Mortality among the Chernobyl emergency workers: estimation of radiation risks (preliminary analysis).

This paper presents results of the analysis of mortality among Chernobyl accident emergency workers who are resident in Russia. The analysis is based on information for the cohort of emergency workers (males) from six regions of Russia including 65,905 persons with documented external doses in the range 0.005-03 Sv. These data were gathered during the period 1991 to 1998 and cover a total of 426,304 follow-up person-y. In this period, 4,995 deaths occurred in the cohort under study. The mortality analysis was performed for four groups of causes of death (ICD-9 codes): (1) malignant neoplasms (140-239); (2) cardiovascular diseases (390-459); (3) injuries, poisoning and violent deaths, (800-999); and (4) the remainder (other than the above). The standardized mortality rate for groups 1, 3, and 4 is less than unity and varies from 0.6 to 0.9. For group 2 (death from cardiovascular diseases) the standardized mortality rate conforms with the control within 95% confidence intervals. The control was the mortality rate (males) for the corresponding ages in Russia in general and the internal control, the spontaneous mortality among emergency workers, derived from the equation of the observed and expected number of cases in the followed up cohort. Dose response of mortality was studied. Statistically significant radiation risks were obtained for mortality from malignant neoplasms (515 cases) and cardiovascular diseases (1,728 cases). The values of the excess relative risk per unit dose (ERR Sv(-1)) for malignant neoplasms and cardiovascular diseases are estimated as 2.11 (1.31, 2.92 95% CI) and 0.54 (0.18,0.91 95% CI) (for external control), 2.04 (0.45, 4.31 95% CI) and 0.79 (0.07, 1.64 95% CI) (for internal control), respectively. The risk of death from all noncancer causes is close to zero and not statistically significant.     

Further follow up of mortality in a United Kingdom oil distribution centre cohort.

The results of an extension of follow up (1976 to 1989) of a cohort of workers employed for at least one year between 1 January 1950 and 31 December 1975 at eight oil refineries in Britain are reported. Over 99% of the workers were successfully traced to determine their vital status at 31 December 1989. The mortality observed was compared with that expected from the death rates of all the male population of England and Wales and Scotland. The mortality from all causes of death for the total study population was lower than that of the comparison population, and reduced mortality was also found for many of the major non-malignant causes of death. Raised mortality patterns were found for diseases of the arteries, in particular aortic aneurysm, and accidental fire and explosion, for the total study population, and across several refineries and other subgroups. Mortality from all neoplasms was lower than expected overall, largely due to a deficit of deaths from malignant neoplasm of the lung. Raised mortality from all neoplasms was found for labourers and in particular for malignant neoplasms of the oesophagus, stomach, and lung, although the mortality was also high for all men in this social class in the national population. Regional variations may have accounted for some of the high mortality. There were other raised mortality patterns in malignant neoplasms of the intestine, rectum, larynx, and prostate but these tended to be isolated and not consistent across refineries and other subgroups. As in the earlier follow up there was raised mortality from melanoma in several job groups.     

Further follow up of mortality in a United Kingdom oil refinery cohort.

The results of an extension of follow up (1976 to 1989) of a cohort of workers employed for at least one year between 1 January 1950 and 31 December 1975 at eight oil refineries in Britain are reported. Over 99% of the workers were successfully traced to determine their vital status at 31 December 1989. The mortality observed was compared with that expected from the death rates of all the male population of England and Wales and Scotland. The mortality from all causes of death for the total study population was lower than that of the comparison population, and reduced mortality was also found for many of the major non-malignant causes of death. Raised mortality patterns were found for diseases of the arteries, in particular aortic aneurysm, and accidental fire and explosion, for the total study population, and across several refineries and other subgroups. Mortality from all neoplasms was lower than expected overall, largely due to a deficit of deaths from malignant neoplasm of the lung. Raised mortality from all neoplasms was found for labourers and in particular for malignant neoplasms of the oesophagus, stomach, and lung, although the mortality was also high for all men in this social class in the national population. Regional variations may have accounted for some of the high mortality. There were other raised mortality patterns in malignant neoplasms of the intestine, rectum, larynx, and prostate but these tended to be isolated and not consistent across refineries and other subgroups. As in the earlier follow up there was raised mortality from melanoma in several job groups.     

