Exposure to naturally occurring mineral fibers due to off-road vehicle use: A review

Our plain-English summary of Exposure to naturally occurring mineral fibers due to off-road vehicle use: A review, by C. Wolfe, B. Buck, A. Miller, et al (International Journal of Hygiene and Environmental Health, 2017).

The study

• Authors: C. Wolfe, B. Buck, A. Miller, J. Lockey, C. Weis, D. Weissman, A. Jonesi, P. Ryan
• Journal: International Journal of Hygiene and Environmental Health
• Published: 2017;220(8):1230-1241
• Type of article: Review
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The use of off-road vehicles (ORVs) is a popular source of outdoor recreation in the United States. While personal injury has been the focus of most epidemiologic investigations regarding ORV use to date, other health effects associated with ORV use have not been adequately examined. ORVs have been designed to operate in rugged, unpaved terrain, and ORVs can produce copious amounts of fugitive dust. ORV use in geographic regions with naturally occurring asbestos (NOA) and erionite (NOE) may result in the liberation of these minerals from underlying rocks and soil, which may put ORV participants at risk to potentially hazardous inhalation exposures.

Methods: A comprehensive narrative review of existing literature and reports relevant to off-road recreation and mineral fiber exposure was conducted. Manuscripts and reports included in the review were limited to those that contained quantitative data regarding concentrations of mineral fibers recorded during vehicular traffic on an unpaved road and publication in a peer-reviewed journal, official report composed by a government agency, or a report generated under the endorsement of a government agency. In addition, the potential public health impact of ORV use in regions with NOA/NOE was estimated by calculating the proximity of known mineral fiber occurrences to areas of ORV use.

Results: A total of 15 publications met inclusion criteria. Exposures to NOA/NOE observed from personal sampling in the included studies ranged from less than 0.01-5.6 f/cc. ORV position while riding in a group and vehicle speed were frequent determinants of measured concentrations. Multiple studies also suggest that children may experience higher exposures to mineral fibers in comparison to adult ORV riders. Information on ORV trails and 665 known occurrences of NOA/NOE was available for five states located in the western United States. Of these 665 known occurrences, approximately 80% (n=515) were located within 20 miles of an ORV trail, and nearly a third were located within one mile.

Conclusions: Individuals who operate ORVs in regions where NOA/NOE is a component of the underlying soil or unpaved road may experience elevated exposures to mineral fibers. Given the prevalence of ORV trails in close proximity to these natural fiber occurrences, epidemiologic and surveillance studies of individuals who frequently engage in ORV use are recommended. Public health initiatives should concentrate on increasing awareness of these risks, allowing ORV users to make informed choices and take appropriate measures to limit these risks where possible.

Copyright © 2017 Elsevier GmbH. All rights reserved.

In plain English

This article was a narrative review, not a new measurement study. The authors looked for published studies and government reports that measured mineral fibers in the air or in settled dust while vehicles traveled on unpaved surfaces. They found 15 that qualified: 14 from the United States and one from Italy. The fibers involved included chrysotile, amphibole asbestos and erionite. Personal exposures in these studies ranged from less than 0.01 to 5.6 fibers per cubic centimeter (f/cc). In one 1979 study, a trailing motorcyclist had 5.6 f/cc compared with 0.9 f/cc for the lead rider. Higher vehicle speed and more vehicles per hour raised roadside levels. In one study, samplers worn at a child's lower breathing height read higher than samplers at adult height. The authors also mapped known natural fiber occurrences against off-road trails in five western states. Of 655 occurrences, 150 lay within one mile of a trail. They noted that no epidemiologic study had explicitly assessed lung disease in relation to fiber exposure from off-road vehicle use. The authors concluded that riders in such areas may experience elevated fiber exposures, and they recommended health studies and public awareness efforts.

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: Narrative review of published studies and government reports, plus a mapping (GIS) analysis comparing known natural fiber deposits with off-road vehicle trails
• Who was studied: 15 publications and reports with fiber sampling results from vehicle travel on unpaved surfaces (14 in the U.S., 1 in Italy), plus known natural asbestos and erionite occurrences and user-recorded off-road trails in Arizona, California, Colorado, Nevada and Utah
• Exposure: Naturally occurring asbestos (chrysotile; amphiboles including Libby amphibole, actinolite, tremolite and a fluoro-amphibole) and naturally occurring erionite stirred up by off-road vehicles, passenger vehicles and bicycles on unpaved roads and trails
• Main results:
  • Across the reviewed studies, personal exposures ranged from less than 0.01 to 5.6 f/cc
  • In Cooper et al. (1979) at Clear Creek, a trailing motorcycle rider had 5.6 f/cc compared with 0.9 f/cc for the lead rider (phase contrast microscopy)
  • In Garden Valley, California, chrysotile concentrations 5 feet from the roadside were 0.755 s/cc with vehicles at 10 miles per hour and 6.3 s/cc at 25 miles per hour
  • At Diamond XX, California, with vehicle speed held constant, roadside concentrations were 0.19 s/cc at 5 vehicles per hour and 1.40 s/cc at 15 vehicles per hour
  • In EPA sampling at Clear Creek during ATV riding, samplers at adult breathing height averaged 0.317 f/cc, and samplers worn lower to represent a child averaged 0.440 f/cc
  • In Fairbanks, Alaska (Perkins et al. 2008), amphibole asbestos was found in all nine personal samples (mean 0.049 f/cc) taken in a car driven with the windows open behind a heavy vehicle
  • In EPA sampling at Clear Creek, SUV travel with the windows closed and air recirculating gave 0.14 f/cc, compared with 0.22 f/cc with the windows open
  • The five-state study region contained 655 known fiber occurrences (614 naturally occurring asbestos, 41 erionite)
  • About 40% (241) of the asbestos deposits were within 5 miles of an off-road trail, and nearly 80% (515) were within 20 miles
  • 150 mineral fiber occurrences were within one mile of an off-road trail
  • The authors noted that no epidemiologic study had explicitly assessed the relationship between mineral fiber exposure from off-road vehicle use and pulmonary disease
• The authors' conclusion: The authors concluded that people who ride off-road vehicles where naturally occurring asbestos or erionite is in the soil or road surface may experience elevated fiber exposures. They recommended epidemiologic and surveillance studies and public awareness efforts.
• Limitations the authors state:
  • The reviewed studies differed in design, soil, weather, fiber type and methods, so their results may not be directly comparable
  • The trails were self-reported GPS tracks and likely underestimate the true length of off-road trails
  • Sparse trail data limited the mapping analysis to five states
  • Fiber occurrences were counted as single mapped sites, although deposits are spread widely, so trail mileage near deposits is likely underestimated
  • Estimating disease risk from these exposures was outside the scope of the review

Topics

Medical terms in this study, explained in our Lexicon: Mineral Fiber, naturally occurring asbestos (NOA), erionite.

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• Biological effects of naturally occurring and man-made fibres: in vitro cytotoxicity and mutagenesis in mammalian cells — R. Okayasu, L. Wu, et al. (1999)
• Morphological and chemical mechanisms of elongated mineral particle toxicities — A.E. Aust, P.M. Cook, et al. (2011)

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