One Fiber: Why Recent Rulings and Studies May Revive the Asbestos Policy Debate

One Fiber: Why Recent Rulings and Studies May Revive the Asbestos Policy Debate

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  • 2:28PM Jul 30, 2012
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In a recent Pennsylvania Supreme Court ruling on the asbestos toxic tort case Betz v Pneumo Abex LLC, an expert witness simultaneously claimed that asbestos disease is dose dependent and that the inhalation of a single asbestos fiber can cause disease1. The court rejected these contradictory points and stated that use of the single fiber argument cannot be used in lieu of providing actual evidence to quantify exposure and dose. This ruling is significant because it may require future toxic tort cases to provide preliminary evidence of dose, before a trial can occur, thereby reducing the number of unsubstantiated claims.

The Betz v Pneumo Abex LLC case refocuses attention on debates surrounding the toxicity of asbestos and its subsequent regulation. Current asbestos risk models and regulations originated in the 1970s, soon after the Occupational Safety and Health Administration (OSHA) was created2.

Sieving building in Bolivian cement plant
Photograph taken in the sieving building of the Bolivian cement plant showing the dusty nature (about 1000f/ml) of the operation.

During that time, asbestos knowledge was evolving. OSHA moved away from relying on total dust particle counts to estimate exposure and began counting only the number of fibers assumed to be asbestos under phase contrast microscopy (PCM) 2,3. While PCM is an improvement over total dust particle counts, it is a limited method for identifying asbestos fibers, and cannot detect all fibers smaller than 0.25 micrometers in diameter3,4. Further, attempting to convert historical worker exposure data from total dust particle counts in millions of particles per cubic foot to fibers per cubic centimeter only provides rough estimates, at best. As a result of these limitations, the risk models developed in the 70s, and still in use today, are inherently uncertain. Now that sophisticated analytical tools like transmission electron microscopy (TEM) are more widely accessible, it is feasible to detect fibers <0.25 micrometers and then use electron diffraction and energy-dispersive spectroscopy (EDS) to provide information about crystal structure and elemental composition to identify the mineral5. These additional data make it possible to re-evaluate risk and glean new insights about asbestos fibers and their correlation to epidemiological findings.

Sample of fibers from Bolivian plant under SEM
Samples collected during the sieving operation at the Bolivian cement plant were overloaded with fibers. We employed an indirect preparation procedure and analyzed by scanning electron microscopy to obtain qualitative results that suggest concentrations were on the order of 500-1000 f/ml.

In an effort to learn more about the shortcomings of historical analytical methods and their impact on risk models, Van Orden et al. conducted an industrial hygiene study at a Bolivian cement tile plant that used both optical and TEM measurements3,5. Until now, no study has employed modern collection and analytical techniques to assess airborne asbestos in settings comparable to historical workplaces prior to dust controls and occupational exposure regulations5. In the Bolivian study, TEM results found 100-1000 fibers/cc in air samples at the crocidolite processing plant5. Compare these exposures to a similarly uncontrolled cement plant study from 1948-1952 where asbestos fiber counts were estimated at 8-40 f/cc6, and the disparity between actual and estimated historical data becomes apparent. Given the extreme exposure to crocidolite at the Bolivian plant, workers would expect a high incidence of mesothelioma according to the US and World Health Organization’s (WHO) recommended level of 0.1 f/cc3. Yet, in nearly 60 years of operation, none of the plant’s workers has reportedly suffered from asbestos-related disease7 in sharp contrast to studies of Australian crocidolite where mesothelioma levels were elevated8. These findings resurrect several arguments:

  1. Advanced analytical techniques should be used to re-inform asbestos policy5.
  2. If occupational exposures were underestimated in previous epidemiology studies, then an overestimation of risk occurs when extrapolating to everyday, ambient exposures.
  3. The correlation between fiber dimension and pathogenicity is not accounted for in current risk models and regulations5,9.

These studies provide additional evidence that any exposure to asbestos does not necessarily translate to an adverse epidemiological response.

Though the Betz v Pneumo Abex LLC case marks the court’s recognition that possible asbestos exposure without substantive dose is not proof of causation in toxic tort cases, we are long overdue to incorporate modern scientific insights into asbestos risk analyses and policy. A review of how and why asbestos became regulated, and the scientific developments that occurred simultaneously, may lead to better insights that inform future policy.

For an in-depth review of the historical developments in science, industry, and policy that have influenced asbestos regulations, schedule a consultation with one of our experts at 1.855.275.7554.


1Betz v Pneumo Abex LLC., 38 WAP 2010.

2Occupational Safety and Health Administration (OSHA). 1971. Federal Register. 29 CFR 1910.93a. 36(235):35-37.

3Van Orden, D. R., Lee, R. J., Sanchez, M.S., Zock, M.D., Ilgren, E. B., Kamiya, Y. 2012. “Evaluation of Airborne Crocidolite Fibers at an Asbestos-Cement Plant.” Annals of Respiratory Medicine.

4Agency for Toxic Substances and Disease Registry. 2001. Toxicological profile for asbestos (update). Atlanta: U.S. Department of Health and Human Services. i-327.

5Van Orden, D. R., Lee, R. J., Sanchez, M.S., Zock, M.D. 2012. “The Size Distribution of Airborne Bolivian Crocidolite Fibers.” Annals of Respiratory Medicine.

6 Nicholson, W.J. 1986. “Airborne Asbestos Health Assessment Update.” Environmental Protection Agency. EPA/600/8-84/003F.

7Ilgren, E., Ramirez, R., Carlos, E., Fernandez, P., Guardia, R., Dalenz, J., Kamiya, Y., Hoskins, J. 2012. “Fiber Width as a Determinant of Mesothelioma Induction and Threshold—Bolivian Crocidolite: Epidemiological Evidence from Bolivia—Mesothelioma Demography and Exposure Pathways.” Annals of Respiratory Medicine.

8Shedd, K.B. 1985. “Fiber Dimensions of Crocidolites from Western Australia, Bolivia, and the Cape and Transvaal Provinces of South Africa.” US Department of the Interior, Bureau of Mines Report of Investigations. RI 8998.1-33.

9Berman,D.W., Crump, K.S. 2008. “A Meta-Analysis of Asbestos-Related Cancer Risk That Addresses Fiber Size and Mineral Type.” Critical Reviews in Toxicology. 38(S1):49-73.