Cohort Mortality Study Of Workers Research Articles

Mortality Patterns Among Industrial Workers Exposed to Chloroprene and Other Substances: Extended Follow-Up.

To update the U.S. portion of an historical cohort mortality study of workers with potential exposure to chloroprene (CD) and vinyl chloride (VC) with focus on lung and liver cancer. Subjects were 6864 workers from two sites with vital status determined through 2017 for 99% of subjects and cause of death for 97.2% of deaths. Historical exposures to CD and VC were estimated quantitatively. We performed external and internal mortality comparisons. External comparisons revealed mostly deficits in deaths; internal comparisons revealed no consistent evidence of exposure-response relationships with CD or VC. Our update continues to support the conclusion that the risk of death from lung or liver cancer is unrelated to exposure to CD or VC at levels experienced by workers in the two U.S. sites.

Quantifying and Adjusting for Disease Misclassification Due to Loss to Follow-Up in Historical Cohort Mortality Studies.

The purpose of this analysis was to quantify and adjust for disease misclassification from loss to follow-up in a historical cohort mortality study of workers where exposure was categorized as a multi-level variable. Disease classification parameters were defined using 2008 mortality data for the New Zealand population and the proportions of known deaths observed for the cohort. The probability distributions for each classification parameter were constructed to account for potential differences in mortality due to exposure status, gender, and ethnicity. Probabilistic uncertainty analysis (bias analysis), which uses Monte Carlo techniques, was then used to sample each parameter distribution 50,000 times, calculating adjusted odds ratios (ORDM-LTF) that compared the mortality of workers with the highest cumulative exposure to those that were considered never-exposed. The geometric mean ORDM-LTF ranged between 1.65 (certainty interval (CI): 0.50–3.88) and 3.33 (CI: 1.21–10.48), and the geometric mean of the disease-misclassification error factor (εDM-LTF), which is the ratio of the observed odds ratio to the adjusted odds ratio, had a range of 0.91 (CI: 0.29–2.52) to 1.85 (CI: 0.78–6.07). Only when workers in the highest exposure category were more likely than those never-exposed to be misclassified as non-cases did the ORDM-LTF frequency distributions shift further away from the null. The application of uncertainty analysis to historical cohort mortality studies with multi-level exposures can provide valuable insight into the magnitude and direction of study error resulting from losses to follow-up.

A Cohort Mortality Study of Workers in a Second Soup Manufacturing Plant

The authors previously reported on mortality among workers in a Baltimore soup plant. Increased mortality was observed for cancers of the floor of the mouth, rectosigmoid colon/rectum/anus, epilepsy, and chronic nephritis. Here, the authors report on mortality on a second soup plant in the same locality. Excess mortality was similarly recorded for cancers of the tonsils/oropharynx, rectosigmoid colon/rectum/anus, and lung and myelofibrosis. Excess risk from cardiovascular, cerebrovascular, kidney, and infectious diseases was also observed. These 2 studies are important because firstly, to the authors’ knowledge, they are the only reports of mortality in this occupational group in spite of their having a potential for exposure to hazardous carcinogenic agents. Secondly, there is no information on any exposure assessment in this industry. These 2 reports will draw attention to the need to conduct more detailed exposure and mortality investigations in this little-studied group.

Cohort Mortality Study of Workers Exposed to Perfluorooctanoic Acid

Perfluorooctanoic acid (PFOA) is persistent in the human body; the general population has serum levels of approximately 4 ng/mL. It causes tumors of the liver, pancreas, and testicles in rodents. The authors studied the mortality of 5,791 workers exposed to PFOA at a DuPont chemical plant in West Virginia, using a newly developed job exposure matrix based on serum data for 1,308 workers from 1979-2004. The estimated average serum PFOA level was 350 ng/mL. The authors used 2 referent groups: other DuPont workers in the region and the US population. In comparison with other DuPont workers, cause-specific mortality was elevated for mesothelioma (standardized mortality ratio (SMR) = 2.85, 95% confidence interval (CI): 1.05, 6.20), diabetes mellitus (SMR = 1.90, 95% CI: 1.35, 2.61), and chronic renal disease (SMR = 3.11, 95% CI: 1.66, 5.32). Significant positive exposure-response trends occurred for both malignant and nonmalignant renal disease (12 and 13 deaths, respectively). PFOA is concentrated in the kidneys of rodents, and there are prior findings of elevated kidney cancer in this cohort. Multiple-cause mortality analyses tended to support the results of underlying-cause analyses. No exposure-response trend was seen for diabetes or heart disease mortality. In conclusion, the authors found evidence of positive exposure-response trends for malignant and nonmalignant renal disease. These results were limited by small numbers and restriction to mortality data, which are of limited relevance for several nonfatal outcomes of a priori interest.

