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Environmental Factor, March 2012

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Interagency mineral fibers group meets at NIEHS

By Eddy Ball

microscopic view of anthophyllite

Mineral fibers such as anthophyllite, one of the five amphibole forms of asbestos, are a public health concern because of their toxicity and widespread presence in the environment. (Photo courtesy of USGS)

Senior Medical Officer Aubrey Miller, M.D.

“We thought we were busy enough with Libby,” Miller told the audience. “Now we had erionite, too.” (Photo courtesy of Steve McCaw)

Chris Weis, Ph.D.

“Nanomaterials are a little out of topic for this asbestos conference,” Weis conceded, “but we have an opportunity at this stage, right now, to avoid many, many mistakes that we’re still trying to overcome with respect to mineral fiber environmental health and safety.” (Photo courtesy of Steve McCaw)

The NIEHS commitment to mineral fibers research was front and center at the most recent meeting of the Interagency Asbestos Working Group Feb. 2-3, hosted by NIEHS. Speakers addressed developments in understanding and addressing public health consequences of exposures to asbestos and asbestos-like fibers (see text box).

The meeting was chaired by David Weissman, M.D., director of the Division of Respiratory Disease Studies at the National Institute for Occupational Safety and Health (NIOSH).

Welcoming members from nine federal agencies on day one was NIEHS/NTP Deputy Director Rick Woychik, Ph.D. The agenda prominently featured a review of NIEHS/NTP work by Senior Medical Officer Aubrey Miller, M.D.; Health Scientist Administrator Danielle Carlin, Ph.D., who updated attendees on the NIEHS asbestos grant portfolio; and NTP toxicologist Scott Masten, Ph.D. Masten also joined toxicologist Matt Stout, Ph.D., in the afternoon for a presentation on the NTP research program.

NIEHS/NTP Director Linda Birnbaum, Ph.D., attended most of the meeting and was on hand the second day, as the group heard presentations on erionite by Miller and on carbon nanotube issues relevant to asbestos by Toxicology Liaison Chris Weis, Ph.D.

Asbestos concerns rooted in NTP listing

As Woychik told the group, “NIEHS has longstanding involvement and concern regarding the health effects stemming from asbestos fibers. Our NTP program listed asbestos as a carcinogen in 1980 and did some of the early pioneering toxicology work.” Along with ongoing support for research, he noted, in 2009, NIEHS sponsored a state of the science workshop on asbestos and related fibers (see story).

In an update on NTP’s ongoing research on the health effects of fibers, Masten and Stout reported on the comprehensive NTP naturally occurring asbestos and related mineral fibers program, triggered by nominations from the U.S. Environmental Protection Agency (EPA) and the U.S. Centers for Disease Control and Prevention (CDC) in 2006. The agencies cited widespread community exposures, insufficient toxicity data, and a need to better understand the influence of mineralogy and morphology on toxicity.

Efforts are currently underway to identify and procure suitable natural mineral fiber samples of amosite, Libby amphibole, and possibly erionite, as well as complete detailed physical and chemical characterizations, to be used as the basis for proceeding to short-term in vivo toxicity and biopersistence studies, and chronic toxicity and carcinogenicity studies. According to Stout, one of the first important questions to answer involves the dose-response characterization for the fibers, both inside the respiratory tract and in other organs.

Erionite — another mineral fiber of concern

Concerns about erionite, Miller explained, date back to epidemiological studies in the Cappadocian Region of Turkey that inspired animal toxicity studies and in vitro experiments leading to findings by the World Health Organization and the NTP branding the mineral a known human carcinogen. With the discovery of erionite in the cap rock of the Killdeer Mountains in North Dakota in the mid-2000s, concern among U.S. scientists has increased exponentially (see related story ).

Miller reported on investigations of erionite in Turkish villages with high rates of mesothelioma compared to N.D. This work showed similarity of the physical and chemical properties of the erionite at both locations and ongoing exposures of concern in N.D. (see story and study ). He pointed to the identification of additional erionite deposits in the western U.S., the emergence of cases of erionite-related mesothelioma in North America, and the possibility that other mineral fibers in the zeolite group may also be a public health concern.

Nano — manmade fibers that may act like asbestos

Following a report by NIOSH industrial hygienist Ralph Zumwalde, Weis reported on NIEHS activities in the area of nanotechnology environmental health and safety. As he explained, the initiatives have four primary goals:

  • Understand engineered nanomaterials (ENM) biological actions
  • Identify methods to quantify exposure in diverse matrices
  • Develop predictive models for health effects assessment
  • Guide development of second generation ENMs with minimal adverse biological and health effects

“There are so many parallels here with particle and fiber toxicology,” Weis said about the urgency of research on ENMs, which is being conducted by the three research divisions of NIEHS/NTP.

Additional interagency representatives presenting at the meeting included:

  • CDC Agency for Toxic Substances and Disease Registry — Vik Kapil, D.O., and Vinicius Antao, M.D., Ph.D.
  • CDC NIOSH — Martin Harper, Ph.D., and Patricia Sullivan, Sc.D.
  • U.S. Consumer Product Safety Commission — Kris Hatlelid, Ph.D.
  • Mine Safety and Health Administration — Chris Findlay
  • Occupational Safety and Health Administration — Dan Crane
  • EPA — Helen Dawson, Ph.D., Philip Cook, Ph.D., Stephen Gavett, Ph.D., David Berry, Ph.D., Danielle DeVoney, Ph.D., Ann Strickland, J.D., and Phillip King
  • U.S. Food and Drug Administration (FDA) — Steven Wolfgang, Ph.D.
  • U.S. Geological Survey (USGS) — Greg Meeker

In addition to NTP research programs, ongoing topics of discussion included: 1) standardization of terminology; 2) activities concerning Libby, Mont., and other EPA Superfund sites; 3) availability of research materials; 4) EPA clarification that the Alternative Asbestos Control Method is not approved; 5) fiber mesothelioma potency related to fiber surface area; 6) fluidized bed method for asbestos contaminated soils; and 7) concern of the widespread use of Libby-derived vermiculite in U.S. and Canadian schools and homes.

Along with erionite and nanomaterials, new topics for discussion included FDA concerns about asbestos-contaminated talc and clinical issues in asbestos-related disease, including lung cancer screening with CT scans, use of digital imaging versus plain films for B-reading, and recent changes in diagnostic criteria for asbestosis by the College of American Pathologists that are not consistent with previous guidelines nor scientifically supported or justified.

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