ASTM Conference on Critical Issues in Monitoring Asbestos
The Johnson Conference, as it is traditionally called, was held on the campus of the University of Vermont in Burlington, Vermont on July 14-18, 2008. This triennial event is sponsored by Committee D22 on Air Quality of ASTM International and organized by Subcommitee D22.07 on Sampling and Analysis of Asbestos. The conference chairmen were Michael Beard of RTI International, James Webber of the New York State Department of Health, Harry Rook, recently retired from the National Institute of Standards and Technology, and Robert Lewis, recently retired from EPA. To say that Mike Beard is closely associated with the Johnson Conference is a gross understatement he is the Johnson Conference and his absence while undergoing cancer therapy was keenly felt. Each day opened with a tribute to Mike and his co-chairmen phoned him every night with a report on the day's happenings.
The Johnson Conference is where the latest research on asbestos sampling and analysis is presented, and its implications for health effects, risk assessment and remediation are debated. To encourage open and candid exchange of controversial views, no proceedings are published, electronic recording is not allowed and authors may not be quoted without their written permission. This article honors those constraints. It is an overview of the presentations and discussions, and all conclusions are my own. The abstracts were available in the conference program on the ASTM website at http://www.astm.org/MEETINGS/COMMIT/d22conf.htm at the time this article was posted.
This was the most international Johnson Conference in recent memory with attendees from fourteen countries. Over 200 registered , a record for the event. There were 55 presentations in the platform sessions on:
For the first time at a Johnson Conference, poster presentations supplemented the platform sessions. This allowed attendees to discuss 26 additional papers with the authors at designated times during the week.
Two observations emerged from the week's proceedings:
To quantify the first point, the conference program contains the word soil 94 times and 21 papers (by my count) addressed asbestos in soil, whereas building occurs only 37 times and just six papers concerned installed asbestos building materials or related issues. The trend was set on Monday morning with an overview of contaminated sites in the northwestern United States (I:Wroble)2 and concluded with a detailed description of one of the sites by the same speaker on Thursday evening (VII:Wroble). In between, several speakers addressed: evaluation of communities near closed asbestos mines (I:Jones); contamination of a beach with asbestos-cement manufacturing waste (III:Camplin); contamination at a construction site (VI:Fitzgerald); and remediation of an unintentional disposal site (VI:Colman) for example. All of these papers examined the monitoring and analytical aspects and discussed remediation approaches or the need therefor. A common thread was that community involvement is essential and unavoidable, and that the media will not be ignored.
These papers included a combination of man-made contamination and what is now called naturally-occurring asbestos. The fact that all asbestos is naturally-occurring notwithstanding, this term has gained traction despite some reservations over its precise meaning. Geogenic was suggested and my own definition of NOA is asbestos where it was placed by nature, not by man.
The discussion of asbestos in soils included several cases of activity-based sampling, another term of art now denoted by its own acronym ABS. Studies were reported on driving ATVs over roads covered with asbestos-containing gravel (I:Wheeler); raking and other disturbance of contaminated soil (III:Brass).
Several papers were devoted to analyzing soil for asbestos content: amphiboles (I:Lee); wet sieving (II:Atwood) as part of a regulatory approach to debris remediation; X-ray diffraction of surface and subsurface samples (III:Gunter) and dry sieving (III:Millette). There is a proliferation of soil sampling methods that also include grinding and crushing, and comparability of these methods is far from resolved. The trend is to express the results in terms of percent of asbestos in the soil by weight, but quantifying the fibers or structures per gram of soil is also used.
An alternative to ABS was put forth as a comparable means of measuring airborne fiber release from soil in the form of the Releasable Asbestos Field Sampler (III:Kominsky). Not all papers dealt with soil as the contaminated medium: trees were found to act as receptors for Libby amphiboles (VII:Ward) and some become firewood after their demise, creating a source of possible human exposure.
