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1998 Season Summary
January through August
through September
January through October
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Year-to-Date Ozone Summary
This page updated on November 5, 1999.
The Year-to-Date Ozone Summary contains preliminary 1999 ozone data and historical data from selected monitoring sites in California.  This allows comparison of ozone levels from year to year for part of the season when the ozone levels are highest.
The summary presents, for the last four years:
Maximum 1-hour and 8-hour ozone concentrations, and
The number of days the ozone concentrations exceeded the state 1-hour standard (0.09 ppm) and federal 1-hour and 8-hour ozone standards (0.12 ppm and 0.08 ppm, respectively).
The summary presents this information on a "year-to-date" basis (i.e., January through August, January through September, etc.).
The monitoring sites included in the summary represent the highly populated areas of California that have high pollutant levels.  There may be other monitoring sites that have had higher ozone concentrations or higher numbers of days on which the standards were exceeded.
Special acknowledgement goes to the following districts that provide data for this summary:
Bay Area AQMD
Sacramento Metropolitan AQMD
San Diego County APCD
San Joaquin Valley Unified APCD
South Coast AQMD
In 1999, this summary will be updated monthly to include January through August, January through September, and January through October reports. All 1999 data are preliminary and subject to revision.
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