Susanne Wolf

Lung cancer mortality and fibre exposures among North Carolina asbestos textile workers

Objective: To describe mortality among workers exposed to chrysotile asbestos and evaluate the relationship between lung cancer and asbestos fibre exposure. Methods: Workers employed for at least 1 day between 1 January 1950 and 31 December 1973 in any of four plants in North Carolina, USA that produced asbestos textile products were enumerated. Vital status was ascertained through 31 December 2003. Historical exposures to asbestos fibres were estimated from work histories and 3578 industrial hygiene measurements taken in 1935–1986. Mortality of the cohort was compared with that of the national population via standardised mortality ratios (SMRs). Exposure–response relationships for lung cancer were examined within the cohort using Poisson regression to compute adjusted mortality rate ratios. Results: Follow-up of 5770 workers included in the cohort resulted in 181 640 person-years of observation, with 2583 deaths from all causes and 277 from lung cancer. Mortality from all causes, all cancers and lung cancer was significant higher than expected, with SMRs of 1.47 for all causes, 1.41 for all cancer and 1.96 (95% CI 1.73 to 2.20) for lung cancer. SMRs for pleural cancer, mesothelioma and pneumoconiosis were also elevated. The risk of lung cancer and asbestosis increased with cumulative fibre exposure (RR 1.102 per 100 fibre-year/ml, 95% CI 1.044 to 1.164, and RR 1.249 per 100 fibre-year/ml, 95% CI 1.186 to 1.316, respectively, for total career exposure). Conclusions: This study provides further evidence that exposure to chrysotile asbestos in textile manufacturing is associated with increased risk of lung cancer, asbestosis cancer of the pleura and mesothelioma.

Asbestos fibre dimensions and lung cancer mortality among workers exposed to chrysotile

Objectives To estimate exposures to asbestos fibres of specific sizes among asbestos textile manufacturing workers exposed to chrysotile using data from transmission electron microscopy (TEM) and to evaluate the extent to which the risk of lung cancer varies with fibre length and diameter. Methods 3803 workers employed for at least 1 day between 1 January 1950 and 31 December 1973 in any of three plants in North Carolina, USA that produced asbestos textile products and followed for vital status through 31 December 2003 were included. Historical exposures to asbestos fibres were estimated from work histories and 3578 industrial hygiene measurements taken in 1935–1986. Exposure–response relationships for lung cancer were examined within the cohort using Poisson regression. Results Indicators of fibre length and diameter obtained by TEM were positively and significantly associated with increasing risk of lung cancer. Exposures to longer and thinner fibres tended to be most strongly associated with lung cancer, and models for these fibres fit the data best. Simultaneously modelling indicators of cumulative mean fibre length and diameter yielded a positive coefficient for fibre length and a negative coefficient for fibre diameter. Conclusions The results support the hypothesis that the risk of lung cancer among workers exposed to chrysotile asbestos increases with exposure to longer fibres. More research is needed to improve the characterisation of exposures by fibre size and number and to analyse the associated risks in a variety of industries and populations.

A case control study of multiple myeloma at four nuclear facilities.

PURPOSE Reported elevations of multiple myeloma among nuclear workers exposed to external penetrating ionizing radiation, based on small numbers of cases, prompted this multi-facility study of workers at US Department of Energy facilities. METHODS Ninety-eight multiple myeloma deaths and 391 age-matched controls were selected from the combined roster of 115,143 workers hired before 1979 at Hanford, Los Alamos National Laboratory, Oak Ridge National Laboratory, and the Savannah River site. These workers were followed for vital status through 1990 (1986 for Hanford). Demographic, work history, and occupational exposure data were derived from personnel, occupational medicine, industrial hygiene, and health physics records. Exposure-disease associations were evaluated using conditional logistic regression. RESULTS Cases were disproportionately African American, male, and hired prior to 1948. Lifetime cumulative whole body ionizing radiation dose was not associated with multiple myeloma, however, there was a significant effect of age at exposure, with positive associations between multiple myeloma and doses received at older ages. Dose response associations increased in magnitude with exposure age (from 40 to 50) and lag assumption (from 5 to 15 years), while a likelihood ratio goodness of fit test reached the highest value for cumulative doses received at ages above 45 with a 5-year lag (X2=5.43,1 df; relative risk = 6.9% per 10 mSv). Dose response associations persisted with adjustment for potential confounders. CONCLUSIONS Multiple myeloma was associated with low level whole body penetrating ionizing radiation doses at older ages. The exposure age effect is at odds with interpretations of A-bomb survivor studies but in agreement with several studies of cancer among nuclear workers.