A Cohort Mortality Study of Workers in a Soup Manufacturing Plant

ABSTRACT There has been no study of disease risk or exposures in workers in soup manufacturing plants. These workers may have hazardous exposures to biological and chemical cancer-causing agents at the workplace. The authors report here on mortality in 1,779 workers from a plant in Baltimore, Maryland. Standardized mortality ratios (SMRs) were estimated using the US population for comparison. Significantly increased mortality was observed for cancer of the floor of the mouth, colon cancer, epilepsy, and chronic nephritis in certain groups. Significantly decreased SMRs were observed for some causes. The findings are important, given the complete absence of data on this occupational group. It is not known whether the associations observed are related to occupational or nonoccupational exposures, or due to chance. The findings do, however, indicate that further studies of this occupational group are warranted.

An updated historical cohort mortality study of workers exposed to asbestos in a refitting shipyard, 1947–2007

To evaluate the long-term health effects of occupational asbestos exposure, an updated historical cohort mortality study of workers at a refitting shipyard was undertaken. The cohort consisted of 249 male ship repair workers (90 laggers, 159 boiler repairers). To determine relative excess mortality, standardized mortality ratios (SMRs) were calculated using mortality rates among the Japanese male population. Mortality follow-up of study subjects was performed for the period from 1947 till the end of 2007. We identified the vital status of 87 (96.7%) laggers and 150 (94.3%) boiler repairers. Of these, 63 (72.4%) and 95 (63.3%), respectively, died. Laggers, who had handled asbestos materials directly, showed a significantly elevated SMR of 2.64 (95% confidence interval [CI]: 1.06-5.44) for lung cancer and 2.49 (95% CI: 1.36-4.18) for nonmalignant respiratory diseases. Boiler repairers, who had many opportunities for secondary exposure to asbestos and a few for direct exposure, showed no significant elevation in SMR for lung cancer but a significantly elevated SMR of 1.78 (95% CI: 1.06-2.81) for nonmalignant respiratory diseases. In an analysis according to duration of employment, there was a significantly elevated SMR of nonmalignant respiratory diseases in the longer working years group. Among workers from both jobs, no deaths caused by mesothelioma in addition to those in the original study were found and no subject died from larynx cancer. This updated study confirmed a significant excess of asbestos-related mortality from diseases such as lung cancer and nonmalignant respiratory diseases among workers in a refitting shipyard in Japan.

Update of a cohort mortality study of workers exposed to methylene chloride employed at a plant producing cellulose triacetate film base

To update the mortality experience of employees of a factory that produced cellulose triacetate film base at Brantham in the United Kingdom and generate information on the effects of exposure to methylene chloride, in particular, mortality from cardiovascular disease and cancers of the lung, liver and biliary tract, pancreas and brain. All 1,785 male employees with a record of employment at the film factory in 1946-1988 were followed through 2006, including 1,473 subjects exposed to methylene chloride on average for 9 years at a concentration of 19ppm (8h time-weighted average). A total of 559 deaths occurred during the follow-up period. In the subcohort of workers exposed to methylene chloride, substantially reduced mortalities compared with national and local rates were found for all causes, all cancers, and all the principal cancer sites of interest except for brain cancer. There was a small excess of brain cancer deaths (8 observed and 4.4 expected), but no evidence of an association with exposure to methylene chloride. Lung cancer mortality was significantly reduced in exposed workers, even compared to the low mortality rate in the local population (SMR 55). In contrast, mortality from ischaemic heart disease in exposed workers was slightly increased compared with local rates (SMR 102), but was lower in active employees (SMR 94; local rates), where a direct effect of exposure to methylene chloride should be concentrated. The study provided no indication that employment at the plant, or exposure to methylene chloride, had adversely affected the mortalities of workers.

