A dose-response analysis and quantitative assessment of lung cancer risk and occupational cadmium exposure.

We performed a quantitative assessment of the risk of lung cancer from exposure to cadmium based on a retrospective cohort mortality study of cadmium-exposed workers. The study population consisted of white male workers who were employed for at least 6 months at a cadmium smelter between January 1, 1940, and December 31, 1969, and who were first employed at the facility on or after January 1, 1926. The study findings were analyzed using a modified life-table analysis to estimate standardized mortality ratios (SMRs), and various functional forms (i.e., exponential, power, additive relative rate, and linear) of Poisson and Cox proportional hazards models to examine the dose-response relationship. Estimates of working lifetime risk (45 years) were developed using an approach that corrects for competing causes of death. An excess in mortality from lung cancer was observed for the entire cohort (SMR = 149, 95% confidence interval (CI) = 95, 222). Mortality from lung cancer was greatest among non-Hispanic workers (SMR = 211, 95% CI = 131, 323), among workers in the highest cadmium exposure group (SMR = 272, 95% CI = 123, 513), and among workers with 20 or more years since the first exposure (SMR = 161, 95% CI = 100, 248). A statistically significant dose-response relationship was evident in nearly all of the regression models evaluated. Based on our analyses, the lifetime excess lung cancer risk at the current Occupational Safety and Health Administration standard for cadmium fumes of 100 micrograms/m3 is approximately 50 to 111 lung cancer deaths per 1000 workers exposed to cadmium for 45 years.     

Mortality among different occupational groups of workers with pneumoconiosis: Results from a register-based cohort study

A mortality cohort study was carried out on 11,224 men with pneumoconiosis diagnosed during the period 1970–1985. The cohort was selected from among subjects entered into the National Register of Occupational Diseases and included 7,065 coal miners, 924 employees of underground work enterprises, 1,796 workers of the metallurgical industry and iron and nonferrous foundries, as well as 1,439 refractory materials, china, ceramics, and quarry workers. The cohort was traced up to the end of 1991. The mortality of all groups enrolled in the study, as compared with that of the general male population of Poland, showed a statistically significant excess of overall mortality (SMRs ranging from 105; 95% confidence interval [CI]: 100–110 to 136; CI: 121–153) as well as a great excess of deaths from diseases of the respiratory system (SMRs from 383; 95% CI: 345–424 to 588; 95% CI: 457–744). In workers of the metallurgical industry, foundries, and those from refractory materials, china, and ceramics manufacturing plants as well as quarries, a statistically significant excess of deaths from infectious diseases (mostly tuberculosis) was found (SMRs: 503; 95% CI: 364–677 and 286; 95% CI: 177–437, respectively). Mortality from lung cancer as significantly elevated only in the group of metallurgical industry and iron and nonferrous foundry workers (SMR: 159; 95% CI: 124–201). In the remaining subcohorts, no significant excess of deaths from lung cancer was noted. The study does not support the hypothesis on the role of exposure to crystalline silica in the induction of lung cancer. Significantly lower mortality was seen for diseases of the circulatory system (SMR: 89; 95% CI: 82–96), hypertensive disease (SMR: 63; 95% CI: 38–98), cerebrovascular disease (SMR: 79; 95% CI: 62–99), atherosclerosis (SMR: 79: 95% CI: 66–93), and injuries and poisonings (SMR: 50; 95% CI: 38–64) in coal miners. In addition, lower mortality was noted for cerebrovascular disease (SMR: 56; 95% CI: 32–91) and injuries and poisonings (SMR: 34; 95% CI: 17–61) in metallurgical industry and iron and nonferrous foundry workers. © 1996 Wiley-Liss, Inc.     

