Mortality of workers employed in refractory ceramic fiber manufacturing: An update.

This study evaluates the possible association between refractory ceramic fiber (RCF) exposure and all causes of death. Current and former employees (n = 1,119) hired from 1952 to 1999 at manufacturing facilities in New York (NY) state and Indiana were included. Work histories and quarterly plant-wide sampling from 1987 to 2015 provided cumulative fiber exposure (CFE) estimates. The full cohort was evaluated as well as individuals with lower and higher exposure, <45 and ≥45 fiber-months/cc. The Life-Table-Analysis-System was used for all standardized mortality rates (SMRs). Person-years at risk were accumulated from start of employment until 12/31/2019 or date of death. There was no significant association with all causes, all cancers, or lung cancer in any group. In the higher exposed, there was a significant elevation in both malignancies of the "urinary organs" (SMR = 3.59, 95% confidence interval [CI] 1.44, 7.40) and "bladder or other urinary site" (SMR = 4.04, 95% CI 1.10, 10.36), which persisted in comparison to regional mortality rates from NY state and Niagara County. However, six of the nine workers with urinary cancers were known smokers. In the lower exposed, there was a significant elevation in malignancies of the lymphatic and hematopoietic system (SMR = 2.54, 95% CI 1.27, 4.55) and leukemia (SMR = 4.21, 95% CI 1.69, 8.67). There was one pathologically unconfirmed mesothelioma death. A second employee currently living with a pathologically confirmed mesothelioma was identified, but the SMR was non-significant when both were included in the analyses. The association of these two mesothelioma cases with RCF exposure alone is unclear because of potential past exposure to asbestos.

Respiratory follow-up pre- and post-engineering controls or cessation of added diacetyl at four microwave popcorn facilities.

In a 7-year study at 4 microwave popcorn facilities, mixing room employees exposed to diacetyl prior to the introduction of respirators showed significant loss of lung function but did not continue to decline longitudinally faster than other job categories http://bit.ly/2xwWRiw.

A 30-year mortality and respiratory morbidity study of refractory ceramic fiber workers.

AIM: Report mortality (n = 1119), cancer incidence (n = 1207) and radiographic (n = 1451) findings from a 30-year investigation of current and former refractory ceramic fiber (RCF) workers. METHODS: Cause of death, health and work histories, radiographs and spirometry were collected. Mortality and cancer incidence were analyzed. Logistic regression analysis investigated the associations of latency and cumulative fiber exposure (CFE) on radiographic changes. RESULTS: The mortality study showed no increase in standardized mortality rates (SMR) for lung cancer, but urinary cancers were significantly elevated in the higher exposed group (SMR = 3.62, 95% CI: 1.33-7.88) and leukemia in the total cohort (SMR = 2.51, 95% CI: 1.08-4.94). One death attributed to mesothelioma was identified (SMR = 2.86, 95% CI: 0.07-15.93) in a worker reporting some asbestos exposure. The overall rate of pleural changes was 6.1%, attaining 21.4% in the highest CFE category for all subjects (adjusted odds ratio (aOR) = 6.9, 95% CI: 3.6-13.4), and 13.0% for those with no reported asbestos exposure (OR= 9.1, 95% CI: 2.5-33.6). Prevalence for recent hires (≥1985) was similar to the background. Interstitial changes were not elevated. Localized pleural thickening was associated with small decreases in spirometry results. CONCLUSION: Increases in leukemia and urinary cancer but not lung cancer mortality were found. One death attributed to mesothelioma was observed in a worker with self-reported asbestos exposure and a work history where occupational asbestos exposure may have occurred, rendering uncertainties in assigning causation. Radiographic analyses indicated RCF exposure alone is associated with increased pleural but not interstitial changes. Reductions in RCF exposure should continue. The mortality study is ongoing.

Childhood exposure to Libby amphibole asbestos and respiratory health in young adults.