Cohort mortality study of workers at seven beryllium processing plants: update and associations with cumulative and maximum exposure

ObjectivesTo extend follow-up of cause-specific mortality in workers at seven beryllium processing plants and to estimate associations between mortality risk and beryllium exposure.Methods9199 workers were followed for mortality from 1940...

Cohort mortality study of workers in an automobile foundry factory

To understand the major causes of death in automobile foundry workers and investigate casting manipulations hazards to health. A cohort study of 3529 foundry workers registered in one big automobile factory in Shiyan city of China was performed. Standardized mortality ratios (SMRs) were calculated for the main causes of death by using Chinese national mortality rates as reference. The cohort mortality was traced from 1980 to the end of 2005 with an accumulation of 84 999 person-years, revealed 265 deaths. The results of this study showed that the standardized mortality ratio for all subjects was 0.96 (95% CI: 0.85 approximately 1.08), which was very close to that expected on the basis of the China national mortality rates. The SMR increased with age, the SMR became greater than 1 in all groups of age 50 and higher. The results showed that malignant neoplasm (3.43%), accidents (1.16%), cerebro-vascular diseases (1.08%), cardio-vascular diseases (0.79%) were the first four illnesses that threatened workers' life span. Statistically significant mortality of malignant neoplasm (SMR = 7.87), accidents (SMR = 2.70), cardio-vascular diseases (SMR = 2.68) and digestive diseases (SMR = 2.79) were found in the foundry workers. The relative risk of malignant neoplasm for first line workers to assistant workers was 1.99 (P < 0.05). The occupational hazards in foundry factory have harmful impact on the workers' health and life span.

A cohort study of uranium millers and miners of Grants, New Mexico, 1979–2005

A cohort mortality study of workers engaged in uranium milling and mining activities nearGrants, New Mexico, during the period from 1955 to 1990 was conducted. Vital status wasdetermined through 2005 and standardised mortality ratio (SMR) analyses wereconducted for 2745 men and women alive after 1978 who were employed for at leastsix months. Overall, mortality from all causes (SMR 1.15; 95% CI 1.07–1.23;n = 818) and all cancers (SMR 1.22; 95% CI 1.07–1.38;n = 246) was greater than expected on the basis of US mortality rates. Increasedmortality, however, was seen only among the 1735 underground uraniumminers and was due to malignant (SMR 2.17; 95% CI 1.75–2.65;n = 95) and non-malignant (SMR 1.64; 95% CI 1.23–2.13;n = 55) respiratory diseases, cirrhosis of the liver (SMR 1.79;n = 18) and externalcauses (SMR 1.65; n = 58). The lung cancer excess likely is attributable to the historically high levels of radon inuranium mines of the Colorado Plateau, combined with the heavy use of tobaccoproducts. No statistically significant elevation in any cause of death was seenamong the 904 non-miners employed at the Grants uranium mill. Among 718 millworkers with the greatest potential for exposure to uranium ore, no statisticallysignificant increase in any cause of death of a priori interest was seen, i.e., cancers ofthe lung, kidney, liver, or bone, lymphoma, non-malignant respiratory disease,renal disease or liver disease. Although the population studied was relativelysmall, the follow-up was long (up to 50 yrs) and complete. In contrast to minersexposed to radon and radon decay products, for uranium mill workers exposed touranium dusts and mill products there was no clear evidence of uranium-relateddisease.

