#63 Cancer incidence in the u. s. radiologic technologists health study, 1983–1998

PURPOSE: Few studies have evaluated cancer risk associated with low-dose occupational ionizing radiation exposure to women. We present data on incident cancer risks among a predominantly (77%) female cohort of 73,963 U. S. radiologic technologists followed up from 1983 through 1998.METHODS: Cancer incidence information and data on work history, selected cancer risk factors, personal radiation exposure and other health outcomes were obtained from two mailed questionnaires (administered ~1984 and ~1995). Incident cancers were ascertained from the second survey and supplemented by mortality records. Medical records, obtained for 74% of all self-reported cancers, confirmed the cancer in 85%. We computed standardized incidence ratios (SIR) using cancer incidence rates from the National Cancer Institute's Surveillance Epidemiology and End Results Program.RESULTS: The SIR for all cancers combined in both sexes was 1.04 (95% confidence interval (CI): 1.00, 1.07; n = 3292). The incidence of solid cancers was elevated in women (SIR = 1.06, 95% CI: 1.02, 1.10), but lower than expected among men (SIR = 0.92 , 95% CI 0.85, 0.98). Female technologists had an elevated incidence of breast cancer (SIR = 1.16, 95% CI: 1.09, 1.23). Among both sexes combined, elevated risks were seen for melanoma (SIR = 1.59, 95% CI: 1.38, 1.80) and thyroid cancers (SIR = 1.61, 95% CI: 1.34, 1.88), and decreased risks were observed for buccal cavity/pharynx (SIR = 0.73, 95% CI: 0.55, 0.90), rectum (SIR = 0.62, 95% CI: 0.48, 0.76), and lung (SIR = 0.77, 95% CI: 0.70, 0.85) cancers.CONCLUSION: The elevated risk for breast cancer may be related to occupational radiation exposure. The observed melanoma and thryoid cancer excesses may reflect, at least in part, increased screening among medical workers with easy access to health care.     

Cancer incidence and mortality in a Swedish rubber tire manufacturing plant

BACKGROUND: A classification of 12 work categories was used to evaluate the cancer incidence and mortality among a cohort of Swedish rubber tire workers. METHODS: Cancer incidence and mortality in the cohort was compared with expected values from national rates. Standardized incidence and mortality ratios were calculated for the total cohort, for sub-cohorts and with the inclusion of a latency requirement. RESULTS: Among men, increased incidence and mortality risks were found for cancer in the larynx; SIR=2.10; 95% confidence intervals (95% CI): 1.05-3.76, SMR=2.08; 95% CI: 0.42-6.09. Increased risks were also seen for cancer in the trachea, bronchus, and lung; SIR=1.62; 95% CI: 1.28-2.02, SMR=1.54; 95% CI: 1.21-1.94, the incidence risk was highest among those with the longest exposure duration and among workers in compounding/mixing, milling, and maintenance. Decreased incidence risks were seen for cancer of the prostate (SIR=0.74; 95% CI: 059-0.92) and skin (SIR=0.57; 95% CI: 0.36-0.84). CONCLUSIONS: The finding of an excess of tumors in the respiratory system is in agreement with earlier findings in other studies on rubber tire workers. The results on other cancer types are compared to earlier findings and related to work processes and chemical exposures of possible causal importance.     

Wood dust exposure and cancer incidence: a retrospective cohort study of furniture workers in Estonia

BACKGROUND: Occupational wood dust exposure is associated with increased risk of sinonasal cancer in men. However, little is known whether it is associated with sinonasal cancer in women or with malignancies of other sites. METHODS: In a retrospective cohort study of furniture workers, cancer incidence in 3723 men and 3063 women between 1968 and 1995 was compared to the incidence in the general population of Estonia. Cancer risks were analyzed by employment duration and occupation. RESULTS: The standardized incidence ratio (SIR) for all cancers did not differ significantly from one. Two men and one woman had sinonasal cancer (expected 1.07 and 0.53, respectively). Significantly increased risk of colon cancer was seen in the cohort (SIR 1.65, 95% confidence interval (CI) 1.22-2.17). Subjects employed for 10 years and over had significant excess of colon cancer (SIR 2.29, 95% CI 1.28-3.77) and rectal cancer (SIR 2.10, 95% CI 1.05-3.76) in the analysis by employment duration using exposure with a latency of 20 years. The nonsignificant excess of pharyngeal cancer in men (SIR 1.82) and lung cancer in women (SIR 1.43) was restricted to short-term workers. CONCLUSIONS: This study found an excess of colon and rectal cancer in furniture workers. There was no increase in total cancer risk.     

