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BACKGROUND: Ionizing radiation at very high (radio-therapeutic) dose levels can cause diseases other than cancer, particularly heart diseases. There is increasing evidence that doses of the order of a few sievert (Sv) may also increase the risk of non-cancer diseases. It is not known, however, whether such effects also occur following the lower doses and dose rates of public health concern. METHODS: We used data from an international (15-country) nuclear workers cohort study to evaluate whether mortality from diseases other than cancer is related to low doses of external ionizing radiation. Analyses included 275 312 workers with adequate information on socioeconomic status, over 4 million person-years of follow-up and an average cumulative radiation dose of 20.7 mSv; 11 255 workers had died of non-cancer diseases. RESULTS: The excess relative risk (ERR) per Sv was 0.24 [95% CI (confidence intervals) -0.23, 0.78] for mortality from all non-cancer diseases and 0.09 (95% CI -0.43, 0.70) for circulatory diseases. Higher risk estimates were observed for mortality from respiratory and digestive diseases, but confidence intervals included zero. Increased risks were observed among the younger workers (attained age <50 years, identified post hoc) for all groupings of non-cancer causes of death, including external causes. It is unclear therefore whether these findings reflect real effects of radiation, random variation or residual confounding. CONCLUSIONS: The most informative low-dose radiation study to date provides little evidence for a relationship between mortality from non-malignant diseases and radiation dose. However, we cannot rule out risks per unit dose of the same order of magnitude as found in studies at higher doses.

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A 15-Country collaborative cohort study was conducted to provide direct estimates of cancer risk following protracted low doses of ionizing radiation. Analyses included 407,391 nuclear industry workers monitored individually for external radiation and 5.2 million person-years of follow-up. A significant association was seen between radiation dose and all-cause mortality [excess relative risk (ERR) 0.42 per Sv, 90% CI 0.07, 0.79; 18,993 deaths]. This was mainly attributable to a dose-related increase in all cancer mortality (ERR/Sv 0.97, 90% CI 0.28, 1.77; 5233 deaths). Among 31 specific types of malignancies studied, a significant association was found for lung cancer (ERR/Sv 1.86, 90% CI 0.49, 3.63; 1457 deaths) and a borderline significant (P = 0.06) association for multiple myeloma (ERR/Sv 6.15, 90% CI <0, 20.6; 83 deaths) and ill-defined and secondary cancers (ERR/Sv 1.96, 90% CI -0.26, 5.90; 328 deaths). Stratification on duration of employment had a large effect on the ERR/Sv, reflecting a strong healthy worker survivor effect in these cohorts. This is the largest analytical epidemiological study of the effects of low-dose protracted exposures to ionizing radiation to date. Further studies will be important to better assess the role of tobacco and other occupational exposures in our risk estimates.

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Radiation protection standards are based mainly on risk estimates from studies of atomic bomb survivors in Japan. The validity of extrapolations from the relatively high-dose acute exposures in this population to the low-dose, protracted or fractionated environmental and occupational exposures of primary public health concern has long been the subject of controversy. A collaborative retrospective cohort study was conducted to provide direct estimates of cancer risk after low-dose protracted exposures. The study included nearly 600,000 workers employed in 154 facilities in 15 countries. This paper describes the design, methods and results of descriptive analyses of the study. The main analyses included 407,391 nuclear industry workers employed for at least 1 year in a participating facility who were monitored individually for external radiation exposure and whose doses resulted predominantly from exposure to higher-energy photon radiation. The total duration of follow-up was 5,192,710 person-years. There were 24,158 deaths from all causes, including 6,734 deaths from cancer. The total collective dose was 7,892 Sv. The overall average cumulative recorded dose was 19.4 mSv. A strong healthy worker effect was observed in most countries. This study provides the largest body of direct evidence to date on the effects of low-dose protracted exposures to external photon radiation.

