Identification of occupational cancer risks in British Columbia. A population-based case-control study of 995 incident breast cancer cases by menopausal status, controlling for confounding factors

Risk of breast cancer in daughters of agricultural workers in Denmark

OBJECTIVES

Agricultural workers face unique occupational hazards such as pesticide exposure, which has been associated with breast cancer. However, research considering the association between parental agricultural work and breast cancer in female offspring is lacking. Therefore, the aim of the present nested case-control study was to explore this association.

METHODS

The Danish Cancer Registry was utilized to identify women diagnosed with primary breast cancer. A total of 5587 cases were included in the study, and for each case, 20 cancer-free female controls were selected, matched on year of birth. It was a requisition that both cases and controls were born in Denmark and that either maternal or paternal employment history was available.

RESULTS

Adverse associations were consistently noted for different time windows of maternal employment in "Horticulture" and breast cancer. Inverse associations were observed for paternal employment in most of the examined agricultural industries, although a small increased risk was indicated for perinatal employment in "Horticulture". Furthermore, maternal preconceptional employment in "Horticulture" was observed to increase the risk of ER positive tumors (odds ratio [OR] = 1.79, 95% confidence interval [CI]: 1.13-2.85, whereas parental perinatal employment was linked to an elevated risk of ER negative tumors (maternal employment: OR = 2.48, 95% CI: 1.18-5.21; paternal employment: OR = 1.62, 95% CI: 0.70-3.77).

CONCLUSIONS

The present study indicates that maternal horticultural employment in different potential susceptible time windows may elevate the risk of breast cancer subtypes in daughters. These findings need to be reproduced in future prospective cohort studies, including information on e.g., pesticide exposure withing agricultural job categories and lifestyle factors.

Occupational Cancers among Employed Women: A Narrative Review

The facts that occupational cancer in women is under-investigated, with few in-depth analyses are well known. In recent decades the workforce has changed, with an increasing number of women employed. Therefore, the inclusion of women in occupational cancer studies has become more urgent and feasible than in the past decades. The difficulties to evaluate occupational causes of female gynecologic tumors in most past cohorts and the potential variation in outcome responses between men and women must be taken into consideration. This narrative review discusses women's occupational cancer as a current area of research, focusing on three groups of workers characterized by peculiar exposure to occupational carcinogens and where women are often employed: beauticians and hairdressers; farmers; and healthcare workers. We discuss the most relevant cancers in each working category, with a particular focus on female breast cancer. In the three industries reviewed in detail, there are some risk factors which may affect primarily women, inducing breast cancer and cervical cancer, as well as risk factors that are carcinogenic in both genders, but whose effects are less well known in women.

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.

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.

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.

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.

Female white-collar workers remain at higher risk of breast cancer after adjustments for individual risk factors related to reproduction and lifestyle

Objectives

The aim was to investigate the variation in risk of breast cancer between occupational groups with a focus on white-collar and blue-collar workers and to investigate to what extent the differences were explained by risk factors related to reproduction and lifestyle.

Methods

Between 1991 and 1996, 14 119 women born between 1923 and 1950 and residents of Malmö, Sweden, were included in this cohort study. Individual data on risk factors (eg, age, parity, age at first child, months of breast feeding per child, hormonal replacement therapy, physical activity, alcohol consumption, smoking, height and body mass index) and occupational history were assessed using a questionnaire. First-time diagnoses of invasive breast cancer were identified through the Swedish Cancer Registry up until 31 December 2013.

Results

A total of 897 women were diagnosed with breast cancer. Analyses adjusted for age showed an increased risk for white-collar workers compared with blue-collar workers and indicated higher risks in the occupational categories: professionals, administrative and bookkeeping than among women in sales, transportation, production and service work. This difference was only marginally attenuated after adjustment for an extensive set of risk factors related to reproduction and lifestyle.

Conclusion

Reproductive and lifestyle factors explain only a minor part of the increased risk of breast cancer in white-collar workers. Further studies are needed to investigate the remaining factors for the difference in risk between occupational groups.

Environmental and occupational exposure to bisphenol A and endometriosis: urinary and peritoneal fluid concentration levels

OBJECTIVES

The study aimed to give a first data set of bisphenol A (BPA) levels in the peritoneal fluid of patients suffering from endometriosis and to investigate the relationship between BPA exposure and endometriosis.

METHODS

A questionnaire investigating the occupational context, life environment, and habits was administered to 68 patients suffering from endometriosis and 60 endometriosis-free subjects (control group). Urine and peritoneal fluids samples were collected and analysed by GC/MSMS for BPA dosage.