Cancer morbidity in iron and steel workers in Korea

BACKGROUND: In the iron and steel industry, workers are potentially exposed to a number of carcinogens and are involved in a number of processes of a hazardous nature. The cancer morbidity of iron and steel workers from modern plants in a developing country is described. METHODS: Cancer morbidity at two Korean iron and steel complexes was analyzed using Poisson regression methods. Work histories were merged with the national cancer registry for 44,974 workers who were followed from 1988-2001. RESULTS: Four hundred sixty-four cancers, in 1% of the population, were diagnosed over 14 years. Based on national cancer rates, the cohort exhibited a healthy worker effect for all cancer (SIR = 0.87, 95% CI = 0.79-0.95) reflecting relative good health, particularly for lung cancer (SIR = 0.58, 95% CI = 0. 04-0.82), stomach cancer (SIR = 0.78, 95% CI = 0.64-0.93), and liver cancer (SIR = 0.83, 95% CI = 0.68-1.01). Lung cancer morbidity was significantly elevated at the affiliated plants versus the parent plants (SRR = 2.35, 95% CI = 1.07-4.92), and all-cancer morbidity was significantly elevated for maintenance workers compared to office and production workers (SRR = 1.27, 95% CI = 1.00-1.60). Lymphohematopoietic cancer incidence was higher in the coke plants (SRR = 3.46, 95% CI = 1.02-8.91) and stomach cancer incidence was higher in the maintenance departments (SRR = 1.66, 95% CI = 1.05-2.56). CONCLUSIONS: This recent steelworker cohort exhibits possible excess cancer morbidity in some processing areas. Further follow-up of this cohort and alternate study designs such as case-control study will be needed to elucidate the relationship of exposure and health risks of iron and steel workers.     

Biliary tract cancers among textile and other workers in Shanghai,China

Using occupational data for more than 500 patients with cancers of the biliary tract (CBT) diagnosed between 1980 and 1984 in Shanghai, and employment information from the 1982 census for the Shanghai population, the associations between CBT and occupational categories were examined by standardized incidence ratios (SIR). Compared to the general population, risk was elevated by nearly 40% among textile workers (SIR for women = 137, 95% CI = 106–175 and SIR for men = 137, 95% CI = 76–217), consistent with other investigations linking CBT to textile work. Increased risks were observed also among waiters/waitresses, male sanitation personnel and chemical workers, and female janitor and similar workers. Although causal inferences cannot be firmly drawn, our findings add to the limited evidence linking CBT to occupational exposures, especially in the textile industry. © 1996 Wiley-Liss, Inc.     

Risk of cancer in pesticide applicators in Swedish agriculture

The risk of cancer was analysed in a cohort of 20,245 licensed pesticide applicators in agriculture who had licences issued between 1965 and 1976. Most were men (99%) and about 50% had been born in 1935 or later. The cohort was followed up in the Swedish Cancer Register from date of licence until death or 31 December 1982. The mean follow up time was 12.2 years. Average time since first exposure was longer, however, since one fifth of the cohort was exposed in the 1950s. A total of 558 malignant tumours was found compared with 649.8 expected, which resulted in a statistically significantly decreased standardised incidence ratio (SIR) of 0.86 (95% confidence interval (CI): 0.79-0.93). Significantly decreased risks of cancer were also found for liver (SIR = 0.45, 95% CI: 0.18-0.93), pancreas (SIR = 0.50, 95% CI: 0.26-0.87), lung (SIR = 0.50, 95% CI: 0.35-0.68), and kidney (SIR = 0.53, 95% CI: 0.32-0.84). No statistically significantly increased risks or any time trends were observed. SIR for testicular cancer was increased (SIR = 1.55, 95% CI: 0.92-2.45) and increased with period since licence. Eighteen cases with testicular cancer were found. For those born in 1935 or later a non-significant increased overall risk of cancer was observed (SIR = 1.07, 95% CI: 0.82-1.37). Comparisons were made with agricultural workers in general since pesticide applicators are mainly farmers that use or have used pesticides to a greater extent. Higher risks for pesticide applicators were found for testicular cancer, tumours of the nervous system and endocrine glands, and Hodgkin's disease.     

Risk of cancer in pesticide applicators in Swedish agriculture.

