Public Health Assessment Work Group
Meeting Minutes
July 15, 2002
Attendance
ORRHES Members attending:
Bob Craig, Kowetha Davidson, David Johnson, Susan Kaplan, James F. Lewis,
LC Manley
Public Members attending:
Iulian Apostoaei, Gordon Blaylock, Walter Coin, Al Brooks, David Fields,
Melissa Fish, Timothy Joseph, Mike Knapp
ATSDR staff attending:
Karl Markiewiez (phone), Bill Murray
Agenda
The purpose of the meeting it to have the PHAWG members finalize a set
of comments (questions, issuesm concerns, etc.) on:
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The draft ATSDR radiation screening for the Work Group to submit
to ATSDR from the Work Group. A primary issue is the screening value
selected
(5 rem) and that rationale for selecting the value. ATSDR staff will
respond to these comments.
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The I-131 presentation by Kowetha Davidson for the Work Group to
submit to her from the Work Group. A primary isse is wheter dose or
risk should
be used in the health assessment. Dr. Davidson will respond to these
comments
Issue #1: Minutes
Discussion of June 3, 2002, minutes. Members will mark up the minutes
and submit them to Bill Murray by July 19, 2002, for revision.
Issue #2 Draft ATSDR radiation screening document
Paul Charp (ATSDR) is recommending that we remain with the
screening level of 0.71 millisieverts (mSv) {71 millirem (mrem)}, and
a lifetime dose of 50 mSv (5 rem).
Bill Murray: Correct. The effective dose equivalent over your whole lifetime
is 5 rem, which is 71 mrem per year when averaged out over a 70- year
life span. Bob Peelle commented that he is not comfortable with 5 rem
over 70 years. He would rather refer back to the general CERCLA cancer
risk (1 in 10,000).
Susan Kaplan: That is the foundation of our recommendation (1 in 10,000).
What is the exposure this risk is related to? You have to quantify the
exposure to do this?
What does a 1/10,000 risk relate to in terms of whole body dose?
Bill Murray: If you’re talking about cancer risk, we’re talking
about 5 ×10-4 fatal cancers per rem.
Bob Craig: How would 1/10,000 risk relate to 5 rem lifetime doses? Is
it 10 or 2 or what?
Bill Murray: It is something like 2.5 per 1,000 for 5 rem total lifetime
dose. The CEDE is the dose equivalent integrated over a 70-year period.
Al Brooks: There are a number of statements in the recommendation which
seem to be made without any technical justification. One: Risk associated
with screening limit of 50 mSv is too high to be used as a screening criterion.
This is not a technical statement. This is a political statement about
how many false negatives you’re willing to accept. Second: Using
background radiation as a benchmark is not desirable for screening, exposure
is incremental to background. Why aren’t we considering background
and other sources?
Does this include average medical exposure?
Yes.
I don’t consider that background.
We need a definition of background here.
Bill Murray: The 360 includes 150 mrem from cosmic and terrestrial sources,
200 mrem to the lungs from radon. When experts talk, they always throw
in that lung burden.
Al Brooks: You can take any minuscule risk and make it sound very important
by comparing it to an even more minuscule risk. Paul’s paper seems
reasonable to me and conservative. We need to be able to figure out what
radiation doses we need to keep studying. Does anybody feel strongly against
the study?
James Lewis: How do we define background? I have never assumed that background
was 360.
Bill Murray: Most people in health physics use background to mean naturally
occurring background levels. That would include cosmic radiation,
radionuclides on ground (external and internal), 0.2 rem/year from radon.
The level is 75 to 200 mrem per year, based on altitude and latitude,
without radon.
Al Brooks: I thought it was 360 mrem; 300 natural and 60 medical.
How about average dose to Oak Ridge citizens as a definition of background?
Al Brooks: I don’t care which one we use, just as long as it’s
fixed.
When you’re talking about NTS data and background are you talking
about a 360 background?
No.
Shall we accept 360 mrem as our standard?
Bill Murray: I think it’s several hundred per year from medical
x-rays.
Is it important that we pick a number?
Al Brooks: We should decide whether we’re going to go with risk
or dose?
Gordon Blaylock: The report should be as clear as possible. Most people
don’t understand radiation dose measurements. However, most people
can understand the concept of risk. For that reason, risk is much more
comprehensible.
Al Brooks: You have to then compare all the risks that people undergo
in life, not just minimal risks.
Gordon Blaylock: Let’s have a table showing voluntary and involuntary
risks.
Kowetha Davidson: You can’t have risk without dose. You have to
relate the two things together before you can make meaningful statements.
David Fields: Risk can serve as a common denominator for comparing risks
Susan Kaplan: ATSDR’s chosen dose has a risk of 7 in 1,000. Right?
We’re comparing 7 in 1,000 with 1 in 10,000.
Al Brooks: You have to let people know that state regulatory limits are
not safety limits. If you are 20% over a regulatory limit, people might
call that a “disaster,” but there wouldn’t necessarily
be any public health risk.
Return to key point. Should we use dose or risk?
Iulian Apostoaei: How would one compare exposure to a radionuclide and
exposure to something like mercury? How would you know which one was more
important?
Bill Murray: We are trying to collect questions and comments for Paul
Charp to address: Questions received so far include:
- What is background? What does background include? Does background
include medical radiation?
- What is the 5 rem based on? Does it matter at what age you get it?