RESULTS

Some of the investigated environmental/lifestyle risk factors (closeness to industries/activities at risk) were associated with an increase in endometriosis; smoking resulted as protective factor; others (use of food plastic boxes) did not seem to influence the onset of pathology. The association between the occupational exposure summarising all examined risk factors (working activity, personal protective equipment, seniority) and endometriosis was statistically significant (χ ² = 5.252, p = 0.02). Contrasting results were obtained when specific activities were examined. Detectable urinary BPA levels were found in all analysed samples (patients: 1.17-12.68 pg/µl; mean ± SD, 5.31 ± 3.36 pg/µl; control group: 1.28-2.35 pg/µl; mean ± SD, 1.64 ± 0.49 pg/µl; median; 1.46 pg/µl), with a statistically significant difference between patients and controls, showing an association between BPA exposure and endometriosis. Only a few subjects from the control group supplied peritoneal fluid; hence, no comparison test with patients (range 0.39-1.46 pg/µl; mean ± SD, 0.67 ± 0.30 pg/µl; median, 0.58 pg/µl) was carried out.

CONCLUSIONS

Results highlight the potential association between BPA exposure and endometriosis, as well as the current lack of knowledge regarding occupational exposure to BPA and the need of epidemiological studies focused on single activities/occupations, such as housewives, cleaners, students.

Occupational exposure and risk of breast cancer

Breast cancer is a multifactorial disease and the most commonly diagnosed cancer in women. Traditional risk factors for breast cancer include reproductive status, genetic mutations, family history and lifestyle. However, increasing evidence has identified an association between breast cancer and occupational factors, including environmental stimuli. Epidemiological and experimental studies demonstrated that ionizing and non-ionizing radiation exposure, night-shift work, pesticides, polycyclic aromatic hydrocarbons and metals are defined environmental factors for breast cancer, particularly at young ages. However, the mechanisms by which occupational factors can promote breast cancer initiation and progression remains to be elucidated. Furthermore, the evaluation of occupational factors for breast cancer, particularly in the workplace, also remains to be explained. The present review summarizes the occupational risk factors and the associated mechanisms involved in breast cancer development, in order to highlight new environmental exposures that could be correlated to breast cancer and to provide new insights for breast cancer prevention in the occupational settings. Furthermore, this review suggests that there is a requirement to include, through multidisciplinary approaches, different occupational exposure risks among those associated with breast cancer development. Finally, the design of new epigenetic biomarkers may be useful to identify the workers that are more susceptible to develop breast cancer.

Chemical exposures in the workplace and breast cancer risk: A prospective cohort study

We investigated the relationship between workplace chemical exposures and breast cancer risk among women enrolled in the Sister Study, a prospective cohort study of US and Puerto Rican women. A total of 47,640 participants reported work outside of the home. Workplace exposure to eleven agents (acids, dyes or inks, gasoline or other petroleum products, glues or adhesives, lubricating oils, metals, paints, pesticides, soldering materials, solvents and stains or varnishes) was characterized based on self-reports of frequency and duration of use. Approximately 14% of the study population reported exposure to only one agent and 11% reported working with two or more of the 11 agents in their lifetime. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for each agent, adjusting for established breast cancer risk factors. During follow-up, 1,966 cases of breast cancer were reported. Although there were no significant associations between ever use of the eleven agents evaluated and breast cancer risk, women with cumulative exposure to gasoline or petroleum products at or above the highest quartile cutoff had an elevated risk of total (HR: 2.3, 95%CI: 1.1-4.9) and invasive (HR: 2.5, 95%CI: 1.1-5.9) breast cancer compared with women in the lowest quartile group (ptrend  = 0.03). Workplace exposure to soldering materials was associated with an increased risk of premenopausal breast cancer (HR = 1.8, 95% CI = 1.1-3.0). Findings support the need for further studies to elucidate the role of occupational chemicals in breast cancer etiology.

Occupational exposure to solvents and risk of breast cancer

BACKGROUND

Occupational exposure to some organic solvents may increase risk of breast cancer.

METHODS

In a population-based case-control study, 1,205 women diagnosed with primary breast cancer between 2009 and 2011 were drawn from the Western Australian Cancer Registry and matched to 1,789 controls from the electoral roll. Exposure to solvents was determined through telephone interviews using OccIDEAS.

RESULTS

About a third of women were occupationally exposed to solvents. Age adjusted breast cancer risks were elevated for women who had been exposed to aliphatic solvents odds ratio (OR) 1.21 (95%CI 0.99-1.48) and aromatic solvents OR 1.21 (95%CI 0.97-1.52). For most solvents the ORs were higher for those diagnosed before menopause.

CONCLUSIONS

This study suggests that there may be an association between occupational exposure to aliphatic and aromatic solvents and the risk of breast cancer at the low levels of exposure experienced by women in this study.

the risk of cancer among Taiwanese female registered nurses: a nationwide retrospective study

Background

To evaluate the risk of cancer among Taiwanese female registered nurses (RNs) using a nationwide population-based dataset.