Historical cohort study of US man-made vitreous fiber production workers: II. Mortality from mesothelioma

As part of our ongoing mortality surveillance program for the US man-made vitreous fiber (MMVF) industry, we examined mortality from malignant mesothelioma using data from our 1989 follow-up of 3478 rock/slag wool workers and our 1992 follow-up of 32,110 fiberglass workers. A manual search of death certificates for 1011 rock/slag wool workers and 9060 fiberglass workers revealed only 10 death certificates with any mention of the word "mesothelioma." A subsequent review of medical records and pathology specimens for 3 of the 10 workers deemed two deaths as definitely not due to mesothelioma and one as having a 50% chance of being caused by mesothelioma. Two other deaths, for which only medical records were available, were given less than a 50% chance of being due to mesothelioma. Eight of the 10 decedents had potential occupational asbestos exposure inside or outside the MMVF industry. We also estimated the mortality risk from malignant mesothelioma in the cohort using two cause-of-death categorizations that included both malignant and benign coding rubrics. Using the more comprehensive scheme, we observed overall deficits in deaths among the total cohort and fiberglass workers and an overall excess among rock/slag wool workers. The excess in respiratory system cancer is largely a reflection of elevated lung cancer risks that we attributed mainly to confounding by smoking, to exposures outside the MMVF industry to agents such as asbestos, or to one or more of the several co-exposures present in many of the study plants (including asbestos). The second scheme, which focused on pleural mesothelioma in time periods when specific malignant mesothelioma coding rubrics were available, classified only one cohort death as being caused by malignant mesothelioma, compared with 2.19 expected deaths (local county comparison). We conclude that the overall mortality risk from malignant mesothelioma does not seem to be elevated in the US MMVF cohort.     

Mortality among employees of lead battery plants and lead-producing plants, 1947-1980

Two cohorts of male lead workers, 4 519 battery plant workers and 2 300 lead production workers, all of whom had been employed for at least one year during the period 1 January 1946 through 31 December 1970, were observed for mortality during the 34 years from 1 January 1947 through 31 December 1980. Vital status as of the closing date was determined for 94.7% of the former group and 91.6% of the latter. There were 1 718 deaths in the first cohort and 621 in the second. Mortality from all causes combined was significantly greater than expected in each cohort, the standardized mortality ratio (SMR) being 107 and 113, respectively. Among the battery plant workers the greater than expected mortality rate resulted in large part from a significant number of excess deaths from malignant neoplasms (SMR 113), other hypertensive disease (mainly renal) (SMR 320), chronic nephritis (SMR 222), and a group of ill-defined conditions (SMR 355). Among the lead production workers the pattern was similar, with a significant number of excess deaths from other hypertensive disease (SMR 475), hypertensive heart disease (SMR 203), chronic nephritis (SMR 265), and ill-defined conditions (SMR 214). There was also a significant excess of deaths from external causes (SMR 143). The SMR for total malignancies was 113, but this value was not significantly elevated at the 5% level. In neither cohort were deaths from cerebrovascular disease in significant excess, the SMR being 93 and 132, respectively. A proportionate mortality analysis showed that the excess deaths from cerebrovascular disease and from hypertensive heart disease among smelter workers were in part due to the high proportion of nonwhites in the smelter populations. The stomach, liver, and lungs were the sites responsible for most excess cancer deaths in both cohorts, but the elevated SMR values were statistically significant only for gastric and lung cancers in battery plant workers. There were no excess deaths from malignancies of the kidney, brain, or lymphopoietic system in either cohort. It is impossible to relate the observed mortality to levels of lead exposure; because of meager quantitative information prior to 1960. It is known that past exposures had been very high. Ethnicity, diet, alcohol, and cigarette smoking could not be ruled out as possible confounding etiologic factors for the cancer deaths.     