OBJECTIVES: Vermiculite ore containing Libby amphibole asbestos (LAA) was mined in Libby, MT, from the 1920s-1990. Recreational and residential areas in Libby were contaminated with LAA. This objective of this study was to characterize childhood exposure to LAA and investigate its association with respiratory health during young adulthood. METHODS: Young adults who resided in Libby prior to age 18 completed a health and activity questionnaire, pulmonary function testing, chest x-ray and HRCT scan. LAA exposure was estimated based on participant report of engaging in activities with potential LAA exposure. Quantitative LAA estimates for activities were derived from sampling data and literature reports. RESULTS: A total of 312 participants (mean age 25.1 years) were enrolled and reported respiratory symptoms in the past 12 months including pleuritic chest pain (23%), regular cough (17%), shortness of breath (18%), and wheezing or whistling in the chest (18%). Cumulative LAA exposure was significantly associated with shortness of breath (aOR = 1.12, 95% CI 1.01-1.25 per doubling of exposure). Engaging in recreational activities near Rainy Creek Road (near the former mine site) and the number of instances heating vermiculite ore to make it expand or pop were also significantly associated with respiratory symptoms. LAA exposure was not associated with pulmonary function or pleural or interstitial changes on either chest x-ray or HRCT. CONCLUSIONS: Pleural or interstitial changes on x-ray or HRCT were not observed among this cohort of young adults. However, childhood exposure to LAA was significantly associated with respiratory symptoms during young adulthood. Pleuritic chest pain, in particular, has been identified as an early symptom associated with LAA exposure and therefore warrants continued follow-up given findings of progressive disease in other LAA exposed populations.

Noise and neurotoxic chemical exposure relationship to workplace traumatic injuries: A review.

INTRODUCTION: More than 5,000 fatalities and eight million injuries occurred in the workplace in 2007 at a cost of $6 billion and $186 billion, respectively. Neurotoxic chemicals are known to affect central nervous system functions among workers, which include balance and hearing disorders. However, it is not known if there is an association between exposure to noise and solvents and acute injuries. METHOD: A thorough review was conducted of the literature on the relationship between noise or solvent exposures and hearing loss with various health outcomes. RESULTS: The search resulted in 41 studies. Health outcomes included: hearing loss, workplace injuries, absence from work due to sickness, fatalities, hospital admissions due to workplace accidents, traffic accidents, hypertension, balance, slip, trips, or falls, cognitive measures, or disability retirement. Important covariates in these studies were age of employee, type of industry or occupation, or length of employment. DISCUSSION: Most authors that evaluated noise exposure concluded that higher exposure to noise resulted in more of the chosen health effect but the relationship is not well understood. Studies that evaluated hearing loss found that hearing loss was related to occupational injury, disability retirement, or traffic accidents. Studies that assessed both noise exposure and hearing loss as risk factors for occupational injuries reported that hearing loss was related to occupational injuries as much or more than noise exposure. Evidence suggests that solvent exposure is likely to be related to accidents or other health consequences such balance disorders. CONCLUSIONS: Many authors reported that noise exposures and hearing loss, respectively, are likely to be related to occupational accidents. Practical applications: The potential significance of the study is that findings could be used by managers to reduce injuries and the costs associated with those injures.

HRCT/CT and associated spirometric effects of low Libby amphibole asbestos exposure.

OBJECTIVE: Evaluate the relationship between cumulative fiber exposure and high-resolution or conventional chest computed tomography (HRCT/CT) changes and spirometry of workers with Libby amphibole asbestos exposure. METHODS: Of the original 1980 cohort (n = 513), 431 were living and asked to participate. Images were evaluated for localized pleural thickening (LPT), diffuse pleural thickening (DPT), and parenchymal changes. RESULTS: A total of 306 participants provided either HRCT/CT scans (n = 191) or chest radiographs (n = 115). Of the 191 with HRCT/CT, 52.9% had pleural changes and 13.1% had parenchymal changes. Those with LPT only, LPT and/or DPT, or DPT and/or parenchymal changes had mean 6.1, 8.0, and 18.0 loss in percent predicted forced vital capacity, respectively. CONCLUSIONS: Exposure to vermiculite containing amphibole fibers is associated with pleural and parenchymal HRCT/CT changes at low cumulative fiber exposure; these changes are associated with spirometric decrements.

Biopersistence of refractory ceramic fiber in human lung tissue and a 20-year follow-up of radiographic pleural changes in workers.

OBJECTIVE: The biopersistence of refractory ceramic fiber (RCF) in human lung tissue is unknown and may contribute to an association between cumulative fiber exposure and radiographic changes. METHODS: Lung tissue fiber was analyzed for a case series of 10 RCF workers and a 20-year longitudinal chest radiograph study of 1323 workers was conducted. RESULTS: Within lung tissue, RCF comprised 14% to 100% of fibers 5 µm or more in length and was identified up to 20 years after RCF employment. Among workers with no reported asbestos exposure, cumulative exposure of more than 63 to 110 and more than 110 fiber-months/cm was associated with radiographic pleural changes of 8.5% (odds ratio, 7.2; 95% confidence interval, 1.4 to 36.8) and 11.6% (odds ratio, 10.3; 95% confidence interval, 2.1 to 49.9), respectively. CONCLUSIONS: Refractory ceramic fiber can persist in human lung tissue for up to 20 years and may contribute to the significant association between cumulative fiber exposure and radiographic pleural changes.