Methods

We recruited female RNs without antecedent cancer from the Taiwan National Health Insurance Research database during 2000–2010. Standardized incidence ratios (SIRs) of cancer were calculated. We also compared rates of Papanicolaou (Pap) smear use between the RNs and the general population matched by age and sex.

Results

A total of 2,077 cancers developed among 184,809 female RNs, with a follow-up of 1,371,910 person-years (median follow-up of 7.86 years), leading to an increased SIR of 1.10 [95% confidence interval (CI) 1.05–1.15]. RNs aged between 40–59 years also had a significantly increased SIR (1.14, 95% CI 1.08–1.21). For specific cancer types, RNs had an increased SIR for breast (1.28, 95% CI 1.19–1.37), thyroid (1.26, 95% CI 1.10–1.43), lung and mediastinum (1.36, 95% CI 1.13–1.62), and uterine cancers (1.23, 95% CI 1.01–1.49). A decreased SIR was found for cervix (0.48, 95% CI 0.37–0.61) and liver and biliary tract cancers (0.68, 95% CI 0.50–0.90). Pap smear use averaged 5.80 times per person among female RNs aged 35 years or older and 5.50 times per person in the age-matched control group (p = 0.009).

Conclusion

This study found that overall cancer risk was higher among female RNs than general population. For individual cancers, the risks of breast, lung, thyroid and uterine cancer were higher and the risks of cervix and liver cancer were lower than general population. The lower risk of cervical cancer might be partially explained by the increased use of Pap smears in the RNs group. Further large, unbiased population-based prospective studies are needed to investigate the association between nurses and cancer risk and identify the risk factors of cancer in nurses.

The mammary gland carcinogens: the role of metal compounds and organic solvents

The increased rate of breast cancer incidences especially among postmenopausal women has been reported in recent decades. Despite the fact that women who inherited mutations in the BRCA1 and BRCA2 genes have a high risk of developing breast cancer, studies have also shown that significant exposure to certain metal compounds and organic solvents also increases the risks of mammary gland carcinogenesis. While physiological properties govern the uptake, intracellular distribution, and binding of metal compounds, their interaction with proteins seems to be the most relevant process for metal carcinogenicity than biding to DNA. The four most predominant mechanisms for metal carcinogenicity include (1) interference with cellular redox regulation and induction of oxidative stress, (2) inhibition of major DNA repair, (3) deregulation of cell proliferation, and (4) epigenetic inactivation of genes by DNA hypermethylation. On the other hand, most organic solvents are highly lipophilic and are biotransformed mainly in the liver and the kidney through a series of oxidative and reductive reactions, some of which result in bioactivation. The breast physiology, notably the parenchyma, is embedded in a fat depot capable of storing lipophilic xenobiotics. This paper reviews the role of metal compounds and organic solvents in breast cancer development.

Pesticides and human chronic diseases: evidences, mechanisms, and perspectives

Along with the wide use of pesticides in the world, the concerns over their health impacts are rapidly growing. There is a huge body of evidence on the relation between exposure to pesticides and elevated rate of chronic diseases such as different types of cancers, diabetes, neurodegenerative disorders like Parkinson, Alzheimer, and amyotrophic lateral sclerosis (ALS), birth defects, and reproductive disorders. There is also circumstantial evidence on the association of exposure to pesticides with some other chronic diseases like respiratory problems, particularly asthma and chronic obstructive pulmonary disease (COPD), cardiovascular disease such as atherosclerosis and coronary artery disease, chronic nephropathies, autoimmune diseases like systemic lupus erythematous and rheumatoid arthritis, chronic fatigue syndrome, and aging. The common feature of chronic disorders is a disturbance in cellular homeostasis, which can be induced via pesticides' primary action like perturbation of ion channels, enzymes, receptors, etc., or can as well be mediated via pathways other than the main mechanism. In this review, we present the highlighted evidence on the association of pesticide's exposure with the incidence of chronic diseases and introduce genetic damages, epigenetic modifications, endocrine disruption, mitochondrial dysfunction, oxidative stress, endoplasmic reticulum stress and unfolded protein response (UPR), impairment of ubiquitin proteasome system, and defective autophagy as the effective mechanisms of action.

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.

Schizophrenia, cancer and obstetric complications in an evolutionary perspective-an empirically based hypothesis

OBJECTIVE

Patients diagnosed with schizophrenia have reduced fecundity and premature mortality (both accidental and violent) with no obvious compensatory advantages among kin. The prevalence of the disorder is around 0.7/1%, higher than the expected prevalence of spontaneous mutations. Genes favoring schizophrenia may have been positively selected in the environment of evolutionary adaptation. Literature on potential adaptive genes is reviewed within an evolutionary framework.

