Occupation and cancer – follow-up of 15 million people in five Nordic countries

Shift Work and Cancer: State of Science and Practical Consequences

In 2007, an expert Working Group convened by the IARC Monographs Programme concluded that shift work that involves circadian disruption is probably carcinogenic to humans (Group 2A). We scrutinised the epidemiological basis for this conclusion, with a focus on, but not limited to, breast and prostate cancers. We further considered practical consequences for shift workers in our industry against the background of new findings.

We carried out a literature search including the epidemiological studies cited by IARC and newer available literature on shift work and cancer.

Since the IARC assessment, eleven new studies have emerged, ten of which have already been published, with inconclusive results. Heterogeneity of exposure metrics and study outcomes and emphasis on positive but non-significant results make it difficult to draw general conclusions. Also, several reviews and commentaries, which have been published meanwhile, came to equivocal results. Published evidence is widely seen as suggestive but inconclusive for an adverse association between night work and breast cancer, and limited and inconsistent for cancers at other sites and all cancers combined.

At this point in time it can not be ruled out that shift work including night work may increase the risk for some cancers in those who perform it. However, shift schedules can be organised in ways that minimise the associated health risks, and the risks may be further reduced through the implementation of structured and sustained health promotion programs specifically tailored to the needs of shift workers.

Cancer incidence among Swedish pulp and paper mill workers: a cohort study of sulphate and sulphite mills

PURPOSE

Associations between various malignancies and work in the pulp and paper industry have been reported but mostly in analyses of mortality rather than incidence. We aimed to study cancer incidence by main mill pulping process, department and gender in a Swedish cohort of pulp and paper mill workers.

METHODS

The cohort (18,113 males and 2,292 females, enrolled from 1939 to 1999 with >1 year of employment) was followed up for cancer incidence from 1958 to 2001. Information on the workers' department and employment was obtained from the mills' personnel files, and standardized incidence ratios (SIRs) were calculated using the Swedish population as reference.

RESULTS

Overall cancer incidence, in total 2,488 cases, was not increased by work in any department. However, risks of pleural mesothelioma were increased among males employed in sulphate pulping (SIR, 8.38; 95 % CI, 3.37-17) and maintenance (SIR, 6.35; 95 % CI, 3.47-11), with no corresponding increase of lung cancer. Testicular cancer risks were increased among males employed in sulphate pulping (SIR, 4.14; 95 % CI, 1.99-7.61) and sulphite pulping (SIR, 2.59; 95 % CI, 0.95-5.64). Female paper production workers showed increased risk of skin tumours other than malignant melanoma (SIR, 2.92; 95 % CI, 1.18-6.02).

CONCLUSIONS

Incidence of pleural mesothelioma was increased in the cohort, showing that asbestos exposure still has severe health consequences, and highlighting the exigency of strict asbestos regulations and elimination. Testicular cancer was increased among pulping department workers. Shift work and endocrine disruptors could be of interest in this context.

Circadian disruption, sleep loss, and prostate cancer risk: a systematic review of epidemiologic studies

Disruption of the circadian system has been hypothesized to increase cancer risk, either because of direct disruption of the molecular machinery generating circadian rhythms or because of disruption of parameters controlled by the clock such as melatonin levels or sleep duration. This hypothesis has been studied in hormone-dependent cancers among women, but data are sparse about potential effects of circadian disruption on the risk of prostate cancer. This review systematically examines available data evaluating the effects of light at night, sleep patterns, and night shift work on prostate cancer risk.

Lung cancer risk among construction workers in California, 1988-2007

BACKGROUND

Although lung cancer risks can vary by race/ethnicity and by construction occupation, these risks have not been examined extensively.

METHODS

This study analyzed 110,937 lung cancer cases identified from the California Cancer Registry between 1988 and 2007. Mean age at diagnosis, proportion diagnosed at an advanced stage, and proportion with 3-year survival were calculated for lung cancer cases employed in the construction industry. Case-control methodology was also used to assess the risk of lung cancer. Morbidity odds ratios (MORs) were estimated by conditional logistic regression.

RESULTS

Construction workers were found to have a significantly elevated risk for all lung cancer combined (MOR = 1.57) and for each lung cancer histologic subtype examined. All construction occupations, except managers/engineers and supervisors, had a significantly elevated risk for all lung cancer combined. Roofers and welders had the highest risks for total lung cancer and for each of the histologic subtypes. Construction workers in each of the four race/ethnicity groups also had significantly increased lung cancer risks. Compared to non-construction workers, construction workers were diagnosed at an earlier age, at a more advanced stage, and had significantly lower 3-year survival, though differences were modest.

CONCLUSION

These findings justify additional reductions in carcinogenic exposures in construction, and increased support for smoking cessation programs at construction sites.