Mortality of a cohort of men in a silicosis register: further evidence of an association with lung cancer

Lung cancer mortality from 1980 to 1986 was studied in a cohort of 1,419 men in a silicosis register who had no previous exposure to asbestos and polyaromatic hydrocarbons. The 28 deaths from lung cancer were statistically in excess of expected (SMR 2.03; 95% CI 1.35-2.93). Excess risks of lung cancer were found in both underground workers (SMR 3.41; 95% CI 1.10-7.97; based on 5 deaths) and surface workers (SMR 1.87, 95% CI 1.18-2.81; based on 23 deaths). All lung cancer deaths were smokers. There was an increase in SMRs with longer latency periods and years of exposure, with the greatest risk found in those who had worked for 30 or more years after more than 30 years since first exposed (SMR 3.07, based on 16 deaths). The risk for lung cancer was higher in those with tuberculosis (SMR 2.52; 95% CI 1.52-3.94) and showed an increasing trend with severity of silicosis, from category 1 to 3 and from category A to C, with highest risk in those with tuberculosis and category 3 (SMR 4.44 based on 3 deaths) or tuberculosis and category C (SMR 7.63 based on 7 deaths). Most of the excess lung cancer risk in silicotics is due to smoking, but a synergistic effect between smoking and silica/silicosis on the risk of lung cancer is also likely. In particular, a possible role of silicosis and tuberculosis as the fibrotic seedbed for malignant growth in the lung is strongly supported.     

Mortalities of workers at the Nitro plant with exposure to 2-mercaptobenzothialzole

OBJECTIVES: An update of a study of workers exposed to 2- mercaptobenzothiazole (MBT) at a rubber chemicals plant in Nitro, West Virginia is reported. The earlier study found high rates of lung cancer, prostate cancer, and bladder cancer in these workers who also had potential exposure to 4-aminobiphenyl (PAB), a potent bladder carcinogen. METHODS: This cohort mortality study examines the mortalities of 1059 full time white male production workers employed at the plant from 1955 to 1977. A detailed exposure assessment was done on the 600 workers with exposure to MBT. Nine years of additional follow up to the previous study are added. RESULTS: It was found that MBT workers have expected rates of lung (standardised mortality ratio (SMR) = 1.0 95% confidence interval (95% CI) 0.7 to 1.5) and prostate (SMR = 0.9, 95% CI 0.2 to 2.3) cancer. There was an excess of bladder cancer among MBT workers who had definite exposure to PAB (SMR = 27.1, 95% CI 11.7 to 53.4), and MBT workers with potential exposure to PAB (SMR = 4.3, 95% CI 1.4 to 10.0). However, there were no deaths from bladder cancer among workers with no exposure to PAB (SMR = 0.0, 95% CI 0.0 to 24.7), although there were only 0.2 deaths expected. CONCLUSIONS: The potential confounding of exposure to an unknown portion of PAB in the MBT workers makes it impossible to evaluate risk of bladder cancer in this population at this time. However, exposure to MBT does not seem to increase the risk of most cancers including cancers of the lung and prostate.

 

     

A mortality cohort study of seamen in Italy.

A total of 2,208 male subjects, enrolled as merchant marine seamen at the Civitavecchia (Italy) harbor from 1936 to 1975 were followed up through 1989 in order to evaluate their mortality experience. Available information about the number of sailings made it possible to divide subjects into two subgroups: 948 workers with at least one sailing (cohort A) and 1,260 with no reported sailing (cohort B). Fewer than expected overall deaths were observed in both cohorts (cohort A: SMR = 0.83; cohort B: SMR = 0.81), mainly due to a lower mortality from circulatory, respiratory, and digestive diseases. Lung cancer deaths were significantly increased in cohort A (O = 30, SMR = 1.71, 95% CI = 1.15-2.44), whereas no excess was observed in cohort B (O = 6, SMR = 0.57, 95% CI = 0.21-1.26). Among subjects employed aboard ship, a trend in SMRs for lung cancer increasing with duration of employment was observed. Furthermore, three neoplasms of other parts of the respiratory system (including one mesothelioma) were detected in cohort A (SMR = 5.87), and one in cohort B. The study substantiates an increased risk of respiratory cancer among subjects with an occupational history of sailing; past exposure to asbestos and to other environmental carcinogens aboard could be implicated.     

