K&L Gates : Newsstand : Revising the U.S. Asbestos Hazard Risk Assessment Model: EPA’s Ongoing Efforts to Modernize its Outdated 1986 Model to Reflect Current Scientific Understandings About the Actual Hazards Associated with Asbestos

Revising the U.S. Asbestos Hazard Risk Assessment Model: EPA’s Ongoing Efforts to Modernize its Outdated 1986 Model to Reflect Current Scientific Understandings About the Actual Hazards Associated with Asbestos
Environmental/Toxic Tort Alert

by John F. Spinello, Chris M. Temple . December 4, 2008

The United States Environmental Protection Agency (“EPA”) is in the midst of updating its asbestos risk assessment method. To date, the EPA’s approach to assessing disease risk from asbestos exposures drew no distinctions among fiber types or fiber sizes despite the fact that scientific literature has established potency differences based primarily on these factors. Driven by concerns over establishing scientifically correct risk assessment models in connection with the asbestos remediation work in Libby, Montana, the EPA’s Office of Solid Waste and Emergency Response (“OSWER”) asked EPA’s Science Advisory Board (“SAB”) to consider a new proposed approach for assessing cancer potency factors for exposure to asbestos premised upon differences in cancer potency of different mineral types and fiber sizes.

The SAB Asbestos Committee met for two days in July 2008 to discuss and to debate the proposal. On November 14, 2008, the SAB Asbestos Committee issued a report on EPA’s Proposed Approach for Estimation of Bin-Specific Cancer Potency Factor for Inhalation Exposure to Asbestos (“Report”). The Report summarizes and supplements the observations and recommendations offered during the two-day session in July 2008. This Alert outlines key conclusions of the Report and its potential implication for changes in asbestos risk assessment.

The cover letter transmitting the Report makes it clear that a “group consensus was not sought for (this) consultation.” As a result, the Report does not expressly present a consensus view on any subject, including threshold questions about differences in cancer potency of different mineral types and particle dimensions. Rather, the Report presents a collection of comments on OSWER’s proposed risk assessment model. Nevertheless, the following major themes emerge from these comments:

Chrysotile poses substantially less risk of mesothelioma than amphibole asbestos.
Differences in potency between mineral types have been observed, but are less established with respect to lung cancer.
Different fiber dimensions may present significantly different risks, especially for lung cancer, but additional research and integration of existing data is needed.
Biopersistence or clearance behavior appears to be a substantial factor bearing upon cancer potency and should be considered in risk assessment models.
The role of hereditary susceptibility and the effect of smoking is material and should be considered in risk assessment models.
The scientific basis outlined by OSWER in support of its Proposed Model is weak and inadequate.

Background
Asbestos fibers come in a range of sizes and types. The three asbestos mineral types most commonly used commercially in the United States were amosite, crocidolite, and chrysotile. Although some scientists opine that all asbestos fiber types cause all forms of asbestos-related disease (i.e., asbestosis, lung cancer, and mesothelioma), a substantial and growing body of recent studies have concluded that chrysotile is less capable of producing mesothelioma than amosite or crocidolite.

When assessing asbestos-related health risks (something EPA must do when, for example, its personnel work at a Superfund site), EPA relies on a risk assessment model completed in 1986. The 1986 model considers all asbestos mineral types and all asbestos fibers greater than five microns in length to be equally capable of causing mesothelioma and lung cancer. Since 1986, certain studies have found toxicity differences among the asbestos mineral types and among fibers of various sizes. EPA’s model, however, has not been updated to reflect the findings and conclusions of these studies.

From approximately 1999 to 2003, Dr. Wayne Berman and Dr. Ken Crump reviewed the 1986 EPA asbestos risk assessment model and prepared a different model they contend accounts for fiber type and size differences. The two scientists were retained by OWSER. In their final draft report to EPA, Berman & Crump concluded chrysotile is approximately 800 times less capable of causing mesothelioma than amosite or crocidolite. Their data have been argued to support the hypothesis that one cannot experience enough chrysotile exposure in a lifetime to cause mesothelioma. Other recent studies have reached similar conclusions, but neither the Berman & Crump report nor other studies with similar conclusions has been recognized or adopted by the EPA.