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OBJECTIVES: To provide direct estimates of risk of cancer after protracted low doses of ionising radiation and to strengthen the scientific basis of radiation protection standards for environmental, occupational, and medical diagnostic exposures. DESIGN: Multinational retrospective cohort study of cancer mortality. SETTING: Cohorts of workers in the nuclear industry in 15 countries. PARTICIPANTS: 407 391 workers individually monitored for external radiation with a total follow-up of 5.2 million person years. MAIN OUTCOME MEASUREMENTS: Estimates of excess relative risks per sievert (Sv) of radiation dose for mortality from cancers other than leukaemia and from leukaemia excluding chronic lymphocytic leukaemia, the main causes of death considered by radiation protection authorities. RESULTS: The excess relative risk for cancers other than leukaemia was 0.97 per Sv, 95% confidence interval 0.14 to 1.97. Analyses of causes of death related or unrelated to smoking indicate that, although confounding by smoking may be present, it is unlikely to explain all of this increased risk. The excess relative risk for leukaemia excluding chronic lymphocytic leukaemia was 1.93 per Sv (< 0 to 8.47). On the basis of these estimates, 1-2% of deaths from cancer among workers in this cohort may be attributable to radiation. CONCLUSIONS: These estimates, from the largest study of nuclear workers ever conducted, are higher than, but statistically compatible with, the risk estimates used for current radiation protection standards. The results suggest that there is a small excess risk of cancer, even at the low doses and dose rates typically received by nuclear workers in this study.

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STUDY DESIGN: Register study enhanced and verified by medical records and personal interviews and examinations. SETTINGS: Sweden. OBJECTIVES: To define a method of identifying a study population of rare events. To point out the relative importance of every step, an example is given of identifying persons who sustained traumatic spinal cord injury (SCI) in childhood. METHODS: Cases were identified in seven steps that all needed to be fulfilled, from definition of selection criteria through combination of several data sources, to the use of several verification methods. RESULTS: Initial screening by registers identified 384 possible cases, which however were found by subsequent analysis to include a large number of incorrect cases. At completion of all analytic steps, 35 living cases could be fully verified and 14 deceased cases could be partially verified. CONCLUSIONS: Registers offer a practical initial source for study population identification. The screening of International Classification of Diseases codes defining SCI only included less than 30% of 'true' SCIs. Subsequently, further refinement and quality control is necessary in order to ensure validity. Such further verification is time-consuming, but nevertheless necessary in order to verify a true cohort.

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To provide new leads regarding occupational prostate cancer risk factors, we linked 36,269 prostate cancer cases reported to the Swedish National Cancer Registry during 1961 to 1979 with employment information from the 1960 National Census. Standardized incidence ratios for prostate cancer, within major (1-digit), general (2-digit), and specific (3-digit) industries and occupations, were calculated. Significant excess risks were seen for agriculture-related industries, soap and perfume manufacture, and leather processing industries. Significantly elevated standardized incidence ratios were also seen for the following occupations: farmers, leather workers, and white-collar occupations. Our results suggest that farmers; certain occupations and industries with exposures to cadmium, herbicides, and fertilizers; and men with low occupational physical activity levels have elevated prostate cancer risks. Further research is needed to confirm these findings and identify specific exposures related to excess risk in these occupations and industries.

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Some earlier reports have indicated increased incidence or mortality of specific tumor types in various health care professions. In this study we have evaluated cancer incidence in physicians, dentists, and other health care workers using the Swedish Cancer Environment Register (CER), which was formed by record-linkage between the 1970 census on current occupation and Cancer Register incidence data in 1971-84. In all three profession categories studied an increased risk was found, as well for all malignant tumors combined, as for specific tumor types regarding the different occupations. Possible etiological factors responsible for these risks are discussed.

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Epidemiological and experimental studies concerning extremely low frequency electromagnetic field exposure and malignant diseases published up to 1 July 1994 were evaluated to assess the possible carcinogenicity of electromagnetic fields and the scientific basis for environmental and occupational standard setting. We concluded that there are possible associations between (i) an increased risk of leukaemia in children and the existence of, or distance to, power lines in the vicinity of their residence, (ii) an increased risk of chronic lymphatic leukaemia and occupational exposure to low frequency electromagnetic fields and (iii) an increased risk of breast cancer, malignant melanoma of the skin, nervous system tumours, non-Hodgkin lymphoma, acute lymphatic leukaemia or acute myeloid leukaemia and certain occupations. There is no scientific basis for occupational or environmental standard setting for low frequency electric or magnetic fields.

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A population-based linked-registry was used to evaluate incidence of malignant melanoma of the skin among Swedish men by industry and occupation. There were 3850 cutaneous melanoma cases identified in the 19-year follow-up of men employed in 1960. New associations were observed for men employed in the breweries and malt-processing industry and in shoe fabrication from leather and skins. Several findings supported associations previously reported in other countries, including an excess risk among workers in basic chemical production and the printing industry and among professional, technical, and white-collar workers. Risk overall was not increased among farmers, despite a significant excess of melanoma of the face, neck, and scalp. Although this linked registry analysis lacked information about specific agents, duration of employment, and occupational and recreational sun exposures, it did provide leads for new associations and confirmed previous ones. Nevertheless, because of these limitations, etiologic clues must be interpreted cautiously.