Follow-up study of chrysotile asbestos textile workers: Cohort mortality and case-control analyses

Previous studies of mortality among white males employed in a Charleston, South Carolina asbestos textile plant using chrysotile demonstrated significant excess mortality due to asbestos-related disease and a steep exposure-response relationship for lung cancer. This cohort was further studied by adding 15 years of follow-up and including mortality among white female and black male workers. Nested case-control analyses were undertaken to further explore possible differences in lung cancer risk by textile operation as well as possible confounding by mineral oil exposures. Preliminary data for white males have been previously published. White males experienced statistically significant excess mortality due to lung cancer (standardized mortality ratio [SMR] = 2.30; confidence interval [CI] = 1.88–2.79), all causes (SMR = 1.48; CI = 1.38–1.58), all cancers (SMR = 1.50; CI = 1.29–1.72), diabetes mellitus (SMR = 2.05; CI = 1.18–3.33), heart disease (SMR = 1.41; CI = 1.26–1.58), cerebrovascular disease (SMR = 1.50; CI = 1.08–2.02), pneumoconiosis and other respiratory diseases (SMR = 4.10; CI = 3.10–5.31), and accidents (SMR = 1.49; CI = 1.15–1.91). Among white females, statistically significant excesses occurred for lung cancer (SMR = 2.75; CI = 2.06–3.61), all causes (SMR = 1.21; CI = 1.11–1.32), pneumoconiosis and other respiratory diseases (SMR = 2.40; CI = 1.53–3.60), and other respiratory cancers (SMR = 14.98; CI = 4.08–38.7). Among the total cohort of black males, the only statistically significant excess observed was for pneumoconiosis (SMR = 2.19; CI = 1.23–3.62). Based on historical exposure measurements at the plant, there was a positive exposure-response relationship for both lung cancer and pneumoconiosis. Data for the entire cohort demonstrate an increase in the lung cancer relative risk of 2–3% for each fiber/cc-year of cumulative chrysotile exposure. This relationship was more consistent for the white male workers. The excess risk for lung cancer among white males and females appeared to occur at cumulative exposures lower than those for black males. Possible reasons for the lesser lung cancer risk among black males include less smoking and differences in airborne fiber characteristics experienced by black males as a result of plant job placement patterns. The case-control analysis found employment in preparation and carding operations (where most of the black males worked) to be associated with a slightly reduced lung cancer risk, although not statistically significant, whereas spinning and twisting employment was associated with a statistically significant increased lung cancer risk compared to other plant operations. Airborne fiber size data, determined by transmission electron microscopy, demonstrated slightly longer fibers in spinning and twisting compared to other textile operations. Case-control analyses demonstrated little effect of mineral oil exposures on the lung cancer exposure-response estimates. Two deaths due to mesothelioma were observed among this cohort.     

Mortality among taxi drivers in Rome: A cohort study

The mortality pattern of taxi drivers in Rome as possibly exposed mainly to gasoline engine exhausts was evaluated by means of a historical cohort study. A total of 2,311 male subjects registered as taxi drivers between 1950 and 1975 was followed from 1965 through 1988. The overall mortality was lower than expected on the basis of regional (Latium) reference rates (692 deaths, standardized mortality ratio [SMR] = 0.89, 95% confidence interval [CI] 0.82–0.96), whereas the number of recorded deaths for malignant neoplasms was about the expected (205 deaths, SMR = 0.99, 95% CI 0.86–1.13). Mortality from circulatory and respiratory diseases was lower than expected. Diabetes was significantly increased (42 deaths, SMR = 1.73, 95% CI = 1.25–2.34). An increased SMR appeared for respiratory cancer (SMR = 1.23, 95% CI = 0.98–1.50), mainly due to lung cancer (observed [O] = 76, SMR = 1.23, 95% CI = 0.97–1.54); two pleural cancers were also recorded. The excess of lung cancer deaths was present only among those enrolled in the most recent period (1965–1975) (45 deaths, SMR = 1.40, 95% CI = 1.02–1.87), especially among those of younger age (<65 years) (SMR = 1.86); there was no relation between lung cancer mortality and latency since first enrollment in the cooperatives or duration of membership. There are difficulties in interpreting the excess of lung cancer on the basis of occupational exposures; however, the increased risk observed among workers employed in more recent calendar periods may be due to heavier exposure in the last decades; further follow-up of the cohort may elucidate whether there is an increasing lung cancer risk among taxi drivers. © 1994 Wiley-Liss, Inc.     