OSWER’s Proposed Approach for Estimation of Bin-Specific Cancer Potency Factors for Inhalation Exposure to Asbestos
In 2007, the SAB formed its Asbestos Committee with a broad mission to provide advice to EPA on the scientific aspects of various types of asbestos exposure. EPA estimates the Asbestos Committee’s mission will unfold over approximately three years. As its initial task, the Asbestos Committee was asked to review and comment on the Proposed Approach for Estimation of Bin-Specific Cancer Potency Factors for Inhalation Exposure to Asbestos (“Proposed Approach”) recently developed by OSWER. The Proposed Approach, which draws on Berman & Crump’s work, was prepared for OSWER by an outside consulting group, the Syracuse Research Corporation in 2008. The Proposed Approach deviates from EPA’s 1986 model by accounting for fiber type and size in risk assessment. In contrast to the 1986 model, the Proposed Approach attempts to develop different “bins” of asbestos exposure reflecting different levels of risk (for instance, a short-fiber amphibole bin versus a short-fiber chrysotile bin).

The first question the Asbestos Committee was asked to answer in reviewing OSWER’s Proposed Approach is indicative of EPA’s larger concerns and goals in forming the Committee and was posed by OSWER as follows:

The proposed approach is based on the hypothesis that there may be significant difference in potency for lung cancer and/or mesothelioma as a function of asbestos mineral type and particle dimensions.

Do you agree that the data are sufficient to indicate that such differences may exist and that an effort of this type is warranted?

The Asbestos Committee discussed OSWER’s Proposed Approach during a two-day public session conducted on July 21 and 22, 2008, in Washington, D.C. On November 14, 2008, the Asbestos Committee issued its Report. The Report generally parallels the comments Asbestos Committee members offered during the public discussion in July. In general, the Asbestos Committee agreed with OSWER that there appears to be significant differences in cancer potency based upon mineral type and particle size, but concluded OSWER’s Proposed Approach did not adequately present or consider a number of critical factors which the Committee found wanting. Indeed, the Asbestos Committee concluded that the Approach suffered from a number of fatal deficiencies.

The Science Advisory Board Asbestos Committee Report
The Report begins by framing the background and the Asbestos Committee’s task as follows:

The EPA’s current method for quantifying cancer risk from asbestos inhalation exposure utilizes measurements based upon phase contrast microscopy. The current method uses published epidemiologic studies of miners and manufacturing workers to select empirical risk models to derive cancer potency factors for lung cancer and mesothelioma.
To address the potential limitations of EPA’s 1986 method, OSWER proposed an interim approach to account for potential differences of cancer potency between mineral groups and fiber size distributions.
The new proposal would establish a multi-bin mathematical model to estimate cancer risk according to mineral groups (amphibole and chrysotile) and measurements of particle dimensions (length and width) based on transmission electron microscopy (TEM).

In a brief cover letter transmitting the Report, the Asbestos Committee’s Chair, Dr. Agnes Kane, states that a “group consensus was not sought for (this) consultation.” Rather, the Report presents a collection of comments on OSWER’s Proposed Approach. Most comments generally support OSWER’s objective, hypothesis and conclusion – that there are demonstrated differences in potency based on mineral type and fiber size and EPA should develop a better, more scientifically-based risk assessment method that recognizes these differences. The Report, however, sharply criticizes OSWER’s Proposed Approach as lacking adequate support.

