Larry J. Elliott - 4 April 30, 2001

These comments are brief, and I would be happy to expand on them in much more detail if
needed. There is a substantial body of literature on the topics of probability of causation, the
linear-no-threshold model, and dose reconstruction. The Advisory Board on Radiation and
Worker Health will need to review and be familiar with this body of literature as it prepares to
address the guidelines and regulations associated with the Energy Employees Occupational
Illness Compensation Act.

Thank you for the opportunity to provide these comments. They represent my personal views,
and none of the statements herein are endorsed by or represent the positions of Purdue University
or its officers.

Sincerely,

Paul L. Ziemer, Ph.D., CHP
Professor Emeritus

School of Health Sciences
Purdue University


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PURDUE UNIVERSITY

SCHOOL OF
HEALTH SCIENCES

April 30, 2001

Larry J. Elliott, MSPH, CIH

Acting Director, Office of Compensation Analysis and Support
National Institute of Occupational Safety and Health

Robert A. Taft Laboratories

4676 Columbia Parkway

Cincinnati, OH 45226-1998

Dear Mr. Elliott:

In response to your letter of April 6, 2001, I am pleased to provide some comments relating to
the responsibilities of the Advisory Board on Radiation and Worker Health. In doing so, I must
emphasize that my comments are very preliminary in nature and are made in the absence of
complete information pertaining to the subject.

1. Concerning the promulgation of regulations for use by the Department of Labor and by
NIOSH:

¢ The “probability of causation” issue, while conceptually sound, has some
serious aspects and pitfalls that must be addressed. Development of
probability of causation values is very dependent on the dose-effect model(s)
used and upon the assumptions made concerning the role of radiation as a
cancer-causing or cancer-promoting agent. Use of this approach requires a
careful evaluation of both the reliability of and variations in risk coefficients
for development of cancer due to radiation exposure. In addition, risks for
other carcinogenic agents, and for natural causes for the particular individual
must be taken into account. Among the current issues for which there is not
agreement in scientific circles is the matter of the “linear-no-threshold” (LNT)
model on the dose-effect relationship. The issue of whether or not there is a
threshold dose below which there is no effect is critical tothe matter. It is not
an issue that is likely to be resolved by epidemiological studies, nor is it likely
to be resolved within the time frame of iniplementation of the current
regulations. It should also be noted that the idea of attributing cancer solely to

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Larry J. Elliott

2 April 30, 2001

radiation exposure in the absence of information on other exposures to
carcinogenic agents that the individual has incurred would be inappropriate.
Other agents that would have to be considered and addressed include

= Cigarette smoking

= Chemical carcinogens

= Biohazards

= Natural radioactivity and radiation (e.g., radon gas)

A key issue that must be addressed is finding a fair way of sorting valid
claims from invalid claims. Basically this is the matter of a claimant being
able to show that it is more likely than not that his/her health effect was
caused by radiation. A probability of causation (PC) value below 0.5 implies
that is more likely than not that an effect was not caused by radiation. Thus,
use of PC values below 0.5 to establish compensation must rely completely on
hypothetical models to calculate odds for low doses at which effects have not
been actually observed experimentally. From a legal point of view it would
probably be better to use relative risk (RR) as the tool for establishing a claim.
RR has already been used successfully in the case law of many courts. It
requires a determination of the dose to the individual and a determination of
the scientifically observed RR for individuals who have received that dose. If
the RR is greater than 2.0, then it is more likely than not that the health effect
was caused by the agent in question (radiation).

Dose reconstruction, although critical to the assignment of past doses, is
inherently an inexact science. It is vary dependent on the mathematical
models and assumptions used and is thus subject to great uncertainties.
Indeed, it would not be surprising for the uncertainties to be as great as an
order of magnitude in some cases. Finding an appropriate approach for
addressing this uncertainty in the regulatory framework will be challenge. In
Great Britain, where a probability of causation scheme is used to reimburse
for radiation-linked diseases, “generosity factors” factors are used to account
for such uncertainties. These are generally applied in a manner that will favor
the claimants.

2. Estimation of doses incurred by individual claimants.

Claimants who have been monitored in the past (e.g., radiation workers) can
be expected to have doses that are known to within about + 20%, depending
on the exposure conditions involved. For individuals for whom doses are
reconstructed from secondary information, the uncertainties will undoubtedly
be much greater as suggested in item 1, above. In either case, it will be

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Larry J. Elliott

3 April 30, 2001

important to identify and estimate the uncertainties when assigning individual
dose values.

The estimation of doses through dose reconstruction methods has been
evolving over several years. For certain scenarios, there are well-accepted
models that can be applied, and these should be used consistently whenever
possible. In general it will be important to identify and standardize the
methodologies that will be used to carry out dose reconstructions at various
facilities and locations.

Since dose reconstruction models typically are based on standard assumptions
concerning personal characteristics and eating habits, adjustments may need to
be made when applying the models to specific individuals for purposes of
estimating dose.

3. Establishing a process to decide whether additional classes of workers should be

included:

In item 1, above, I indicated that there indeed could be other agents in the
workplace that could adversely impact on worker health. One’example is
beryllium, exposure to which has already been identified and is being dealt
with legislatively. Because the cause-effect issues of this agent are clear-cut,
it is one that can be addressed in a straightforward manner. Unfortunately,
most other chemical, physical, biological, and radiological agents do not
present such clear relationships, especially at low doses. Long-term dose-
effect responses are not always well known, and the associated health effects
are often difficult to distinguish from normal background effects or normal
incidence rates. Unless there are cases similar to the beryllium case where the
dose-effect responses are clear, it would seem to be premature to add
additional classes of workers at this time.

Epidemiological studies and occupational health surveillance should be
emphasized and supported in cases where suspect agents are in use. Decisions
on adding additional worker classes must be based on scientific evidence and
not on speculation. The National Occupational Health Agenda (NORA)
might be a potential route for identifying worker classes that are experiencing
elevated rates of long-term health effects. Appropriate studies on these groups
could then be directed toward isolating and identifying potential associations
with suspect agents. .