Cancer mortality in ethylene oxide workers.

A cohort of 1971 chemical workers licensed to handle ethylene oxide was followed up retrospectively from 1940 to 1984 and the vital status of each subject was ascertained. No quantitative information on exposure was available and therefore cohort members were considered as presumably exposed to ethylene oxide. The cohort comprised 637 subjects allowed to handle only ethylene oxide and 1334 subjects who obtained a licence valid for ethylene oxide as well as other toxic gases. Potential confounding arising from the exposure to these other chemical agents was taken into consideration. Causes of death were found from death certificates and comparisons of mortality were made with the general population of the region where cohort members were resident. Seventy six deaths were reported whereas 98.8 were expected; the difference was statistically significant. The number of malignancies for any site exceeded the expected number (standardised mortality ratio (SMR) = 130; 43 observed deaths; 95% confidence interval (95% CI) 94-175) and approached statistical significance. For all considered cancer sites the SMRs were higher than 100 but the excess was only significant (p < 0.05, two sided test) for lymphosarcoma and reticulosarcoma (International Classification of Diseases--9th revision (ICD-9) = 200; SMR = 682; four observed deaths; 95% CI 186-1745). The excess of cases for all cancers of haematopoietic tissue (ICD-9 = 200-208) also approached statistical significance (SMR = 250; six observed deaths; 95% CI 91-544). Focusing the analysis on the subcohort of the ethylene oxide only licensed workers, who are likely to have experienced a more severe exposure to this gas, it became evident that all but one of the observed cases of haematopoietic tissue cancers in the cohort were confined to this subgroup, enhancing the relevant SMR to 700 (95% CI 237-1637) and the SMR of lymphosarcoma and reticulosarcoma to 1693 (95% CI 349-4953).     

Mortality patterns among workers exposed to acrylamide: updated follow up

OBJECTIVE: The objective of this study was to update the mortality experience of a cohort of workers with and without potential exposure to acrylamide (AMD) at three U.S. plants (n = 8508) and one plant in The Netherlands (n = 344). METHODS: We computed standardized mortality ratios (SMRs) using national and local rates and modeled internal cohort rates to assess site-specific cancer risks by demographic and work history factors and several exposure indicators for AMD. RESULTS: For the 1925-2002 study period, we observed both deficit and excess overall mortality risks among the U.S. cohort for cancer sites implicated in experimental animal studies: brain and other central nervous system (SMR = 0.67, confidence interval [CI] = 0.40-1.05), thyroid gland (SMR = 1.38, CI = 0.28-4.02), testis and other male genital organs (SMR = 0.64, CI = 0.08-2.30); and for sites selected in earlier exploratory analyses of this cohort: respiratory system cancer (RSC) (SMR = 1.17, CI = 1.06-1.27), esophagus (SMR = 1.20, CI = 0.86-1.63), rectum (SMR = 1.25, CI = 0.84-1.78), pancreas (SMR = 0.94, CI = 0.70-1.22), and kidney (SMR = 1.01, CI = 0.66-1.46). Except for RSC, attributed earlier to muriatic acid exposure, none of the mortality excesses was statistically significant. In the Dutch cohort, we observed deficits in deaths for all sites of a priori interest. An updated analysis of our previous exploratory findings for pancreatic cancer in the U.S. cohort revealed much less evidence of a possible exposure-response relationship with AMD. CONCLUSION: AMD exposure at the levels present in our study sites was not associated with elevated cancer mortality risks.     