The risk of cancer was analysed in a cohort of 20,245 licensed pesticide applicators in agriculture who had licences issued between 1965 and 1976. Most were men (99%) and about 50% had been born in 1935 or later. The cohort was followed up in the Swedish Cancer Register from date of licence until death or 31 December 1982. The mean follow up time was 12.2 years. Average time since first exposure was longer, however, since one fifth of the cohort was exposed in the 1950s. A total of 558 malignant tumours was found compared with 649.8 expected, which resulted in a statistically significantly decreased standardised incidence ratio (SIR) of 0.86 (95% confidence interval (CI): 0.79-0.93). Significantly decreased risks of cancer were also found for liver (SIR = 0.45, 95% CI: 0.18-0.93), pancreas (SIR = 0.50, 95% CI: 0.26-0.87), lung (SIR = 0.50, 95% CI: 0.35-0.68), and kidney (SIR = 0.53, 95% CI: 0.32-0.84). No statistically significantly increased risks or any time trends were observed. SIR for testicular cancer was increased (SIR = 1.55, 95% CI: 0.92-2.45) and increased with period since licence. Eighteen cases with testicular cancer were found. For those born in 1935 or later a non-significant increased overall risk of cancer was observed (SIR = 1.07, 95% CI: 0.82-1.37). Comparisons were made with agricultural workers in general since pesticide applicators are mainly farmers that use or have used pesticides to a greater extent. Higher risks for pesticide applicators were found for testicular cancer, tumours of the nervous system and endocrine glands, and Hodgkin's disease.     

Cancer incidence among Norwegian airline cabin attendants

BACKGROUND: Cabin crews are exposed to cosmic radiation at work and this may increase their incidence of radiation-induced cancers. Former studies indicate an increased risk of breast cancer. METHODS: A retrospective cohort study was performed. The cohort was established from the files of the Civil Aviation Administration and included people with a valid licence as a cabin attendant between 1950 and 1994. The cohort was linked to the Cancer Registry of Norway. Observed number of cases was compared with expected, based on national rates. Breast cancer incidence was analysed, adjusting for individual fertility variables. RESULTS: A group of 3693 cabin attendants were followed over 72 804 person-years. Among the women, 38 cases of breast cancer were observed (standardized incidence ratio (SIR) = 1.1, 95% CI : 0.8-1.5). Among men excess risks were found for cancers in the upper respiratory and gastric tract (SIR = 6.0, 95% CI : 2.7-11.4) and cancer of the liver (two cases, SIR = 10.8, 95% CI : 1.3-39.2). For both sexes elevated risks were found for malignant melanoma and non-melanoma skin cancer; for men these were SIR = 2.9 (95% CI : 1.1-6.4) and SIR = 9.9 (95% CI : 4.5-18.8) respectively, while for women these were SIR = 1.7 (95% CI : 1.0-2.7) and SIR = 2.9 (95% CI : 1.0-6.9) respectively. For no cancer site was a significant decreased risk found. CONCLUSIONS: An increased risk of radiation-induced cancers was not observed. The excess risks of some other cancers are more probably explained by factors related to lifestyle.     

Exposure to chemical carcinogens and risk of cancer among Finnish laboratory workers

BACKGROUND: Laboratory workers have long been suspected of having increased risks of cancer due to their occupation. We evaluated occupational exposure and cancer incidence among Finnish laboratory workers. MATERIALS AND METHODS: The cohort was comprised of 4,722 laboratory workers reported to the Finnish Register of Workers Exposed to Carcinogens in 1979-1988. The standardized incidence ratios (SIR) for cancers and their 95% confidence intervals (CI) were calculated based on data of the Finnish Cancer Registry. RESULTS: The most common carcinogens, to which these workers were potentially exposed, were chromium (VI), carbon tetrachloride, cadmium, benzene, and chloroform. From this cohort, 174 persons were recorded with primary tumors in 1980-1999. The SIR for cancer of all sites combined was 0.99 (CI 0.85-1.14). None of the cancer-specific SIRs were significantly elevated. Slight excesses were found, e.g., for non-Hodgkin's lymphoma (seven observed, 4.8 expected) and leukemia (four observed, three expected). CONCLUSIONS: This study did not suggest any major cancer risks among Finnish laboratory workers but the follow-up time of the cohort was too short (on an average 15.7 years) to reveal possible cancer risks requiring a longer induction period.     

