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M. J. A. van Tongeren1, S. J. Hepworth2, K. R. Muir3, P. A. McKinney4, A. Bolton5. 1Institute of Occupational Medicine; 2Leeds Institute of Genetics, Health and Therapeutics (LIGHT); 3University of Nottingham; 4Leeds Institute of Genetics, Health and Therapeutics; 5University of Manchester
ObjectivesTo investigate whether certain occupations and exposure to solvents and pesticides are associated with an increased risk of developing glioma, meningioma and acoustic neuroma.
MethodsA population based case‐control study was conducted in four regions in the UK: Trent, West Midlands, West Yorkshire and central Scotland. Occupational histories were collected from all participants, whilst detailed information on pesticide and solvent exposure was collected from most of the controls and about half of the cases. Occupational exposure to solvents and pesticides was determined based on the information provided in the questionnaire by a team of experts. Occupations were selected a priori for analyses based on information from the literature.
ResultsData were obtained from 2078 eligible participants: 978 cases of brain tumours (gliomas n=593; meningiomas n=250; acoustic neuromas n=135) and 1100 controls. Agricultural or related work was statistically significantly associated with an increased risk of developing meningioma (OR 2.0, 95% CI 1.1 to 3.5); no other occupations were associated with increased risk. No associations were observed between any occupations and glioma or acoustic neuroma. For exposure to solvents or pesticides, no significant ORs were observed for any type of brain tumour.
ConclusionThe results of this study suggest that working in agriculture or related sectors is associated with an increased risk of developing meningioma but not glioma or acoustic neuroma. However, no association was observed with occupational pesticide or solvent exposure.
Key wordsbrain tumour; epidemiology; occupation
Y. S. Ahn1, R. M. Park2, D. H. Koh3. 1Dongguk University International Hospital; 2National Institute for Occupational Safety and Health; 3Korea Occupational Safety and Health Agency
ObjectivesSurveillance for exposure to low levels of ionising radiation has been conducted for Korean workers since 1983. The cancer mortality and morbidity experience of these workers is described for the first time in Korea.
MethodsCancer mortality from 1992 to 2004 was analysed in a large Korean National Dose Registry cohort with individual annual dosimetry from 1 January 1983 to 31 December 2004. The comparison group was workers in motor vehicle manufacturing who had taken the annual special health examination and were exposed only to noise. Standardised mortality ratios (SMR) and standardised rate ratios (SRR) were estimated by Poisson regression methods. Similar analyses for cancer morbidity were conducted, using cases identified from admissions records of specialty hospitals.
ResultsThe 935 deaths observed during 13 years of follow‐up represented a large healthy worker effect (HWE) for all causes (SMR 0.58, 95% CI 0.54 to 0.62) and for all cancer (SMR 0.73, 95% CI 0.64 to 0.82). Compared to automobile workers, radiation workers displayed decreased all‐cancer mortality. Only workers at nuclear power plants had non‐significant increased all‐cancer mortality (SRR 1.16, 95% CI 0.82 to 1.64). Compared to workers with 0 mSv, workers with 10.00–49.99 mSv cumulative exposure experienced increased mortalities for all cancer (SRR 1.20, 95% CI 0.75 to 1.85), lung cancer (SRR 1.26, 95% CI 0.34 to 3.75), leukaemia (SRR 1.47, 95% CI 0.17 to 12.7) and lymphohaematopoietic cancer (SRR 1.04, 95% CI 0.26 to 3.64) that were not statistically significant. Cancer admissions in radiation workers compared to auto workers were generally reduced with the possible exception of nuclear power plant workers (SRR 1.13, 95% CI 0.94 to 1.36). Thyroid cancer admissions were statistically significantly elevated in women radiation workers in medical/research institutions (SRR 2.9 to 5.1) and in nuclear power workers (SRR 2.59, 95% CI 1.33 to 5.13) who had a significant upward trend on cumulative dose (RR 1.75 per 50 mSv dose, 95% CI 0.95 to 2.54, p=0.033, one‐tailed).
ConclusionThis radiation worker cohort with short follow‐up periods exhibits a strong HWE. Several radiogenic cancers appear to be elevated but causal interpretation is constrained by limited statistical power due to small numbers of deaths. Thyroid cancer morbidity was elevated, most clearly among women and among nuclear power plant employees. More detailed investigation of confounding variables and future follow‐up of this cohort will better define health risks in radiation workers.
