Eric K. Borton

Airway obstruction related to diacetyl exposure at microwave popcorn production facilities.

Obstructive lung diseases including bronchiolitis obliterans have been reported among microwave popcorn production employees. Butter flavourings including diacetyl have been associated with these findings. The present study was initiated at four microwave popcorn production plants to determine if exposure to diacetyl was associated with decrements in pulmonary function. Comprehensive diacetyl exposure assessment was undertaken for all job tasks. Spirometry was conducted for 765 full-time employees between 2005 and 2006. Outcomes included decrement in forced expiratory volume in one second (FEV1) % predicted, airway obstruction and persistent decline in FEV1. Inclusion in the high-exposure group (mixers) prior to respirator use was associated with a significantly decreased FEV1 % pred in non-Asian and Asian males at -6.1 and -11.8% pred, respectively, and an eight-fold increased risk for airway obstruction. Cumulative diacetyl exposure ≥0.8 ppm-yr caused similar results. No significant impact was seen in nonmixers or between current diacetyl exposure and persistent decline in FEV1. Unprotected exposure as a mixer to butter flavouring including diacetyl resulted in decrements in FEV1 (% pred) and increased airway obstruction. Control of employee exposure to butter flavouring additives is warranted in regard to both short-term peak and 8-h workday exposure.

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.

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.

Mesothelioma associated with commercial use of vermiculite containing Libby amphibole.

Objectives: To describe asbestos-related mortality among manufacturing workers who expanded and processed Libby vermiculite that contained amphibole fiber. Methods: Standardized mortality ratio was calculated for 465 white male workers 31 years after last Libby vermiculite exposure. Results: Two workers died from mesothelioma, resulting in a significantly increased standardized mortality ratio of 10.5 (95% confidence interval, 1.3 to 38.0). These workers were in the upper 10th percentile of cumulative fiber exposure, that is, 43.80 and 47.23 fiber-years/cm3, respectively. One additional worker with cumulative fiber exposure of 5.73 fiber-years/cm3 developed mesothelioma but is not deceased. There were no other significantly increased standardized mortality ratios. Conclusions: Workers expanding and processing Libby vermiculite in a manufacturing setting demonstrated an increased risk for the development of mesothelioma following exposure to the amphibole fiber contained within this vermiculite ore source.

Functional impairment and quality of life in retired workers of the construction trades.

ABSTRACT This cross-sectional study compared the quality of life and physical health of retirees from the construction industry to that of retirees from more sedentary occupations. The feasibility of cooperation from the unions and their retirees for a larger health study was also examined. The mailed health survey assessed current physical functioning, role limitations as a result of poor health, pain, and past and current problems with falls and injuries. The survey was completed by 77 construction and 174 nonconstruction retirees. Results were striking with 42.1% of the construction retirees, compared to 12.9% of the male and 14.3% of female nonconstruction retirees reporting significantly poorer health. A multiple regression analysis comparing male construction to male nonconstruction retirees showed male construction retirees were almost five times more likely to report their health as being fair or poor. Further, significantly more male construction, versus male nonconstruction retirees, reported that their physical health reduced the time they were able to spend on daily activities. Almost one in five (19.4%) construction retirees described themselves as having severe to very severe pain versus 3.1% of the male nonconstruction retirees. Construction retirees reported significantly greater problems with their vision, neck and shoulders, hands and wrists, hips, knees, and ankle/feet joints. These findings suggest that with our rapidly aging population, there will be enormous physical, emotional, and financial costs related to construction work and that prevention and intervention measures are needed for current employees in this profession.

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 &mgr;m 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/cm3 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.

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.

Asbestos-related radiographic findings among household contacts of workers exposed to Libby vermiculite: impact of workers' personal hygiene practices.

Objective: To explore the potential impact of worker hygiene by determining the prevalence of radiographic changes consistent with asbestos exposure among household contacts of workers exposed to Libby vermiculite that contained amphibole fibers. Methods: Workers and household contacts had chest radiographs and completed questionnaires regarding hygiene and potential exposure pathways. Results: Participants included 191 household contacts of 118 workers. One household contact (0.5%) had localized pleural thickening, and three (1.6%) had irregular opacities at profusion category 1/0 or greater. Worker radiographs demonstrated pleural changes in 45% and irregular opacities at profusion category 1/0 or greater in 8%. Conclusions: Libby vermiculite-exposed workers demonstrated an elevated prevalence of pleural and interstitial chest radiographic changes. There was, however, no increased prevalence of similar changes among household contacts, likely because of personal hygiene measures taken by the majority of workers.