Industrial pollution and pleural cancer mortality in Spain

Pleural cancer mortality is an acknowledged indicator of exposure to asbestos and mesothelioma mortality but in 15%-20% of cases no exposure can be recalled. In the past, asbestos was used in many industries and it is still found in many installations. Our objective was to ascertain whether there might be excess pleural cancer mortality among populations residing in the vicinity of Spanish industrial installations that are governed by the Integrated Pollution Prevention and Control (IPPC) Directive and the European Pollutant Release and Transfer Register Regulation and report their emissions to air. An ecological study was designed to examine pleural cancer mortality at a municipal level (8098 Spanish towns) over the period 1997-2006, during which 2146 deaths were registered. We conducted an exploratory "near vs. far" analysis to estimate the relative risks (RRs) of towns situated at a distance of <2 km from installations. This analysis was repeated for each of the 24 industrial groups. RR and their 95% credible intervals (95% CIs) were estimated on the basis of a Poisson conditional autoregressive Bayesian model with explanatory variables. Integrated nested Laplace approximations were used as a Bayesian inference tool. Analysis showed statistically significant RRs in both sexes in the vicinity of 7 of the 24 industrial groups studied (RR, 95% CI), namely, biocide facilities (2.595, 1.459-4.621), ship-building (2.321, 1.379-3.918), glass and mineral fibre production (1.667, 1.041-2.665), non-hazardous waste treatment (1.737, 1.077-2.799), galvanising (1.637, 1.139-2.347), organic chemical plants (1.386, 1.075-1.782) and the food and beverage sector (1.255, 1.006-1.562). In the proximity of sources pertaining to the biocide, organic chemical and galvanising sectors, the risk was seen to be rising among men and women, a finding that could indicate airborne environmental exposure. These results support that residing in the vicinity of IPPC-registered industries that release pollutants to the air constitutes a risk factor for pleural cancer.

Rotating night shift work and mammographic density

BACKGROUND

An increased risk of breast cancer has been observed in night shift workers. Exposure to artificial light at night and disruption of the endogenous circadian rhythm with suppression of the melatonin synthesis have been suggested mechanisms. We investigated the hypothesis that rotating night shift work is associated with mammographic density.

METHODS

We conducted a cross-sectional study on the association between rotating night shift work characteristics, 6-sulfatoxymelatonin (MT6s) creatinine adjusted in a spot morning urine sample, and a computer-assisted measure of mammographic density in 640 nurses and midwives ages 40 to 60 years. The associations were evaluated using regression models adjusted for age, body mass index, menopausal status, age at menopause, age at menarche, smoking, and the calendar season of the year when mammography was conducted.

RESULTS

The adjusted means of percentage of mammographic density and absolute density were slightly higher among women working rotating night shifts but not statistically significant [percentage of mammographic density = 23.6%, 95% confidence interval (CI), 21.9%-25.4% vs. 22.5%, 95% CI, 20.8%-24.3%; absolute density = 23.9 cm(2), 95% CI, 21.4-26.4 cm(2) vs. 21.8 cm(2), 95% CI, 19.4-24.3 cm(2) in rotating night shift and day shift nurses, respectively). There were no significant associations between the current or cumulative rotating night shift work exposure metrics and mammographic density. No association was observed between morning MT6s and mammographic density.

CONCLUSIONS

The hypothesis on the link between rotating night shift work, melatonin synthesis disruption, and mammographic density is not supported by the results of the present study.

IMPACT

It is unlikely that the development of breast cancer in nurses working rotating night shifts is mediated by an increase in mammographic density.

Prostate cancer and occupational whole-body vibration exposure

Prostate cancer is common and its etiology largely unknown; therefore, it is important to explore all potential risk factors that are biologically plausible. Recent literature suggests a relationship between whole-body vibration (WBV) and prostate cancer risk. The aim of this study was to determine whether occupational WBV was a risk factor for prostate cancer. Existing data, collected on 447 incident cases and 532 population controls (or their proxies), in Montreal, Canada, were used to evaluate this question. Personal interviews collected detailed job descriptions for every job held, the tasks involved, and type of equipment used. For each job, experts assessed the intensity and daily duration of WBV exposure. Inter-rater agreement for WBV ratings was examined using the kappa statistic, with values that ranged from 0.83 to 0.94. Logistic regression models explored the relationship between WBV exposure and prostate cancer, using various combinations of intensity, daily duration, and years of exposure. Potential confounders were also examined. Occupations with WBV exposure demonstrated an increased statistically non-significant risk [odds ratio (OR) = 1.44, 95% confidence interval (CI): 0.99-2.09]. The risk for transport equipment operation, a job with WBV exposure, was significantly elevated (OR = 1.90, 95% CI: 1.07-3.39). These results, together with those of an earlier study, suggest that workers in heavy equipment and transport equipment operation may have increased risk of prostate cancer. Further investigation is warranted.

Cancer incidence among Nordic airline cabin crew

Airline cabin crew are occupationally exposed to cosmic radiation and jet lag with potential disruption of circadian rhythms. This study assesses the influence of work-related factors in cancer incidence of cabin crew members. A cohort of 8,507 female and 1,559 male airline cabin attendants from Finland, Iceland, Norway and Sweden was followed for cancer incidence for a mean follow-up time of 23.6 years through the national cancer registries. Standardized incidence ratios (SIRs) were defined as ratios of observed and expected numbers of cases. A case-control study nested in the cohort (excluding Norway) was conducted to assess the relation between the estimated cumulative cosmic radiation dose and cumulative number of flights crossing six time zones (indicator of circadian disruption) and cancer risk. Analysis of breast cancer was adjusted for parity and age at first live birth. Among female cabin crew, a significantly increased incidence was observed for breast cancer [SIR 1.50, 95% confidence interval (95% CI) 1.32-1.69], leukemia (1.89, 95% CI 1.03-3.17) and skin melanoma (1.85, 95% CI 1.41-2.38). Among men, significant excesses in skin melanoma (3.00, 95% CI 1.78-4.74), nonmelanoma skin cancer (2.47, 95% CI 1.18-4.53), Kaposi sarcoma (86.0, 95% CI 41.2-158) and alcohol-related cancers (combined SIR 3.12, 95% CI 1.95-4.72) were found. This large study with complete follow-up and comprehensive cancer incidence data shows an increased incidence of several cancers, but according to the case-control analysis, excesses appear not to be related to the cosmic radiation or circadian disruptions from crossing multiple time zones.