Key wordsradiation workers; cancer mortality; thyroid cancer
J. Sonderskov1, K. Bendix2, F. D'Amore3, J. S. Kristensen3, J. P. Bonde1, H. A. Kolstad1. 1Department of Occupational Medicine, Aarhus University Hospital; 2Department of Pathology, Aarhus University Hospital; 3Department of Haematology, Aarhus University Hospital
ObjectivesAn increased risk of leukaemia has repeatedly been reported in workers co‐exposed to styrene and 1,3‐butadiene, but it is an open question if the increased risk is due to exposure to styrene, 1,3‐butadiene, the mixture of both, or neither. We analysed the risk of myeloid leukaemia and other myeloid stem cell disorders among styrene‐exposed workers with no 1,3‐butadiene exposure.
MethodsWe conducted a nested case‐control study among 79000 workers employed in the reinforced plastics industry in 1968–1997. Incident cases of acute (n=52) and chronic myeloid leukaemia (n=23), myelodysplastic syndome (n=16), polycythemia vera (n=61), chronic idiopathic myelofibrosis (n=13) and essential thrombocythemia (n=37) were identified by record linkage with national cancer and hospital registries. We also identified 817 controls within the population. Styrene exposure assessment relied on individual work histories reported by cases and controls or their next of kin (43%), or estimates of the likelihood of styrene exposure reported by colleagues, employers and dealers (57%) in addition to historical styrene exposure levels. A semi‐quantitative cumulative styrene exposure score was computed that integrated exposure probability and styrene exposure level and classified all but three subjects.
ResultsWe observed increasing risk of chronic idiopathic myelofibrosis by increasing cumulative styrene exposure (p value, test for trend 0.03). For the highest exposure category the risk was increased fourfold (OR 4.18, 95% CI 0.70 to 26.63). We also observed increased risks for acute myeloid leukaemia (OR 2.52, 95% CI 1.09 to 5.88) and myelodysplastic syndrome (OR 2.23, 95% CI 0.54 to 9.25) when account was taken of a 10‐year exposure lag, but these findings were less consistent. The study did not support an association between styrene exposure and chronic myeloid leukaemia, polycythemia vera or essential thrombocythemia.
ConclusionOur findings need to be corroborated and updates of established epidemiological studies of the reinforced plastics industry as well as the styrene‐butadiene rubber industry that sub‐classify leukaemia by cell line and clinical entities and pay special attention to myeloid stem cell disorders, may bring us closer to solving the styrene‐butadiene enigma.
Key wordsstyrene; leukaemia; haematopoietic disorders
B. T. Ji1, X. O. Shu2, Y. T. Gao3, A. Blair1, J. Lubin1, G. Yang2, S. Z. Xue1, W. Zheng2, W. H. Chow1. 1National Cancer Institute, NIH; 2Vanderbilt University, Nashville, TN; 3Shanghai Cancer Institute, Shanghai
ObjectivesNight shift work can suppress melatonin release and alter reproductive hormone profiles and thus may increase the risk of hormonal related cancers, including colorectal cancer. We tested this hypothesis in the Shanghai Women's Health Study, a population‐based prospective study conducted in Shanghai, China.
MethodsA lifetime occupational history and other exposure data were obtained from 74942 women aged 40–70 years at baseline (1997–2000). Subjects have been followed up by in‐person survey and linkage with cancer registry data. By December 2005, 225 incident colon and 142 rectal cancer cases were identified among study participants. An index was developed to score each job on exposure to night shift work (0 ‐ no night shift, 1 ‐ occasional late evening work, 2 ‐ consistent late night work, 3 ‐ overnight shift with intermittent sleep, 4 ‐ over night duty with no sleep) according to job title information. A lifetime average exposure was estimated by multiplying the score and duration of each job, summing over all jobs and dividing by the total duration of work history. Additional data on night shift work history were obtained in the first follow‐up survey (2000–2002). Subjects were asked if ever started work after 10 pm on at least three shifts per month that lasted over 1 year, as well as frequencies and years of the shift work. The Cox proportional hazards model was used to estimate relative risks (RR) and 95% confidence intervals (CI) associated with night shift job, adjusting for age, education and other confounding variables.
ResultsCompared to no or occasional night shift work, the RR (95% CI) of lifetime average night shift work for colon cancer were 1.17 (0.84 to 1.63), 1.42 (0.96 to 2.10), and 1.60 (1.03 to 2.46) at low, moderate and high levels of exposure, respectively (ptrend=0.017) based on job title information. Similarly, the risk for colon cancer was also positively associated with self‐reported overnight shifts (RR 1.63, CI 1.04 to 2.56 for >8 overnight shifts per month and RR 1.43, CI 0.87 to 2.08 for holding shift work for over 20 years). No consistent relationship between night shift work and rectal cancer risk was noted.