Cancer mortality among licensed herbicide applicators.

This retrospective cohort study investigated the cancer mortality of 1341 herbicide applicators licensed before 1 January 1980. The cohort was followed for mortality until 1 January 1988 by means of the Dutch system of population registers. For the subjects who died before 1 January 1988 the cause of death was obtained from the Central Bureau of Statistics. The cause of death was obtained for 98.4% of the deceased subjects. The total mortality was lower than expected according to mortality rates of the total male Dutch population. The total number of deaths from cancer was however slightly higher than expected [standardized mortality ratio (SMR) 114]. Mortality from several subtypes of cancer was also higher than expected, that for multiple myeloma being statistically significantly higher than unity (SMR 815, 95% confidence interval 164-2382). Occupational exposure to herbicides appears to increase the risk for multiple myeloma and possibly other malignant neoplasms.     

Mortality of a municipal worker cohort: II. Females

Women have become an increasingly important segment of the total work force, yet there are very few published occupational mortality studies of female workers. This paper reports the findings of a retrospective cohort mortality study of 1,371 full-time female municipal employees of the City of Buffalo, New York, who were employed at least 1 day between January 1, 1950, and October 1, 1979, and who worked a minimum of 5 years. Vital status was ascertained for 88% of the female cohort, resulting in the identification of 214 observed deaths. This predominantly white-collar, service-oriented female cohort demonstrated significantly lower mortality than that expected based on U.S. mortality rates for white females. This strong "healthy-worker effect" was consistent across the time period of the study, across cause-specific mortality especially for all malignant neoplasms and all diseases of the circulatory system, and across different workers groups. Findings are discussed in light of the methodological issues involved in occupational studies of female workers.     

PMR study of mortality among Alabama workers and farmers

Computerized records of all Alabama deaths occurring to persons 16 years of age and over for the 5-year period 1984-1988 were obtained from the Alabama Department of Public Health. Using proportionate mortality ratio (PMR) methodology and death certificate occupation, cause-specific mortality patterns were examined for all Alabama decedents (N = 182,178), for all Alabama workers (N = 125,369), and for the occupational group of “farm operators and managers” (N = 11,691). In comparison with the U.S. general population, little difference was found between cause-specific PMR results for the total Alabama population and those for all workers, suggesting the absence of a generalized “healthy worker effect.” In comparison with the U.S. population, PMR results for farmers suggested lowered mortality from all malignant neoplasms and all heart disease, and elevated mortality from all external causes of death. In comparison with the Alabama population, PMR results for farmers continued to suggest lowered mortality from all malignant neoplasms, specifically for cancers of the respiratory, digestive and lymphopoietic systems. However, significantly elevated PMRs for external causes of death appeared only among nonwhite female farmers. Further investigation of these deaths suggested that this finding was more likely attributable to an increased risk of housefire deaths associated with rural lifestyle than with occupational factors.     

Mortality among workers in an Italian cigarette factory

A cohort study was conducted to evaluate the mortality pattern among female and male workers in a cigarette factory. The study followed 972 female workers and 761 male workers with at least 6 months of cumulative employment from 1 January 1962 through 1 July 1996. Among women, mortality from all causes of death [standardized mortality ratio (SMR) = 0.9; 95% confidence interval (CI) = 0.8-1.1] and mortality from all malignant neoplasms (SMR = 1.1; CI = 0.9-1.3) were consistent with reference rates. Male workers had a significantly reduced overall mortality (SMR = 0.8; CI = 0.7-0.9), while mortality from all malignant neoplasms was as expected (SMR = 0.9; CI = 0.7-1.0). Among female workers the frequencies of deaths from diseases of nervous system (SMR = 2.0; CI = 1.1-3.4) and from non-Hodgkin's lymphoma (NHL) (SMR = 2.7; CI = 1.0-5.6) were elevated at a statistically significant level. No association between duration of employment and diseases of nervous system was observed. A higher risk for NHL, based on three deaths, was reported among female workers with 15 or more years of employment (SMR = 8.1; CI = 2.2-21.0). Although based on small numbers, the excess of NHL here reported suggests that potential exposure to foliar residues of pesticides should be thoroughly considered in tobacco manufacturing.     