Cancer incidence among Australian nuclear industry workers

To assess whether workers at Lucas Heights Science and Technology Centre (LHSTC) had different levels of cancer incidence from the New South Wales (NSW) population in Australia. A retrospective cohort study was undertaken at LHSTC. Data on 7,076 workers employed between 1957-98 were abstracted from personnel, dosimetry, and medical files. An inception cohort was defined which included 4,523 workers in employment between 1972-96 to examine cancer incidence. Cancer registrations in the inception cohort were identified to 1996 through electronic linkage of records with the NSW and the Australian national registers of cancer incidence. All-cancer incidence in workers at LHSTC was 15% below the NSW rates [SIR=0.85; 95% CI=(0.75, 0.95)]. Of 37 specific cancers and groups of cancers examined, statistically significant excesses relative to NSW rates were observed only for pleural cancer incidence [SIR=17.71; 95%=(7.96, 39.43)], and for incidence of cancer of the small intestine [SIR=4.34; 95% CI=(1.40, 13.46)]. This study gives little evidence of an increased risk of cancers associated with radiation exposure in a cohort of nuclear workers in Australia. The observed increase in the risk of cancer of the pleura was probably due to unmeasured exposures, given the lack of an established association with radiation exposure, and the strong link to asbestos exposure. Findings for cancers of the small intestine were based on small numbers and were likely to be due to chance.     

Bladder cancer and occupation in Shanghai, 1980-1984.

To investigate occupational determinants of bladder cancer in the urban area of Shanghai, occupation and industry information for 1,219 incident bladder cancer cases diagnosed during the period 1980 to 1984 were compared with 1982 census data on employment. Standardized incidence ratios (SIR) for bladder cancer were estimated for occupation and industry classifications. Significant excess risks were observed for plastic products workers (male: SIR = 432; female: SIR = 368); textile bleachers, dyers, and finishers (male: SIR = 169); metal refining and processing workers (male: SIR = 139; female: SIR = 197); petroleum refining workers (male: SIR = 2152); railway engine drivers and firemen (male: SIR = 683); and workers employed in industries of apparel and other textile products manufacturing (female: SIR = 204); paper processing (male: SIR = 146; female: SIR = 226); organic chemical manufacturing (male: SIR = 186); plastic product manufacturing (male: SIR = 218; female: SIR = 272); and metallurgy (male: SIR = 107; female: SIR = 561). This study indicates that many of the industries and occupations that are responsible for increased risk throughout the world are also associated with occupational bladder cancer in Shanghai.     

Cancer risk among glass factory workers: an excess of lung cancer?

A total of 3749 workers employed for at least three months in two Finnish glass factories (cohorts A and B) were followed up for cancer in 1953-86 through the Finnish Cancer Registry. In cohort A (1353 men, 1261 women), 106 primary cancers were diagnosed among men, and their standardised incidence ratio (SIR) for all cancers was 99. Among women the risk was low (65 cases, SIR 64). In cohort B (450 men, 685 women), the relative risk of cancer was close to unity for both men (57 cases) and women (75 cases). The risk of cancer was analysed by primary site, type of work, years since first exposure, and age at diagnosis. The only significantly increased risks were those of lung cancer among men (SIR 130, 95% CI 100-167, cohorts A and B combined), and skin cancer among glass blowers (SIR 625, 95% CI 129-1827). An increased risk of lung, stomach, and colon cancer as well as of brain tumours has been reported in previous studies. It is postulated that the excess risk of lung cancer, detected in this study, can also be accounted for by lifestyle, and not only by possible occupational exposures, because a similar excess risk of lung cancer has been found previously for all industrial workers in Finland. Although the risk of stomach cancer in this study was increased among glass blowers, it was not high in the largest groups of plain glass workers. The risks of tumours of the central nervous system and colon were not increased either.     

Cancer risk among glass factory workers: an excess of lung cancer?

A total of 3749 workers employed for at least three months in two Finnish glass factories (cohorts A and B) were followed up for cancer in 1953-86 through the Finnish Cancer Registry. In cohort A (1353 men, 1261 women), 106 primary cancers were diagnosed among men, and their standardised incidence ratio (SIR) for all cancers was 99. Among women the risk was low (65 cases, SIR 64). In cohort B (450 men, 685 women), the relative risk of cancer was close to unity for both men (57 cases) and women (75 cases). The risk of cancer was analysed by primary site, type of work, years since first exposure, and age at diagnosis. The only significantly increased risks were those of lung cancer among men (SIR 130, 95% CI 100-167, cohorts A and B combined), and skin cancer among glass blowers (SIR 625, 95% CI 129-1827). An increased risk of lung, stomach, and colon cancer as well as of brain tumours has been reported in previous studies. It is postulated that the excess risk of lung cancer, detected in this study, can also be accounted for by lifestyle, and not only by possible occupational exposures, because a similar excess risk of lung cancer has been found previously for all industrial workers in Finland. Although the risk of stomach cancer in this study was increased among glass blowers, it was not high in the largest groups of plain glass workers. The risks of tumours of the central nervous system and colon were not increased either.     

