Retrospective exposure assessment of airborne asbestos related to skilled craftsmen at a petroleum refinery in Beaumont, Texas (1940-2006)

Trends in Airborne Chrysotile Asbestos Fibre Concentrations in Asbestos Cement Manufacturing Factories in Zimbabwe from 1996 to 2016

Zimbabwe has two major factories that have been manufacturing chrysotile asbestos cement products since the 1940s. Exposure monitoring of airborne fibres has been ongoing since the early 1990s. This study examines trends in personal exposure chrysotile asbestos fibre concentrations for the period 1996–2016. Close to 3000 historical personal exposure measurements extracted from paper records in the two factories were analysed for trends in exposure. Exposure over time was characterised according to three time periods and calendar years. Mean personal exposure chrysotile asbestos fibre concentrations generally showed a downward trend over the years in both factories. Exposure data showed that over the observed period 57% and 50% of mean personal exposure chrysotile asbestos fibre concentrations in the Harare and Bulawayo factories, respectively, were above the OEL, with overexposure being exhibited before 2008. Overall, personal exposure asbestos fibre concentrations in the factories dropped from 0.15 f/mL in 1996 to 0.05–0.06 f/mL in 2016—a decrease of 60–67%. These results can be used in future epidemiological studies, and in predicting the occurrence of asbestos-related diseases in Zimbabwe.

Pulmonary Function and CT Scan Imaging at Low-Level Occupational Exposureto Asbestos

Background: In spite of the reduced exposure level, and its ban in numerous countries, compensation claims for asbestos-related diseases are far from decreasing. Methods: We used retrospective exposure assessment techniques to explore respiratory function and a computerized tomography (CT) scan in relation to past asbestos exposure in 115 male workers retired from an acrylic and polyester fiber plant. Based, on detailed information on exposure circumstances, we reconstructed a cumulative exposure estimate for each patient. Results: Time-weighted average exposure in our study population was 0.24 fibers/ml (95% confidence inteval (CI) 0.19-0.29), and the average cumulative exposure was 4.51 fibers/mL-years (95% CI 3.95-5.07). Exposure was elevated among maintenance workers, compared to other jobs (p = 0.00001). Respiratory function parameters did not vary in relation to the exposure estimates, nor to CT scan results. Risk of interstitial fibrosis showed a significant upward trend (Wald test for trend = 2.62, p = 0.009) with cumulative exposure to asbestos; risk associated with 5.26 fibers/mL-years or more, was 8-fold (95% CI 1.18-54.5). Conclusions: Our results suggest that a CT scan can detect pleuro-parenchymal lung alterations at asbestos exposure levels lower than previously thought, in absence of respiratory impairment. Further studies are required to validate our techniques of retrospective assessment of asbestos exposure.

An analysis of workplace exposures to asbestos at three steel mills located in the United States (1972-1982)

The objective is to present historical asbestos airborne concentrations associated with activities involving presumably asbestos-containing materials in steel mills. A total of 138 historical industrial hygiene air samples collected in three US steel mills from 1972 to 1982 were analyzed. The majority of samples were collected during relining of open hearth furnaces, stoves, and blast furnaces by steel mill bricklayers and bricklayer helpers. Over 75% of the samples (n = 106) were collected for 50 min or less, four samples were collected for 227 to 306 min, and sample durations were not reported for the remaining 28 samples. Average airborne fiber concentrations measured during relining activities of open hearth furnaces, stoves, and blast furnaces were 0.21 f/cc, 0.72 f/cc and 0.13 f/cc phase-contrast microscopy (PCM), respectively. Measured airborne fiber concentrations of four time-weighted average (TWA) samples (>227 min) averaged 0.045 f/cc. Estimated 8-h TWAs concentrations averaged 0.34 f/cc for bricklayers and 0.2 f/cc bricklayer helpers. While 8-h TWA concentration estimates for monitored tasks/jobs may often have exceeded current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs), they did not exceed relevant contemporaneous occupational exposure standards. This analysis provides a better understanding of historical airborne asbestos exposures that bricklayers and other tradesmen experienced during furnace and stove work in the US steel mills.

Analysis of workplace compliance measurements of asbestos by the U.S. Occupational Safety and Health Administration (1984-2011)

The United States Occupational Safety and Health Administration (OSHA) maintains the Chemical Exposure Health Data (CEHD) and the Integrated Management Information System (IMIS) databases, which contain quantitative and qualitative data resulting from compliance inspections conducted from 1984 to 2011. This analysis aimed to evaluate trends in workplace asbestos concentrations over time and across industries by combining the samples from these two databases. From 1984 to 2011, personal air samples ranged from 0.001 to 175 f/cc. Asbestos compliance sampling data associated with the construction, automotive repair, manufacturing, and chemical/petroleum/rubber industries included measurements in excess of 10 f/cc, and were above the permissible exposure limit from 2001 to 2011. The utility of combining the databases was limited by the completeness and accuracy of the data recorded. In this analysis, 40% of the data overlapped between the two databases. Other limitations included sampling bias associated with compliance sampling and errors occurring from user-entered data. A clear decreasing trend in both airborne fiber concentrations and the numbers of asbestos samples collected parallels historically decreasing trends in the consumption of asbestos, and declining mesothelioma incidence rates. Although air sampling data indicated that airborne fiber exposure potential was high (>10 f/cc for short and long-term samples) in some industries (e.g., construction, manufacturing), airborne concentrations have significantly declined over the past 30 years. Recommendations for improving the existing exposure OSHA databases are provided.

Dust diseases and the legacy of corporate manipulation of science and law

BACKGROUND

The dust diseases silicosis and asbestosis were the first occupational diseases to have widespread impact on workers. Knowledge that asbestos and silica were hazardous to health became public several decades after the industry knew of the health concerns. This delay was largely influenced by the interests of Metropolitan Life Insurance Company (MetLife) and other asbestos mining and product manufacturing companies.

OBJECTIVES

To understand the ongoing corporate influence on the science and politics of asbestos and silica exposure, including litigation defense strategies related to historical manipulation of science.

METHODS

We examined previously secret corporate documents, depositions and trial testimony produced in litigation; as well as published literature.

RESULTS

Our analysis indicates that companies that used and produced asbestos have continued and intensified their efforts to alter the asbestos-cancer literature and utilize dust-exposure standards to avoid liability and regulation. Organizations of asbestos product manufacturers delayed the reduction of permissible asbestos exposures by covering up the link between asbestos and cancer. Once the decline of the asbestos industry in the US became inevitable, the companies and their lawyers designed the state of the art (SOA) defense to protect themselves in litigation and to maintain sales to developing countries.

CONCLUSIONS

Asbestos product companies would like the public to believe that there was a legitimate debate surrounding the dangers of asbestos during the twentieth century, particularly regarding the link to cancer, which delayed adequate regulation. The asbestos-cancer link was not a legitimate contestation of science; rather the companies directly manipulated the scientific literature. There is evidence that industry manipulation of scientific literature remains a continuing problem today, resulting in inadequate regulation and compensation and perpetuating otherwise preventable worker and consumer injuries and deaths.