Proportionate mortality among current and former members of the United Farm Workers of America, AFL-CIO, in California 1973-2000

CONTEXT: To further investigate mortality among farm workers, a proportionate mortality ratio (PMR) analysis was conducted among the membership of the United Farm Workers of America (UFW), a farm worker labor union, for the years 1973-2000 in the state of California. PURPOSE: This report compares proportionate mortality for 118 causes of death in the UFW and the general United States population, adjusting for age, sex, race and calendar year of death. In addition, an exploratory analysis was conducted comparing deaths in the UFW to deaths in the California Hispanic population. METHODS: A roster of members of the UFW was compared to the death certificate master files of the state of California for the years 1973 to 2000. Matches were detected using automated techniques and visual review. PMR and associated confidence intervals were calculated using the National Institute for Occupational Safety and Health Life Table Analysis System using deaths in the U.S. as the standard. A similar analysis was conducted limiting attention to the time period 1988-2000 and using deaths in the California Hispanic population as the standard. FINDINGS: There were a total of 139,662 members of the union included in the linkage that yielded 3,977 deaths in the time period 1973-2000. Proportionate mortality in the farm workers was significantly elevated for respiratory tuberculosis, malignant neoplasms of the stomach, biliary passages, liver and gallbladder, and uterine cervix, diabetes mellitus, cerebrovascular disease, cirrhosis of the liver, and "other diseases of the digestive system." Transportation injuries including motor vehicles deaths, deaths from machine injuries, unintentional poisonings and assault and homicide were significantly elevated as well. Farm workers were at significantly lower risk of death from HIV-related disease, malignant neoplasms of the esophagus, intestine, pancreas, lung, urinary bladder, melanoma, and brain, all cancer deaths, "other diseases of the nervous system," ischemic heart disease, conductive disorder, "other diseases of the heart," emphysema, "other respiratory diseases," and symptoms and ill-defined conditions. These results were similar when using California Hispanic deaths as the standard for the years 1988-2000. There was still excess proportionate mortality from tuberculosis, cerebrovascular disease and unintentional injuries among the UFW members and lowered mortality from HIV related deaths, all cancer deaths combined and diseases of the heart. CONCLUSIONS: These results include some unique findings in regard to both excess and deficits of mortality that may be explained by the Hispanic ethnicity and recent immigration of the cohort.     

汽车铸造作业工人队列死因研究

目的 分析危害汽车铸造作业工人健康的主要疾病,探讨铸造作业有害因素对工人寿命的影响.方法 采用流行病学队列研究方法,以某汽车铸造厂1980年在册的3529名职工为研究对象,从1980年随访至2005年底,以全国城市居民年龄别死亡率均值为参照,用标化死亡比(SMR)作为统计指标,并计算95%可信区间.结果 随访至2005年底,共计84 999人年,共死亡265人,死亡率3.12‰,累积死亡率为7.51%.铸工队列全死因SMR为0.96(95%CI:0.85～1.08)与全国平均水平持平,随着年龄增长,全死因SMR呈现升高趋势,50岁以上组工人的SMR均大于1.影响铸造工人寿命的主要疾病按累积死亡率从高到低排序分别是:恶性肿瘤(3.43%)、意外伤害(1.16%)、脑血管疾病(1.08%)、心血管疾病(0.79%).恶性肿瘤占总死亡原因的45.7%.铸造工人中死亡率明显升高的疾病有恶性肿瘤(SMR=7.87)、意外伤害(SMR=2.70)、心血管疾病(SMR=2.68)、消化系统疾病(SMR=2.79).一线作业工人恶性肿瘤死亡是辅助丁人的1.95倍(RR=1.95,P<0.05).结论 铸造作业中粉尘等职业危害因素明显影响工人的健康,恶性肿瘤死亡明显增加,应加强防护.     