Rare cancers of the head and neck area in Europe

The RARECARE project has proposed a different and more detailed grouping of cancers, based on localisation and histological type, in order to identify rare entities with clinical meaning. RARECARE gathered data on cancer patients diagnosed from 1978 to 2002 and archived in 76 population-based cancer registries, all of which had vital status information available up to at least 31st December 2003. This study provides incidence, prevalence and survival rates for rare head and neck epithelial (H&N) cancers. Among the rare H&N cancers, those of oral cavity had the highest annual crude incidence rate of 48 per million, followed by oropharynx and 'major salivary glands and salivary gland type tumours' (28 and 13 per million, respectively). Incidence rates of epithelial tumours of nasal cavities, nasopharynx, eye and adnexa and middle ears were all lower than 5 per million. The prevalence for all investigated entities was lower than 35 per 100,000. The 5-year relative survival rates ranged from 40% for epithelial cancer of oropharynx to 85% for epithelial cancer of eye and adnexa. Survival rates were lower for men and for patients aged ≥65 years. With few exceptions, the lowest and highest survival figures were observed for Eastern Europe and Northern Europe, respectively. According to the definition for rare tumours by RARECARE (incidence<6 per 100,000), as well as according to the definition for rare diseases by the European Commission (prevalence<50 per 100,000) the H&N cancers described in this paper should be considered rare and diagnosis and treatment of these cancers should therefore be centralised.

The ticking time-bomb of asbestos: its insidious role in the development of malignant mesothelioma

The relationship between asbestos exposure and malignant mesothelioma (MM) has been well established. Despite bans on asbestos use in an increasing number of nations, the prolonged latency from exposure to diagnosis, and the ongoing presence and use of these dangerous fibres, have led to the increasing prevalence of this deadly disease worldwide. Whilst occupational contact has been implicated in the bulk of diagnosed cases over the past 50 years, a significant proportion of disease has been linked to para-occupational, domestic and environmental exposure. In this review, we will provide an update on the impact of historical and ongoing asbestos contact in both occupational and non-occupational settings. Furthermore, we will address the unresolved controversies surrounding the use of chrysotile asbestos, the effect of gender and genetics on development of this disease, childhood mesothelioma and co-aetiological factors including SV40 exposure.

Rare thoracic cancers, including peritoneum mesothelioma

Rare thoracic cancers include those of the trachea, thymus and mesothelioma (including peritoneum mesothelioma). The aim of this study was to describe the incidence, prevalence and survival of rare thoracic tumours using a large database, which includes cancer patients diagnosed from 1978 to 2002, registered in 89 population-based cancer registries (CRs) and followed-up to 31st December 2003. Over 17,688 cases of rare thoracic cancers were selected based on the list of the RACECARE project. Mesothelioma was the most common tumour (19 per million per year) followed by epithelial tumours of the trachea and thymus (1.3 and 1.7, respectively). The age standardised incidence rates of epithelial tumours of the trachea was double in Eastern and Southern Europe versus the other European regions: 2 per million per year. Epithelial tumours of the thymus had the lowest incidence in Northern and Eastern Europe and UK and Ireland(1) and somewhat higher incidence in Central and Southern Europe.(2) Highest incidence in mesothelioma was seen in UK and Ireland(23) and lowest in Eastern Europe.(4) Patients with tumours of the thymus had the best prognosis (1-year survival 85%, 66% at 5 years). Five year survival was lowest for the mesothelioma 5% compared to 14% of patients with tumours of the trachea. Mesothelioma was the most prevalent rare cancer (12,000 cases), followed by thymus (7000) and trachea (1400). Cancer Registry (CR) data play an important role in revealing the burden of rare thoracic cancers and monitoring the effect of regulations on asbestos use and smoking related policies.

Incidence of uterine leiomyosarcoma and endometrial stromal sarcoma in Nordic countries: results from NORDCAN and NOCCA databases

OBJECTIVES AND STUDY DESIGN

Uterine sarcomas are an uncommon and heterogeneous group of malignancies. Their etiology is mainly unknown. Here, we analyzed trends in incidence and occupational variation in risk of uterine leiomyosarcomas (LMS) and endometrial stromal sarcomas (ESS) in the Nordic countries aided by NORDCAN and NOCCA (Nordic Occupational Cancer) databases.

MAIN OUTCOME MEASURES

Incidence rates per 100,000 and Standardized incidences rates (SIR) obtained from NORDCAN and NOCCA databases.

RESULTS

The incidence rates were about 0.3 per 100,000 for ESS and about 0.4 per 100,000 for LMS in Denmark, Finland, Iceland, and Norway. During the study-period (1978-2007), the incidence rates in each country were quite similar and constant. The age-specific incidence of LMS showed a peak around menopause. Significantly increased risk for LMS occurred in shoe and leather workers, farmers and teachers, whereas significantly low risk was detected with packers in the NOCCA data from Finland, Norway, and Sweden. For ESS no occupations showed either increased or decreased incidences.

CONCLUSIONS

The incidence trends of LMS and ESS in our study were constant in four Nordic countries over time. The elevated risk for LMS with women exposed to leather work and animal dust indicates further exploration.

Mortality patterns of Australian male farmers and farm managers

OBJECTIVE

To compare the all-cause and specific-cause death rates of Australian male farmers and farm managers aged 25-74 years, with other Australian men.

