Childhood exposure to Libby amphibole during outdoor activities

Our plain-English summary of Childhood exposure to Libby amphibole during outdoor activities, by P.H. Ryan, G.K. LeMasters, J. Burkle, et al (Journal of Exposure Science & Environmental Epidemiology, 2015).

The study

• Authors: P.H. Ryan, G.K. LeMasters, J. Burkle, J.E. Lockey, B. Black, C. Rice
• Journal: Journal of Exposure Science & Environmental Epidemiology
• Published: 2015;25(1):4-11
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Residents of Libby, MT were exposed to amphibole asbestos through multiple environmental pathways. Previous exposure characterization has primarily relied on qualitative report of these exposure activities. The objectives of this study were to describe available data from the US EPA preremediation actions for Libby amphibole (LA) exposure in Libby, MT and develop an approach to characterize outdoor residential exposure to LA among children. Homes in Libby, MT included in the US EPA preremediation Contaminant Screening Survey (CSS) were categorized by the presence of interior and/or exterior visible vermiculite and concentrations of LA were measured in samples of dust and soil. Airborne exposure to LA while digging/gardening, raking, and mowing were estimated using US EPA activity-based sampling (ABS) results. Residential histories and frequency/duration of childhood activities were combined with ABS to demonstrate the approach for estimating potential exposure. A total of 3154 residential properties participated in the CSS and 44% of these had visible exterior vermiculite. Airborne concentrations of LA where there was visible vermiculite outdoors were 3-15 times higher during digging/gardening, raking, and mowing activities compared with homes without visible outdoor vermiculite. Digging and gardening activities represented the greatest contribution to estimated exposures and 73% of the participants reported this activity before the age of 6 years. This methodology demonstrated the use of historical preremediation data to estimate residential exposures of children for specific activities. Children younger than age 6 years may have been exposed to LA while digging/gardening, especially at homes where there is visible outdoor vermiculite. This approach may be extended to other activities and applied to the entire cohort to examine health outcomes.

In plain English

This study described US Environmental Protection Agency (EPA) cleanup-screening data from Libby, Montana, and tested a way to use them to estimate children's exposure to Libby amphibole asbestos during outdoor activities. Of 3154 screened homes, 1400 (44.4%) had visible vermiculite outdoors and 737 (23.4%) indoors. In 2007 to 2008, EPA air-sampled digging, raking and mowing at 57 categorized homes among 62 properties it defined as post-cleanup. During digging/gardening, average airborne levels were 0.447 fibers per cubic centimeter at homes with visible outdoor vermiculite, versus 0.030 where outdoor soil samples showed non-detectable or trace asbestos. During raking and mowing, levels were 3.5 to 4 times higher at visible-vermiculite homes. The authors applied the method to the first 22 young adults in a Libby health study; 17 had at least one screened home. Digging/gardening contributed most of the estimated exposure, and 11 participants reported it before age 6. The authors concluded that the method can estimate activity-specific childhood exposure. They noted the screening was not designed for exposure assessment, the air samples may represent upper-bound values, and recall was uncertain.

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: Exposure-assessment methods study combining existing US EPA screening and activity-based air sampling data with questionnaire data from an initial sample of a cohort study
• Who was studied: 3154 residential properties in the Libby, MT area screened in the EPA Contaminant Screening Study. 57 of 62 homes in EPA outdoor activity-based air sampling (summer 2007 and spring 2008), all defined by EPA as post-cleanup properties. The first 22 participants (aged 21 to 28) of the CHIEFS cohort, enrolled September 2010 to June 2011, 17 of whom had at least one home with a screening category.
• Exposure: Libby amphibole (winchite, richterite and tremolite fibers in Libby vermiculite) at homes, classed by visible vermiculite and asbestos levels in dust and soil. Airborne exposure during outdoor digging/gardening, raking and mowing in childhood.
• Main results:
  • Of 3154 screened homes, 1400 (44.4%) had visible vermiculite outdoors and 737 (23.4%) had visible vermiculite indoors
  • Average airborne Libby amphibole during digging/gardening was 0.447 f/cm3 (SD 1.910) at homes with visible outdoor vermiculite (category 5, n = 43). At homes whose outdoor soil samples had non-detectable or trace levels (categories 1 or 2, n = 14), it was 0.030 f/cm3 (SD 0.067).
  • During raking and mowing, airborne levels at visible-vermiculite homes were on average 3.5 to 4 times those at category 1 or 2 homes
  • Of the 17 participants with at least one screened home, 12 had lived in at least one home where visible vermiculite was observed
  • Among the 17 participants, the average cumulative outdoor activity exposure estimate using home categories was 0.76 (SD 1.18) f/cm3-months. Using the overall average air concentration instead, it was 0.65 (SD 0.87).
  • Digging/gardening contributed most of the estimated exposure. No participant reported raking or mowing before age 6, but 11 reported digging/gardening before age 6, six of them at a home with visible vermiculite.
• The authors' conclusion: The authors concluded that they had provided a method combining EPA screening and air sampling results with reported residential histories and outdoor activities to estimate childhood exposure levels for specific activities. They plan to apply it to the whole cohort to examine health outcomes.
• Limitations the authors state:
  • Possible exposure misclassification, because the exact locations of visible vermiculite and of participants' digging/gardening were unknown
  • Children also played at other properties, not just their own yards
  • Uncertain recall of the age, frequency and duration of childhood activities
  • Air sampling was done about 7 years after screening began and after considerable cleanup. It was also designed to stir up fibers, so it may represent upper-bound values.
  • Air concentrations were highly variable, especially for digging
  • Screening data were incomplete for participants' residential histories: 17 of 22 had a category for at least one home, but only 7 for all homes before age 18
  • The screening survey was not designed for exposure assessment, took no air samples and had limited dust samples. Concentrations at homes while participants lived there are unknown.

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: Libby amphiboles, Amphibole Asbestos, vermiculite.

Related studies

• Childhood exposure to Libby amphibole asbestos and respiratory health in young adults — P.H. Ryan, C.H. Rice, et al. (2017)
• Pulmonary abnormalities as a result of exposure to Libby amphibole during childhood and adolescence-The Pre-Adult Latency Study (PALS) — J. Szeinuk, C.W. Noonan, et al. (2017)
• Exposure to asbestos-containing vermiculite ore and respiratory symptoms among individuals who were children while the mine was active in Libby, Montana — L.C. Vinikoor, T.C. Larson, et al. (2010)
• A review of scientific literature examining the mining history, geology, mineralogy, and amphibole asbestos health effects of the Rainy Creek igneous complex, Libby, Montana, USA — B.R. Bandli, M.E. Gunter (2006)
• Exposure to airborne amphibole structures and health risks: Libby, Montana — B. Price (2008)
• Low levels of exposure to libby amphibole asbestos and localized pleural thickening — K.Y. Christensen, T.F. Bateson, et al. (2013)

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