Mortality in workers employed in pig abattoirs and processing plants

Objective: workers in slaughterhouses and processing plants that handle pigs, and pork butchers/meatcutters have been little studied for health risks associated with employment, in spite of the fact that they are potentially exposed to oncogenic and non-oncogenic transmissible agents and chemical carcinogens at work. We report here on an update of mortality in 510 workers employed in abattoirs and processing plants that almost exclusively handled pigs and pork products.Methods: standardized mortality ratios (SMRs) were estimated for the cohort as a whole, and in subgroups defined by race and sex, using the corresponding US general population mortality rates for comparison. Study subjects were followed up from January 1950 to December 2006, during which time 45% of them died.Results: mortality was significantly increased overall in the cohort. A statistically significant excess of deaths was observed for colon and lung cancers in the entire cohort, SMR=2.7 (95% CI, 1.2–5.1), SMR=1.8 (95% CI, 1.1–2.7), respectively. Significant SMRs in the cohort as a whole were also observed for senile and pre-senile psychotic conditions (SMR=5.1, 95% CI, 1.4–13.1), and pneumonia (SMR=2.6, 95% CI, 1.3–4.8). An observed excess of subarachnoid hemorrhage was seen mainly in whites (SMR=10.1, 95% CI, 1.2–36.3). There was a suggestion of an excess of deaths from ischemic heart disease also, but the elevated SMR was confined to men and was not statistically significant.Conclusion: this study confirms the excess occurrence of lung and colon cancers, and stroke previously reported in this occupational group. New findings are the excess of risk for senile and pre-senile psychotic conditions and pneumonia, which together with the excess of colon cancer appear specific for pig/pork workers, as they were not evident in much larger studies of workers in abattoirs and processing plants handling cattle and sheep. However, caution should be exercised in interpreting these findings, since some of them could have occurred by chance, resulting from our examination of a large number of causes of death in multiple study subgroups. For the moment, the significance of these findings remains unknown until they are confirmed in larger studies of adequate statistical power. Studies that will take into account possible occupational and non-occupational confounding factors are needed.     

Workplace risk factors for cancer in the German rubber industry: Part 1. Mortality from respiratory cancers

OBJECTIVES: To determine the cancer specific mortality by work area among active and retired male workers in the German rubber industry. METHODS: A cohort of 11,663 male German workers was followed up for mortality from 1 January 1981 to 31 December 1991. Cohort members were classified as active (n = 7536) or retired (n = 4127) as of 1 January 1981 and had been employed for at least one year in one of five study plants producing tyres or technical rubber goods. Work histories were reconstructed with routinely documented "cost centre codes" which were classified into six categories: I preparation of materials; II production of technical rubber goods; III production of tyres; IV storage and dispatch; V maintenance; and VI others. Standardised mortality ratios (SMRs) adjusted for age and calendar year and 95% confidence intervals (95% CIs), stratified by work area (employment in respective work area for at least one year) and time related variables (year of hire, lagged years of employment in work area), were calculated from national reference rates. RESULTS: SMRs for laryngeal cancer were highest in work area I (SMR 253; 95% CI 93 to 551) and were significant among workers who were employed for > 10 years in this work area (SMR 330; 95% CI 107 to 779). Increased mortality rates from lung cancer were identified in work areas I (SMR 162; 95% CI 129 to 202), II (SMR 134; 95% CI 109 to 163), and V (SMR 131; 95% CI 102 to 167). Mortality from pleural cancer was increased in all six work areas, and significant excesses were found in work areas I (SMR 448; 95% CI 122 to 1146), II (SMR 505; 95% CI 202 to 1040), and V (SMR 554; 95% CI 179 to 1290). CONCLUSION: A causal relation between the excess of pleural cancer and exposure to asbestos among rubber workers is plausible and likely. In this study, the pattern of excess of lung cancer parallels the pattern of excess of pleural cancer. This points to asbestos as one risk factor for the excess deaths from lung cancer among rubber workers. The study provides further evidence for an increased mortality from laryngeal cancer among workers in the rubber industry, particularly in work area I.       

Retrospective follow-up study of foundry and engine plant workers

A retrospective follow-up study of 21,013 workers employed at a foundry and two engine manufacturing plants was conducted to determine if these workers had an unusual mortality experience. A total of 2,235 deaths occurred during the follow-up period of 1970–1987. Mortality from all causes was lower than expected. Men experienced a 6–13% excess of lung cancer deaths, depending on the choice of the comparison group. The data displayed evidence of a positive trend between lung cancer mortality and increasing duration of employment (p = 0.008). White men experienced a statistically significant excess of deaths from stomach cancer (standardized mortality ratio [SMR] = 158; 95% confidence interval [CI] = 101–234). Black men had increased mortality from pancreatic cancer, especially among engine plant workers (SMR = 303; CI = 121–624), and an excess of prostate cancer, concentrated among foundry workers (SMR = 234; CI = 112–430). © 1993 Wiley-Liss, Inc.     