Cancer in the Norwegian printing industry

OBJECTIVES: The aim of this study was to investigate cancer risk among Norwegian workers in the printing industry, particularly lung and bladder cancer. METHODS: Cancer incidence was investigated from 1953 through 1998 in a cohort of 10 549 male members of a trade union in the printing industry in Oslo and nearby areas. Rates from the region, were used to calculate standardized incidence ratios (SIR) separately for the skilled and unskilled workers. Smoking data from a sample of the cohort were utilized for evaluating the risk estimates of smoking-related cancers. Specific exposure data were not available. RESULTS: Among the skilled workers, significantly elevated risks of cancer of the urinary bladder [standardized incidence ratio (SIR) 1.47, 95% confidence interval (95% CI) 1.19-1.79], liver (SIR 1.92, 95% CI 1.15-2.99), pancreas (SIR 1.46, 95% CI 1.07-1.94) and colon (SIR 1.27, 95% CI 1.05-1.55) were observed, whereas an increased risk of lung cancer in this group was confined to those born before 1910. Among the unskilled workers, there were significantly increased risks of cancer of the mouth, esophagus, stomach, larynx, lung, and all sites. CONCLUSIONS: The study showed that workers in the printing industry were at increased risk of several types of cancer. In particular the increased risk of bladder cancer among the skilled workers is suggestive of an occupational cause. However, no specific agent could be identified as an occupational carcinogen. The results did not support the hypothesis of a generally increased risk of lung cancer. The risk pattern for unskilled workers may reflect confounding by nonoccupational factors.     

Primary liver cancer, other malignancies, and mortality risks following porphyria: a cohort study in Denmark and Sweden.

Cancer incidence and mortality risks were evaluated in a combined cohort of patients who were hospitalized for porphyria in Denmark (1977-1989) and Sweden (1965-1983). Patients were identified by using population-based hospitalization registries. The unique individual identification numbers of 530 patients with porphyria cutanea tarda (PCT) and 296 with acute intermittent porphyria (AIP) were linked to the nationwide cancer and death registries. Among patients with both types of porphyria, the authors found small but significantly elevated risks of all cancers combined (PCT: standardized incidence ratio (SIR) = 1.7, 95% confidence interval (CI) 1.3-2.2; AIP: SIR = 1.8, 95% CI 1.1-2.8) due to pronounced excesses of primary liver cancer (PCT: SIR = 21.2, 95% CI 8.5-43.7; AIP: SIR = 70.4, 95% CI 22.7-164.3) and moderate increases in lung cancer (PCT: SIR = 2.9, 95% CI 1.5-5.2; AIP: SIR = 2.8, 95% CI 0.3-10.2). PCT patients had a significantly increased risk of mortality from liver cirrhosis (standardized mortality ratio (SMR) = 8.4, 95% CI 3.1-18.4) or chronic obstructive pulmonary disease (SMR = 3.1, 95% CI 1.1-6.7). The increased risk of primary liver cancer and the increased risk of mortality from cirrhosis of the liver are consistent with findings from previous clinical surveys, but the new observations of excess lung cancer and chronic obstructive pulmonary disease require confirmation.     

Risk of second primary malignancies in women with papillary thyroid cancer

Second malignancies in women diagnosed with thyroid cancer are of concern given the young average age at diagnosis and excellent survival. Data from the California Cancer Registry were used to evaluate the risk of second primary cancers among a retrospective population-based cohort of 10,932 women diagnosed with papillary thyroid cancer between 1988 and 1999. Follow-up was calculated from 2 months until the diagnosis of a second primary cancer, death, loss to follow-up, or December 31, 1999, whichever occurred first. Standardized incidence ratios, based on age-specific cancer incidence rates for California women, were calculated. During a total of 50,938 person-years of follow-up (mean: 4.7 years), 279 women developed a second primary cancer. The incidence of invasive breast cancer was not elevated compared with California women overall (standardized incidence ratio (SIR) = 0.9, 95% confidence interval (CI): 0.7, 1.1) or when stratified by age, race/ethnicity, follow-up, or radiation treatment. An excess of in situ breast cancer (SIR = 1.6, 95% CI: 1.0, 2.4), kidney cancer (SIR = 3.9, 95% CI: 2.2, 6.3), and melanoma (SIR = 2.1, 95% CI: 1.3, 3.2) limited to the first 5 years after diagnosis was observed. Women with papillary thyroid cancer are at increased risk of in situ, but not invasive, breast cancer, kidney cancer, and melanoma.     

