Sunday, April 12, 2015

OELs and Politics

I often stated that I believe that the setting of Occupational Exposure Limits is a political process; however, just as important as the politics, it is a process that needs to be informed by science.   This fact came into sharp focus for me when I read a recent article in this month’s (April 2015) issue of The Synergist (a publication of the American Industrial Hygiene Association).    The articles is entitled “ABCs and Asbestos Risk Assessment” by Dr. Frank Mirer.   Frank walks us through the available science and provides his conclusions concerning the potential for less risk from chrysotile asbestos than for other forms of this mineral.   Within this article Frank reviews a controversial analysis and conclusion presented to the EPA’s Science Advisory Board by Drs. Crump and Berman.   Dr. Mirer referred to them as contractors who presumably were supported by the asbestos industry.   

Drs. Crump and Berman concluded that:
 “The best estimates of the potency of chrysotile (for mesothelioma) ranged from zero only up to 1/200th of the potency of amphibole asbestos… Furthermore, the hypothesis that chrysotile does not cause mesothelioma could not be rejected in any analysis that allowed at least some amphibole contamination in the locations where exposures were principally to chrysotile…(F)or lung cancer … the best estimates of the potency of chrysotile were at least six-fold smaller than the corresponding estimates for amphibole asbestos.” 
I strongly recommend that you obtain and read the article by Frank where he outlines and presents the reasons for his primary conclusion; namely, that even if chrysotile is somewhat less potent than amphibole, a significant risk of cancer remains at the current OSHA PEL.   He also concludes that the link between chrysotile and mesothelioma has not been broken.   Reportedly, most SAB members agree with him.

For me this discussion really brings home the fact that the exposure limit setting process is, at its heart, political.   We cannot ban everything that is toxic.  However, there may be a reasonable argument for banning asbestos given our current state of control and assessment technology. 

I think it is very healthy for the process that accomplished and capable technologists like Drs. Crump and Berman present these arguments in the service of economic interests just as long as their intellectual treatments and suppositions are completely open properly vetted.   My sense is that this happened in this case.

It may be entirely possible that chrysotile does not cause mesothelioma in humans.  From what I can determine, it simply has not been satisfactorily proven in the context of a reasonably precautionary approach.   Perhaps one day we will have tools that allow it to be proven to a reasonable scientific and political certainty, until then we default to considering it to be a cause of this dreaded and invariably fatal disease.

Although many of our politicians have not acquitted themselves well of late, politics per se is not a dirty word.  It should be a noble endeavor that is ideally how democracies are supposed to settle questions of the general public good.   Indeed, given the uncertainty that we are constantly facing in the realm of human risk assessment, there are many issues that cannot be answered with certainty but that must be decided.   We cannot force all exposures and risks from chemicals to zero; however, we can attempt to estimate, limit and equitably balance allowable exposure (i.e., exposure limits) with the benefits derived from these exposures.  I believe that to ensure the integrity of the process, we need to do this while also admitting the limits of our scientific knowledge and the inevitable fact that our knowledge will get better with time


  1. ERATA: This is an email from Frank Mirer correcting my mistake in thinking that Drs. Crump and Berman were contractors for industry.


    Regarding the asbestos piece. First, thanks for noticing it and your thoughtful comments.

    Second, more important, when I wrote that Kenny Crump was a “contractor,” I had intended to convey that he was an EPA contractor, not writing a study for management. Can you correct this? This support is disclosed in one of the papers (although the authors do disclose support from a management group as well). In recent years, EPA has commissioned scientific documents of this type which were subsequently published in peer reviewed journals. Kenny Crump co-authored a commentary on formaldehyde for EPA which was helpful to the precautionary side, and which was (in my opinion) validated by recent new knowledge. In the asbestos case, increased risk estimates for amphiboles would support lower tolerances for Libby asbestos, which would be precautionary for Libby and which was EPA’s main concern.

    [Can you include the above in your next post, and, if you have an email, forward it to Kenny. Thanks.]

  2. When Chrysotile fibres are attacked by acids the magnesium ions are dissolved, leaving a silica skeleton. The products would be magnesium iodide, water and silica but don't ask me for the equation.

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