No Excess Cancer Risk among Veterinarians in Denmark, Finland, Iceland, Norway, and Sweden after the 1980s

The cancer profile of veterinarians has received little research attention, despite the profession potentially being exposed to a wide range of known and suspected carcinogens. In this large-scale cohort study, we assessed cancer incidence in veterinarians in Denmark, Finland, Iceland, Norway, and Sweden, across more than 40 years (1961-2005). The cohort comprised 4708 veterinarians and 119,503 person-years at follow-up. The overall cancer incidence in veterinarians was close to the incidence in the total population in all countries and in all age groups. In male veterinarians, the standardized incidence ratios (SIR) in 1961-1990 were elevated for colon cancer (1.86, 95% confidence interval (CI) 1.39-2.44), prostate cancer (1.35, 95% CI 1.07-1.67), and especially skin melanoma (3.62, 95% CI 2.78-2.84), while there was no longer any statistically significant excess in the more recent follow-up period. Decreased SIRs were observed for lip cancer (0.11, 95% CI 0.00-0.62), laryngeal cancer (0.38, 95% CI 0.12-0.89), lung cancer (0.59, 95% CI 0.47-0.74), and stomach cancer (0.58, 95% CI 0.38-0.86), without a marked change in SIR over time. Non-significant excesses among male veterinarians were also observed in Hodgkin lymphoma (1961-1990 only), and leukaemia. This multi-country study indicates that there was an elevated incidence of several cancer types among male veterinarians before the 1990s but not after that. Some of the findings might rather be attributed to lifestyle factors and not directly to work conditions, but the excess risk of cancers of kidney and bladder, for example, might be related to work exposures.

Occupation and cutaneous melanoma: a 45-year historical cohort study of 14·9 million people in five Nordic countries

BACKGROUND

The age-adjusted incidence of cutaneous melanoma (CM) in the Nordic countries has increased during the last 60 years. Few prospective population-based studies have estimated the occupational variation in CM risk over time.

OBJECTIVES

To determine occupational variation in CM risk.

METHODS

A historical prospective cohort study with a 45-year follow-up from 1961 to 2005 (Nordic Occupational Cancer Study, NOCCA) based on record linkages between census and cancer registry data for Nordic residents aged 30-64 years in Denmark, Finland, Iceland, Norway and Sweden. National occupational codes were converted to 53 occupational categories, and stratified into indoor, outdoor and mixed work, and into socioeconomic status. The standardized incidence ratios (SIRs) were estimated as observed number of CM cases divided by the expected number calculated from stratum-specific person-years and national CM incidence rates.

RESULTS

During a follow-up of 385 million person-years, 83 898 incident cases of CM were identified. In all countries combined, men with outdoor work had a low SIR of 0·79 [95% confidence interval (CI) 0·77-0·81] and men with indoor work had a high SIR of 1·09 (95% CI 1·07-1·11). Differences in women pointed in the same direction. High socioeconomic status was associated with an excess risk: SIR 1·34 (95% CI 1·28-1·40) in men and SIR 1·31 (95% CI 1·26-1·36) in women. Technical, transport, military and public safety workers with potential skin exposure to carcinogens had excess risks.

CONCLUSIONS

Occupational variation in CM risk may be partly explained by host, socioeconomic and skin exposure factors. Differences in CM risk across socioeconomic groups attenuated slightly over time.

Occupational exposures and male breast cancer: A nested case-control study in the Nordic countries

BACKGROUND

Male breast cancer (MBC) is a rare and understudied disease. There is limited evidence on association between environmental and occupational agents and MBC. Some similarities in risk factors may be shared with female breast cancer. We evaluated solvents, metals, exhaust gases and other agents in relation to MBC within the large Nordic Occupational Cancer Study (NOCCA).

METHODS

The study included 1469 MBC cases and 7345 controls from Finland, Iceland and Sweden, matched for the date of birth, sex and country. Cases were identified through national cancer registries. Data on occupation and other demographic indicators were collected from census records and population registries. Overall, 24 occupational exposures were assessed. Exposure estimates were assigned by linking job titles to job-exposure matrices (NOCCA-JEM). Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated by using conditional logistic regression models.

RESULTS

Significantly decreased overall OR was observed for physical workload (OR = 0.78, 95% CI 0.67-0.91). Protective effect of physical workload was stronger by increasing exposure level with significant dose-response relationship (p-trend<0.01). Non-significantly increased ORs were observed for trichloroethylene, iron, lead, chromium, welding fumes and wood dust, and decreased ORs for asbestos, silica dust and perchloroethylene. However, these results were not consistent across all analyses.

CONCLUSIONS

The current study showed 20-25% protective effect for physical workload at work, while no strong evidence for other agents was observed.

Workplace Diesel Exhausts and Gasoline Exposure and Risk of Colorectal Cancer in Four Nordic Countries

BACKGROUND

Evidence on associations between occupational diesel exhaust and gasoline exposure and colorectal cancer is limited. We aimed to assess the effect of workplace exposure to diesel exhaust and gasoline on the risk of colorectal cancer.

METHODS

This case-control study included 181,709 colon cancer and 109,227 rectal cancer cases diagnosed between 1961 and 2005 in Finland, Iceland, Norway, and Sweden. Cases and controls were identified from the Nordic Occupational Cancer Study cohort and matched for country, birth year, and sex. Diesel exhaust and gasoline exposure values were assigned by country-specific job-exposure matrices. Odds ratios and 95% confidence intervals were calculated by using conditional logistic regression models. The results were adjusted for physical strain at work and occupational exposure to benzene, formaldehyde, ionizing radiation, chlorinated hydrocarbons, chromium, and wood dust.