METHODS

Data were extracted from the Australian Bureau of Statistics Death Registration Collection covering the calendar years of 1999-2002. Denominator data for male farmers and farm managers were drawn from the 2001 Australian Population Census. Direct age-standardized death rates were calculated and compared with the general Australian male population.

RESULTS

The 4025 male farmers or farm managers who died in this period represented 3.35% of all male deaths in the 25-74 year age range. The all-cause death rate for farmers and farm managers (730/100,000) was 33% higher than that of the Australian male population of the same age (549/100,000) (standardized mortality ratio (SMR)=1.33). Causes of death related to neoplasms (SMR=1.37), circulatory disease (SMR=1.40) and all external causes (SMR=1.37), were all statistically higher than the comparison population. Within these groupings, ischaemic heart disease (SMR=1.39), other circulatory disease (SMR=1.42), prostate cancer (SMR=2.40), lymphohaematopoietic cancer (SMR=1.80) and transport injuries (SMR=2.06), were all significantly higher.

CONCLUSION

These data indicate that Australian male farmers and farm managers are a disadvantaged group in terms of health status. The elevated rates of all-cause and specific-cause mortality compared with the Australian comparison population, illustrate both the need and scope for further investigation of these issues.

Cardiorespiratory fitness, different measures of adiposity, and total cancer mortality in women

The objective was to examine associations among cardiorespiratory fitness (CRF), adiposity, and cancer mortality in women. Healthy women (N = 14,256) without cancer history completed a baseline health examination 1970-2005. Measures included BMI, percent body fat (%Fat), and CRF quantified as duration of a maximal treadmill test. CRF was classified as low (quintile 1), moderate (Q2-3), and high fit (Q4-5) by age. Standard BMI cutpoints were used, while participants were classified by %Fat quintiles. Cancer mortality rates were calculated following age, exam year, and smoking adjustment. During a mean follow-up period of 15.2 ± 9.4 years, 250 cancer deaths occurred. Adjusted mortality rates across BMI groups were 4.6, 5.7, and 8.8 (P trend 0.08); %Fat 3.0, 4.9, 2.9, 3.8, and 6.9 (P trend 0.17); and CRF 7.9, 5.5, and 2.9 (P trend 0.003). When grouped into categories of fit and unfit (upper 80% and lower 20% of CRF distribution), and using BMI as the adiposity exposure, cancer mortality rates of unfit-obese women were significantly higher than fit-normal weight women (9.8 vs. 4.1 deaths/10,000 woman-years; P = 0.02), while fit-overweight and fit-obese women had no greater risk of mortality than fit-normal weight women. Using %Fat as the adiposity exposure, unfit-obese women tended to have higher cancer mortality than fit-normal weight women (7.0 vs. 3.3 deaths/10,000 woman-years, P = 0.10). Higher levels of CRF are associated with lower cancer mortality risk in women and attenuate the risk of cancer mortality in overweight women. Using adiposity measures to estimate cancer mortality risk in women can be potentially misleading unless CRF is considered.

Vitamin D, sun, sunbeds and health

Objective

To review the health effects of solar radiation, sunbeds and vitamin D.

Design

The literature was searched in the electronic database MEDLINE to indentify published data between 1981 and 2011. Studies were included if they reported relative risk for cutaneous malignant melanoma (CMM) associated with sunbed use, vitamin D and UV effects on human health.

Setting

Data from different time periods for populations at different latitudes.

Subjects

Persons of different ages and ethnic groups.

Results

UV from sun and sunbeds is the main vitamin D source. Young people with white or pigmented skin in northern Europe have a low vitamin D status. A number of health benefits from sufficient levels of vitamin D have been identified. However, UV exposure has been suspected of causing skin cancer, notably CMM, and authorities warn against it.

Conclusions

The overall health benefit of an improved vitamin D status may be more important than the possibly increased CMM risk resulting from carefully increasing UV exposure. Important scientific facts behind this judgement are given.

Occupation and risk of primary fallopian tube carcinoma in Nordic countries

The aetiology of primary Fallopian tube carcinoma (PFTC) is poorly understood. Occupational exposures may contribute to PFTC risk. We studied incidence of PFTC in occupational categories in the Nordic female population aged 30-64 years during the 1960, 1970, 1980/1981 and/or 1990 censuses in Denmark, Finland, Iceland, Norway and Sweden. Standardized incidence ratios (SIRs) for the years following inclusion in the study up to 2005 were calculated for 53 occupations; the expected numbers of cases were based on PFTC incidence in the national populations. Altogether 2,206 PFTC cases were detected during follow up via data linkages with the Nordic cancer registries. Significantly increased risks of PFTC were observed for smelting workers (SIR 3.99, 95% confidence interval 1.46-8.68, Obs = 6), artistic workers (2.64, 1.44-4.43, Obs = 14), hairdressers (2.18, 1.41-3.22, Obs = 25), packers (1.62, 1.11-2.29, Obs = 32), nurses (1.49, 1.14-1.92, Obs = 60), shop workers (1.25, 1.07-1.46, Obs = 159) and clerical workers (1.20, 1.07-1.35, Obs = 271) and these sustained over times and different Nordic countries. There was a nonsignificant increased risk for PFTC among welders, printers, painters and chemical process workers. The risk was significantly and consistently low for women working in farming (0.68, 0.47-0.95, Obs = 34) and among economically inactive women (0.88, 0.82-0.94, Obs = 833). The possible role of occupational exposures to the PFTC risks found in this study must be further evaluated in studies with a possibility to adjust for possible confounding factors, such as reproductive and life-style factors, which was not possible in our study.

