State of California
                           AIR RESOURCES BOARD
                            Los Angeles Hilton
                            Golden State Room
                          930 Wilshire Boulevard
                          Los Angeles, CA  90017
                              April 27, 1977
                                10:00 a.m.

77-8-1    Minutes of the October 4, 1976 Board Meeting.

77-8-2    Public Hearing to Reconsider the California Air             1
          Quality Standard for Sulfur Dioxide.

77-8-3    Other Business
          a.   Executive Session - Personnel & Litigation
          b.   Research Proposals

                        ITEM NO.:  77-8-2

Public Hearing to Reconsider the California Air Quality Standard
for Sulfur Dioxide.


Based on the staff's analysis of the data presented in the
accompanying report and the conclusions set forth below, we make
the following recommendations:

1.   That the Board adopt a 24-hour ambient air quality standard
     for SO2 at a level of 0.04 ppm;

2.   That the Board adopt an additional ambient air quality
     standard for SO2, based on a 4-hour averaging period, at a
     level of 0.05 ppm; and

3.   That the Board, for the interim, retain the currently
     accepted measurement methods for SO2 pending the completion
     of research studies currently in progress.


The staff has reviewed a large volume of information pertaining
to SO2 and its effects, much of it published within the past 5
years.  A portion of this has been summarized in the accompanying
staff report.  The following conclusions represent the results of
our analysis of this information:

1.   The federal 24-hour ambient air quality standard for sulfur
     dioxide, 0.14 ppm, does not provide adequate health
     protection for the vast majority of Californians.  The
     federal standard does not take into account the known
     consequences of interactions of sulfur dioxide with ozone
     and other photochemical oxidants in producing or aggravating
     disease.  It does not adequately consider interactions of
     sulfur dioxide with other pollutants, such as nitrogen
     oxides and suspended particulate matter, or the suspected
     role of SO2 as a cocarcinogen in producing cancer of the
     lung.  Finally, the federal standard was apparently set
     without incorporating a margin of safety.  The staff has
     concluded that California requires a separate, more
     stringent 24-hour ambient air quality standard for SO2.

2.   As summarized in Section II. A. of the report, the results
     of recent toxicological and epidemiological studies indicate
     that simultaneous exposure to sulfur compounds and ozone and
     other photochemical oxidants leads to consequences that are
     significantly more serious than exposure to either pollutant
     alone.  This is supported by at least two studies showing
     effects at 0.06 ppm SO2 (24-hour average) in the presence of
     oxidant at about 0.15 ppm.  Many additional studies show
     effects in the range of 0.10 to 0.15 ppm SO2 in the presence
     of suspended particulate matter.

     Since, in the presence of even moderate amounts of oxidant
     and suspended particulate matter, effects upon human health
     are observed with 24-hour SO2 levels in the range of 0.06 to
     0.10 ppm, and since a margin of safety is desirable, the
     staff concludes that a 24-hour SO2 standard of approximately
     0.04 ppm will provide adequate protection to the health of
     essentially all residents in all areas of California.

     The proposed 24-hour standard assumes the presence of
     photochemical oxidant at ambient levels in excess of the
     State 1-hour standard (0.10 ppm) and includes a margin of
     safety to ensure adequate health protection for sensitive
     groups within the larger population.

3.   There is a substantial body of evidence showing that damage
     to vegetation occurs at SO2 levels as low as 0.025 to 0.1
     ppm (two to eight-hour averages for single and multiple
     exposures) and in the presence of oxidants at levels as low
     as 0.05 ppm or possibly lower.  Since California's prime
     agricultural areas frequently experience ambient ozone
     levels above 0.10 ppm, the board should assume the presence
     of ozone in considering the need for a standard that will
     minimize the impact of SO2 on vegetation.

     It is also clear that protection of vegetation requires that
     special consideration be given to SO2 levels for averaging
     periods shorter than 24 hours.  Based on the data discussed
     in Section II.B. of the report, it appears that a 4-hour
     averaging period would be reasonable.

