associated with various occupations and industries after control for potential confounders.

RESULTS

We found statistically significant excesses of breast cancer among engineers (OR=2.0; 95% CI: 1.0-3.8), economists (2.1; 1.1-3.8), sales occupations-retail (1.2; 1.0-1.5), and other sales occupations (1.2; 1.0-1.5). Industries showing significantly elevated risks included special trade contractors (2.2; 1.2-4.3), electronic and electric equipment manufacturers (1.7; 1.1-2.7); and public administration/general government n.e.c. (2.7; 1.3-5.7). Each of these findings was supported by a statistically significant positive trend for duration of employment (P<0.05). A decreased breast cancer risk was observed in janitors and cleaners (0.7; 0.5-0.8).

CONCLUSIONS

In this study, we found few associations for breast cancer and occupations or industries. The suggestive findings for the electronic and electric equipment manufacturing industry and for the occupations with potential exposure to magnetic fields deserve further evaluation.

Risk of breast cancer among enlisted Army women occupationally exposed to volatile organic compounds

BACKGROUND

The military presents a unique opportunity to study the incidence of disease in a population with complete knowledge of person-time and occupation. Women in the Army are employed more frequently in non-traditional, industrial jobs such as auto mechanic and motor transport operators than in the general US population, increasing the probability of exposure to industrial chemicals. A cohort to investigate the risk of breast cancer among active duty Army women occupationally exposed to volatile organic chemicals (VOCs) was constructed.

METHODS

Age-adjusted incidence rates for breast cancer were calculated for more than 270,000 enlisted women who served between 1980-1996. Twenty-one VOCs, described in previously published literature as having a potential risk of breast cancer, were identified in an Army industrial hygiene survey database. Job title histories were linked to workplace chemical evaluations conducted by Army industrial hygienists, which included a subjective exposure potential rating (high, medium, low, and none) for each VOC. Poisson regression analysis was used to evaluate the association between the exposure rating by job title and breast cancer.

RESULTS

The incidence of breast cancer in the cohort was significantly elevated in women younger than 35 years of age, especially among black women, when compared to the age-specific rates in the general population. Women who worked in occupations with a moderate to high exposure potential to at least one VOC had a 48% increased risk (P < 0.05) of breast cancer while on active duty between 1980-1996 when compared to those women with low to no exposure potential.

CONCLUSIONS

This study provides preliminary evidence that exposure to one or more of the study VOCs is associated with an increased risk of breast cancer. Further substance-specific, quantitative analyses are warranted.

Residential proximity to agricultural pesticide use and incidence of breast cancer in California, 1988-1997

California is the largest agricultural state in the United States and home to some of the world's highest breast cancer rates. The objective of our study was to evaluate whether California breast cancer rates were elevated in areas with recent high agricultural pesticide use. We identified population-based invasive breast cancer cases from the California Cancer Registry for 1988-1997. We used California's pesticide use reporting data to select pesticides for analysis based on use volume, carcinogenic potential, and exposure potential. Using 1990 and 2000 U.S. Census data, we derived age- and race-specific population counts for the time period of interest. We used a geographic information system to aggregate cases, population counts, and pesticide use data for all block groups in the state. To evaluate whether breast cancer rates were related to recent agricultural pesticide use, we computed rate ratios and 95% confidence intervals using Poisson regression models, adjusting for age, race/ethnicity, and neighborhood socioeconomic status and urbanization. This ecologic (aggregative) analysis included 176,302 invasive breast cancer cases and 70,968,598 person-years of observation. The rate ratios did not significantly differ from 1 for any of the selected pesticide categories or individual agents. The results from this study provide no evidence that California women living in areas of recent, high agricultural pesticide use experience higher rates of breast cancer.