Lung cancer risk in painters: a meta-analysis

We conducted a meta-analysis to quantitatively compare the association between occupation as a painter and the incidence or mortality from lung cancer. PubMed and the reference lists of pertinent publications were searched and reviewed. For the meta-analysis, we used data from 47 independent cohort, record linkage, and case-control studies (from a total of 74 reports), including > 11,000 incident cases or deaths from lung cancer among painters. Three authors independently abstracted data and assessed study quality. The summary relative risk (meta-RR, random effects) for lung cancer in paint-ers was 1.35 [95% confidence interval (CI), 1.29-1.41; 47 studies] and 1.35 (95% CI, 1.21-1.51; 27 studies) after controlling for smoking. The relative risk was higher in never-smokers (meta-RR = 2.00; 95% CI, 1.09-3.67; 3studies) and persisted when restricted to studies that adjusted for other occupational exposures (meta-RR = 1.57; 95% CI, 1.21-2.04; 5 studies). These results support the conclusion that occupational exposures in painters are causally associated with the risk of lung cancer.

Occupational exposures to asbestos, polycyclic aromatic hydrocarbons and solvents, and cancers of the oral cavity and pharynx: a quantitative literature review

PURPOSE

The role of occupational risk factors in oral and pharyngeal cancer is not well known and is possibly underestimated. This quantitative review summarizes epidemiological findings on exposure to asbestos, polycyclic aromatic hydrocarbons and solvents, and cancers of the oral cavity and pharynx.

METHODS

A systematic literature search was performed. We analyzed 63 publications: 8 from case-control studies and 55 from cohort studies. For agents with at least five available studies with homogenous exposure, a series of meta-analyses was conducted to provide quantitative pooled estimates of risks, using random effect models.

RESULTS

Exposure to asbestos (meta-RR 1.25; 95% CI 1.10-1.42) and to polycyclic aromatic hydrocarbons (meta-RR 1.14; 95% CI 1.02-1.28) was found to be associated with oral and pharyngeal cancer risk. On the other hand, no association was found with exposure to solvents in general (meta-RR 0.98; 95% CI 0.77-1.23) but the strong heterogeneity between studies suggested differences in exposures. The small number of studies with homogeneous exposure did not allow meta-analyses for specific solvents.

CONCLUSIONS

Future investigations should overcome common weaknesses of past studies, in terms of sample size, characterization of exposure, and classification of cancer sites.

Occupation and cancer risk by use of Danish registers

Introduction: Based on evidence from animal experiments and case reports, certain occupational exposures may contribute to yet undetected cancer risk in humans. Since traditional epiemiological studies are time consuming, the use of existing information from registers may facilitate the research process. Due to the existence of a unique personal identification number (CPR-number), a national cancer register operating since 1943, a nationwide pension fund scheme with compulsory membership for all employees covering long-term individual employment history, and sometimes with addition of information from external sources, e.g. interviews or job exposure matrices, it is possible to conduct large nationwide studies of occupational exposures and cancer risk in Denmark. Research topics: In this review we give three examples of cancer studies of widespread occupational exposures: formaldehyde, night shift work, and bitumen. Conclusion: Results from register-based studies have contributed to the now-existing evidence on occupational exposures and risk of cancer.

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.

A current global view of environmental and occupational cancers

This review is focused on current information of avoidable environmental pollution and occupational exposure as causes of cancer. Approximately 2% to 8% of all cancers are thought to be due to occupation. In addition, occupational and environmental cancers have their own characteristics, e.g., specific chemicals and cancers, multiple factors, multiple causation and interaction, or latency period. Concerning carcinogens, asbestos/silica/wood dust, soot/polycyclic aromatic hydrocarbons [benzo(a) pyrene], heavy metals (arsenic, chromium, nickel), aromatic amines (4-aminobiphenyl, benzidine), organic solvents (benzene or vinyl chloride), radiation/radon, or indoor pollutants (formaldehyde, tobacco smoking) are mentioned with their specific cancers, e.g., lung, skin, and bladder cancers, mesothelioma or leukemia, and exposure routes, rubber or pigment manufacturing, textile, painting, insulation, mining, and so on. In addition, nanoparticles, electromagnetic waves, and climate changes are suspected as future carcinogenic sources. Moreover, the aspects of environmental and occupational cancers are quite different between developing and developed countries. The recent follow-up of occupational cancers in Nordic countries shows a good example for developed countries. On the other hand, newly industrializing countries face an increased burden of occupational and environmental cancers. Developing countries are particularly suffering from preventable cancers in mining, agriculture, or industries without proper implication of safety regulations. Therefore, industrialized countries are expected to educate and provide support for developing countries. In addition, citizens can encounter new environmental and occupational carcinogen nominators such as nanomaterials, electromagnetic wave, and climate exchanges. As their carcinogenicity or involvement in carcinogenesis is not clearly unknown, proper consideration for them should be taken into account. For these purposes, new technologies with a balance of environment and gene are required. Currently, various approaches with advanced technologies--genomics, exposomics, etc.--have accelerated development of new biomarkers for biological monitoring of occupational and environmental carcinogens. These advanced approaches are promising to improve quality of life and to prevent occupational and environmental cancers.

Global mesothelioma deaths reported to the World Health Organization between 1994 and 2008

OBJECTIVE

To carry out a descriptive analysis of mesothelioma deaths reported worldwide between 1994 and 2008.

METHODS

We extracted data on mesothelioma deaths reported to the World Health Organization mortality database since 1994, when the disease was first recorded. We also sought information from other English-language sources. Crude and age-adjusted mortality rates were calculated and mortality trends were assessed from the annual percentage change in the age-adjusted mortality rate.