Cancer incidence in a cohort of Swedish sewage workers: extended follow up

OBJECTIVES: To study the cancer incidence in a cohort of Swedish sewage workers. An increased incidence of cancer of the stomach, the kidney and the nervous system in this cohort was previously reported. This new analysis reports on 9 more years of follow up. METHODS: The study is an analysis of a cohort of all 711 employees at 17 Swedish sewage plants employed for at least for 1 year during the years 1965-86. Assessment of exposures was performed by classification of work tasks. Standardised incidence ratios (SIRs), and 95% confidence intervals (95% CIs) were calculated. RESULTS: The total cancer incidence was not significantly increased (SIR = 1.2, 95% CI 0.92 to 1.5) but the incidence of prostate cancer was (SIR = 1.6, 95% CI 1.0 to 2.5), and based on two cases only, there seemed to be a significant increase of cancer of the nose and the nasal sinuses (SIR = 12, 95% CI 1.5 to 44). The incidence of stomach cancer was also increased (SIR = 2.3, 95% CI 0.99 to 4.5). There was no relation between cancer incidence and level of sewage exposure. CONCLUSIONS: Sewage workers did not have an increased risk of cancer, and the increased risk estimates for some specific cancer sites were not conclusive.       

Cohort study of cancer risk among male and female shift workers

OBJECTIVES: Melatonin, a hormone that inhibits experimentally induced cancers, is suppressed by nighttime exposure to light so that nighttime shift workers may be at an increased risk of cancer. Previous studies of shift workers found an increased risk of breast cancer among women and suggested a possible increased risk of colon cancer among women and prostate cancer. The present study was conducted to see whether these previous findings could be confirmed and whether shift workers are at elevated risk for cancer at additional sites. METHODS: Altogether 2 102 126 male and 1 148 661 female workers were identified who worked in both 1960 and 1970. Their jobs were classified according to the percentage of shift workers, and they were followed from 1971 through 1989 or until they were diagnosed with cancer or died. Standardized incidence ratios (SIR) were used to compare the adjusted cancer incidence rates for shift workers with those for nonshift workers. RESULTS: Cancer rates were not elevated for the male shift workers [all sites combined: N=6524 cases among shift workers, SIR 1.02, 95% confidence interval (95% CI) 1.00-1.05; prostate: N=1319, SIR 1.04, 95% CI 0.99-1.10] or for the female shift workers (all sites combined: N=268, SIR 1.00, 95% CI 0.89-1.13; breast: N=70 cases, SIR 0.94, 95% CI 0.74-1.18). CONCLUSIONS: No evidence was found for an association between shift work and breast or prostate cancer, or all cancer sites combined among shift workers.     

Gliomas among men employed in the Swedish pulp and paper industry

OBJECTIVES: This study investigated whether previous findings of an increased risk of gliomas among workers in some pulp and paper mills could be confirmed for all Swedish pulp and paper mill workers and whether the increase could be attributed to certain occupational groups. METHODS: The study was based on the Swedish Cancer Environment Register, which links the incidence of cancer from 1971 to 1990 and the 1960 and 1970 census data on codes of occupation and industry for the whole population. Standardized incidence ratios (SIR) were used to estimate the risks for men in different occupations in pulp (N = 28,142) and paper (N = 39,169) mills in 1960, 1970 or both years as compared with those of all gainfully employed men in Sweden. RESULTS: Maintenance workers employed in pulp or paper mills in 1960, 1970 or both years, as well aspulp workers, showed an increased incidence of gliomas in 1971-1990 [SIR 1.5, 95% confidence interval (95% CI) 1.1-2.1 and SIR 1.5,95% CI 1.0-2.2, respectively], whereas the incidence among process workers in paper mills was lower than expected (SIR 0.6, 95% CI 0.3-0.9). Taken together, all employed men in the pulp mill industry had an increased incidence of gliomas (SIR 1.3, 95% CI 1.0-1.7). CONCLUSIONS: Pulp mill workers, but not paper mill workers, were found to have more gliomas in 1971-1990 than expected. There was an increased risk of gliomas among maintenance workers in both pulp and paper mills. Few risk factors for brain tumors are recognized, and the causes of the increase are not obvious.