Kathleen J. Kennedy

Long-term health experience of jet engine manufacturing workers: II. Total and cause-specific mortality excluding central nervous system neoplasms.

Objective: As part of an exploratory investigation of an unusual occurrence of glioblastoma at one jet engine manufacturing facility located in North Haven, Connecticut (CT), we examined total and cause-specific (excluding central nervous system neoplasms) mortality rates at eight of the company’s CT facilities. Methods: Subjects were 223,894 workers ever employed in one or more of the manufacturing facilities from 1952 to 2001. Vital status was determined through 2004 for 99% of subjects and cause of death for 95% of 68,701 deaths. We computed standardized mortality ratios (SMRs) based on US and CT state rates and modeled internal cohort rates. Results: We observed overall deficits in deaths based on national and state comparisons from all causes, all cancers and most of the cause of death categories examined. State comparisons revealed statistically significant excesses in deaths greater than 25% for kidney cancer (68 deaths, SMR = 1.30, CI = 1.01–1.65) and “other non-malignant respiratory disease” (291 deaths, SMR = 1.27, CI = 1.13–1.42) among subjects employed only at North Haven, and for bronchitis (713 deaths, SMR = 1.28, CI = 1.18–1.37) among all hourly workers. These excesses occurred mainly among short-term workers and hourly workers. Conclusions: We found no evidence of elevated mortality risks for all causes combined, all cancers combined and most of the causes of death categories examined. The pattern of findings for kidney cancer, bronchitis and other non-malignant respiratory disease, based on currently available data, suggests these excesses may be due to non-occupational risk factors or to external occupational factors. We will investigate these excesses further when detailed work history and exposure data from the companion exposure assessment project become available.

Methodological Issues in a Retrospective Cancer Incidence Study

The authors traced incidence of central nervous system cancer in a large occupational cohort of jet engine manufacturing workers from 1976 to 2004 in the 24 US states that comprised 95% of the cohort deaths. The cohort of approximately 224,000 employees was matched with cancer registry data; all central nervous system cancer matches were requested with their diagnostic data. This paper highlights the obstacles encountered while conducting this retrospective cancer incidence study. The authors spent approximately 700 hours completing applications and obtaining the cohort matches. Approximately 70% of the cases were identified in the state in which the facility of interest is located. In addition to the large amount of time involved, identified issues include complicated approval processes, high costs, temporal differences among the registries, and registry agency difficulty in performing the matching. Several states do not allow individual-level data to be used for research purposes. Researchers can gain important cancer incidence information by matching retrospective cohorts to multiple state cancer registries. However, they should carefully weigh the time and costs required and plan accordingly. Despite some serious obstacles, many of which are potentially resolvable, cancer incidence studies of retrospective cohorts using multiple cancer registries are feasible.

Long-term health experience of jet engine manufacturing workers: I. Mortality from central nervous system neoplasms

Objective: In response to an unusual occurrence of glioblastoma at one jet engine manufacturing facility located in North Haven (NH), Connecticut (CT), we examined mortality rates from central nervous system (CNS) neoplasms at NH and seven other company facilities. Methods: Subjects were 223,894 workers ever employed in one or more of the company’s eight CT manufacturing facilities from 1952 to 2001. Vital status was determined through 2004 for 99% of subjects and cause of death for 95% of 68,701 deaths. We computed standardized mortality ratios (SMRs) based on US and CT state rates and modeled internal relative risks (RRs). Results: State comparisons revealed overall deficits in deaths from all CNS neoplasms (606 deaths, SMR = 0.84, confidence interval [CI] = 0.78 to 0.91), including all malignant (462 deaths, SMR = 0.87, CI = 0.79 to 0.95), all benign (23 deaths, SMR = 0.65, CI = 0.41 to 0.98), and all unspecified (121 deaths, SMR = 0.79, CI = 0.65 to 0.94). Not statistically significant excesses in deaths from all malignant brain neoplasms were found among subjects who worked only at NH (49 deaths, SMR = 1.11, CI = 0.82 to 1.47) or partly at NH (24 deaths, SMR = 1.04, CI = 0.67 to 1.55) compared with deficits in non-NH plant groups. In the combined NH plant groups, we found not statistically significant higher risks of malignant brain neoplasms for salaried workers, older hires and the most recent time period, but no association with duration of employment or time since first employment. Conclusions: Total cohort mortality rates for malignant, benign or unspecified CNS neoplasms were not elevated relative to the US and CT general populations. The malignant brain neoplasm excesses in certain subgroups of workers from NH may reflect external occupational factors, nonoccupational factors or workplace factors unique to NH that were not measured in the current study. We will explore reasons for the NH excesses and examine specific types of brain neoplasms (eg, glioblastoma) in our companion cancer incidence, case–control and exposure assessment studies.