Using ZIP Code and GIS Studies to Assess Disease Risk

In several recent articles in EHP, investigators have attempted to link proximity to hazardous waste sites, as measured by geographic information systems (GIS) or ZIP codes, with increased incidences of various diseases. An implicit assumption in these studies is that proximity is a surrogate for exposure. However, numerous studies have demonstrated that the presence of chemicals in an individual’s environment does not necessarily translate into a dose. For example, Stehr-Green et al. (1988) found that

Retrospective Cohort Mortality Study of Workers in a Polymer Production Plant Including a Reference Population of Regional Workers

Based on previous reports of increased serum lipid levels in workers at a U.S. polymer manufacturing facility, the study objective was to investigate ischemic heart disease (IHD) mortality as well as a broad range of mortality causes for an occupational cohort at the facility. The cohort comprised 6,027 men and women who had worked at the facility between 1948 and 2002; these years delimit the mortality follow-up period. Standardized mortality ratios (SMR) were estimated to compare observed numbers of deaths to expected numbers derived from mortality rates for 3 reference populations: the U.S. population, the West Virginia state population, and an 8-state regional employee population from the same company. Most SMR estimates based on U.S. and state populations were below 100. Comparison to the employee population also resulted in many SMR estimates at or near a no-effect level. Relative to the regional worker population, a nonsignificant elevation for IHD mortality was observed (SMR = 109, 95% confidence interval [CI]: 96, 124). Mortality associated with diabetes was significantly increased compared to the regional worker population (SMR = 197, 95% CI: 123, 298). A corresponding increase in the SMR for IHD and diabetes mortality was not detected for comparisons with the two general populations. The results reported herein show little evidence of increased cause-specific mortality risks for workers at the plant. This study demonstrates the utility of comparing occupational cohorts with a similar worker reference population in order to reduce bias associated with the healthy worker effect.

Update: cohort mortality study of workers highly exposed to polychlorinated biphenyls (PCBs) during the manufacture of electrical capacitors, 1940-1998

BackgroundThe National Institute for Occupational Safety and Health previously reported mortality for a cohort of workers considered highly exposed to polychlorinated biphenyls (PCBs) between 1939 and 1977 at two electrical capacitor manufacturing plants. The current study updated vital status, examined liver and rectal cancer mortality previously reported in excess in this cohort and evaluated mortality from non-Hodgkin's lymphoma (NHL) and cancers of the stomach, intestine, breast, prostate, skin (melanoma) and brain reported to be in excess in other cohort and case-control studies of PCB-exposed persons.MethodsMortality was updated through 1998 for 2572 workers. Age-, gender-, race- and calendar year-adjusted standardized mortality ratios (SMRs) and 95% confidence intervals (CI) were calculated using U.S., state and county referent rates. SMRs using U.S. referent rates are reported. Duration of employment was used as a surrogate for exposure.ResultsConsistent with the previous follow-up, mortality from biliary passage, liver and gall bladder cancer was significantly elevated (11 deaths, SMR 2.11, CI 1.05 – 3.77), but mortality from rectal cancer was not (6 deaths, SMR 1.47, CI 0.54 – 3.21). Among women, mortality from intestinal cancer (24 deaths, SMR 1.89, CI 1.21 – 2.82) and from "other diseases of the nervous system and sense organs", which include Parkinson's disease and amyotrophic lateral sclerosis, (15 deaths, SMR 2.07, CI 1.16 – 3.42) were elevated. There were four ALS deaths, all women (SMR 4.35, CI 1.19–11.14). Mortality was elevated for myeloma (7 deaths, SMR 2.11, CI 0.84 – 4.34), particularly among workers employed 10 years or more (5 deaths, SMR 2.80, CI 0.91 – 6.54). No linear associations between mortality and duration of employment were observed for the cancers of interest.ConclusionThis update found that the earlier reported excess in this cohort for biliary, liver and gall bladder cancer persisted with longer follow-up. Excess mortality for intestinal cancer among women was elevated across categories of duration of employment; myeloma mortality was highest among those working 10 years or more. The small numbers of deaths from liver and intestinal cancers, myeloma and nervous system diseases coupled with the lack of an exposure-response relationship with duration of employment preclude drawing definitive conclusions regarding PCB exposure and these causes of death.