METHODS

Literature search on major scientific search engine (PubMed/Medline, Ovid/PsychInfo) on papers aimed at investigating potential pathways justifying a mutation-selection balanced model. Findings are presented with a narrative touch to favor readability and understanding.

RESULTS

Reduced incidence of cancer in both patients diagnosed with schizophrenia and their siblings was reported worldwide. Such findings are notable given higher cancer risk factors in schizophrenia, i.e., smoking, alcohol abuse, obesity, poor diet, and poor adherence to therapy. Some genes involved in cancer proliferation might as well confer protective advantage in immune-surveillance, inflammation, vascular proliferation or apoptosis that otherwise will adversely affect early neurodevelopment.

CONCLUSION

Evidence that reduced risk of certain somatic diseases is associated with schizophrenia is quite significant to progress in the evolutionary epidemiological analysis of psychopathology.

Risk of breast cancer following exposure to tetrachloroethylene-contaminated drinking water in Cape Cod, Massachusetts: reanalysis of a case-control study using a modified exposure assessment

BACKGROUND

Tetrachloroethylene (PCE) is an important occupational chemical used in metal degreasing and drycleaning and a prevalent drinking water contaminant. Exposure often occurs with other chemicals but it occurred alone in a pattern that reduced the likelihood of confounding in a unique scenario on Cape Cod, Massachusetts. We previously found a small to moderate increased risk of breast cancer among women with the highest exposures using a simple exposure model. We have taken advantage of technical improvements in publically available software to incorporate a more sophisticated determination of water flow and direction to see if previous results were robust to more accurate exposure assessment.

METHODS

The current analysis used PCE exposure estimates generated with the addition of water distribution modeling software (EPANET 2.0) to test model assumptions, compare exposure distributions to prior methods, and re-examine the risk of breast cancer. In addition, we applied data smoothing to examine nonlinear relationships between breast cancer and exposure. We also compared a set of measured PCE concentrations in water samples collected in 1980 to modeled estimates.

RESULTS

Thirty-nine percent of individuals considered unexposed in prior epidemiological analyses were considered exposed using the current method, but mostly at low exposure levels. As a result, the exposure distribution was shifted downward resulting in a lower value for the 90th percentile, the definition of "high exposure" in prior analyses. The current analyses confirmed a modest increase in the risk of breast cancer for women with high PCE exposure levels defined by either the 90th percentile (adjusted ORs 1.0-1.5 for 0-19 year latency assumptions) or smoothing analysis cut point (adjusted ORs 1.3-2.0 for 0-15 year latency assumptions). Current exposure estimates had a higher correlation with PCE concentrations in water samples (Spearman correlation coefficient = 0.65, p < 0.0001) than estimates generated using the prior method (0.54, p < 0.0001).

CONCLUSIONS

The incorporation of sophisticated flow estimates in the exposure assessment method shifted the PCE exposure distribution downward, but did not meaningfully affect the exposure ranking of subjects or the strength of the association with the risk of breast cancer found in earlier analyses. Thus, the current analyses show a slightly elevated breast cancer risk for highly exposed women, with strengthened exposure assessment and minimization of misclassification by using the latest technology.

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.

Why pesticides could be a common cause of prostate and breast cancers in the French Caribbean Island, Martinique. An overview on key mechanisms of pesticide-induced cancer

Prostate and breast cancers have become very frequent in Martinique. We previously conducted a multifactorial analysis in the French Caribbean Island, Martinique, in order to elucidate the aetiology of prostate cancer. Using a linear regression analysis, we found that the growth curves of incidence rates for Martinique and metropolitan France have been significantly diverging since 1983. Although a Caribbean genetic susceptibility factor may be involved in prostate carcinogenesis: this factor, because it could not have changed during the observation period, cannot per se account for the growing incidence of this cancer in the island. We therefore suggested that among possible environmental factors, the intensive and prolonged exposure to Carcinogenic, Mutagenic and/or Reprotoxic (CMR) or presumed CMR pesticides may account for the observed growing incidence of prostate cancer and thus may be involved in prostate carcinogenesis. In this study, we further attempt to show that due to their carcinogenic properties, pesticides and especially organochlorine pesticides may in fact be causally implicated in the growing incidence of prostate cancer in Martinique. Also, we suggest that CMR or presumed CMR pesticides may be causally involved in the growing incidence of breast cancer through a common endocrine disruption mechanism. We therefore propose that protective medical recommendations should be immediately set up and carried out by general practitioners, paediatricians, obstetricians, gynaecologists and urologists; and that public health measures of primary precaution and prevention should be urgently taken in close collaboration with health professionals in order to protect population, more especially pregnant women and children, with the final objective perhaps that these medical recommendations and public health measures will stop Martinique's cancer epidemic.

