Holmfridur K. Gunnarsdottir

Association between exposure to crystalline silica and risk of sarcoidosis

OBJECTIVES: The possibility of an association between exposure to silica and autoimmune diseases has recently come under discussion. In the following case-referent study, a cohort exposed to diatomaceous earth and cristobalite provided an opportunity to evaluate such an exposure with reference to sarcoidosis. METHODS: The inhabitants of a district served by a single healthcare centre and a hospital formed the study base. A diatomaceous earth plant is located in this community and the medical institutions are responsible for primary and secondary health care of the population. Cases of sarcoidosis were identified from the hospital records according to certain clinical, radiological, and histological criteria. Referents were selected randomly from the population of the district. Information on exposure to crystalline silica, cristobalite, was obtained by record linkage of the cases and referents with a file which included all present and past workers at the diatomaceous earth plant and those who had worked at loading vessels with the product from the plant. RESULTS: Eight cases of sarcoidosis were found, six of which were in the exposed group. Of the 70 referents, 13 were exposed. The odds ratio (95% confidence interval) was 13.2 (2.0 to 140.9). CONCLUSION: The odds ratios were high and there were some indications of a dose-response relation which will hopefully encourage further studies. To our knowledge this is the first study to indicate a relation between sarcoidosis and exposure to the crystalline silica, cristobalite.

Cancer incidence among Icelandic nurses.

This study investigated cancer incidence among Icelandic nurses, with a special focus on breast cancer. Cancer incidence in the study group was compared with that of the general female population. Elevated standardized incidence ratios (SIRs) were seen for some cancer sites, including breast cancer. For all cancers, breast cancer, and selected cancer sites, SIR increased with increasing length of time intervals allowed to elapse before the study period began. The nurses with a shorter employment time had a higher incidence of cancer than those with a longer one. Known confounding factors--parity and age at first birth--do not appear to be a convincing explanation of the excess of breast cancer. The possibility cannot be excluded that the nursing occupation constitutes an independent risk factor for breast cancer.

Risk of lung cancer among masons in Iceland.

OBJECTIVES: To estimate the risk of gastrointestinal cancer and lung cancer in a cohort of masons exposed to cement and hexavalent chromium by a follow up in the Icelandic Cancer Registry. METHODS: The cohort, 1172 men, was defined as those who had served their apprenticeship and were fully licensed as masons (cement finishers) in Iceland, were born after 1880 and were alive in 1955. The men were exposed to an aerosol of wet concrete, particularly when spraying. According to the analyses of urinary chromium the masons were exposed to hexavalent chromium. A computer file on masons was record linked to the Cancer Registry by making use of the personal identification numbers. Expected cancer incidence was calculated on the basis of number of person-years for each five-year age category during the individual calendar years of the study period and multiplied by the specific incidence for cause and calendar year for men in Iceland provided by the Cancer Registry. RESULTS: The standardised incidence ratio (SIR) for all cancers was 1.13 in the total cohort and 1.33 when allowance was made for 30 years to elapse before starting to count person years of risk. The risk for gastrointestinal cancers was not increased. The SIR for lung cancer was 1.69 in the total cohort and 1.77 when a lag of 30 years was included. The SIR for lung cancer among those born in 1920 or later was 1.86. Results from a postal questionnaire showed that fewer masons had never smoked and more masons had stopped smoking than the controls from the general population. CONCLUSION: The increased risk of lung cancer among the masons may be related to their work. The exposure information, although limited, supports the suggestion that hexavalent chromium in the cement may be the causal link, as information on the smoking habits indicate that the control for this important possible confounder is adequate.

Occupational variation in cancer incidence: a 45 year follow-up of five whole-population cohorts in the Nordic countries

Objectives The Nordic Occupational Cancer (NOCCA, http://astra.cancer.fi/NOCCA) study covers all 15 million working-aged persons who participated in population censuses between 1960 and 1990 in Denmark, Finland, Iceland, Norway and Sweden, and the subsequent 2.8 million incident cancer cases diagnosed in these people in a follow-up until 2005. Methods The observed number of cancer cases in 70 diagnostic categories in each occupation was compared with the expected number calculated from the respective incidence rates for the national population. The result was presented as a standardised incidence ratio, SIR, defined as the observed number of cases divided by the expected number. Results For all cancers combined, there was a wide variation among men from an SIR of 0.79 (95% CI 0.66 to 0.95) in domestic assistants to 1.48 (1.43 to 1.54) in waiters. The occupations with the highest SIRs also included workers producing beverage and tobacco, seamen and chimney sweeps (E1) . Among women, the SIRs varied from 0.58 (0.37 to 0.87) in seafarers to 1.27 (1.19 to 1.35) in tobacco workers. Low SIRs were found for farmers, gardeners and forestry workers in both genders. The variation in relative risk across occupational categories varied considerably between cancer types. For mesothelioma, there was a 20-fold variation in risk among plumbers as compared to farmers, while the variation between the lowest and highest occupation-specific incidence of cancers of colon or brain was not even twofold. Conclusions The present study shows that the risk of cancer is highly dependent on the persons occupation, reflecting the position in the society.

Cancer risk among farmers in the Nordic countries

Objectives Both the work and lifestyle of individuals engaged in agriculture may affect their cancer risk. The aim of this study was to describe cancer risk among male and female farmers in the Nordic countries. Methods The study includes 622 000 men and 159 000 women aged 30–64 years registered as farmers in the 1960, 1970, 1980-1 and/or 1990 censuses in Denmark, Finland, Iceland, Norway and Sweden. During follow-up until 2003–5, 140 500 cancer cases were observed among men and 26 900 among women. The standardised incidence ratio (SIR) was computed as a ratio of observed and expected number of cases calculated from incidence rates for each country for the whole follow-up period and for the three periods 1961–75, 1976–90, and 1991–2005. Results Overall cancer incidence among male (SIR=0.83, 95% CI 0.82 to 0.83) and female (0.84, 0.83 to 0.85) farmers was significantly lower than in the general population. Risk of multiple myeloma was slightly elevated in both genders (men: 1.07, 1.03 to 1.11, women: 1.14, 1.05 to 1.24), chronic lymphatic leukaemia in men only (1.09, 1.03 to 1.14). Risk of lip cancer was elevated among men in all countries (1.57, 1.51 to 1.62). For lung cancer (men: 0.56, 0.55 to 0.57, women: 0.46, 0.44 to 0.49) and upper aerodigestive tract cancers (men: 0.52, 0.51 to 0.35, women: 0.74, 0.69 to 0.79) risk was consistently low in both genders. Conclusions While there are specific occupational risk factors in agricultural work, which deserve further attention, the general cancer pattern in this group points to work-related lifestyle factors which appear protective.