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Using the Cancer Environment Registry of Sweden, which links the 1960 census information on employment with cancer incidence data from 1961-1979, we conducted a systematic, population-based assessment of esophageal cancer incidence by industry and occupation for men in Sweden. A general reduction in esophageal cancer incidence was found among agricultural and professional workers, whereas excess incidence was found among business, sales, and some craftsmen and production jobs. Elevated incidence was associated with several specific industries, including the food (SIR = 1.3, p < 0.05), beverage and tobacco (SIR = 1.8, p < 0.05) industries, vulcanizing shops within the rubber industry (SIR = 4.7, p < 0.01), and certain automotive building industries. Incidence also was increased among brewery workers (SIR = 4.2, p < 0.01) and butchers (SIR = 2.1, p < 0.01), and among individuals with certain service jobs, particularly waiters in the hotel and restaurant industry (SIR = 3.1, p < 0.01). Some of the occupational associations may be explained by lifestyle factors such as alcohol drinking and smoking, whereas others are specific and tend to support those of earlier investigations. This study adds to the evidence of a small but possibly important role of occupation in esophageal cancer etiology.

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Using a nationwide linked registry, we evaluated the incidence of several hematopoietic and lymphoproliferative (HLP) malignancies among Swedish women from 1961 to 1979 by industry and occupation. The risks of one or more types of HLP cancers (including the leukemias, non-Hodgkin's lymphoma, multiple myeloma, and mycosis fungoides) were significantly increased among women working in the agriculture and textile industries, housekeepers, and post office employees. Limitations of these linked-registry data include lack of detailed information on specific exposures and duration of employment, and the relatively small sizes of specific occupational cohorts. Nevertheless, as the proportion of women entering the workforce continues to increase, this data resource may provide additional clues to occupational determinants of HLP and other malignancies.

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Using the Cancer-Environment Registry of Sweden, which links the 1960 census information on employment with cancer incidence data from 1961-1979, we conducted a systematic, population-based assessment of stomach cancer incidence by industry and occupation for men in Sweden. Nearly 17,000 stomach cancer cases were diagnosed during the 19 years of follow-up. Stomach cancer incidence was elevated among miners and quarrymen, farmers and fishermen, and craftsmen and production workers. Men who held white collar jobs, including professional and technical, administrative and management, clerical, and sales jobs, had a reduction in stomach cancer incidence. Examination of specific jobs revealed generally elevated rates of stomach cancer among men who may be exposed to dusty work environments, such as quarry workers, stone cutters, circular and plane operators, construction workers, crane operators, heavy laborers, and shop and construction metal workers. These occupational associations mostly were observed for stomach cancers of noncardia origin, and no significant associations were found with cardia cancers. We had no information on dietary or other potential confounding factors and cannot make inferences about the role of occupation per se, but the current findings support those of earlier investigations and add to the evidence of a small but significant occupational role in stomach carcinogenesis.

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Using the Cancer-Environment Registry of Sweden, which links census information (1960) with cancer incidence data (1961 to 1979), we conducted a systematic, population-based assessment of colon cancer incidence among cohorts defined by industry and occupation for all employed persons in Sweden. Small but statistically significant excesses of colon cancer were observed among white-collar occupations, including administrators, professionals, and clerical and sales workers, whereas a reduction in incidence was found among workers in agricultural and related jobs, such as farmers, fishermen, and hunters. Analysis by subsite within the colon revealed little difference in results. The observed risk patterns are consistent with previous reports on colon cancer risk and occupational physical activity levels, ie, elevated risk among sedentary white-collar workers and reduced risk among agricultural workers. Few craftsman and production processing jobs were linked to colon cancer, although statistically significant excesses were observed among shoe and leather workers, metal smiths, and foundry workers in the metal manufacturing industry. The findings indicate that occupation in general is likely to play a relatively small role in colon cancer etiology, with perhaps its major contribution an indirect one via physical activity.