A mortality study of workers at seven beryllium processing plants.

The International Agency for Research on Cancer (IARC) has found that the evidence for the carcinogenicity of beryllium is sufficient based on animal data but "limited" based on human data. This analysis reports on a retrospective cohort mortality study among 9,225 male workers employed at seven beryllium processing facilities for at least 2 days between January 1, 1940, and December 31, 1969. Vital status was ascertained through December 31, 1988. The standardized mortality ratio (SMR) for lung cancer in the total cohort was 1.26 (95% confidence interval [CI] = 1.12-1.42); significant SMRs for lung cancer were observed for two of the oldest plants located in Lorain, Ohio (SMR = 1.69; 95% CI = 1.28-2.19) and Reading, Pennsylvania (SMR = 1.24; 95% CI = 1.03-1.48). For the overall cohort, significantly elevated SMRs were found for "all deaths" (SMR = 1.05; 95% CI = 1.01-1.08), "ischemic heart disease" (SMR = 1.08; 95% CI = 1.01-1.14), "pneumoconiosis and other respiratory diseases" (SMR = 1.48; 95% CI = 1.21-1.80), and "chronic and unspecified nephritis, renal failure, and other renal sclerosis" (SMR = 1.49; 95% CI = 1.00-2.12). Lung cancer SMRs did not increase with longer duration of employment, but did increase with longer latency (time since first exposure). Lung cancer was particularly elevated (SMR = 3.33; 95% CI = 1.66-5.95) among workers at the Lorain plant with a history of (primarily) acute beryllium disease, which is associated with very high beryllium exposure. The lung cancer excess was not restricted to plants operating in the 1940s, when beryllium exposures were known to be extraordinarily high. Elevated lung cancer SMRs were also observed for four of the five plants operating in the 1950s for workers hired during that decade. Neither smoking nor geographic location fully explains the increased lung cancer risk. Occupational exposure to beryllium compounds is the most plausible explanation for the increased risk of lung cancer observed in this study. Continued mortality follow-up of this cohort will provide a more definitive assessment of lung cancer risk at the newer plants and among cohort members hired in the 1950s or later at the older plants. Further clarification of the potential for specific beryllium compounds to induce lung cancer in humans, and the possible contribution of other exposures in specific processes at these plants, would require a nested case-control study. We are currently assessing whether available industrial hygiene data would support such an analysis.     

Cancer mortality study of employees at lead battery plants and lead smelters, 1947-1995

BACKGROUND: This study has examined cancer mortality of a cohort of male U.S. workers exposed to lead. METHODS: The cohort consisted of 4,518 workers at lead battery plants and 2,300 at lead smelters. Vital status was ascertained between 1947 and 1995. Site-specific cancer standardized mortality ratios (SMRs) and 95% confidence intervals (95% CIs), based on the mortality rates of the U.S. male population and adjusted for age and calendar time, were calculated for the total cohort as well as subcohorts stratified by various exposure parameters. In addition, a nested case-control study of stomach cancer (30 cases and 120 age-matched controls) was also conducted. RESULTS: Mortality from all cancers was as expected (897 observed deaths, SMR = 103.8, 95% CI: 97.1-110.8). Mortality was significantly raised for stomach cancer (SMR = 147.4, 95% CI: 112. 5-189.8), lung cancer (SMR = 116.4, 95% CI: 103.9-129.9), and cancer of the thyroid and other endocrine glands (SMR = 308.0, 95% CI: 133. 0-606.8). There was a nonsignificant mortality deficit from kidney cancer (SMR = 63.6, 95% CI: 33.9-108.7). For bladder cancer, mortality was significantly lower than expected (SMR = 55.5, 95% CI: 31.7-90.1). Nonsignificant mortality deficits were also reported for cancer of the central nervous system (SMR = 74.8, 95% CI: 41.9-123. 4) and lymphatic and hematopoietic cancer (SMR = 92.2, 95% CI: 72. 4-115.7). Additional analyses by type of facility (lead battery plants vs. lead smelters), length of employment, latency, and period of hire were also performed. In the nested case-control study of stomach cancer, odds ratios were calculated for various exposure indices, and none was found to be elevated. Furthermore, no exposure-response relationship between lead exposure and stomach cancer was found in the nested case-control study. CONCLUSIONS: A significant mortality increase from stomach cancer was found. However, based on the analyses in the cohort study and the nested case-control study, the increase did not appear to be related to lead exposure. A small, but statistically significant mortality increase from lung cancer was also observed. The small increase, in the absence of an exposure-response relationship, could be the result of confounding due to smoking, and was not likely causally related to lead exposure. Although the significant increase in cancer of the thyroid and other endocrine glands appeared to be consistent with an occupational interpretation, the small number of deaths (8), the lack of information on potential confounding factors, and the lack of reporting of a similar increase in other studies underscore the need to view this finding with caution. No increased mortality was found for kidney cancer, bladder cancer, cancer of the central nervous system, or lymphatic and hematopoietic cancer.     