FINDINGS

In total, 92,253 mesothelioma deaths were reported by 83 countries. Crude and age-adjusted mortality rates were 6.2 and 4.9 per million population, respectively. The age-adjusted mortality rate increased by 5.37% per year and consequently more than doubled during the study period. The mean age at death was 70 years and the male-to-female ratio was 3.6:1. The disease distribution by anatomical site was: pleura, 41.3%; peritoneum, 4.5%; pericardium, 0.3%; and unspecified sites, 43.1%. The geographical distribution of deaths was skewed towards high-income countries: the United States of America reported the highest number, while over 50% of all deaths occurred in Europe. In contrast, less than 12% occurred in middle- and low-income countries. The overall trend in the age-adjusted mortality rate was increasing in Europe and Japan but decreasing in the United States.

CONCLUSION

The number of mesothelioma deaths reported and the number of countries reporting deaths increased during the study period, probably due to better disease recognition and an increase in incidence. The different time trends observed between countries may be an early indication that the disease burden is slowly shifting towards those that have used asbestos more recently.

Night work and breast cancer risk among Norwegian nurses: assessment by different exposure metrics

Associations between night work and breast cancer risk were investigated in a nested case-control study within a cohort of 49,402 Norwegian nurses. A total of 699 (74%) of the live cases diagnosed in 1990-2007 and 895 (65%) controls, cancer free at the time of sampling, were interviewed about work history and potential risk factors. The odds ratios for risk of breast cancer in relation to different exposure metrics were estimated by multivariate unconditional logistic regression models. No increase of risk was found after long duration of work by nurses working ≥3 night shifts per month. Small, nonsignificantly increased risks were observed for exposure to ≥30 years in hospitals or other institutions (odds ratio (OR) = 1.1), ≥12 years in schedules including night work (OR = 1.3), ≥1,007 night shifts during the lifetime (OR = 1.2), and lifetime average number of ≥4 night shifts per month (OR = 1.2). Nonsignificantly increased risks of breast cancer were observed in nurses who worked ≥5 years with ≥4 (OR = 1.4) and ≥5 (OR = 1.6) consecutive night shifts. Significantly increased risks were seen in nurses who worked ≥5 years with ≥6 consecutive night shifts (OR = 1.8, 95% confidence interval: 1.1, 2.8). The results suggest that risk may be related to number of consecutive night shifts.

[Non dietetic environmental risk factors in prostate cancer]

INTRODUCTION

The aim is to update and disclose the main environmental risk factors, excluding dietary factors, involved in the etiopathology of prostate cancer.

MATERIALS AND METHOD

Bibliographic review of the last 25 years of non-dietary environmental risk factors associated with prostate cancer between 1985 and 2010, obtained from MedLine, CancerLit, Science Citation Index and Embase. The search profiles were Environmental Risk Factors/Tobacco/Infectious-Inflammatory Factors/Pesticides/Vasectomy/Occupational Exposures/Chemoprevention Agents/Radiation and Prostate Cancer.

RESULTS

While some non-dietary environmental risk factors increase the risk of acquiring the disease, others decrease it. Of the former, it is worth mentioning exposal to tobacco smoke, chronic infectious-inflammatory prostatic processes and occupational exposure to cadmium, herbicides and pesticides. The first factors that reduce the risk are the use of chemopreventive drugs (Finasterida, Dutasteride) and exposure to ultraviolet solar radiation. With the current data, a vasectomy does not influence the risk of developing the disease.

CONCLUSIONS

The slow process of prostate carcinogenesis is the final result of the interaction of constitutional risk and environmental factors. Non-dietary environmental factors play an important role in the etiopathology of this disease. To appropriately assess the risk factors, extensive case studies that include all the possible variables must be analysed.

AGRICOH: a consortium of agricultural cohorts

AGRICOH is a recently formed consortium of agricultural cohort studies involving 22 cohorts from nine countries in five continents: South Africa (1), Canada (3), Costa Rica (2), USA (6), Republic of Korea (1), New Zealand (2), Denmark (1), France (3) and Norway (3). The aim of AGRICOH, initiated by the US National Cancer Institute (NCI) and coordinated by the International Agency for Research on Cancer (IARC), is to promote and sustain collaboration and pooling of data to investigate the association between a wide range of agricultural exposures and a wide range of health outcomes, with a particular focus on associations that cannot easily be addressed in individual studies because of rare exposures (e.g., use of infrequently applied chemicals) or relatively rare outcomes (e.g., certain types of cancer, neurologic and auto-immune diseases). To facilitate future projects the need for data harmonization of selected variables is required and is underway. Altogether, AGRICOH provides excellent opportunities for studying cancer, respiratory, neurologic, and auto-immune diseases as well as reproductive and allergic disorders, injuries and overall mortality in association with a wide array of exposures, prominent among these the application of pesticides.

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.

