Zonolite attic insulation exposure studies

Our plain-English summary of Zonolite attic insulation exposure studies, by W.M. Ewing, S.M. Hays, R. Hatfield, et al (International Journal of Occupational and Environmental Health, 2010).

The study

• Authors: W.M. Ewing, S.M. Hays, R. Hatfield, W.E. Longo, J.R. Millette
• Journal: International Journal of Occupational and Environmental Health
• Published: 2010;16(3):279-90
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Several studies were designed and conducted to evaluate amphibole asbestos exposures in homes containing Zonolite (expanded vermiculite) attic insulation (ZAI). A range of tasks selected for evaluation included cleaning, working around, moving, and removal of ZAI in attics and living spaces. The fieldwork for these studies was conducted at two homes in Spokane, WA and one home in Silver Spring, MD. Personal and area air samples were collected and analyzed as part of the exposure studies. Surface dust samples and bulk samples were also collected and analyzed. The results demonstrated that airborne concentrations of amphibole asbestos were not elevated if the material is undisturbed. The results also demonstrated that cleaning, remodeling, and other activities did produce significant concentrations of airborne amphibole asbestos when the ZAI was disturbed.

In plain English

The authors measured asbestos in the air at three houses with Zonolite attic insulation (ZAI), an expanded vermiculite product: two homes in Spokane, WA and one in Silver Spring, MD. A worker, helped by an assistant in most tasks, performed six household tasks. These included cleaning attics, cutting a hole in a ceiling below the insulation, moving insulation by two methods, and vacuuming insulation from the tops of wall cavities at the edge of an attic. Air, dust and insulation samples were analyzed. The amphibole asbestos found was reported as "Libby amphiboles" (fibrous tremolite, richterite, winchite and actinolite). Before any activity, attic air did not show elevated asbestos. During tasks, the worker's average level measured by electron microscopy ranged from below detection (less than 0.42 structures per cc, cleaning stored items) to 13.0 structures per cc (moving insulation by a homeowner method). The authors reported that the OSHA 30-minute excursion limit of 1 f/cc was often exceeded, and that misting with water was not very effective. The authors concluded that undisturbed ZAI seems not to raise exposures, while activities that disturb it can. They noted the study covered only three homes.

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: Field exposure study: a series of tasks performed in homes with Zonolite attic insulation, with personal and area air sampling, surface dust sampling and bulk insulation sampling; pre-activity samples served as a baseline
• Who was studied: Three homes containing Zonolite attic insulation: two in Spokane, Washington and one in Silver Spring, Maryland; tasks were performed by a worker, with an assistant for most tasks; study dates are not given
• Exposure: Amphibole asbestos from Zonolite (expanded vermiculite) attic insulation, reported as Libby amphiboles (fibrous tremolite, richterite, winchite, actinolite). Tasks were: cleaning stored items in an attic; cleaning an attic storage area; cutting a ceiling hole; moving insulation by the W.R. Grace & Co. method and by a homeowner method; and removal of insulation from the top of wall cavities with a shop vacuum. Bulk insulation contained a trace (less than 0.1%) in one attic and less than 1% amphibole in another.
• Main results:
  • Background air samples taken in the attics of all three houses before any disturbance did not show elevated asbestos concentrations
  • Cleaning stored items in an attic with ZAI only at the perimeter: no asbestos was detected in personal electron microscopy samples (worker less than 0.42 s/cc, assistant less than 0.33 s/cc); area samples in the cleaning area averaged 0.12 s/cc, 60 times the pre-cleaning background
  • Cleaning a storage area in an attic fully insulated with ZAI: the worker's exposure was almost 1000 times the pre-cleaning background
  • Cutting a hole in a ceiling below ZAI: the worker's 26-minute time-weighted average was 2.48 s/cc (1.32 s/cc for structures longer than 5 micrometers)
  • In the ceiling-cutting test, the stippled finish coat of the ceiling contained about 7% chrysotile, but only Libby amphiboles were detected in the air samples
  • Moving ZAI by the W.R. Grace & Co. method: the worker's 34-minute time-weighted average was 6.29 s/cc (4.85 s/cc for structures longer than 5 micrometers)
  • Moving ZAI by the homeowner method: the worker's 31-minute time-weighted average was 13.0 s/cc (10.3 s/cc for structures longer than 5 micrometers)
  • The authors reported that neither method of moving ZAI effectively controlled amphibole asbestos dust, and that misting with water was not very effective as a dust suppressant
  • Removing ZAI from the top of wall cavities with a shop vacuum: the worker's 46-minute time-weighted average was 1.47 s/cc (0.98 s/cc for structures longer than 5 micrometers)
  • The authors stated that the OSHA excursion limit of 1 f/cc during any 30-minute period was often exceeded in the tasks shown in Tables 2 to 6
• The authors' conclusion: The authors concluded that undisturbed ZAI in home attics seems not to result in elevated exposures, but that routine cleaning, maintenance and remodeling activities that disturb ZAI can generate significant airborne amphibole asbestos exposures, even though bulk amphibole content is usually below 1%
• Limitations the authors state:
  • Only three homes were studied
  • Long-term sampling in occupied homes was not done because of time and budget constraints
  • The standard air sampling methods (phase contrast microscopy and direct-preparation electron microscopy) have shortcomings in dusty air
  • The standard EPA bulk analysis method sometimes fails to detect amphiboles in vermiculite
  • For the assistant in some tasks, the electron microscopy filters were voided by a sampling malfunction, so the phase contrast filters were analyzed instead

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Libby vermiculite mine, Montana

All asbestos mines

Topics

The National Library of Medicine indexes this study under subjects our site covers: Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: Zonolite, Amphibole Asbestos, vermiculite, Settled Dust.

Related studies

• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part I. Exposure estimates — H.E. Amandus, R. Wheeler, et al. (1987)
• Pulmonary inflammatory and fibrotic responses in Fischer 344 rats after intratracheal instillation exposure to Libby amphibole — D.J. Padilla-Carlin, M.C. Schladweiler, et al. (2011)
• Cohort study of mortality of vermiculite miners exposed to tremolite — J.C. McDonald, A.D. McDonald, et al. (1986)
• Vermiculite, respiratory disease, and asbestos exposure in Libby, Montana: update of a cohort mortality study — P.A. Sullivan (2007)
• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part II. Mortality — H.E. Amandus, R. Wheeler (1987)
• Mortality in a cohort of vermiculite miners exposed to fibrous amphibole in Libby, Montana — J.C. McDonald, J. Harris, et al. (2004)

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