Killed on the clock : A population-based study of Workplace homicide, 1977-1991

BACKGROUND This paper describes the epidemiology of workplace homicides in North Carolina, with emphasis on the circumstances. METHODS Workplace homicide victims were identified by and data were abstracted from the North Carolina medical examiner system. RESULTS Workplace homicide rates are highest for men, older and self-employed workers, minorities and specific occupations, especially taxi drivers. Robberies, mostly in retail settings, accounted for half of the cases, while 20% were known to involve disputes, the contexts of which differed by sex. Women were most likely to be killed by estranged partners. CONCLUSIONS Preventive strategies need to address the specific contexts in which workplace homicide occurs, such as retail and taxi robberies, and law enforcement officers interacting with suspects. A workplace response to domestic violence is also needed. Other areas for future research and intervention include environmental modifications, employee screening and training, and identifying more inclusive occupational data sources.

Estimates of historical exposures by phase contrast and transmission electron microscopy in North Carolina USA asbestos textile plants

Objectives: To develop a job-exposure matrix (JEM) for fibre exposures in three asbestos textile plants and to develop estimates of fibre size-specific exposures. Methods: Historical dust samples from three North Carolina, USA asbestos textile plants were obtained. Plant specific samples were used to express impinger dust concentrations as fibre concentrations by phase contract microscopy (PCM). Mixed models were used to estimate PCM exposures by plant, department, job and calendar time. Archived membrane filter samples were analysed by transmission electron microscopy (TEM) to determine the bivariate diameter/length distribution of airborne fibres by plant and operation. Results: PCM fibre levels estimated from the models were very high in the 1930s, with some operations having in excess of 200 fibres/ml, and decreased appreciably over time. TEM results for 77 airborne dust samples found that only a small proportion of airborne fibres were measured by PCM (>0.25 μm in diameter and >5 μm in length) and the proportion varied considerably by plant and operation (range 2.9% to 10.0%). The bivariate diameter/length distribution of airborne fibres demonstrated a relatively high degree of variability by plant and operation. PCM adjustment factors also varied substantially across plants and operations. Conclusions: These data provide new information concerning airborne fibre levels and characteristics in three historically important asbestos textile plants. PCM concentrations were high in the early years and TEM data demonstrate that the vast majority of airborne fibres inhaled by the workers were shorter than 5 μm in length, and thus not included in the PCM-based fibre counts.

Influence of training and experience on selecting criteria to evaluate medical care

To determine whether training and experience affect the selection of process criteria for evaluating medical care, three groups of physicians (family physicians, general pediatricians, and pediatricians specializing in infectious disease) were sent a questionnaire asking their opinions about various clinical actions in 125 clinical situations concerning respiratory infections in infants. Five hundred and twenty-four (54 per cent) physicians returned completed questionnaires. The three groups agreed in 93 (74 per cent) situations, especially about history taking, physical examination, and follow-up observation. Disagreements occurred most often regarding antibiotic use. Of the three groups, the family physicians selected the most extensive list of recommended actions including the greatest number of indications for antibiotics. The general pediatricians selected the fewest situations requiring history taking, physical examination and diagnostic tests. The infectious-disease pediatricians felt the greatest necessity to record history and physical-examination items but were the most restrictive in recommending antibiotics and other drugs.

Estimates of historical exposures by phase contrast and transmission electron microscopy for pooled exposure–response analyses of North Carolina and South Carolina, USA asbestos textile cohorts

Objectives To develop pooled size-specific asbestos fiber exposure estimates for North Carolina and South Carolina asbestos textile plants. Methods Airborne sample data and prior exposure estimates by phase-contrast microscopy (PCM) for the two cohorts were reviewed and compared. Estimates by transmission electron microscopy (TEM) for 160 membrane filter samples from all plant were pooled. Poisson regression models were developed to predict bivariate diameter/length airborne fiber size distributions based on independent categorical variables for fiber diameter, fiber length, plant, and exposure zone. The model predicted bivariate diameter/length distributions were expressed as the proportion of fibers in 28 size-specific cells and these data were used to calculate PCM to TEM adjustment factors in order to estimate fiber size-specific exposures for the pooled cohort. Results Exposure levels in the North Carolina plants were in excess of 50 f/cc for many operations through about 1955 owing to lack of dust control measures in early years whereas levels in the South Carolina plant were generally less than 10 f/cc by about 1950. The Poisson regression models found covariates for plant department to be a stronger predictor of bivariate size proportions than plant; however, a plant effect was observed. The final Poisson models demonstrated good fit to the observed data. Conclusions Consistent with early studies, fiber exposures in the North Carolina plants were much higher than in South Carolina plant. Use of the predicted size-specific TEM exposures by plant and department based on the Poisson model predictions should reduce exposure.