Retrospective Cohort Mortality Study of Workers Engaged in Motion Picture Film Processing

To assess potential health risks associated with work in a large motion picture film-processing facility. A retrospective cohort mortality study was conducted during 1960-2000 among 2646 film workers. Job family categories, created from detailed employee work history information, were used to evaluate chemical exposure patterns. Overall mortality was as expected (standardized mortality ratio [SMR] = 1.1; 95% confidence interval [CI] = 1.0-1.2). Statistically significant associations were found for suicides (SMR = 2.0; 95% CI = 1.2-3.0) among the hourly workers and AIDS (SMR = 5.3; 95% CI = 1.7-12.3) among the administrative workers. Film developers had increases of respiratory cancer (SMR = 1.9; 95% CI = 1.1-3.0) and suicides (SMR = 2.4; 95% CI = 1.0-4.7), whereas film assemblers had an increase in suicides (SMR = 2.4; 95% CI = 1.2-4.4) only. Excess deaths resulting from suicides and AIDS among the workforce suggest that nonoccupational influences may be involved in the mortality of this cohort and warrant further investigations.

A 50-year historical cohort mortality study of workers in a pharmaceutical plant.

An historical cohort study was conducted of workers at a pharmaceutical manufacturing plant. The cohort mortality experience of workers ever employed at the plant over the period from 1950 to 1999 was examined. The 1958 workers accumulated 44,294 person-years of experience at the plant, and a total of 384 deaths were identified. Our findings from external comparisons based on standardized mortality ratios (SMRs) in the cohort provide no evidence of excess mortality risk from all causes combined (SMR=0.75), all cancers combined (SMR=0.96), or from certain other individual causes of death. No patterns of excess mortality risk were apparent after stratifying on age and sex or job classification. The mortality experience of this cohort was generally more favorable than that of the general population.

A cohort mortality study of workers exposed to chlorinated organic solvents in Taiwan.

A retrospective cohort mortality study based on standardized mortality ratios (SMRs) was conducted to investigate the possible association between exposure to chlorinated organic solvents and various types of cancer deaths. Vital status and causes of death of study subjects were determined from January 1, 1985 to December 31, 1997 by linking cohort data with the National Mortality Database. Person-year accumulation began on the date of entry to the cohort, or January 1, 1985 (whichever came later), and ended on the closing date of the study (December 31, 1997), if alive; or the date of death. This retrospective cohort study examined cancer mortality among 86,868 workers at an electronics factory in the northern Taiwan. Using various durations of employment and latency and adjusting for age and calendar year, no significantly elevated SMR was found for any cancer in either male or female exposed workers when compared with the general Taiwanese population. In particular, the risk of female breast cancer was not found to be increased. Although ovarian cancer suggested an upward trend when analyzed by length of employment, ovarian cancer risk for the entire female cohort was not elevated. It is concluded that this study provided no evidence that exposure to chlorinated organic solvents was associated with human cancer risk.

Historical respirable quartz exposures of industrial sand workers: 1946-1996.

Besides a clear relationship to silicosis, crystalline silica-quartz-has been associated with lung cancer, nonmalignant renal disease, and auto-immune disease. To study diseases associated with crystalline silica further, NIOSH conducted a cohort mortality study of workers from 18 silica sand plants, which had quarry, crushing, and bagging operations to produce industrial sand. Twelve of these plants also had grinding mills to produce fine silica powder. The historical crystalline silica exposures of workers at these plants were estimated to facilitate exposure-response analyses in the epidemiologic study. NIOSH obtained personal respirable dust measurement records from Mine Safety and Health Administration (MSHA) compliance inspections at all 18 plants and from the archives of seven plants which had collected samples. These samples had been analyzed for quartz content by x-ray diffraction. Although no personal samples were available before 1974, impinger dust measurements were reported for 19 silica sand plants in 1946; these data were converted and used to estimate exposures prior to 1974. Statistical modeling of the samples was used to estimate quartz exposure concentrations for workers in plant-job-year categories from the 1930s when mortality follow-up of the cohort began until 1988 when follow-up stopped. Between 1974 and 1996, there were 4,269 respirable dust samples collected at these 18 plants. The geometric mean quartz concentration was 25.9 microg/m(3) (GSD = 10.9) with a range from less than 1 to 11,700 microg/m(3). Samples below 1 microg/m(3) were given a value of 0.5 microg/m(3). Over one-third of the samples -37%) exceeded the MSHA permissible exposure limit value for quartz (PEL = 10 mg/m(3)/(%quartz + 2)) and half (51%) of the samples exceeded the NIOSH recommended exposure limit (REL=50 microg/m(3)). The samples were collected from workers performing 143 jobs within the 18 plants, but too few samples were collected from many of the jobs to make accurate estimates. Therefore, samples were combined into 10 categories of jobs performing similar tasks or located within the same plant area. The quartz concentrations varied significantly by plant, job, and year. Quartz concentrations decreased over time, with measurements collected in the 1970s significantly greater than those collected later. The modeled exposure estimates improve upon duration of employment as an estimate of cumulative exposure and reduce exposure misclassification due to variation in quartz levels between plants, jobs, and over time. Am. J. Ind. Med. 38:389-398, 2000. Published 2000 Wiley-Liss, Inc.