Occupational exposure to ionising radiation and mortality among workers of the former Spanish Nuclear Energy Board.

OBJECTIVES: Firstly, to ascertain whether mortality among workers of the former Spanish Nuclear Energy Board (Junta de Energía Nuclear-JEN) was higher than that for the Spanish population overall; and secondly, if this were so, to ascertain whether this difference was associated with exposure to ionising radiation. METHODS: A retrospective follow up of a cohort of 5657 workers was carried out for the period 1954-92. Cohort mortality was compared with that for the Spanish population overall, with standardised mortality ratios (SMRs) adjusted for sex, age, and calendar period. Also, Poisson models were used to analyse mortality from lung cancer in the cohort by level of exposure to ionising radiation. RESULTS: Workers' median and mean cumulative exposures were 4.04 and 11.42 mSv, respectively. Mean annual exposure was 1.33 mSv. Excess mortality due to bone tumours was found for the cohort as a whole (six deaths observed; SMR 2.95; 95% confidence interval (95% CI) 1.08 to 6.43). Among miners, excess mortality was found for non-malignant respiratory diseases (SMR 2.94; 95% CI 2.27 to 3.75), and for lung cancer bordering on statistical significance (SMR 1.50; 95% CI 0.96 to 2.23; P = 0.055). Relative risks of dying of lung cancer from ionising radiation in the dose quartiles 2, 3, and 4 versus the lowest dose quartile, were 1.00, 1.64, and 0.94, respectively. CONCLUSIONS: Excess mortality from lung cancer was found among JEN miners. Nevertheless, no clear relation was found between mortality from lung cancer and level of exposure to ionising radiation in the JEN cohort. Continued follow up of the cohort is required to confirm excess mortality from bone tumours.     

The Drake Health Registry Study: cause-specific mortality experience of workers potentially exposed to beta-naphthylamine

OBJECTIVE: To examine the cause-specific mortality experience of an occupational cohort with probable past exposure to beta-naphythylamine (BNA). METHODS: Subjects were 374 male and 26 female workers employed at a Pennsylvania chemical plant that produced or used beta-naphthylamine (BNA) between 1940 and 1981. Vital status through 1998 was determined for 97.5% of the cohort and cause of death for 100% of 79 deaths. Limited industrial hygiene data and reports from former employees were used to categorize workers as high, medium, or low risk for BNA exposure. Statistical analyses included US and local county-based standardized mortality ratios (SMRs). RESULTS: We observed statistically significantly elevated county rate-based SMRs for all causes combined (SMR = 1.98, 95% confidence interval (CI) = 1.56-2.49), all malignant neoplasms combined (28 deaths, SMR = 3.08, 95% CI = 2.05-4.46), respiratory system cancer (12 deaths, SMR = 3.91, 95% CI = 2.02-6.83), and bladder cancer (four deaths, SMR = 16.83, 95% CI = 4.59-43.1). Three bladder cancer cases were classified as high risk (SMR = 26.79, 95% CI = 5.53-78.29). Mortality risks were also elevated for most other malignant and non-malignant cause of death categories examined. CONCLUSIONS: Bladder cancer risk remains highly elevated among Drake/Kilsdonk workers and appears to be causally related to past BNA exposure. While lifestyle and behavioral risk factors may explain some of the mortality excesses for non-urological cancers, the possibility remains that BNA exposure may have also played a role in these and other observed cancer excesses.     