Occupations and lung cancer: a population-based case-control study in British Columbia

An investigation based on a large population-based case-control study in British Columbia, Canada, was conducted to identify high-risk occupations for lung cancer by histological subtypes. Subjects were 14,755 male incident cancer cases for whom lifetime occupational histories and information on smoking and relevant covariates were collected. Occupational associations for 2998 lung cancer cases, including histological subtypes, were assessed by logistic regression using other cancer cases, excluding smoking-related cancers, as controls. An excess risk of lung cancer was found among workers in metal processing, bakers, and ship deck crew for all histological subtypes, and construction workers, chefs and cooks, and medical workers for specific histological subtypes. Occupational associations that are unique to histological subtypes of lung cancer were identified. Owing to a scarcity of literature in this area, future research needs to focus on confirming these histological associations, and identifying the risk from key exposures found within these occupations (e.g., medical radiation, electromagnetic fields, and cooking fumes).

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.

Risk for leukaemia and brain and breast cancer among Danish utility workers: a second follow-up

OBJECTIVE

To update a study of risks for leukaemia, brain cancer and breast cancer in a Danish nationwide, population-based cohort of utility employees.

METHODS

A multivariate statistical model including information on age, duration of employment, date of first employment and level of occupational exposure to electromagnetic fields was applied.

RESULTS

No increased risk for these cancers was seen among 28,224 subjects with more than 3 months of employment in whom cancer had not been diagnosed before first employment.

CONCLUSION

The results do not support the hypothesis of an association between occupational exposure to magnetic fields in the electric utility industry and risks for leukaemia, brain cancer and 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.

Endocrine disrupters--potential modulators of the immune system and allergic response

Endocrine disrupters (EDs) are environmental pollutants of industrial or agricultural origin (e.g. herbicides, fungicides, insecticides, industrial chemicals) that may influence health of wildlife and human. Endocrine-disrupting effect is obtained by mimicking the action of the steroid hormones and has been associated with several reproductive disorders as well as cancerogenesis both in animals and humans. EDs can also influence synthesis of cytokines, immunoglobulins, and cell mediators as well as immune cell activation and survival. Modulation by EDs of interleukin-4 production, Th1/Th2 balance and IgE production suggest their potential effect on allergic immune responses. The aim of this review was to summarize data indicating a potential effect of EDs exposure on the immune system and allergic responses.

Risk of breast cancer after night- and shift work: current evidence and ongoing studies in Denmark

Breast cancer is the most frequent cancer among women, and the number is increasing worldwide. This tumour is strongly associated with Western lifestyle, but the specific risk factors behind this observation are not well known. Exposure to light-at-night, including disturbance of the circadian rhythm, possibly mediated via the melatonin synthesis and clock genes, has been suggested as a contributing cause of breast cancer. Since shift- and night-time work is prevalent and increasing in modern societies, this exposure may be of public health concern, and contribute to the continuing elevation in breast cancer risk. Until now only few epidemiological studies have evaluated breast cancer risk after shift and night work. Although these studies are all suffering from methodological problems, especially concerning assessment of light exposure, results have consistently shown an increase in risk associated with night and shift work. Good opportunities for epidemiological cancer research exist in Denmark, and several studies on different aspects of breast cancer, work schedules, light exposure and melatonin levels are ongoing in order to further examine different aspects of this issue.

Formative research on adolescent and adult perceptions of risk factors for breast cancer

This study uses the Health Belief Model (HBM) as a framework to guide formative research of the lay public's perceptions of risks associated with breast cancer. Data were collected from adolescent females and adult females across four counties in Michigan, US. Ten focus groups (N=91) were conducted and analyzed with a coding scheme based on the HBM. Participants' responses to focus group questions (N=5168 thought units) reveal beliefs about severity, susceptibility, and efficacy pertaining to breast cancer, nutrition, activity, environment, and the role of government and industry. Chi-squares examined the distribution of statements across categories between adult females and adolescent females. Results revealed that both adolescent and mother groups recognized gender and heredity as relevant risk factors related to susceptibility, and detection as a strategy to decrease severity of breast cancer through early treatment. Beliefs about environmental factors were characterized by uncertainty for both groups. Also, while adolescent girls communicated more about efficacy issues, mothers focused significantly more than adolescent girls on the role of government and industry in breast cancer prevention and treatment. Representative qualitative thought units are included based on their frequency, salience, and relevance to HBM message design guidelines. Formative research is the first phase in the development of health campaigns, informing the creation of health messages for target audiences.