Dr. Kane’s cover letter states, “[T]he Committee would like to underscore major conclusions that emerged from this consultation,” and continues as follows:

“The general view of the Committee was there is sufficient evidence to support the need for the Agency’s effort in developing risk assessment method(s) to account for potential differences in risk on the basis of mineral type and size characteristics of asbestos. There were divergent views regarding whether an effort of this type is warranted at this time. The Committee, however, generally agreed that the scientific basis as laid out in (OSWER’s proposed method) is weak and inadequate. A primary concern is the lack of available data to estimate the TEM specific levels of exposure for the epidemiological studies utilized in this analysis. The Committee also found that the document was woefully inadequate with respect to the representation of available information on epidemiology, toxicology, mechanism of action and susceptibility.”

This is the only passage in the Report or cover letter that expressly presents (or purports to present) the position of the Committee as a whole. As a result, it is unclear how much the Report alone will influence the course of the larger scientific debate about differences in the cancer potency of different asbestos minerals and fiber sizes. However, the Report suggests changes to the 1986 risk assessment model to account for potency differences of different mineral types and sizes are inevitable; those changes to the 1986 model are likely to have implications, not only for how EPA assesses asbestos inhalation risk at Superfund sites, but also for asbestos products liability/toxic tort litigation.

In summary, the Report appears to reflect a recognition that amphibole asbestos presents a markedly greater risk of mesothelioma than chrysotile. Some reviewers note the difference in potency between mineral types is less established with respect to lung cancer. Moreover, most reviewers appear to recognize that differences in fiber dimensions may also present significantly different risks, especially for lung cancer, but believe additional data and analysis are needed. Several reviewers note the significant role of biopersistence or clearance behavior in risk assessment. Some reviewers also commented on the role of hereditary susceptibility and the effect of smoking that should be considered in risk assessment models.

What Next?
Comments provided by the Asbestos Committee generally urge OSWER to consider a wide range of additional information to better support its Proposed Approach or to develop an alternative, including the results of animal studies and research that is still underway. Some reviewers suggested that OSWER take no interim action at this time, but instead focus its attention on longer term efforts to update EPA agency-wide asbestos risk assessment models. OSWER, however, is facing near term decisions requiring asbestos risk assessments at several Superfund sites, including at Libby, Montana, where differences in cancer potency among different mineral types and fiber sizes present in Libby has been the subject of intense public discussion and debate. Accordingly, OSWER is likely to take some near term, interim action to update asbestos risk assessments to address these differences so it is able to make more accurate and justifiable risk assessments at Libby and other Superfund sites.

Consequently, OSWER may, among other steps, refer this Report to EPA’s Science Policy Council for recommendations on how to proceed. In 1986, EPA established the Risk Assessment Council (“RAC”), the Science Policy Council’s predecessor, to oversee virtually all aspects of the Agency’s risk assessment process. The Science Policy Council was established in 1993 with a broader mission and a goal of integrating policies that guide Agency decision-makers in their use of scientific and technical information. For example, the Science Policy Council works to implement initiatives recommended by external advisory bodies such as the National Research Council and the Science Advisory Board.

As part of its global and national environmental and asbestos litigation defense practices, K&L Gates closely monitors developments within the regulatory communities, particularly as it relates to the ongoing study and modification of science’s understandings with respect to the propensity of certain types, forms, and quantities of asbestos fibers to cause illness or disease. K&L Gates will continue to follow the work of the EPA and its various scientific bodies as it seeks to modernize its outdated 1986 asbestos risk assessment with the conclusion of the current literature. In addition, K&L Gates stands ready to address industry’s concerns about the possible impacts and influences these proposed risk assessment modifications will present in the environmental regulatory compliance and remediation fields, as well as in the burgeoning asbestos litigation system.

Contacts:
John F. Spinello, +1.973.848.4061, john.spinello@klgates.com
Chris M. Temple, +1.412.355.6343, chris.temple@klgates.com

This publication/newsletter is for informational purposes and does not contain or convey legal advice. The information herein should not be used or relied upon in regard to any particular facts or circumstances without first consulting a lawyer.