RESULTS

Diesel exhaust exposure was associated with a small increase in the risk of rectal cancer (odds ratio = 1.05, 95% confidence interval 1.02-1.08). Gasoline exposure was not associated with colorectal cancer risk.

CONCLUSION

This study showed a small risk increase for rectal cancer after workplace diesel exhaust exposure. However, this finding could be due to chance, given the limitations of the study.

Benzene exposure at workplace and risk of colorectal cancer in four Nordic countries

OBJECTIVE

The aim of this case-control study was to assess the effect of occupational benzene exposure on the risk of colorectal cancer, including its subtypes.

METHODS

The study included 181,709 colon cancer and 109,227 rectal cancer cases diagnosed between 1961 and 2005 in Finland, Iceland, Norway and Sweden. Cases were identified from the Nordic Occupational Cancer Study (NOCCA) cohort. Five controls per case were selected from the same cohort, matched for country, birth year, and sex. Occupational benzene exposure for each study participant was estimated by linking their job titles to country specific job-exposure matrices. Odds ratios (OR) and 95% confidence intervals (CI) were calculated by using conditional logistic regression models. The results were adjusted for physical strain at work, formaldehyde, ionizing radiation and wood dust.

RESULTS

Increased risk was observed for all colorectal cancer (OR = 1.12, 95% CI 1.05-1.18) for the high decile of cumulative benzene exposure, indicating a statistically significant dose-response relationship. This excess risk was mainly seen in ascending colon (OR = 1.27, 95% CI 1.13-1.43), and transversal colon (OR = 1.21, 95% CI 1.01-1.41). The ORs in the highest exposure category were markedly higher in women than in men in all subsites of colon and rectum.

CONCLUSION

This study showed an association between workplace benzene exposure and colorectal cancer. The risk was restricted to ascending and transversal colon, and was the strongest among women.

Occupational solvent exposure and adult chronic lymphocytic leukemia: No risk in a population-based case-control study in four Nordic countries

The aim of this study was to assess the effect of occupational solvent exposure on the risk of adult chronic lymphocytic leukemia (CLL). The current case-control study was nested in the Nordic Occupational Cancer Study (NOCCA) cohort. 20,615 CLL cases diagnosed in 1961-2005 in Finland, Iceland, Norway, and Sweden, and 103,075 population-based controls matched by year of birth, sex, and country were included. Occupational histories for cases and controls were obtained from census records in 1960, 1970, 1980/1981, and 1990. Exposure to selected solvents was estimated by using the NOCCA job-exposure matrix (NOCCA-JEM). Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated by using conditional logistic regression models. Overall, nonsignificant CLL risk elevations were observed for methylene chloride, perchloroethylene, and 1,1,1-trichloroethane. Compared to unexposed, significantly increased risks were observed for cumulative perchloroethylene exposure ≤13.3 ppm-years (OR = 1.85, 95% CI 1.16-2.96) and average life-time perchloroethylene exposure ≤2.5 ppm (1.61, 95% CI 1.01-2.56) among women, and cumulative methylene chloride exposure ≤12.5 ppm-years (OR = 1.19, 95% CI 1.01-1.41) and 12.5-74.8 ppm-years (OR = 1.23, 95% CI 1.01-1.51) among men in an analysis with 5 years lag-time, though without dose-response pattern. Decreased CLL risk was observed for aliphatic and alicyclic hydrocarbon solvents and toluene. This study did not support associations for solvent exposure and CLL. Observed weak associations for methylene chloride, perchloroethylene, 1,1,1-trichloroethane exposures, aliphatic and alicyclic hydrocarbons and toluene were not consistent across sexes, and showed no gradient with amount of exposure.

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.

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.

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.

Incidence of breast cancer in a Norwegian cohort of women with potential workplace exposure to 50 Hz magnetic fields

BACKGROUND

The risk of breast cancer was investigated in a large dynamic population-based cohort of all 1.1 million economically active women in Norway with potential exposure to 50 Hz magnetic fields at the censuses of 1960, 1970, and 1980.

METHODS

The follow-up period for the cohort was 1961-1992. For each woman, date of birth and census information on occupation and socioeconomic status were ascertained. These data were linked to the breast cancer morbidity information in the Cancer Registry of Norway. Exposure to magnetic fields was assessed a priori using two different approaches. In the first approach, hours per week in a potential magnetic field above background level (0.1 microT) were classified by an expert panel. In the second approach, measured magnetic fields from a separate study of men at work were allocated to the women's census job titles. In both approaches, exposure was cumulated over the years of employment (work hours and microT-years, respectively).

RESULTS

The Poisson regression analysis showed a risk ratio (RR) of 1.14 (95% confidence interval (CI) = 1.10-1.19) in the highest exposure category compared to the lowest when using the first approach, and the corresponding RR was 1.08 (95% CI = 1.01-1.16) when using the second approach. For women younger than 50 years, RR was 1.20 (95% CI = 1.11-1.29) and 1.12 (95% CI = 0.98-1.28), respectively.

CONCLUSIONS

The results give some support to the hypothesis that exposure to 50 Hz magnetic fields may increase the risk of breast cancer. However, since no direct information on exposure was available, no firm conclusions can be drawn.