Occupation and Breast Cancer: A Canadian Case-Control Study

A local collaborative process was launched in Windsor, Ontario, Canada to explore the role of occupation as a risk factor for cancer. An initial hypothesis-generating study found an increased risk for breast cancer among women aged 55 years or younger who had ever worked in farming. On the basis of this result, a 2-year case-control study was undertaken to evaluate the lifetime occupational histories of women with breast cancer. The results indicate that women with breast cancer were nearly three times more likely to have worked in agriculture when compared to the controls (OR = 2.80 [95% CI, 1.6-4.8]). The risk for those who worked in agriculture and subsequently worked in automotive-related manufacturing was further elevated (OR = 4.0 [95% CI, 1.7-9.9]). The risk for those employed in agriculture and subsequently employed in health care was also elevated (OR = 2.3 [95% CI, 1.1-4.6]). Farming tended to be among the earlier jobs worked, often during adolescence. While this article has limitations including the small sample size and the lack of information regarding specific exposures, it does provide evidence of a possible association between farming and breast cancer. The findings indicate the need for further study to determine which aspects of farming may be of biological importance and to better understand the significance of timing of exposure in terms of cancer risk.

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.

An ecological study of the association of environmental chemicals on breast cancer incidence in Texas

PURPOSE

To investigate the role of environment in breast cancer development, we conducted an ecological study to examine the association of releases for selected industrial chemicals with breast cancer incidence in Texas.

METHODS

During 1995--2000, 54,487 invasive breast cancer cases were reported in Texas. We identified 12 toxicants released into the environment by industry that: (1) were positively associated with breast cancer in epidemiological studies, (2) were Environmental Protection Agency (EPA) Toxics Release Inventory (TRI) chemicals designated as carcinogens or had estrogenic effects associated with breast cancer risk, and (3) had releases consistently reported to EPA TRI for multiple Texas counties during 1988--2000. We performed univariate, and multivariate analyses adjusted for race and ethnicity to examine the association of releases for these toxicants during 1988--2000 with the average annual age-adjusted breast cancer rate at the county level.

RESULTS

Univariate analysis indicated that formaldehyde, methylene chloride, styrene, tetrachloroethylene, trichloroethylene, chromium, cobalt, copper, and nickel were positively associated with the breast cancer rate. Multivariate analyses indicated that styrene was positively associated with the breast cancer rate in women and men (beta=0.219, p=.004), women (beta=0.191, p=0.002), and women >or= 50 years old (beta=0.187, p=0.002).

CONCLUSION

Styrene was the most important environmental toxicant positively associated with invasive breast cancer incidence in Texas, likely involving women and men of all ages. Styrene may be an important breast carcinogen due to its widespread use for food storage and preparation, and its release from building materials, tobacco smoke, and industry.

A gene-environment interaction between occupation and BRCA1/BRCA2 mutations in male breast cancer?

The association of male breast cancer (MBC) with a positive breast cancer (BC) family history and with BRCA1/2 germ-line mutations points to a genetic component; a relationship with occupation has also been reported. Recently, we identified pathogenetic BRCA1/2 mutations in a population-based series of Italian MBC patients: here in, we investigated interactions between a carrier status for BRCA1/2 mutations and occupation using a case-case design and estimating case-only odds ratios (CORs). Truck-driving was the most frequent occupation (3/4 BRCA-related cases and 2/19 unrelated cases). An interaction between carrier status and working as a truck-driver emerged, when we classified MBC cases as "ever/never-held" this job title (COR 25.5; 95% Confidence Limits (CL): 1.1-1,412.5) or according to truck-driving as the "longest-held" work (COR 54.0; 95% CL: 1.6-2,997.5). The possible modifying effect on MBC risk in subjects carrying BRCA1/2 germ-line mutations of an occupation characterised by exposure to chemicals such as polycyclic aromatic hydrocarbons (PAH) that are capable of inducing DNA damage, may provide clues to the role of environmental exposures in modifying BC risk in mutation carriers in both genders.

The Effect of Environment on Breast Cancer Risk

Environmental factors are believed to explain a large proportion of breast cancer incidence. Known risk factors for breast cancer, which are related to the reproductive life of women, and other factors, such as inheritance and socioeconomic status, explain only about half of the breast cancer cases in the US. Ionizing radiation is a well established environmental risk factor for breast cancer. Chemicals that induce mammary cancer in rodents have served as leads for studies in humans, but occupational and environmental exposure to these chemicals have for the most part lacked association with breast cancer risk. However, there is recent evidence in rats that cadmium at very low doses acts as an estrogen mimic, indicating a need to investigate the effects of metals on breast cancer risk. Studies suggest that circadian rhythm disruption is linked with breast cancer, but too few studies have been done to be conclusive. Over the years, cigarette smoking as a risk factor for breast cancer has remained controversial. However, recent research has found passive smoke exposure to be associated with increased breast cancer risk, which is hypothesized to be accounted for on the basis of an antiestrogenic effect of smoking. Solar radiation has been noted to be associated with reduced breast cancer, supporting the hypothesis that vitamin D plays a protective role in reducing this risk. Although, most of the environmental factors discussed in this review have not been convincingly found to influence breast cancer risk, research suggests that environmental exposure in combination with genetic pre-disposition, age at exposure, and hormonal milieu have a cumulative effect on breast cancer risk.