Missing annual external radiation dosimetry data among Hanford workers

Epidemiological studies of workers employed at the Hanford Site have been underway for nearly 30 years. Although the external radiation dosimetry program at Hanford has been fairly comprehensive, some workers included in previous epidemiological analyses have periods of employment during which there are missing annual external radiation dosimetry records. In this report, employment history records and annual external dosimetry records have been used to investigate the extent of missing annual external dosimetry records for workers at the Hanford facility. A “nearby” procedure for estimating values for missing annual external dosimetry records was evaluated. Among the 33,459 workers who were employed at least 180 days and had at least one annual external dosimetry record, annual external dosimetry records were missing for 8% of the years of employment (32,323 missing annual external dosimetry records). Missing annual external dosimetry records were more common for female Hanford workers than for male workers, and for workers employed in the early years of Hanfords operation than for workers employed in later years of operation. The nearby procedure provided reliable estimates of values for missing annual external dosimetry records. Using this procedure, 18,937.5 mSv were estimated for missing annual external dosimetry records; this was 2% of the total recorded cumulative external radiation dose for these workers. Missing annual external dosimetry records should be considered as a potential source of bias and uncertainty in investigations of radiation–cancer associations among Hanford workers.

Mortality Among Workers at Oak Ridge National Laboratory

BACKGROUND Workers employed at the Oak Ridge National Laboratory (ORNL) were potentially exposed to a range of chemical and physical hazards, many of which are poorly characterized. We compared the observed deaths among workers to expectations based upon US mortality rates. METHODS The cohort included 22,831 workers hired between January 1, 1943 and December 31, 1984. Vital status and cause of death information were ascertained through December 31, 2008. Standardized mortality ratios (SMRs) were computed separately for males and females using US and Tennessee mortality rates; SMRs for men were tabulated separately for monthly-, weekly-, and hourly-paid workers. RESULTS Hourly-paid males had more deaths due to cancer of the pleura (SMR = 12.09, 95% CI: 4.44, 26.32), cancer of the bladder (SMR = 1.89, 95% CI: 1.26, 2.71), and leukemia (SMR = 1.33, 95% CI: 0.87, 1.93) than expected based on US mortality rates. Female workers also had more deaths than expected from cancer of the bladder (SMR = 2.20, 95% CI: 1.20, 3.69) and leukemia (SMR = 1.64, 95% CI: 1.09, 2.36). The pleural cancer excess has only appeared since the 1980s, approximately 40 years after the start of operations. The bladder cancer excess was larger among workers who also had worked at other Oak Ridge nuclear weapons facilities, while the leukemia excess was among people who had not worked at other DOE facilities. CONCLUSIONS Occupational hazards including asbestos and ionizing radiation may contribute to these excesses.

Association of injury history and incident injury in cadet basic military training

PURPOSE This study aimed to determine the association between injury history at enrollment and incident lower extremity (LE) injury during cadet basic training among first-year military cadets. METHODS Medically treated LE injuries during cadet basic training documented in the Defense Medical Surveillance System were ascertained in a prospective cohort study of three large US military academies from 2005 to 2008. Both acute injuries (International Classification of Disease, Ninth Revision, codes in the 800-900s, including fracture, dislocations, and sprains/strains) and injury-related musculoskeletal injuries (International Classification of Disease, Ninth Revision, codes in the 700s, including inflammation and pain, joint derangement, stress fracture, sprain/strain/rupture, and dislocation) were included. Risk ratio (RR) and 95% confidence interval (CI) were computed using multivariate log-binomial models stratified by gender. RESULTS During basic training, there were 1438 medically treated acute and 1719 musculoskeletal-related LE injuries in the 9811 cadets. The most frequent LE injuries were sprains/strains (73.6% of acute injuries) and inflammation and pain (89.6% of musculoskeletal-related injuries). The overall risk of incident LE injury was 23.2% (95% CI = 22.3%-24.0%). Cadets with a history of LE injury were at increased risk for incident LE injury. This association was identical in males (RR = 1.74, 95% CI = 1.55-1.94) and females (RR = 1.74, 95% CI = 1.52-1.99). In site-specific analyses, strong associations between injury history and incident injury were observed for hip, knee ligament, stress fracture, and ankle sprain. Injury risk was greater (P < 0.01) for females (39.1%) compared with males (18.0%). The elevated injury risk in females (RR = 2.19, 95% CI = 2.04-2.36) was independent of injury history (adjusted RR = 2.09, 95% CI = 1.95-2.24). CONCLUSION Injury history upon entry to the military is associated with the incidence of LE injuries sustained during cadet basic training. Prevention programs targeted at modifiable factors in cadets with a history of LE injury should be considered.