Nor were all papers restricted to the six recognized and regulated forms of asbestos, as Libby amphiboles can include winchite and richterite, for example. Air monitoring in Biancavilla, Sicily was reported (VI:Paglietti) where fibers of fluoro-edenite have been implicated in a cluster of mesotheliomas. Where deposits of NOA do not consist of the commonly-recognized forms of asbestos, should the acronym denote naturally-occurring asbestiform or naturally-occurring amphiboles? Terminology and definitions came up throughout the conference, including an entire session on cleavage fragments.
One paper (VI:Morse) that dealt with asbestos in buildings described the development over 14 years of the ASTM settled dust guide (D7390). Those who are looking for a pass-fail number will be disappointed, however, as the Guide tells how to statistically compare two environments whose surfaces have been sampled according to the ASTM microvacuum (D5755 and D5756) and wipe sampling (D6480) methods.
The validity of analytical methods for bulk samples and the effects on surveys of school buildings was discussed (V:Toyama); fiber release from enclosed ACM in schools was defined in terms of the construction details and forces acting on the structures (VII:Burdett).
A paper on airborne fiber levels from Libby Vermiculite Attic Insulation (VI:Ewing) calls into question one of the regulatory foundations: the definition of asbestos-containing materials as those containing more than one percent asbestos. Personal exposures as high as 14.4 f/cc were measured when this material was disturbed, even though the tremolite asbestos content of the insulation was less than one percent.
The conference concluded Friday with a full day on health effects. The long and short of it was that long, thin fibers have been recognized as more carcinogenic since the 1981 Stanton study (VIII:Cook) but convincing evidence was presented that short (<5m) fibers should not be ignored (VIII:Dodson). Fiber surface area was discussed in the context of potency (VIII:Plumlee) and quantified with aqueous elutriation (VIII:Webber). Does this suggest that fiber surface area is a proper metric for risk assessment, and perhaps for exposure limits as well?
When the program was printed, the 2007 NIOSH document Asbestos and Other Mineral Fibers: A Roadmap for Scientific Research was the subject of a paper (IX:Middendorf). This June, however, the title underwent a subtle change to Asbestos Fibers and Other Elongated Mineral Particles: State of the Science and Roadmap for Research. The distinction between asbestos fibers and asbestiform particle we have another acronym: EMP is significant, but the definition of >5m long and an aspect ratio of >3:1 maintains the focus on the O in NIOSH: Occupational. Those of us who expected guidance on using NIOSH 7400 and 7402 for low fiber levels found in ambient and clearance sampling will not find it in the Roadmap.
There are times I almost think nobody's sure of what he absolutely knowsEverybody finds confusion in conclusion he concluded long agoAnd it puzzles me to learn that though a man may be in doubt of what he knowsVery quickly will he fight he'll fight to prove that what he does not know is SO!
Rodgers and Hammerstein, The King and I
The Johnson Conference was an opportunity to learn a lot but also to realize how much remains unknown. How do we define asbestos in the first place, or distinguish a fiber from a cleavage fragment and does it really matter? Which risk assessment models show which asbestiform fibers by any name to warrant control measures including possible regulation? What is the toxicity mechanism for fiber-induced cancers and how does it relate to the physical and chemical properties of the fibers, not to mention their concentration in air, water, soil and tissue? How do we measure these concentrations and what is the validity of field and laboratory simulations of exposure?
An e-mail I received after the conference offers a fitting observation on the 2008 Johnson Conference by a first-time attendee:
Nice to know I am not the only one still confused about asbestos after all these years! Amazing that we are still arguing over so many basic points but in reality this is due to a lot of smart people still asking very good questions.
He will undoubtedly be back in 2011 to hear these questions debated again by many of the same learned experts. I plan to be there, too.
Received August 14, 2008
2 This notation refers to the session and first author for those who wish to consult the abstracts in the conference program. Contact information for speakers in provided in the program.