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 risk among female nurses: a literature review

Some studies have demonstrated increased risk of different cancers among female nurses. A review of relevant papers was made to assess whether the increase is caused by occupational exposures or other factors. A computerized literature search on combinations of the keywords 'nurses', 'occupation', 'hazards', 'cancer' and 'mortality' and related articles was performed. A total of 30 reports were identified from 19 independent studies conducted between 1983 and 2001. The majority of the studies were registry studies, with limited data on employment history and confounding factors. In conclusion, knowledge about exposures and observed excesses of cancer risk give reason to suspect an occupational influence on breast cancer and leukaemia. The grouping together of nurses from different workplaces may camouflage real differences in risk. Future studies should collect information at the individual level about work history and personal risk factors.

Mortality among a Cohort of Female Farm Residents in New York State

A retrospective cohort study of mortality among 6,405 female farm residents who were New York Farm Bureau members, or spouses or relatives of members, was conducted from 1980 through 1993. Similar to previous findings for male farmers, the cohort experienced significantly lower mortality rates for all causes combined (including malignant neoplasms and cardiovascular disease), compared with rural nonfarm female residents. These findings suggest that farmers and farm residents of both genders have favorable habits with respect to several lifestyle factors. The results of this study were consistent with those from other studies of farm populations worldwide.

Occupational risk factors for sarcoidosis in African-American siblings

OBJECTIVES

To determine whether certain occupations and occupationally related exposures were associated with a history of sarcoidosis in African-American siblings.

METHODS

We collected occupational data from 921 African Americans in 273 sibships that had been identified through a sarcoidosis case. Among the 648 siblings of sarcoidosis index cases enrolled, 30 (4.6%) also had a history of sarcoidosis. A detailed job history was obtained for any job held for > or = 6 months throughout the subject's life.

RESULTS

Having a usual occupation in education (odds ratio [OR], 2.18; 95% confidence interval [CI], 1.07 to 4.44), in metal machining (OR, 7.47; 95% CI, 1.19 to 47.06), and ever working in metalworking, not elsewhere classified (OR, 2.05; 95% CI, 1.14 to 3.70) were associated with increased sarcoidosis risk. Occupations ever held in the transportation services industry (OR, 12.71; 95% CI, 1.32 to 122.56) and usual occupations in the retail trade industry (OR, 0.49; 95% CI, 0.27 to 0.88) also were associated with sarcoidosis risk. Specific occupational exposures that were associated with sarcoidosis included titanium (OR, 3.15; 95% CI, 1.02 to 9.68) and vegetable dust (OR, 1.82; 95% CI, 1.01 to 3.27), and indoor exposure to high humidity (OR, 1.51; 95% CI, 1.13 to 2.02), water damage (OR, 1.50; 95% CI, 1.11 to 2.03), or musty odors (OR, 1.78; 95% CI, 1.32 to 2.40) for > 1 year.

CONCLUSION

Individuals who work in occupations with potential metal exposures or in workplaces with high humidity may be at an increased risk for sarcoidosis, but the complexity of occupationally related exposures makes it difficult to identify specific agents by using job titles as a surrogate for exposure. A more detailed exposure assessment of such jobs, along with the incorporation of genetic risk factors, should help to uncover the complex etiology of sarcoidosis.

Carcinogenic and endocrine disrupting effects of cigarette smoke and risk of breast cancer

BACKGROUND

Results of epidemiological studies, assessing the relation between smoking and breast cancer, have been inconclusive. Our aim was to assess the carcinogenic and possibly antioestrogenic effects of cigarette smoke on risk of breast cancer.

METHODS

We sent a questionnaire to 1431 women younger than age 75 years who had breast cancer and were listed on the population-based British Columbia cancer registry between June 1, 1988, and June 30, 1989. We also sent questionnaires to 1502 age-matched controls, randomly selected from the 1989 provincial voters list. We obtained information on all known and suspected risk factors for breast cancer, and on lifetime smoking, alcohol consumption, and occupational history. We assessed the effect of smoking separately for premenopausal and postmenopausal women, adjusting for confounding variables.