Exposure estimates for workers in a facility expanding Libby vermiculite: updated values and comparison with original 1980 values.

OBJECTIVE: Low cumulative fiber exposure (CFE) has been associated with health effects in a cohort exposed to Libby vermiculite. This study refines the original 1980 exposure estimates and compares the CFE results. METHODS: Cumulative fiber exposure estimates were developed using three times more industrial hygiene measurements and long-term workers' input. New adjustments included vermiculite ore source, seasonal overtime hours, time spent in various tasks, and recollection of historical dustiness. RESULTS: The overall mean (95% confidence interval) CFE (n = 513) in 1980 (0.80 [0.69 to 0.93]) was statistically similar to the overall mean (95% confidence interval) CFE in 2010 (0.74 [0.61 to 0.90]). The mean CFE in the lowest exposure category (<2 fiber-years/cm) decreased from 0.36 to 0.22 fiber-years/cm (P < 0.05). The 2010 CFE estimate extended the upper bound of the range of previous estimates from 28.10 to 106.31 fiber-years/cm. CONCLUSIONS: The range of CFE values was expanded. These estimates may impact the understanding of Libby vermiculite health outcomes.

A long term study of pulmonary function among US refractory ceramic fibre workers.

BACKGROUND: Cross-sectional studies have shown declines in lung function among refractory ceramic fibre (RCF) workers with increasing fibre exposure. This study followed current and former workers (n=1396) for up to 17 years and collected 5243 pulmonary function tests. METHODS: Cumulative fibre exposure and production years were categorised into exposure levels at five manufacturing locations. Conventional longitudinal models did not adequately partition age-related changes from other time-dependent variables. Therefore, a restricted cubic spline model was developed to account for the non-linear decline with age. RESULTS: Cumulative fibre >60 fibre-months/cc showed a significant loss in lung function at the first test. When results were examined longitudinally, cumulative exposure was confounded with age as workers with the highest cumulative exposure were generally older. A longitudinal model adjusted by age groups was implemented to control for this confounding. No consistent longitudinal loss in lung function was observed with RCF exposure. Smoking, initial weight and weight increase were significant factors. CONCLUSION: No consistent decline was observed longitudinally with exposure to RCF, although cross-sectional and longitudinal findings were discordant. Confounding and accelerated lung function declines with ageing and the correlation of multiple time-dependent variables should be considered in order to minimise error and maximise precision. An innovative statistical methodology for these types of data is described.

Exposures to refractory ceramic fibers in manufacturing and related operations: a 10-year update.

Refractory ceramic fiber (RCF) is a man-made vitreous fiber used for its insulating properties. Since 1987, the work environment of approximately 800 persons employed in fiber manufacture or production operations directly related to manufacturing has been monitored to evaluate exposure levels. Samples were collected quarterly from the breathing zones of randomly selected workers. The measurements from those working in areas of similar activities and exposure controls (dust zones or homogeneous exposure groups) were used to calculate a mean exposure during identified time periods. Persons who spent all of their work time in one zone/group were assigned this mean exposure; those with responsibilities in more than one area were assigned an exposure based on a time-weighted formula. A total of 3213 measurements were used to estimate exposure for 130 job titles; because of the mobile jobs, many samples contribute to the estimates of exposure for multiple job titles. The majority of exposure estimates (53%) have remained stable over the operational history of the plant reported here. For 32 job titles (25%) exposures have decreased, and for 28 job titles (22%) exposures have increased. Of the 122 job titles active in 2001, 97 (79%) exposures were estimated to be at 0.25 f/cc or lower; 8 (7%) had an exposure exceeding 0.5 f/cc (range 0.51-0.80) and 17 (14%) of these exposure estimates were in the range of > 0.25 f/cc to 0.5 f/cc. The continuing program to measure exposure supports a respiratory health surveillance program in these facilities.

Mortality of workers occupationally exposed to refractory ceramic fibers.