Long-Term Health Experience of Jet Engine Manufacturing Workers: III. Incidence of Malignant Central Nervous System Neoplasms

Objective: To explore a perceived unusual occurrence of glioblastoma at one jet engine manufacturing facility located in North Haven (NH), Connecticut (CT). Methods: Subjects were 212,513 workers ever employed in 1 of 8 manufacturing facilities from 1952 to 2001 and at risk from 1976 to 2004. We identified 722 cases of CNS neoplasms mainly by tracing through 19 state cancer registries. We computed standardized incidence ratios (SIRs) based on CT state and national rates and modeled internal relative risks (RRs). Results: We found overall deficits in cases for glioblastoma (275 cases, SIR = 0.77, CI = 0.68–0.87) and most other histology categories examined. NH workers had a not statistically significant overall 8% excess in glioblastoma (43 cases, SIR = 1.08, CI = 0.78–1.46). Salaried NH workers had a statistically significant twofold risk of glioblastoma compared with hourly workers (17 cases, RR = 2.04, CI = 1.15–3.57). Other subgroups of NH workers revealed elevated but not statistically significant glioblastoma risks but little evidence of an association with duration of employment or time since first employment. Conclusions: Incidence rates for glioblastoma and other malignant CNS neoplasm histologies were not elevated in the total cohort. The glioblastoma excesses observed among NH workers may reflect external occupational factors, non-occupational factors or workplace factors unique to NH unmeasured in the current study.

Mortality Among Hardmetal Production Workers: Occupational Exposures

Objective: To generate quantitative exposure estimates for use in retrospective occupational cohort mortality studies of the hardmetal industry. Methods: Job-exposure matrices (JEMs) were constructed for cobalt, tungsten, and nickel over the time period 1952 to 2014. The JEMs consisted of job class categories, based on job titles and processes performed, and exposure estimates calculated from available company industrial hygiene measurements. Results: Exposure intervals of one-half order magnitude were established for all three agents. Eight job classes had significantly decreasing time trends for cobalt exposure; no significant time trends were detected for tungsten or nickel exposures. Conclusions: The levels of exposures determined for this study were similar to or lower than those previously reported for the hardmetal industry during the 1952 to 2014 study period.

Mortality Among Hardmetal Production Workers: UK Cohort and Nested Case–Control Studies

Objective: The aim of this study was to characterize the mortality at two hardmetal production factories in the United Kingdom as part of an international study. Methods: Standardized mortality ratios (SMRs) were calculated on the basis of mortality rates for England and Wales, and local rates. A nested case–control study of lung cancer was undertaken. Results: The cohort comprised 1538 workers, with tracing complete for 94.4%. All-cause mortality was statistically significantly low for all cancers and nonmalignant respiratory disease, and for lung cancer was nonsignificantly low. The SMR for lung cancer for maintenance workers was elevated, based on only six deaths. The odds ratio for lung cancer per year of exposure to hardmetal was 0.93 (0.76 to 1.13). Conclusions: In this small study, there is no evidence to support that working in the UK hardmetal manufacturing industry increased mortality from any cause including lung cancer.

Mortality Among Hardmetal Production Workers : The Swedish Cohort.

Background: The mortality pattern was determined in a cohort of 16,999 white and blue-collar workers in the Swedish hardmetal industry, particularly for cobalt exposure and lung cancer. Methods: The mortality follow-up analysis in the Swedish Mortality register covered the period from 1952 to 2012. The exposure measures were ever/never exposed, duration of exposure, cumulative, and mean cobalt concentrations. Results: The mortality of all causes was significantly increased, highly associated with the short-term employed workers. A negative exposure–response was found for lung cancer and duration of exposure. An exposure–response was determined for cumulative and mean cobalt exposures analyzed by quartiles, but not for exposure classes. Internal comparison analysis using proportional hazard showed no exposure–response. Conclusions: The cohort lung cancer mortality showed no correlation to cobalt, nickel, or tungsten exposure.

Long-term health experience of jet engine manufacturing workers: VI: Incidence of malignant central nervous system neoplasms in relation to estimated workplace exposures

Objective: To determine whether glioblastoma (GB) incidence rates among jet engine manufacturing workers were associated with specific chemical or physical exposures. Methods: Subjects were 210,784 workers employed from 1952 to 2001. We conducted a cohort incidence study and two nested case–control studies with focus on the North Haven facility where we previously observed a not statistically significant overall elevation in GB rates. We estimated individual-level exposure metrics for 11 agents. Results: In the total cohort, none of the agent metrics considered was associated with increased GB risk. The GB incidence rates in North Haven were also not related to workplace exposures, including the “blue haze” exposure unique to North Haven. Conclusions: If not due to chance alone, GB rates in North Haven may reflect external occupational factors, nonoccupational factors, or workplace factors unique to North Haven unmeasured in the current evaluation.

Pneumoconiosis in carbon electrode workers.

Pneumoconiosis was diagnosed in five workers involved in the manufacture of carbon electrodes. Possible etiologies are discussed. It is generally believed that pneumoconiosis ceased to be a problem in this industry after World War II; however, the reported cases all resulted from exposures after 1940. These findings question the efficacy of recent and current engineering controls and suggest the need for further study of this industry.

Mortality among Hardmetal Production Workers: Pooled Analysis of Cohort Data from an International Investigation

Objectives: Based on a pooled analysis of data from an international study, evaluate total and cause-specific mortality among hardmetal production workers with emphasis on lung cancer. Methods: Study members were 32,354 workers from three companies and 17 manufacturing sites in five countries. We computed standardized mortality ratios and evaluated exposure-response via relative risk regression analysis. Results: Among long-term workers, we observed overall deficits or slight excesses in deaths for total mortality, all cancers, and lung cancer and found no evidence of any exposure-response relationships for lung cancer. Conclusions: We found no evidence that duration, average intensity, or cumulative exposure to tungsten, cobalt, or nickel, at levels experienced by the workers examined, increases lung cancer mortality risks. We also found no evidence that work in these facilities increased mortality risks from any other causes of death.