Cohort mortality study of employees at the Celanese plant in Pampa,Texas

BACKGROUND: The mortality experience of chemical workers from the Pampa, Texas Celanese Ltd. plant through 1991 has been previously reported. This study updates that effort and presents an additional seven years of data and follow-up that provided 268 additional cohort members and 71 new deaths. METHODS: Mortality was determined through December 31, 1998, the period for which the National Death Index could provide information on deaths. The mortality experience of Celanese Ltd. employees was compared to that of the general population of the United States. All cause and cause-specific standardized mortality ratios (SMRs) were calculated. RESULTS: For the entire cohort, several causes of death including all causes (SMR = 65.9; 95% confidence interval (CI) = 56.9-76.0), heart disease (SMR = 69.1; 95% CI = 53.6-87.8), and all malignant neoplasms (SMR = 74.2; 95% CI = 56.3-95.9) were significantly less than expected. SMRs were also calculated separately for white men, non-white men, and women. Unlike the initial study, the SMR for prostate cancer among white males was not significantly elevated (SMR=176.1; 95% CI = 76.0-347.0) and was much lower than the prior SMR of 330.4. This suggests that the initial findings, which were based on a small number of deaths, were likely due to chance. CONCLUSIONS: Overall, Celanese Ltd. employees from the Pampa plant have significantly lower than expected SMRs for several causes of death, and no causes of death that are significantly elevated.     

Mortality in workers of a primary aluminum foundry in Portovesme in Sardinia]

The standard mortality rates (SMRs) were calculated for 1148 workers of a primary aluminium plant in Portovesme, Sardinia, hired between 1971, when production started, and 1980. Status (living or decreased) was ascertained as at 31 December 1990 and the relationship between observed and expected deaths with respective 95% confidence limits were calculated on the basis of age-specific regional rates for each calendar year of the follow-up. The SMR for all causes was 81 with confidence limits between 61 and 108 based on a total of 48 deaths. Mortality due to malignant neoplasms did not differ from the expected rate. The observed deaths due to lung cancer were decidedly less than the expected number (3 observed versus 4.7 expected). A significant excess of cancer of the pancreas was observed with special reference to anode production, based, however, on only 3 observed cases against 0.8 expected. In the absence of a more precise definition of the causes of death, of the environmental exposure levels and of the non-occupational confounding factors, and considering the young age of the cohort under study, it is at present doubtful whether the excess of cancer of the pancreas can be associated with work in the primary aluminium industry. The results should therefore be taken as preliminary, indicating that further studies are required.     

Mortality and cancer registration experience of the Sellafield employees known to have been involved in the 1957 Windscale accident.

The mortality and cancer morbidity experience of the 470 male Sellafield employees known to be involved in the 1957 Windscale accident is reported. All these employees are known to have been involved in dealing with the fire itself, or in the clean-up operation afterwards. The size of the study population is small, leading to predicted low power to reveal any effects, but the cohort is of interest because of the involvement of the workers in the accident. For 1957-97, using rates for England and Wales to calculate the expected numbers, the all causes standardised mortality ratio (SMR) is 100 (observed = 258, expected = 258.80), and the all malignant neoplasms SMR is 79 (observed = 58, expected = 73.12) which is not significantly different from 100. For 1971-91, the all malignant neoplasms standardised registration ratio (SRR) of 85 (observed = 59, expected = 69.23) is not significantly different from 100. Significant excesses of deaths from diseases of the circulatory system (SMR = 121) and from ischaemic heart disease (SMR = 128), and a significant deficit of deaths from cancer of the genito-urinary organs (SMR = 31), were found. There were no significant differences in mortality rates between workers who had received high recorded external doses during the fire and those who had received low doses, though the power of this comparison was low. Comparison of the mortality rates of workers directly involved in the accident with workers in post, but not so involved, showed no significant differences. This study has been unable to detect any effect of the 1957 fire upon the mortality and cancer morbidity experience of those workers involved in it.     

Mortality from injuries and other causes in a cohort of 21,800 Brazilian steel workers.