Effects of occupation on risks of avoidable cancers in the Nordic countries

Knowledge of cancer risk according to occupational affiliation is an essential part of formatting preventive actions aimed at the adult population. Herein, data on 10 major cancer sites amenable by life style exposures from the Nordic Occupational Cancer Study (NOCCA) are presented. All subjects aged 30-64 years participating in one or more national censuses in Denmark, Finland, Iceland, Norway, or Sweden between 1960 and 1990 were included in the cohort and followed up for cancer from inclusion until 2003/2005 via a linkage with the national cancer registries, and standardised incidence ratios (SIRs) were computed. Variation in risk across occupations was generally larger in men than in women. In men, the most consistent cluster with high risk of numerous cancer types included waiters, cooks and stewards, beverage workers, seamen, and chimney sweeps. Two clusters of occupations with generally low cancer risks were seen in both men and women. The first one comprised farmers, gardeners, and forestry workers, the second one included groups with high education, specifically those in health and pedagogical work. Although cancer risk varies by occupation, only a smaller part of the variation can be attributed to occupational exposures in the strict sense. Preventive measures at the work place are important to avoid established and new occupational health hazards. This study also indicates that the work place in addition should be seen as a useful arena for reaching groups of adults with more or less similar habits and attitudes for general health promotion.

Factors that impact susceptibility to fiber-induced health effects

Asbestos and related fibers are associated with a number of adverse health effects, including malignant mesothelioma (MM), an aggressive cancer that generally develops in the surface serosal cells of the pleural, pericardial, and peritoneal cavities. Although approximately 80% of individuals with MM are exposed to asbestos, fewer than 5% of asbestos workers develop MM. In addition to asbestos, other mineralogical, environmental, genetic, and possibly viral factors might contribute to MM susceptibility. Given this complex etiology of MM, understanding susceptibility to MM needs to be a priority for investigators in order to reduce exposure of those most at risk to known environmental carcinogens. In this review, the current body of literature related to fiber-associated disease susceptibility including age, sex, nutrition, genetics, asbestos, and other mineral exposure is addressed with a focus on MM, and critical areas for further study are recommended.

Biobanks and registers in epidemiologic research on cancer

The Nordic countries have a long tradition of register-based epidemiologic studies. Numerous population-based specialized registers offer high-quality data from individuals, and the extensive use of register data further improves the quality of the registers. Unique personal identity codes given to every resident and used in all registers guarantee easy and accurate record linkage. A legislation that makes the use of the existing data possible for purposes that benefit both registered individuals and the society - instead of forcing researchers to use their energy in repeated questionnaire studies, disturbing individuals' privacy and leading to response and recall biases - is a prerequisite for effective epidemiologic research. Biobanks can be considered an additional type of registers. They may offer data from individuals that cannot be reliably collected via questionnaire surveys. In turn, other types of registers are crucial in biobank-based studies (1) in defining for how long the persons in biobank cohorts are at risk of getting the diseases, (2) to get information on cofactors that may modify the relative risk measured by the biomarkers, and (3) to get information on the long-term outcome events. This chapter describes the possibilities of register use mainly in Finland - a typical representative of the Nordic "paradise of register-based epidemiological research" - in research of cancer etiology. The ongoing Nordic research project Changing work life and cancer risk in the Nordic countries (NOCCA) will be described as an example of a massive register use, including both direct linkages on an individual level and indirect group level linkages.

Familial risks in cancer of unknown primary: tracking the primary sites

PURPOSE

Cancer of unknown primary (CUP) is diagnosed at the metastatic stage, and despite extensive diagnostic work-up, the primary tumor often remains unidentified. No data are available on familial clustering of CUP. We hypothesize that familial clustering of CUP with other cancers may be informative of the primary sites.

PATIENTS AND METHODS

A total of 35,168 patients with CUP were identified in the Swedish Family-Cancer Database, and risks between family members were calculated for concordant (CUP-CUP) and discordant (CUP-any other cancer) cancers using standardized incidence ratio (SIR).

RESULTS

Familial cases of CUP accounted for 2.8% of all CUP cases in the offspring generation. Familial SIR for CUP was 1.69 when a sibling was diagnosed with CUP. As to discordant associations between siblings, CUP was associated with lung (SIR, 1.87), kidney (SIR, 1.82), liver (SIR, 1.67), ovarian (SIR, 1.45), colorectal (SIR, 1.26), and breast (SIR, 1.15) cancers and melanoma (SIR, 1.26). Upper aerodigestive tract, bladder, pancreatic, and prostate cancers were additionally associated with CUP. Notably, CUP was associated with families of kidney, lung, and colorectal cancers.

CONCLUSION

The present data show that CUP is not a disease of random metastatic cancers but, instead, a disease of a defined set of cancers. The association of CUP with families of kidney, lung, and colorectal cancers suggests a marked genetic basis and shared metastatic mechanisms by many cancer types. Familial sites shared by CUP generally match those arising in tissue-of-origin determinations and, hence, suggest sites of origin for CUP. Mechanistic exploration of CUP may provide insight into defense against primary tumors and the metastatic process.

Wood dust exposure and risk of lung cancer

OBJECTIVES

Despite the compelling association between wood dust and sinonasal cancer, there has been little systematic and rigorous study of the relationship between wood dust and lung cancer. We investigated whether a history of wood dust exposure through occupational and hobby-related activities was associated with increased lung cancer risk.

METHODS

We conducted a population-based case-control study, with 440 cases and 845 age-matched controls. Using detailed work and personal histories, quantitative estimates of cumulative exposure to wood dust (thought to be primarily from softwood) were calculated for each participant. Using unconditional logistic regression adjusted for age and smoking status, risk of lung cancer was examined in relation to employment in wood-related occupations, working with wood as a hobby, as well as cumulative wood dust exposure that took into account both occupational and hobby-related sources.

RESULTS

While we observed an increased risk of lung cancer associated with working in a sawmill (OR=1.5; 95% CI: 1.1, 2.1), we found no evidence of increased risks with other occupations, working with wood as a hobby or with estimated cumulative exposure to wood dust. Contrary to our hypothesis, we observed modest decreased risks with exposure to wood dust, although no dose-response relationship was apparent.

