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Technical Responses to Multiple Air Toxics Exposure Study-II Final Report

SYNOPSIS: 

At its March 17, 2000 meeting, the Board directed staff to prepare certain technical responses to the Multiple Air Toxics Exposure Study (MATES)-II Final Report. These include: (1) a position paper compiled from comments received from members of the Air Toxics Study Technical Review Group (ATSRG); and (2) staff responses to the MATES-II comments made by those addressing the Board at the March meeting. Staff has written to each of the ATSTRG members requesting input on the overall evaluation and scientific basis of the report, as well as the adequacy of the ATSTRG involvement. A summary of their positions, as well as copies of the response letters, and the minutes of all ATSTRG meetings, are provided. Also provided is a summary of the MATES-II comments received at the March 17, 2000 Board meeting, along with staff responses.

RECOMMENDED ACTION:

Receive and file this report.

Barry R. Wallerstein, D.Env.
Executive Officer

Background

Upon the receipt and file of the MATES-II Final Report at its March 17, 2000 meeting, the Board directed staff to prepare certain technical responses, and report back to the Board in April. Specifically, the Board asked for: (1) a position paper reflecting the comments received from members of the Air Toxics Study Technical Review Group (ATSTRG); and (2) staff responses to the MATES-II comments made by those addressing the Board at the March meeting.

Staff Actions

Staff sent each member of the ATSTRG a letter asking the following questions:

(1) What is your overall assessment of the MATES-II report?

(2) In your opinion, is the report scientifically sound? If not, what are the deficiencies?

(3) What specific comments do you have, if any?

(4) Has the level of involvement by the ATSTRG members during the course of the
     MATES-II study been appropriate?

(5) What recommendations would you make if we were to undertake a future toxics
      monitoring program?

Of the 15 members of the ATSTRG, responses were received from 8 individuals. Attachment 1 provides a summary of positions compiled from the responses, along with copies of the letters received. The most common elements of concern are: (1) the level of uncertainty associated with the risk estimates based on monitoring and modeling, and (2) the limitations of the microscale study. So that the public is aware of the degree of involvement by the ATSTRG, copies of the minutes from 22 meetings, held between November 5, 1997 and January 12, 2000, are provided as Attachment 3.

Regarding the comments made at the March 17, 2000 Board meeting, staff has reviewed the record of the comments, and has responded to each. Attachment 2 provides a summary of the comments made along with the staff responses.

Staff also believes that an independent scientific review is appropriate. Several noted scientists have been contacted, and have indicated a willingness to review, in an expedited manner, and as their time permits, the issue regarding the estimate of diesel particulate from measurements of elemental carbon. These scientists include Dr. Judy Chow, Desert Research Institute; Dr. Glen Cass, Georgia Institute of Technology; and Dr. Susanne Hering, Aerosol Dynamics, Inc. Staff will forward their comments to the Board and make them available to the public when received.

For a full peer review, staff is now in the process of preparing a technical journal article based on the MATES-II study. This process will allow for a full formal peer review in a major journal, and ultimately publication for widespread availability.

Staff believes the MATES-II study is truly a groundbreaking effort, and despite many areas of uncertainty, remains a solid and credible scientific effort. Recognizing the substantial level of uncertainties, especially with regard to the issue of estimating diesel particulate, staff believes it is important to play a leadership role in the development of techniques to directly measure diesel particulate in ambient air samples. To that end, staff is proposing to reconvene the ATSTRG, and include other scientists with expertise in this area, in order to prepare and implement a workplan for developing the needed analytical methods. Funding will be sought from ARB and EPA for this purpose.

Attachments

Attachment 1 - Summary of Positions from Members of the Air Toxics Study Technical
                        Review Group
Attachment 2 - Response to Comments Made at March 17, 2000 Board Meeting
Attachment 3 - Minutes of the Meetings of the Air Toxics Study Technical Review Group

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