     From the brief analysis presented in Section VI of the
     report, it appears that a 24-hour standard alone cannot be
     expected to provide adequate protection against expected
     short-term fluctuations in SO2 levels above levels that are
     clearly harmful to vegetation.

     On this basis, the staff has concluded that a separate SO2
     standard of 0.05 ppm with an averaging time of 4 hours is
     desirable to protect vegetation in the presence of
     photochemical oxidant at levels above 0.10 ppm.

     Even at the level of the proposed 4-hour standard, some
     damage to vegetation is expected to occur when moderate
     oxidant levels coincide with SO2 concentrations at 0.05 ppm. 
     However, achievement of this standard will reduce
     economically significant damage to an acceptable level and
     prevent widespread irreversible damage to forests and to
     sensitive ecosystems.

4.   A 24-hour SO2 standard of about 0.04 ppm is consistent with
     reducing ambient levels of sulfate aerosol to acceptable
     levels.  The following points are made in support of this:

     a.   The 0.04 ppm SO2 standard is expected to yield maximum
          24-hour sulfate levels of about 22 ug/m3 in the South
          Coast Air Basin, consistent with the Board's interim
          24-hour sulfate standard of 25 ug/m3.

     b.   Reduction of sulfate aerosol to approximately these
          levels will be required as a part of the broader effort
          to meet the State and federal ambient air quality
          standards for total suspended particulate matter.

     c.   Sulfate aerosol contributes substantially to visibility
          degradation.  No strategy for approaching the
          visibility standard can fail to require substantial
          reductions in sulfate aerosol.  Even at the levels
          consistent with the proposed SO2 standard, i.e.,
          sulfate levels of 25 ug/m3, sulfate aerosol alone will
          account for more than half the total allowable
          visibility degradation consistent with the visibility

5.   Many types of materials are damaged after long-term
     exposures to ambient levels of SO2.  Studies on the exposure
     of steels and cotton fabrics to gaseous SO2 show that damage
     is linearly proportional to SO2 concentration.  Therefore,
     the lower the SO2, the less damage incurred.  Clearly, a
     zero level is desirable, but as a practical matter
     protection of materials must be based on economic
     consideration.  Accordingly, the staff declines to identify
     a specific level, and suggests that the Board would be
     justified in relying on the standards needed to protect
     health and vegetation to provide an acceptable degree of
     protection against damage to materials.

6.   The staff concludes that none of the measurement methods
     currently in use in California for monitoring ambient levels
     of SO2 is entirely satisfactory.  The ARB staff and EPA
     scientists are currently evaluating a "new generation" of
     monitoring instruments that promise improved sensitivity and
     will be less subject to interferences from other pollutants. 
     this work is still in progress and the staff is not yet able
     to make a final assessment.  For the interim, it seams
     appropriate to retain the measurement methods currently in
     use.  Within the next year, a recommendation for adoption of
     a new method or methods will be forthcoming, along with
     recommendations to establish equivalency with current

ATTACHMENTS:   Resolution - 77-22
               Staff Report 77-8-2
               Recommendation from the State of California
               Department of Health on the Air Quality Standard
               for Sulfur Dioxide

                           STAFF REPORT

                        Table of Contents

                                                         Page No.
I.   Introduction                                               1

II.  Effects of Sulfur Dioxide                                  4

     A.   Human Health Effects

     B.   Vegetation Effects                                   49

     C.   Effects on Ecosystems

          1.   Lichens and Bryophytes                         128

          2.   Acid Precipitation                             131

     D.   Effects on Materials                                138

III. Sulfate Aerosol Formation                                158

IV.  Atmospheric Concentrations                               173

V.   Air Monitoring Measurements                              193

VI.  Comparability of Air Quality Standards for Different
     Averaging Periods                                        204

VII. Conclusions                                              209

VIII.     Recommendations                                     217