Mortality in dry-cleaning workers: an update

BACKGROUND: A cohort of 1,708 dry-cleaning workers identified from union records was exposed to perchloroethylene (PCE), a known animal carcinogen and probable human carcinogen, for at least 1 year before 1960. Many workers also had exposure to Stoddard solvent, a petroleum-based dry-cleaning solvent. METHODS: Vital status was updated through 1996 and life table analyses conducted. RESULTS: The cohort had excess cancer mortality (271 deaths, standardized mortality ratio [SMR] 1.25, 95% confidence interval [CI] 1.11-1.41). Elevated SMRs for tongue, bladder, esophagus, intestine, lung, and cervical cancer, pneumonia, and diseases of the stomach and duodenum were statistically significant. CONCLUSION: The current study confirms findings of prior updates and other studies that dry-cleaning workers have excess cancer mortality at several sites. Although important lifestyle and socioeconomic risk factors exist for both cervical and esophageal cancer mortality, excesses of these sites in the PCE only subcohort and among workers with longer duration of PCE exposure suggest an association with PCE exposure.     

Mortality of workers at a nickel carbonyl refinery, 1958-2000

Background: Excess risks of respiratory cancer have been shown in some groups of nickel exposed workers. It is clear, however, that not all forms of nickel exposure are implicated in these excess risks.

Aim: To determine whether occupational exposures received in a modern nickel carbonyl refinery lead to increased risks of cancer, in particular nasal cancer and lung cancer.

Methods: The mortality experienced by a cohort of 812 workers employed at a nickel refinery was investigated. Study subjects were all male workforce employees first employed in the period 1953–92 who had at least five years' employment with the company. Observed numbers of cause specific deaths were compared with expectations based on national mortality rates; SMRs were also calculated by period from commencing employment, year of commencing employment, and type of work.

Results: Overall, standardised mortality ratios (SMRs) were close to 100 for all causes (Obs 191, SMR 96, 95% CI 83 to 111), all neoplasms (Obs 63, SMR 104, 95% CI 80 to 133), non-malignant diseases of the respiratory system (Obs 18, SMR 97, 95% CI 57 to 153), and diseases of the circulatory system (Obs 85, SMR 94, 95% CI 75 to 116). There were no significantly increased SMRs for any site of cancer. There was a non-significant excess for lung cancer (Obs 28, Exp 20.17, SMR 139, 95% CI 92 to 201), and in subgroup analyses a significantly increased SMR of 231 (Obs 9) was found for those 142 workers with at least five years' employment in the feed handling and nickel extraction departments. In the total cohort there was a single death from nasal cancer (Exp 0.10).

Conclusions: The non-significant excess of lung cancer deaths may well be a chance finding, but in light of previous studies some role for nickel exposures cannot be excluded.

     

Mortality of mastic asphalt workers

This study was conducted to investigate the adverse health effects of exposure to bitumen fumes. A cohort of 679 mastic asphalt workers was followed from 1959 to 10 June 1986, during this period 169 deaths occurred. The overall standardized mortality ratio (SMR) was 163 (95% confidence interval (95% CI) 141-190), the SMR was 225 (95% CI 172-288) for cancer and 223 (95% CI 130-358) for external causes. Among persons aged 40 to 89 years, significant increases were seen for lung cancer (SMR 290, 95% CI 188-429), nonpulmonary cancer (SMR 200, 95% CI 141-276), and liver cirrhosis (SMR 467, 95% CI 188-962). Bronchitis, emphysema, and asthma also occurred in excess (SMR 207, 95% CI 95-393). In conclusion, the inhalation of bitumen fumes may have contributed to the elevated mortality from cancer and respiratory diseases among mastic asphalt workers.