FINDINGS

318 premenopausal women and 340 controls replied. Risk of breast cancer was significantly increased (adjusted odds ratio 1.69, 95% CI 1.13-2.51) in women who had been pregnant and who started to smoke within 5 years of menarche, and in nulliparous women who smoked 20 cigarettes daily or more (7.08, 1.63-30.8) and had smoked for 20 cumulative pack-years or more (7.48, 1.59-35.2). Postmenopausal women (700 breast cancer and 685 controls) whose body-mass index increased from age 18 to current and who started to smoke after a first fullterm pregnancy had a significantly reduced risk of breast cancer (0.49, 0.27-0.89).

INTERPRETATION

Our results suggest that cigarette smoke exerts a dual action on the breast, with different effects in premenopausal and postmenopausal women. Our observations reinforce the importance of smoking prevention, especially in early adolescence, and draw attention to the timing of exposure in relation to susceptibility and refractory windows in the design of studies to investigate associations between environmental carcinogens or putative endocrine disruptors and risk of breast cancer.

Occupations and breast cancer risk among Chinese women in urban Shanghai

BACKGROUND

Although, an elevated risk of breast cancer has been suggested for a number of occupations, many earlier studies were limited by selection biases, the incomplete assessment of job histories, and the inability to control for confounding.

METHODS

We examined the relationship between occupational history and breast cancer risk using data from a population-based case-control study of 1,458 cases and 1,556 age-matched controls (90% response rate) conducted in Shanghai, China. Unconditional logistic regression models were used to derive odds ratios (ORs) and 95% confidence intervals (95% CIs) of breast cancer risk associated with occupations and duration of employment adjusting for non-occupational risk factors.

RESULTS

The following occupations were found to be associated with an increased risk of breast cancer: laboratory technicians (OR 9.94, 95% CI 1.20-82.37), telephone and telegraph operators (OR 4.63, 95% CI 1.85-11.59), leather and fur processors (OR 3.25, 95% CI 1.11-9.53), and glass-manufacturing workers (OR 2.08, 95% CI 1.14-3.82). A dose-response pattern for years of employment was observed for leather and fur processors (P = 0.02) and glass-manufacturing workers (P = 0.01). Stratified analyses also revealed dose-response relationships between the risk of breast cancer and years of employment as inspector and product analysts among pre-menopausal women (P = 0.02), and as farmers among post-menopausal women (P = 0.04).

CONCLUSIONS

This study found that several occupations are associated with an increased risk of breast cancer among women. Studies examining various occupational exposures in these high-risk occupations are warranted to identify carcinogens that may play a role in the increased breast cancer risk.

On the rumors about the silent spring. Review of the scientific evidence linking occupational and environmental pesticide exposure to endocrine disruption health effects

Occupational exposure to some pesticides, and particularly DBCP and chlordecone, may adversely affect male fertility. However, apart from the therapeutic use of diethylstilbestrol, the threat to human reproduction posed by "endocrine disrupting" environmental contaminants has not been supported by epidemiological evidence thus far. As it concerns other endocrine effects described in experimental animals, only thyroid inhibition following occupational exposure to amitrole and mancozeb has been confirmed in humans. Cancer of the breast, endometrium, ovary, prostate, testis, and thyroid are hormone-dependent, which fostered research on the potential risk associated with occupational and environmental exposure to the so-called endocrine-disrupting pesticides. The most recent studies have ruled out the hypothesis of DDT derivatives as responsible for excess risks of cancer of the reproductive organs. Still, we cannot exclude a role for high level exposure to o,p'-DDE, particularly in post-menopausal ER+ breast cancer. On the other hand, other organochlorine pesticides and triazine herbicides require further investigation for a possible etiologic role in some hormone-dependent cancers.

Pesticides and mortality from hormone-dependent cancers

Endocrine-disrupting chemicals are considered to be a possible cause of hormone-dependent cancers. In areas of high exposure to pesticides, people are concerned about the long lasting toxicity of pesticides, some of which are possibly hormonally active. We collected for each Belgian municipality (n = 589) the latest mortality statistics from breast and prostate cancer (period 1985-1994) and the latest data on crops and pesticides (1998). In addition, data on possible confounders such as population density, degree of urbanization, industrial activity and the presence of an incinerator were collected as well. The data were analysed with spatial statistics that takes into account the spatial nature of the data. There is a large variation in crops and pesticide exposure among the municipalities, the highest exposure being seen in the fruit production area. Apart from use of defoliants and potato cultivation, no consistent correlation was detected between crops, pesticides and mortality from breast and prostate cancer. Our data cannot support the hypothesis of a relationship between total and class-related pesticide use and breast and prostate cancer mortality. However, the increased mortality due to breast cancer and to a lesser extent due to prostate cancer in traditional potato-growing areas needs attention and more research.