A historical cohort mortality study of workers exposed to asbestos in a refitting shipyard.

To investigate the risks of developing asbestos-related diseases we conducted a historical cohort mortality study on 249 ship repair workers (90 laggers and 159 boiler repairers) in a single U.S. Navy shipyard in Japan. We successfully identified the vital status of 87 (96.7%) laggers and 150 (94.3%) boiler repairers, and, of these, 49 (56.3%) and 65 (43.3%) died, respectively, during the follow-up period from 1947 till the end of 1996. Our in-person interviews with some of the subjects clarified that asbestos exposure was considered to be substantially high in the 1950-60s, decreased thereafter gradually but remained till 1979 in the shipyard. The laggers, who had handled asbestos materials directly, showed a significantly elevated SMR of 2.75 (95% C.I.: 1.08-6.48) for lung cancer. The risk developing the disease was greater in the laggers after a 20-year latency (SMR = 3.42). Pancreatic cancer yielded a greater SMR than unity (7.78, 90% C.I.: 2.07-25.19) in a longer working years group. Four laggers died from asbestosis. The boiler repairers, who had many chances for secondary exposure to asbestos and a few for direct exposure, showed no elevation of the SMR of lung cancer overall, but there was a borderline statistically significant SMR of 2.41 (90% C.I.: 1.05-5.45) in a longer working years group. One boiler repairer died from mesothelioma and four from asbestosis.

Exposure-response analysis of risk of respiratory disease associated with occupational exposure to chrysotile asbestos.

OBJECTIVES: To evaluate alternative models and estimate risk of mortality from lung cancer and asbestosis after occupational exposure to chrysotile asbestos. METHODS: Data were used from a recent update of...

An updated cohort mortality study of workers at a northeastern United States petroleum refinery.

An update of a cohort study of 4855 employees at a Paulsboro, New Jersey refinery was conducted to further examine mortality patterns. The earlier study investigated refinery workers employed for a minimum of 1 year between 1 January 1946 and 1 January 1979. The vital status of these workers was ascertained through 1979. The update extended enrollment in the study and vital status follow-up for an additional 8 years (1980-1987). As in the previous study, mortality from all causes [standardized mortality ratio (SMR) = 87; 95% confidence interval (95% CI): 83-91] was significantly lower than expected compared with the general population. Total cancer mortality was also lower than expected (SMR = 96; 95% CI: 86-106). A borderline significant mortality increase in prostatic cancer was found (SMR = 144; 95% CI: 106-190). This increase was similar to the nonsignificant increase reported in the original study (SMR = 135; 95% CI: 90-196). The excess was of comparable magnitude among white males and nonwhite males, although it was not significant for the latter. Detailed analysis indicated that the prostatic cancer was not likely to be related to employment at the refinery. Mortality from lymphatic and hematopoietic cancers was similar to the expected mortality. Mortality from overall leukemia was as expected and detailed analyses by specific cell type showed no increase. An increase in mortality occurred from non-Hodgkin's lymphoma among male workers (SMR = 132; 95% CI: 74-217). The increase was not statistically significant and unlikely to be associated with refinery employment. Mortality from multiple myeloma among male employees was lower than expected (SMR = 74; 95% CI: 20-190). Mortality from asbestos-related diseases (pulmonary fibrosis, lung cancer, malignant mesothelioma) was also lower than expected among male workers. No cause-specific mortality was found to be associated with duration of employment at the refinery, including several causes which have been reported to be elevated in previous studies. The findings of this updated study indicate, as in the previous report, the generally favorable mortality experience of Paulsboro refinery workers.