Letters to the Editor.

Dear Editor:

The subject of this letter is the article "When Science Crosses Politics, I: The Case of Naturally Occurring Asbestos," by Rebecca Berg, which appeared in the June 2004 issue of the Journal.

Until my retirement in December 2004, I was the senior environmental scientist for the U.S. Environmental Protection Agency's (U.S. EPA's) Superfund program and was responsible for the development of risk assessment and field sampling methods, and analytical requirements necessary to measure naturally occurring asbestos (NOA) in Superfund cleanup sites.

Concerning the question of exposure discussed in the article, I want to point out a new technique that is under development by U.S. EPA's headquarters and regional scientists. The technique called activity-based scenarios (ABS) is designed to measure and quantify the release of asbestos fibers from the soils. The measure and quantification of such releases remains one of the most difficult problems for assessing risk from asbestos. Much of U.S. EPA's data expressing this relationship was developed in the high-growth area of El Dorado County, where there are high levels of NOA that are prone to release. Other data sources included sites in Oregon, Washington State, Michigan, and Libby, Montana.

U.S. EPA chose scenarios that represented typical activities that residents and visitors would perform and that included playing sports, gardening, and young children's activities. Personal monitors were worn by U.S. EPA staff dressed in appropriate protective clothing. Total exposures from the activity-based exercises were determined from the personal monitoring data. Risk calculations were then made based upon measured exposures from the activity-based exercises. There are several technical problems that still need to be resolved, but this technique is the most promising. The article infers that grass is a reasonable cover and will minimize the release of asbestos fibers. This isn't the case, as early data using the ABS technique show that asbestos fibers will be released into the air and are potentially available for inhalation by the local residents.

The article also raises questions concerning U.S. EPA's 1 percent action level. My former Superfund office (OSRTI) revised this policy in August 2004. Superfund sites that have asbestos (NOA or waste product) are required to base cleanups on a risk assessment.

The article also raised issues on sampling protocols, particularly on the aspect ratio of fibers. In reality recognizing the aspect ratio is only one part of the sampling and analytical problems. U.S. EPA held a national meeting on asbestos site cleanup practices in December 2004, and one of the outcomes was to agree on a standard method of identifying and recording data. This method should soon be released and used nationally for collecting asbestos data. We expect that the method will eliminate the misapplication of collected data because while aspect ratios are a part of determining the biological activity of a fiber, they are not the only measurement necessary.

In February 2003, U.S. EPA sponsored the "Workshop to Discuss a Proposed Protocol to Assess Asbestos Related Risk." The meeting's panel comprised nationally recognized experts in asbestos toxicity. In its report, the panel agreed that the amphibole was likely to be more toxic than chrysotile and that fiber sizes of 0.5-1.5 microns and longer than 5 microns were the most biologically active. Notably, the panel didn't say that fibers less than 5 microns represented no risk, only that the data for quantifying the risk were not yet available. The report from this workshop also indicated that epidemiological and pathological data demonstrate that mesothelioma is related to amphibole asbestos exposure. Variability in the finding depends on the population size and time period covered; occupations with heavy amphibole asbestos exposure have the highest percentage of mesothelioma (often this includes relatives of those primarily exposed to the amphibole asbestos). The panel stated that there was sufficient information to conclude that amphibole fibers have a greater potential for causing mesothelioma and are more toxic than chrysotile. The major concern with mesothelioma that seems to been overlooked in the article is that mesothelioma has a long latency period; exposures that occur at a young age will begin to develop into frank disease between age 30 and 40. Therefore, exposure that occurred as a result of activities to a young person will begin to develop into disease at age 40 or later. This is a serious risk area that simply cannot be overlooked. Clearly, then, the reasonably conservative view would be to regard any amphibole exposure as potentially carcinogenic until data to the contrary become available.

One final point to make concerning U.S. EPA's efforts is the development of a new slope factor that integrates the amphibole risk with the existing IRIS slope factor values and updated mortality information. These data and methodology for assessing the new values were also discussed at the December 2004 national meeting. U.S. EPA is now reviewing all the supporting information, and the method ought to be available for use by regulators in establishing reasonable risk parameters once the reports from this meeting are released.

Sincerely,

Richard Troast

Retired Senior Scientist, Office of Superfund Remediation and Technology Innovation, U.S. EPA

Currently Ph.D. Candidate, Environmental Science and Policy, George Mason University, Fairfax, Virginia 

Editor's note: The current staff at U.S. EPA's Office of Superfund Remediation and Technology Innovation were invited to review the discussion of U.S. EPA's positions and activities presented in the above letter, but declined to comment.

Rebecca Berg responds:

I thank Mr. Troast for sharing news of the latest developments with respect to naturally occurring asbestos. There is much valuable information in his letter, and some of the steps he reports on are of precisely the type that several parties I interviewed for the article were calling for. It seems that substantial progress is being made on the issue.

Mr. Troast's statement about the inadequacy of a grass covering to protect people from exposure, however, raises a point about which JEH has found U.S. EPA's thinking to be fairly complex. Last June, the agency published a list of questions and answers based on a meeting held with concerned residents. This document does warn that activities such as "dry-sweeping" or "leaf-blowing" are not recommended in any area with naturally occurring asbestos, even if there is a grass covering (U.S. EPA Region IX, 2004, p. 20). In the same document, however, U.S. EPA provides concerned parents with the following advice: "If your children are playing on bare soil that might contain asbestos, it would be prudent to provide a barrier such as landscape materials or grass, to prevent contact with the soil" (U.S. EPA Region IX, 2004, p. 6). This advice seems to suggest that if grass does not guarantee safety in every activity, it is at least preferable to bare soil.

If activity-based monitoring techniques have now found that exposure is associated with activities other than "dry-sweeping" and "leaf-blowing" in grassy areas, the question arises of what warnings should be issued to parents and how they should be told to mitigate bare soil.

Mr. Troast points out that the latency period for mesothelioma is an important part of the picture, and he is quite right to do so. He is, however, quite mistaken in saying that this issue was "overlooked" in my article. It was raised--emphatically so--as an answer to an argument frequently made by those skeptical about the extent of the hazard, namely that there is no epidemiological evidence of a problem (the notorious and discredited "Where are the dead bodies?" argument). Indeed JEH cited a U.S. EPA spokesperson to this effect:

     "One thing we are fairly certain of is that there won't be any
     [epidemiological] evidence ... for quite some time." He points to
     the long incubation period for mesothelioma.

The point was reinforced with a statement from a local public health official to the same effect:

     "What's not understood .... is that we're dealing with a very rare
     disease that takes 30 years to develop ...."

And again, for good measure, this time from an academic expert:

     "If we have to wait for cancers to occur in order to say there's a
     hazard, ... it's too late."

Although the term "latency" does not appear explicitly in these quotations, I believe that most readers will recognize the concept being invoked.

Reference

U.S. EPA Region IX. (June 8, 2004). Naturally occurring asbestos in El Dorado Hills: Questions and answers. http://www.epa.gov/region09/toxic/noa/noa-qa-061404.pdf (11 Mar. 2005).