The purpose of this meeting is for the PHAWG members to finalize the
list of comments, questions, issues, and concerns dealing with the ATSDR
radiation screening document. We can then move on to discuss the iodine-131
presentation by Kowetha Davidson.
Kowetha Davidson: How is the screening level going to be used? I understand
the contaminants are not to be ranked. They will be treated equally.
But the public will care about ranking.
Al Brooks: Another question that needs to be answered: For what individual
in the population will 1 in 10,000 be calculated?
Why not set the risk level at a fixed level of 1 and 10,000 and then
calculate the doses that would correspond to that for different individuals?
That sounds like a Phase II assessment, not a screening.
Iulian Apostoaei: You can pick the most vulnerable individual and calculate
dose for that person, for the purposes of the screening,
Kowetha Davidson: You get 5 × 10-4 fatal cancers per
rem of exposure. Maybe we ought to make up a table of doses and risks.
So we’re really talking about reducing the screening level from
5 rem to 1. Right?
Action Items: We’re going submit comments to Paul Charp for
him to answer in next meeting or the meeting after.
A) We need to know the nationally accepted levels of backgrounds
B) We need to put together a table of risks
C) We need to know how this screening will be used
Motion: We submit the recommendation on radiation screening with
the additions that Bill Murray has documented to Paul Charp for comments.
[All vote Yes]
Issue #3: Kowetha Davidson’s Presentation on Iodine-131
It was reported that Bob Peele made a comment that he wanted passed on
to the group: He wasn’t sure if we should be using dose or risk.
If it wasn’t going to make a big difference to the overall dose,
he didn’t see any reason to use a combined dose.
Al Brooks: It doesn’t do any harm to add the two kinds of data.
Kowetha Davidson recommends not adding the doses but having a dose calculator.
She interprets the NAS report as meaning that there are things more important
than adding doses. Namely, these more important things are risk factors.
Even Owen Hoffman didn’t recommend adding doses. He recommended
adding probability of causation. Charlie didn’t say that we had
to add the doses. At a later point, additional data will be coming in
on global exposure. If new data becomes available, will we have to go
back in and update our results to account for the new data? Let’s
just stick to the Oak Ridge data.
If we can add the two values together, we should. There is agreement
within the scientific community that this can be done.
Kowetha Davidson: The question is not whether you can add the doses but
whether you should add them. I don’t think the level of certainty
is there for adding the doses.
Iulian Apostoaei: From the point of view of a health assessment, you
should add the two doses, related to the level of uncertainty. The uncertainty
in the doses from NTS is comparable or even lower than the uncertainty
about the doses from Oak Ridge. See Table 11-16 in Report on Task 1
of the Oak Ridge Dose Reconstruction.
Kowetha Davidson: So you’re saying the National Academy of Sciences
report is wrong?
Al Brooks: Since one can add the doses and combine the uncertainties,
anything this committee puts out has got to combine the NTS and the Oak
Ridge data. If we do not do this, we will run a terrible risk of discrediting
ourselves. Also, we should be dealing with central values when we have
distributions of values.
Susan Kaplan: In the next meeting, can we bring this issue of central
values to the table for discussion?
Al Brooks: You might want to describe the whole distribution quotient
to certain technically-oriented people. However, you shouldn’t talk
about the 95 or 97th percentile when you have errors that are “blowing
up” that percentile.
Al Brooks: My recommendation is that you add doses and that you be very
careful to discuss how the uncertainties combine.
Kowetha Davidson: Here’s a resolution: “Considering the uncertainties
of estimated local I-131 doses from NTS and Oak Ridge, ORRHES recommends
that ATSDR present doses from Oak Ridge and NTS in the dose reconstruction
for the purposes of public health assessment.”
“We recommend that the NTS and Oak Ridge data be presented independently,
and in total, and the uncertainties involved should be explained in lay
terms.”
Iulian Apostoaei: We should look at effects to both the entire population
and to individuals as well.
If you can evaluate individual situations based on risk factors, then
why not?
Kowetha Davidson: Individuals are outside ATSDR’s mandate. CDC
is already working on individuals.
Al Brooks: I don’t think it’s true that we are only concerned
with public health. Much of the work that this group has done deals with
people. I strongly recommend that we make it possible for people to calculate
their exposure.
James Lewis: We are getting challenges from different groups of scientists
in different groups.
Kowetha Davidson: Because of Al Brooks’ concerns, I think we should
include the individual dose calculator.
If we agree that we’re going to add doses, we should also agree
to publicize the existence of the dose calculator. The dose calculator
should provide a risk to correspond to each individual dose.
Kowetha Davidson: “Considering the uncertainties of estimating
local I-131 doses from NTS and Oak Ridge, ORRHES recommends that ATSDR
present doses from NTS and from the Oak Ridge Reservation for the purpose
of the public health assessment for the Oak Ridge Area. Doses should be
presented along with their range of uncertainty with an explanation of
the level of uncertainty for public understanding.”
This could be a PHWAG recommendation to ORRHES
Should we be put some mention of risk into this resolution?
Let’s discuss this further by e-mail and deal with it formally
in the next meeting.
Action Items:
Susan Kaplan will send Al Brooks something on central values
Compile issues for Paul Charp to address
Comments on adding doses
James Lewis: How do you deal with anecdotal information? Whatever information
we put out, we have to think of how the public will use it, and the emotional
impact.
We should emphasize that these are past doses, not present doses.
Meeting Adjourned
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