Oak Ridge Reservation: Public Health Assessment Work Group

Public Health Assessment Work Group

July 15, 2002 - Meeting Minutes

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:

1. 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.

2. 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 97^th 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