Gliomas and farm pesticide exposure in women: the Upper Midwest Health Study

An excess incidence of brain cancer in male farmers has been noted in several studies, but few studies have focused on women. The National Institute for Occupational Safety and Health Upper Midwest Health Study evaluated effects of rural exposures for 341 female glioma cases and 528 controls, all adult (18-80 years of age) nonmetropolitan residents of Iowa, Michigan, Minnesota, and Wisconsin. On average, controls lived longer on farms than did cases. After adjusting for age, age group, education, and farm residence, no association with glioma was observed for exposure to arsenicals, benzoic acids, carbamates, chloroacetanilides, dinitroanilines, inorganics, organochlorines, organophosphates, phenoxys, triazines, or urea-based or estrogenic pesticides. An increased risk of glioma was observed for carbamate herbicides but was not statistically significant (odds ratio = 3.0; 95% confidence interval, 0.9-9.5). No association was observed between glioma and exposure to 12 widely used specific pesticides, after adjustment for age, age group, education, and any other pesticide exposure. These results were not affected after exclusion of proxy respondents (43% of cases, 2% of controls). Women were less likely than men to have applied pesticides, but more likely to have laundered pesticide-contaminated clothes. Storing pesticides in the house was associated with a statistically non-significant increased risk. Results show that exposure to pesticides was not associated with an increased risk of intracranial gliomas in women. Other farm-related factors could be etiologic factors and will be discussed in future reports.

Occupational exposures to extremely low frequency magnetic fields and postmenopausal breast cancer

BACKGROUND

The association between occupational exposure to extremely low frequency magnetic fields (ELF-MF) and risk of postmenopausal breast cancer was assessed in a case-control study.

METHODS

Breast cancer cases were compared to cancer controls. Interviewers elicited information on risk factors and on lifetime work history. Industrial hygienists assigned to each job average duration of exposure to ELF-MF at four levels of intensities ("none," <0.2 microT; "low," 0.2-<0.5microT; "medium," 0.5-<1microT; "high," > or =1-10microT). Unconditional logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

A total number of 608 cases and 667 controls participated. Adjusting for accepted breast cancer risk factors, we found an OR of 1.13 for lifetime occupational exposure to ELF-MF at medium or high intensities. Risks were larger for exposures before age 35 (OR = 1.40), and statistically significant for exposures before 35 among cases with progesterone receptor positive tumors (OR = 1.56, 95% CI=1.02-2.39).

CONCLUSIONS

There appears to be a small increased risk for breast cancer among postmenopausal women exposed occupationally to ELF-MF.

Cancer among women textile workers in Shanghai, China: overall incidence patterns, 1989-1998

BACKGROUND

Cancer incidence in women textile workers has not been adequately studied. The aim of this study was to examine site-specific cancer incidence patterns in a cohort of 267,400 women textile workers in Shanghai, China.

METHODS

Women employed by the Shanghai Textile Industry Bureau (STIB) were followed for cancer incidence from 1989 to 1998. Age-adjusted standardized incidence ratios (SIRs) and 95% confidence intervals (CI) were computed based on Shanghai Cancer Registry (SCR) rates.

RESULTS

There was a decrease in cancer incidence for the cohort compared with urban Shanghai women (SIR = 0.91, 95% CI = 0.89-0.93). There were small increased risks of other endocrine tumors (SIR = 1.31, 95% CI = 1.02-1.65). There were decreased risks for esophageal (SIR = 0.54, 95% CI = 0.44-0.66), stomach (SIR = 0.79, 95% CI = 0.73-0.85), rectal (SIR = 0.88, 95% CI = 0.78-0.98), lung (SIR = 0.80, 95% CI = 0.74-0.86), cervical (SIR = 0.37, 95% CI = 0.28-0.50), ovarian (SIR = 0.85, 95% CI = 0.75-0.96), and bladder cancers (SIR = 0.63, 95% CI = 0.46-0.85).

CONCLUSIONS

Women employed in the textile industry had a lower than expected cancer experience compared with urban Shanghai women. Further research on this cohort will examine associations between site-specific cancers and occupational exposures to dusts and chemicals.