Reactivity Scientific Advisory Committee (RSAC) Meeting
August 26, 1998

This page last reviewed August 1, 2008

Reactivity Scientific Advisory Committee (RSAC)
Meeting Summary
August 26, 1998


  A meeting of the RSAC was held by conference call on August 26, 1998 to discuss the proposed California Low Emissions and Reactivity (CLEAR) regulation for aerosol coatings. The meeting was chaired by Dr. Roger Atkinson at the University of California, Riverside. Other committee members participating included Dr. Jack Calvert, Dr. Harvey Jeffries, Dr. Jana Milford and Dr. Armistead Russell. Opening remarks and an introduction were given by Genevieve Shiroma, Chief of the Air Quality Measures Branch, Stationary Source Division, and Dr. Randy Pasek, Manager of the Atmospheric Process Research Section, Research Division, of the California Air Resources Board (ARB). Other representatives of the ARB included Carla Takemoto, Andrew Chew and Dr. Eileen McCauley. Dr. William Carter was present to address questions concerning the most recent update of his MIR values.


Presentation on the CLEAR Regulation
  Stationary Source Division staff gave a presentation on the proposed CLEAR regulation for aerosol coatings. The regulation is a voluntary alternative to the mass based VOC limits for aerosol coatings and would use the revised Maximum Incremental Reactivity (MIR) values as a means to quantify the reactivity of a VOC. These revised MIR values were published by Dr. William Carter on August 6, 1998. Treatment of uncertainty of the MIR values and a method to establish MIR values for hydrocarbon solvents were presented.
  To address the uncertainty in the individual MIR values, Dr. Carter assigned each compound an uncertainty rank between 1 and 11, with 1 being the least uncertain and 11 the greatest. A rank of 9 was assigned to compounds where the current mechanism is expected to overpredict reactivity. Staff proposed that for ranks 1 through 5 and 9 an uncertainty adjustment factor of 1 would be applied. Ranks 6 through 8 and 10 through 11 would have an adjustment factor of 2. However, if the twice the MIR is greater than the calculated upper limit MIR, the calculated upper limit MIR will be used.


Committee Discussion
  After the staff's presentation, the members of the RSAC and Dr. Carter discussed the proposed use of reactivity in the regulation. Dr. Carter explained that the new MIR values were calculated with a completely updated mechanism. The committee agreed that a peer review of the mechanism and the handling of the uncertainty
was needed.
  The committee discussed in detail the handling of the uncertainty associated with the estimated MIR values and points which were addressed include the following. The committee's opinion was that while it is appropriate to have no adjustment for some classes of compounds, there was concern about bin 5. Bin 5 contains compounds which have not been thoroughly studied, however, in Dr. Carter's judgement, the mechanism will probably change by less than a factor of 2. Bin 5 includes high molecular weight, branched hydrocarbons, alcohols and ethers.
  The committee unanimously recommended that both the mechanism and the uncertainties be reviewed by two people if possible. Additionally, they recommended that the MIRs be updated on a three-year basis. The committee felt that, with these 3 points addressed, the methodology for addressing reactivity in the CLEAR regulation made technical sense.

Other comments for the staff to consider included:

  • Concern with the use of the adjusted MIR valves in the base value case. It was felt that inflation of the base case could result in more reactive products than are desirable.

  • Manufacturers' choice of compounds should be tracked, specifically the percentage of compounds with higher uncertainty versus compounds with lower uncertainty.

  • The alkene content in hydrocarbon solvents should be considered in establishing MIR values for
    the solvents.

  • The possibility was suggested that of the use of large amounts of halogenated compounds would be attractive due to their low rate constants. Staff pointed out that the regulation addresses this concern by limiting the use of methylene chloride and perchloroethylene so that there are no new uses of these compounds.

  • Consider formal review or update of the MIR values every few years. At that time a decision would be made as to whether the magnitude of change in MIR values warrants changing the regulation.

  • Possible topic for the next RSAC meeting is updating the MIR values using a regional multiday


Public Comments
  • After the committee discussion every participant in the conference call was given an opportunity to comment. A summary of the comments follows.

  • A peer review of the MIR values was needed and should be done as soon as possible.

  • Several people stated that the process was moving too fast and that a delay would allow better information to become available.

  • After an update of the MIR values, when would the revised values become effective? Manufacturers would need time to adjust their formulations.

  • Concern was expressed with the use of the adjustment factors in the base case.

  • RSAC committee members restated their position that no compounds should be exempt. They felt the CLEAR regulation does not act as a disincentive since formerly exempt compounds have
    low MIR values.

  • It is important that ARB and EPA work together.

  • A peer review of the hydrocarbon solvent list was necessary.

August 1998 - RSAC Meeting