A meta-analysis of airborne asbestos fiber concentrations from work with or around asbestos-containing floor tile

Our plain-English summary of A meta-analysis of airborne asbestos fiber concentrations from work with or around asbestos-containing floor tile, by A.L. Perez, M.L. Nelson, T.J. Cheng, et al (International Journal of Occupational and Environmental Health, 2018).

The study

• Authors: A.L. Perez, M.L. Nelson, T.J. Cheng, C.E. Comerford, P.K. Scott
• Journal: International Journal of Occupational and Environmental Health
• Published: 2018;24(3-4):134-148
• Type of article: Meta-analysis
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

In this meta-analysis, exposures to airborne asbestos during work with or around floor tiles were characterized according to several variables: study, sample type, activity, and task. Personal breathing zone, bystander, and area sample exposure concentrations were differentiated and compared against current occupational exposure limits to asbestos. In total, 22 studies, including 804 personal, 57 bystander, and 295 area samples, were included in the analysis. The arithmetic mean airborne fiber concentrations were 0.05, 0.02, and 0.01 f/cm3 for personal, bystander, and area samples, respectively. Arithmetic mean time-weighted-average fiber concentrations over an 8-h working day were 0.02 and 0.01 f/cm3 for personal and bystander samples, respectively. Phase contrast microscopy (PCM) personal airborne fiber concentrations were highest for maintenance activities, followed by removal and installation. Tasks that involved buffing or burnishing, scoring or snapping, and scraping or lifting had the highest personal PCM concentrations, while stripping floor tile and removing it with chemical solvent had the lowest concentrations. Exposures associated with handling asbestos floor tiles, under working conditions normally encountered, do not generally produce airborne concentrations at levels that exceed the current OSHA PEL nor do they appear to approach the threshold cumulative asbestos dose concentrations that have been previously associated with an increased risk of asbestos-related disease.

In plain English

This meta-analysis pooled airborne asbestos measurements from 22 studies of installing, maintaining, removing and walking on asbestos-containing floor tile. They held 804 personal (breathing-zone), 57 bystander and 295 area samples. Average concentrations were 0.05, 0.02 and 0.01 f/cm3 for personal, bystander and area samples; calculated 8-hour averages were 0.02 and 0.01 f/cm3 for personal and bystander samples. Short-duration personal samples during maintenance were highest (average 0.15 f/cm3, up to 1.7 f/cm3); without nine ultra-high-speed burnishing samples, the average was 0.04 f/cm3. Among the raw-data personal samples, all 52 with a reported sampling time of 30 minutes or less were below OSHA's 30-minute limit of 1.0 f/cm3. Four burnishing samples collected over longer periods had concentrations above that number. Nine of 10 calculated 8-hour averages above OSHA's 0.1 f/cm3 limit came from the ultra-high-speed burnishing study, which used dry methods. In short-term samples, bystander levels were about 35% of personal levels. The authors concluded that normal floor tile handling has not been shown to exceed the OSHA 8-hour limit. Limitations included missing raw data, differing counting methods and few bystander samples.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Meta-analysis (statistical pooling) of published and unpublished airborne asbestos measurements taken during work with or around asbestos-containing floor tile
• Who was studied: 22 studies, giving 804 personal, 57 bystander and 295 area air samples. Settings were mostly commercial buildings such as schools, unoccupied commercial buildings, hospitals and churches; two studies were in homes.
• Exposure: Airborne fibers from maintenance, removal, installation, clean-up, wear or traffic, and abatement of asbestos-containing floor tiles. The five studies that distinguished fiber types identified only chrysotile asbestos.
• Main results:
  • Arithmetic mean airborne fiber concentrations were 0.05 f/cm3 for personal samples, 0.02 f/cm3 for bystander samples and 0.01 f/cm3 for area samples
  • Arithmetic mean 8-hour time-weighted-average concentrations were 0.02 f/cm3 for personal samples and 0.01 f/cm3 for bystander samples
  • The highest PCM concentrations were in short-duration personal samples during maintenance activities: arithmetic mean 0.15 f/cm3, range 0.002 to 1.7 f/cm3. This set included ultra-high-speed burnishing samples from Kominsky et al.
  • Without the nine ultra-high-speed burnishing samples, the arithmetic mean for short-duration personal maintenance samples was 0.04 f/cm3 (range 0.002 to 0.3 f/cm3)
  • Among the raw-data personal samples, all 52 with a reported sampling duration of 30 minutes or less were below the OSHA short-term exposure limit of 1.0 f/cm3
  • When personal samples of all durations (10 to 515 minutes) were compared with the short-term limit value, all but 4 of 218 personal PCM samples were below it
  • Those 4 samples were all collected over more than 30 minutes (mean 78 minutes), all during ultra-high-speed burnishing reported by Kominsky et al.
  • 10 calculated 8-hour time-weighted-average samples exceeded the OSHA limit of 0.1 f/cm3. Nine of the 10 came from the Kominsky et al. ultra-high-speed burnishing study.
  • The ultra-high-speed burnishing samples were done with dry methods; the other samples in the buffing and burnishing category used wet methods
  • In short-term samples from the same studies, bystander concentrations were about 35% of personal concentrations (p = 0.0058)
  • By activity, personal PCM concentrations were highest for maintenance, followed by removal and then installation
  • By task, buffing or burnishing, scoring or snapping, and scraping or lifting gave the highest personal PCM concentrations. Stripping and chemical-solvent removal gave the lowest.
  • In matched samples, PCM concentrations averaged 6.2 times TEM concentrations (95% confidence interval 3.8 to 10.3)
  • The authors estimated a cumulative dose of 1.5 to 2.3 f/cm3 years over a 45-year working lifetime. They compared this with 4.5 f/cm3 years at the OSHA limit.
• The authors' conclusion: The authors concluded that handling and using asbestos floor tiles under normally encountered conditions has not been shown to produce airborne concentrations above the current OSHA 8-hour limit. They also concluded that such exposures would not approach cumulative doses previously associated with increased disease risk.
• Limitations the authors state:
  • Raw data were not available for all studies, so overall averages relied on imputed methods
  • Samples analyzed and counted by differing methods were compared, especially among the TEM samples
  • Samples that would otherwise have been considered statistical outliers were included
  • There were very few bystander samples
  • Most studies did not define the bystander's distance from the work
  • Data on mastic exposures separate from floor tile were very limited
  • It is unclear whether exposures differ between vinyl-asbestos and asphalt-asbestos tiles

Topics

Medical terms in this study, explained in our Lexicon: Meta-Analysis, Occupational Exposure, phase contrast microscopy (PCM), Permissible Exposure Limit (PEL).

Related studies

• Airborne exposure during asbestos abatement of floor tile, wall plaster, and pipe insulation — J.H. Lange (2005)
• Airborne asbestos exposures associated with gasket and packing replacement: a simulation study of flange and valve repair work and an assessment of exposure variables — A.K. Madl, K.D. Devlin, et al. (2015)
• Asbestos abatement of pipe and floor tile/mastic and comparison of critical plastic barrier controls — J.H. Lange (2004)
• Type and amount of asbestos in floor tile and mastic — J.H. Lange (2006)
• Impact of asbestos concentrations in floor tiles on exposure during removal — J.H. Lange (2002)
• Exposure to airborne asbestos during abatement of ceiling material, window caulking, floor tile and roofing material — J.H. Lange, S.L. Sites, et al. (2008)

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