OBJECTIVES: Injury is the leading cause of death in the male working population of Brazil. An important fraction of these deaths are work related. Very few cohort studies of steel workers, and none from developing countries, have reported on mortality from injuries. This paper analyses mortality from work and non-work related injuries among Brazilian steel workers. METHODS: Deaths during employment from 1 January 1977 to 30 November 1992 were analysed in a cohort of 21,816 male steel workers. Mortality rates specific for age and calendar year among the workers were compared with those of the male population of the state where the plant is located. Work related injuries were analysed by comparing the mortality rates for different subgroups of the cohort. RESULTS: The number of deaths (391) was less than half that expected based on death rates of the general population. Over 60% (242) of deaths were due to injuries. Mortality from most causes was substantially below that in the general population, but that from unintentional injury, was 50% above that of the general population. Standardised mortality ratios (SMRs) were highest for the youngest and the oldest employees and for labourers and clerical workers. Mortality from motor vehicle injury was twice that expected from population rates (SMR = 209, 95% confidence interval (95% CI) 176-244). There was a 67% fall in the age adjusted mortality from occupational injuries in the study period. CONCLUSION: The healthy worker effect in this cohort was greater than that commonly found in studies of occupational groups in developed countries, probably because of a greater socioeconomic gap between employed and unemployed populations in Brazil, and unequal distribution of health care resources. Mortality was especially high for motor vehicle injuries. The fall in mortality from occupational injuries during the study period was probably due to improvement in safety standards, increased automation, and better medical care. There is a need to investigate risk factors for unintentional injuries among steel workers, especially those due to motor vehicle injuries. Prevention of occupational and nonoccupational injuries should be a main priority in Brazil.     

Mortality and cancer morbidity after heavy occupational fluoride exposure

A cohort of 431 male cryolite workers employed for at least six months between 1924 and 1961 was identified from personnel records at the Copenhagen cryolite factory. During this period, heavy fluoride exposure resulted in at least 74 cases of skeletal fluorosis. All workmen in the cohort were followed up in Denmark until July 1, 1981. During 1941-1981, 206 men died, while only 149.3 deaths were expected from national mortality statistics. Significant excesses were seen in the following causes of death: violent death and all cancers, in particular cancer of the respiratory system. When compared with specific mortality rates for the Copenhagen area, violent death (and suicide taken alone) remained in significant excess among employees hired before 1940. Cancer morbidity data for the 35-year period 1943-1977 showed 78 cases of malignant neoplasms in the cryolite workers against 53.2 expected for Denmark as a whole and 67.9 for Copenhagen. The excess was almost entirely due to an excess number of respiratory cancers. Cancer morbidity showed no apparent correlation with length of employment or time from first exposure. Because detailed information on predictors for respiratory cancer was unavailable, a possible residual effect of fluoride cannot be excluded. However, any major carcinogenic effect of heavy fluoride exposure would be very unlikely.     

Mortality in a cohort of asbestos cement workers in Bari

The study describes the mortality of 417 workers employed in a asbestos-cement plant, located in Bari, Puglia, Southern Italy. Follow up started on February 1st 1972. The vital status and cause of death were ascertained at 1995. The mortality experience of the Apulian population was used as comparison. Using 90% confidence limits (CLs), a significant increase in mortality was observed in our cohort from: all causes of death (SMR 118, CL 100-139), pneumoconiosis (SMR 14810, CL 10298-20683), all types of cancer (SMR 139, CL 105-181), lung (SMR 191, CL 126-277), pleural (SMR 1560 CL 431-4081) and peritoneum (SMR 1705, CL 303-5367) malignant neoplasms. In our cohort, the discrepancy between observed and expected mortality for lung and pleural cancer occurred 30 years after the first exposure, after 40 years for all neoplasms and peritoneum cancer. Under the Cox regression model, lung cancer SMR showed a curvilinear trend along time since first exposure, the peak being detected at 35 years. Finally, SMRs from our cohort were compared to a previously described cohort including workers from the same plant compensated for asbestosis by INAIL.     

A multicentre mortality study of workers exposed to ethylene oxide.