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This study investigated how ergonomic design influences neck-and-shoulder muscle strain, through keyboard assessment. Muscular activity was measured electromyographically (EMG) from six muscles in the forearm and shoulders of eight experienced typists using each of five different types of keyboard: one mechanical, one electromechanical, and one electronic typewriter; one personal computer/word processor (PC-XT) keyboard; and one angled at 20 degrees in the horizontal plane. The impact on muscular activity of using a palmrest was also studied. The mechanical typewriter induced a higher strain in the forearm and finger muscles than did the modern typewriters and keyboards. These induced no different strain on the neck-and-shoulder muscles, except for the right shoulder muscle, which was more active with the electronic typewriter than with the other machines. Using a palmrest did not decrease the strain on the muscles investigated. Use of the 'angled' PC-XT keyboard did not influence the measured muscular load on the forearm and finger muscles compared to typing on an ordinary PC-XT keyboard, but decreased the extensor muscular strain compared to the electronic typewriter.

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In an effort to evaluate a hypothesis raised by findings in Denmark that painters might experience an increased risk for pharyngeal and oral cancer, data were collected about these cancers among painters in Norway, Sweden, and Finland. The possible confounding effects of alcohol and tobacco were gauged by collecting data about cancer of the lung, larynx, esophagus, liver, and bladder, and about mortality from liver cirrhosis. Consistently increased risks for lung cancer among painters were found. The risks for cancer of the oral cavity and/or pharynx were increased in Norway, Sweden, and Finland, but not to the same extent as was observed in Denmark. The risks for cancer of the esophagus were slightly increased as were the risks for cancer of the liver and for cirrhosis of the liver in Denmark and Finland. The data from Norway, Sweden, and Finland could thus neither substantiate nor disprove the hypothesis that painters may experience an increased risk for cancer of the pharynx and oral cavity as a result of occupational exposures.

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Incidence of non-Hodgkin's lymphoma in different employment categories was evaluated from the Swedish Cancer-Environment Registry, which links cancer incidence during 1961 to 1979 with occupational information from the 1960 census. New associations were found for men employed in shoemaking and shoe repair, porcelain and earthenware industries, education, and other white collar occupations. Several findings supported associations found in other countries, including excesses among woodworkers, furniture makers, electric power plant workers, farmers, dairy workers, lorry drivers, and other land transport workers. Risks were not increased among chemists, chemical or rubber manufacturing workers, or petrochemical refinery workers. Caution must be used in drawing causal inferences from these linked registry data because information on exposure and duration of employment is not available. Nevertheless, this study has suggested new clues to possible occupational determinants of non-Hodgkin's lymphoma.

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The Swedish Cancer Environment Register (CER) is a linkage of census data (e.g., on occupations) with the Swedish Cancer Register. It has been used in different studies to generate hypotheses on occupational risk factors for malignant tumors. In this study the risk for malignant lymphoma and multiple myeloma in occupations with potential exposure to phenoxyacetic acids or other related substances were investigated. An increased standardized incidence ratio (SIR) of 1.3 for multiple myeloma was verified in farmers (no. of cases = 335). This finding applied to both sexes, and the SIR increased over successive time periods. Regarding malignant lymphoma an increased SIR of 1.2 was found in farmers (no. = 227) for the latest time period studied (i.e. 1979-1984). When non-Hodgkin's lymphoma was studied separately, an increased risk (SIR = 1.2) was found only in carpenters (no. = 149), whereas for Hodgkin's disease, sawmill workers (no. = 10) had an increased SIR of 2.1. Physicians also had an elevated risk for malignant lymphoma. A major shortcoming in register studies such as CER is that no individual exposure data on different agents are available. Lack of an association between an occupation and a specific malignant disease, therefore, may not be taken as evidence that persons within that occupation are not at increased risk for that disease.

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The Swedish Cancer-Environment Registry was used to evaluate a recent report of a large excess risk of renal cell cancer among architects in Los Angeles. We identified 131 renal cell cancers among male Swedish architects and allied professionals during a 19-year follow-up period (1961-1979). Compared with the Swedish population, there was no significant excess of renal cell cancer among architects and allied professionals (standardized incidence ratio (SIR) = 1.15; 131 cases). Although it was not possible to estimate the risk for architects alone, the SIR was only 1.06 (16 cases) in a subset of professionals employed in architectural and engineering firms. However, a significant increase in risk (SIR = 1.38) was observed in a related group of workers employed as engineers and construction supervisors in the home construction industry.

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