ConclusionThese results suggest that night shift work may affect the risk of colon cancer, but not rectal cancer.
Key wordsnight shift work; colorectal cancer; Shanghai Women Health Study
J. Hansen. Institute of Cancer Epidemiology, Danish Cancer Society
ObjectivesAbout 20% of the workforce in Denmark has been exposed to organic solvents. Certain such volatile chemicals cause mammary gland tumours in animal assays. Breast cancer is the most common cancer among women, and less than 40% of the cases can be explained by known risk factors. Few epidemiological studies on breast cancer have evaluated exposure to organic solvents, and results are conflicting.
MethodsWe conducted a population based nested case‐control study among women born 1935–1980 and employed within seven selected industries with widespread exposure to organic solvents. Information about individual employments in such industries was obtained from computerised files from the national Pension Fund, in which all employees are compulsory members. Cases, obtained from the nationwide Danish Cancer Registry, were women diagnosed with breast cancer during 2001–2003, who had been employed in the selected industries. One control, free of breast cancer at the time of diagnosis of the case, born in the same year as the case and employed in the same industries was individually matched to each case. Study subjects were interviewed blindly and information was obtained on work tasks, exposure to organic solvents in general and specific solvents (ethanol, methylene chloride, styrene), suspected and known risk factors for breast cancer (eg, reproductive history, alcohol consumption, contraceptive use, etc). Adjusted odds ratios were estimated by logistic regression. In total 544 cases (77%) and 544 controls (77%) were interviewed.
ResultsOR for breast cancer was 1.6 (1.1 to 2.0) after exposure to unspecific organic solvents. OR increased by 2% per year of organic solvent exposure (p<0.01). The first 5 years of exposure showed no increased risk. Breast cancer was associated with exposure to ethanol: OR 2.8 (1.8 to 4.4). No increased breast cancer risk was observed after exposure to methylene chloride or styrene.
ConclusionIncreased risk for breast cancer was observed for self‐reported occupational exposure to unspecific solvents, and to ethanol. Recall bias may be a problem but is less likely to explain all the increased risk, indicated by the observed positive dose–response relationship, and the absent association with two of the other studied solvents.
Key wordsbreast cancer; organic solvents; epidemiology
M. T. Do1,2, L. D. Marrett1,2, J. Purdham2,3, W. Lou2, J. I. Payne4, N. Chong1. 1Cancer Care Ontario, Toronto, ON; 2Department of Public Health Sciences, University of Toronto; 3Gage Occupational and Environmental Health Unit, University of Toronto; 4Dalhousie University, Halifax, Nova Scotia, Canada
ObjectivesExcess lung cancer risk associated with exposure to radon daughter products among uranium miners is well established. Although ingestion is also an important exposure route, the relationship between radon and digestive tract cancers is not well examined. Even less understood are the cancer effects of gamma radiation, which is emitted by natural uranium decay and is capable of penetrating human tissues. Over 30000 men worked in Ontario's uranium mines between 1954 and 1996, according to Ontario's Mining Master File (MMF) and the National Dose Registry (NDR). This group provides a unique opportunity to examine the long‐term cancer effects of ionising radiation. To determine the relationship between ionising radiation (radon, gamma) and the incidence and mortality of gastrointestinal (oesophagus, stomach and colorectal) cancers in men employed as uranium miners in Ontario.
MethodsA retrospective cohort design will be used to estimate gastrointestinal cancer risks associated with radon and gamma radiation exposures. The cohort will be created by linking the MMF and NDR. The cohort comprises Ontario male uranium miners recorded in either the MMF or the NDR. Radon daughter exposure was previously estimated using area measurements. Gamma radiation exposure is available only since 1981. Algorithms using work history and uranium ore grade geological data are being developed to estimate gamma radiation exposure prior to 1981. Cancer diagnoses (1964–2004) and deaths (1954–2004) are being ascertained by probabilistic record linkage with the Ontario Cancer Registry. Date of death from any cause will also be determined. Relative risks will be estimated by standardised incidence ratios and Poisson regression.
ResultsThere are 30914 Ontario uranium miners in either the MMF or the NDR (MMF: 26367 and NDR: 29865). Over 25000 men were in both the MMF and NDR. On average, miners were born in 1937 and most were employed in 1954–1960 and 1975–1981.
ConclusionExposures to radon daughters were highest prior to 1969 when mines were less well ventilated. Historical gamma exposure is currently being estimated. Outcomes linkage will be completed by April 2007, enabling estimation of relative risks associated with gamma and radon exposure.
Key wordsuranium miners; ionising radiation; cancer