A multicentre cohort study was carried out to study the possible association between exposure to ethylene oxide and cancer mortality. The cohort consisted of 2658 men from eight chemical plants of six chemical companies in the Federal Republic of Germany who had been exposed to ethylene oxide for at least one year between 1928 and 1981. The number of subjects in the separate plants varied from 98 to 604. By the closing date of the study (31 December 1982) 268 had died, 68 from malignant neoplasms. For 63 employees who had left the plant (2.4%) the vital status remained unknown. The standardised mortality ratio for all causes of death was 0.87 and for all malignancies 0.97 compared with national rates. When local state rates were used the SMRs were slightly lower. Two deaths from leukaemia were observed compared with 2.35 expected (SMR = 0.85). SMRs for carcinoma of the oesophagus (2.0) and carcinoma of the stomach (1.38) were raised but not significantly. In one plant an internal "control group" was selected matched for age, sex, and date of entry into the factory and compared with the exposed group. In both groups a "healthy worker effect" was observed. The total mortality and mortality from malignant neoplasms was higher in the exposed than in the control group; the differences were not statistically significant. There were no deaths from leukaemia in the exposed group and one in the control group.     

A multicentre mortality study of workers exposed to ethylene oxide

A multicentre cohort study was carried out to study the possible association between exposure to ethylene oxide and cancer mortality. The cohort consisted of 2658 men from eight chemical plants of six chemical companies in the Federal Republic of Germany who had been exposed to ethylene oxide for at least one year between 1928 and 1981. The number of subjects in the separate plants varied from 98 to 604. By the closing date of the study (31 December 1982) 268 had died, 68 from malignant neoplasms. For 63 employees who had left the plant (2.4%) the vital status remained unknown. The standardised mortality ratio for all causes of death was 0.87 and for all malignancies 0.97 compared with national rates. When local state rates were used the SMRs were slightly lower. Two deaths from leukaemia were observed compared with 2.35 expected (SMR = 0.85). SMRs for carcinoma of the oesophagus (2.0) and carcinoma of the stomach (1.38) were raised but not significantly. In one plant an internal "control group" was selected matched for age, sex, and date of entry into the factory and compared with the exposed group. In both groups a "healthy worker effect" was observed. The total mortality and mortality from malignant neoplasms was higher in the exposed than in the control group; the differences were not statistically significant. There were no deaths from leukaemia in the exposed group and one in the control group.     

Mortality in a cohort of pentachlorophenol manufacturing workers, 1940–1989

Mortality in a cohort of 770 workers with potential pentachlorophenol (PCP) exposure was evaluated from 1940 through 1989. The study cohort is a subset of a larger cohort of workers with potential exposure to higher chlorinated dioxins. Total mortality and cancer mortality, in the PCP cohort were slightly lower than expected in comparison to the U.S. white male population. There were 229 total deaths with 242.5 expected (SMR = 94, 95% confidence interval 83–108), and 50 cancer deaths with 52.6 expected (SMR = 95, 95% confidence interval 71–125). In comparison with unexposed employees, the risk ratio for total mortality was 1.03 (95% confidence internal 0.90–1.17), and the risk ratio for all cancer mortality was 0.95 (95% confidence interval 0.71–1.26). In most cause of death categories of a priori interest no deaths were observed in the cohort. A small excess of other and unspecified lymphopoietic cancer deaths was observed but did not appear to be related to exposure. Excesses of deaths due to cancer of the kidney, gastric and duodenal ulcer, cirrhosis of the liver, and all accidents were observed in comparison with the U.S. white male population and with unexposed employees. These were associated with increasing estimated cumulative PCP exposure after lagging exposures by 5 and 15 years. Despite the limited size and the generally favorable total mortality experience of the cohort, it was concluded that cohort members may have incurred increased risk of death due to some specific causes. The risks could not, however, be attributed conclusively to PCP exposure and may have been associated with other occupational and nonoccupational factors. Additional mortality surveillance of this cohort will be performed. © 1996 Wiley-Liss, Inc.