This study was prompted by refractory ceramic fibers (RCF) inhalation studies at high dose levels in animals that demonstrated positive effects for lung fibrosis, mesothelioma, and lung cancer. Current and former male workers employed between 1952 and 2000 at two RCF manufacturing facilities were followed to investigate a possible excess in mortality. The mortality analytic methods included: (1) standardized mortality ratios comparing this cohort to the general and state populations, and (2) a proportional hazards model that relates risk of death to the lifetime cumulative fiber-months/cc exposure among the RCF cohort, adjusted for age at hire and for race. There was no excess mortality related to all deaths, all cancers, or malignancies or diseases of the respiratory system including mesothelioma, but there was a statistically significant association with cancers of the urinary organs SMR = 344.8 (95% CL of 111.6, 805.4). The quality of the data for job history, exposure, and smoking history were very high. Although the cohort was relatively small and young with an average age of 51, the mean latency period was over 21 years. Because of these limitations, the preliminary findings warrant the continuation of this mortality registry for future analyses.

Pulmonary deposition modeling with airborne fiber exposure data: a study of workers manufacturing refractory ceramic fibers.

Increasing production of refractory ceramic fiber (RCF), a synthetic vitreous material with industrial applications (e.g., kiln insulation), has created interest in potential respiratory effects of exposure to airborne fibers during manufacturing. An ongoing study of RCF manufacturing workers in the United States has indicated an association between cumulative fiber exposure and pleural plaques. Fiber sizing data, obtained from electron microscopy analyses of 118 air samples collected in three independent studies over a 20-year period (1976-1995), were used with a computer deposition model to estimate pulmonary dose of fibers of specified dimensions for 652 former and current RCF production workers. Separate dose correction factors reflecting differences in fiber dimensions in six uniform job title groups were used with data on airborne fiber concentration and employment duration to calculate cumulative dose estimates for each worker. From review of the literature, critical dimensions (diameter <0.4 microm, length <10 microm) were defined for fibers that may translocate to the parietal pleura. Each of three continuous exposure/dose metrics analyzed in separate logistic regression models was significantly related to plaques, even after adjusting for possible past asbestos exposure: cumulative fiber exposure, chi(2) = 15.2 (p < 0.01); cumulative pulmonary dose (all fibers), chi(2) = 14.6 (p < 0.01); cumulative pulmonary dose (critical dimension fibers), chi(2) = 12.4 (p < 0.01). Odds ratios (ORs) were calculated for levels of each metric. Increasing ORs were statistically significant for the two highest dose levels of critical dimension fibers (level three, OR = 11, 95%CI = [1.4, 98]; level four, OR = 25, 95%CI = [3.2, 190]). Similar associations existed for all metrics after adjustment for possible asbestos exposure. It was concluded that development of pleural plaques follows exposure- and dose-response patterns, and that airborne fibers in RCF manufacturing facilities include those with critical dimensions associated with pleural plaque formation. Analysis of additional air samples may improve estimates of the dose-response relationship.

Effect of occupational silica exposure on pulmonary function.

STUDY OBJECTIVES: To assess the effect of occupational silica exposure on pulmonary function. DESIGN: Epidemiologic evaluation based on employee interview, plant walk-through, and information abstracted from company medical records, employment records, and industrial hygiene measurements. PARTICIPANTS: Drawn from 1,072 current and former hourly wage workers employed before January 1, 1986. Thirty-six individuals with radiographic evidence of parenchymal changes consistent with asbestosis or silicosis were excluded. In addition, eight individuals whose race was listed as other than white or black were excluded. MEASUREMENTS AND RESULTS: Analysis of spirometry data (FVC, FEV1, FEV1/FVC) only using the test results that met American Thoracic Society criteria for reproducibility and acceptability shows decreasing percent-predicted FVC and FEV1 and decreasing FEV1/FVC in relationship to increasing silica exposure among smokers. Logistic regression analyses of abnormal FVC and abnormal FEV1 values (where abnormal is defined as < 95% confidence limit for predicted using the Knudson prediction equations) show odds ratios of 1.49 and 1.68, respectively, for occurrence of abnormal result with 40 years of exposure at the Occupational Safety and Health Administration (OSHA)-allowable level of 0.1 mg/m3. Longitudinal analyses of FVC and FEV1 measurements show a 1.6 mL/yr and 1.1 mL/yr, respectively, decline per milligram/cubic meter mean silica exposure (p = 0.011 and p = 0.001, respectively). All analyses were adjusted for weight, height, age, ethnicity, smoking status, and other silica exposures. Systematic problems leading to measurement error were possible, but would have been nondifferential in effect and not related to silica measurements. CONCLUSIONS: There is a consistent association between increased pulmonary function abnormalities and estimated measures of cumulative silica exposure within the current allowable OSHA regulatory level. Despite concerns about the quality control of the pulmonary function measurements use in these analyses, our results support the need to lower allowable air levels of silica and increase efforts to encourage cessation of cigarette smoking among silica-exposed workers.