CONCLUSIONS

This study provided somewhat reassuring evidence that softwood dust does not increase the risk of lung cancer, but future studies should evaluate exposure to hardwood dusts. Suggestive evidence for an inverse association may be attributable to the presence of endotoxin in the wood dust, but the lack of a dose-response relationship suggests a non-causal relationship.

Parental occupation and preterm births: a nationwide epidemiological study in Sweden

The hypothesis was that some occupations could lead to preterm birth (PTB) because of potential exposures to various agents. The objective in this nationwide follow-up study was to analyse the association between PTB and parental occupational groups, controlling for potential confounders. Data from the Swedish Medical Birth Register, in which all children born in Sweden from 1990 onward are registered with their parents, were linked to census data. Inclusion criteria for the study population were employment (both women and men) and age >20 years (women). There were 816,743 first singleton live births from 1990 to 2004, of whom 43,956 were PTBs. A total of 7659 of the 43,956 PTBs were very PTBs. Odds ratios (ORs) with 95% confidence intervals were calculated separately for mothers and fathers to estimate the odds of PTB and very PTB in 51 occupational groups (reference groups: mothers or fathers who were 'Technical, science research-related workers and physicians') and by family income level. Women and men with low family incomes had increased ORs of PTB and very PTB. Significantly increased ORs of PTB (including very PTB) were found in four maternal and nine paternal occupational groups after accounting for family income, geographic region of residence, civil status, smoking habits, maternal age at infant's birth and period of birth. Further studies should examine specific agents in those parental occupations that were associated with increased odds of PTB and very PTB.

Outdoor work and risk for Parkinson's disease: a population-based case-control study

OBJECTIVES

Sunlight is the main contributor to vitamin D in humans. Since inadequate levels of vitamin D have been linked to increased risks for neurodegenerative diseases, we examined whether outdoor work is associated with a reduced risk for Parkinson's disease in a population-based case-control study of Danish men.

METHODS

We identified 3819 men with a primary diagnosis of Parkinson's disease in the period 1995-2006 in the Danish National Hospital Register and selected 19,282 age- and sex-matched population controls at random from the Central Population Register. Information on work history was ascertained from the Danish Supplementary Pension Fund and the Central Population Register. Based on trade grouping codes and job titles, we evaluated the extent of outdoor work of study subjects as a proxy of exposure to sunlight.

RESULTS

Relying on trade grouping codes, we estimated ORs for study subjects with moderate, frequent and maximal outdoor work compared with exclusive indoor work of 0.90 (95% CI 0.78 to 1.02), 0.86 (95% CI 0.75 to 0.99) and 0.72 (95% CI 0.63 to 0.82), respectively, for Parkinson's disease. Reduced risks were also found for Parkinson's disease among outdoor workers based on study subjects' job titles.

CONCLUSIONS

Our findings suggest that men working outdoors have a lower risk for Parkinson's disease. Further studies of measured vitamin D levels in outdoor workers are warranted to clarify a potential inverse association between vitamin D and the risk for Parkinson's disease.

Education, survival and avoidable deaths in cancer patients in Finland

BACKGROUND

Relative survival after cancer in Finland is at the highest level observed in Europe and has, in general, been on a steady increase. The aim of this study is to assess whether the high survival is equally shared by different population subgroups and to estimate the possible gains that might be achieved if equity prevailed.

MATERIALS AND METHOD

The educational level and occupation before the cancer diagnosis of patients diagnosed in Finland in 1971-2005 was derived from an antecedent population census. The cancers were divided into 27 site categories. Cancer (cause)-specific 5-year survival proportions were calculated for three patient categories based on the educational level and for an occupational group of potentially health-conscious patients (physicians, nurses, teachers etc.). Proportions of avoidable deaths were derived by assuming that the patients from the two lower education categories would have the same mortality owing to cancer, as those from the highest educational category. Estimates were also made by additionally assuming that even the mortalities owing to other causes of death were all equal to those in the highest category.

RESULTS

For almost all the sites considered, survival was consistently highest for patients with the highest education and lowest for those with only basic education. The potentially health-conscious patients had an even higher survival. The differences were, in part, attributable to less favourable distributions of tumour stages in the lower education categories. In 1996-2005, 4-7% of the deaths in Finnish cancer patients could have potentially been avoided during the first 5-year period after diagnosis, if all the patients had the same cancer mortality as the patients with the highest educational background. The proportion would have also been much higher, 8-11%, if, in addition, the mortality from other causes had been the same as that in the highest educational category.

INTERPRETATION

Even in a potentially equitable society with high health care standards, marked inequalities persist in cancer survival. Earlier cancer diagnosis and the ability to cope within the health care system may be a partly relevant explanation, but personal habits and lifestyles also have a role, particularly for the cancer patients' mortality from other causes of death than cancer.

Invited commentary: Evaluating epidemiologic research methods--the importance of response rate calculation

Epidemiologic research that uses administrative records (rather than registries or clinical surveys) to identify cases for study has been increasingly restricted because of concerns about privacy, making unbiased population-based research less practicable. In their article, Nattinger et al. (Am J Epidemiol. 2010;172(6):637-644) present a method for using administrative data to contact participants that has been well received. However, the methods employed for calculating and reporting response rates require further consideration, particularly the classification of untraceable cases as ineligible. Depending on whether response rates are used to evaluate the potential for bias to influence study results or to evaluate the acceptability of the method of contact, different fractions may be considered. To improve the future study of epidemiologic research methods, a consensus on the calculation and reporting of study response rates should be sought.