2003 OZONE DATA SHARING PROJECT UPDATE Air Quality Advisory Committee September 23, 2003

Ozone Data Sharing Project Project runs from April 1 – October 31 EWGCC acts as clearinghouse Data is examined for problems, missing values and exceedances of the 1-hour and 8-hour ozone standard

Ozone Data Sharing Project Data is collected from a network of 16 monitors Monitors are operated and maintained by Missouri Department of Natural Resources, Illinois Environmental Protection Agency, St. Louis County and City of St. Louis

1-Hour Ozone Standard Health-based standard is parts per million or ppm (or 120 parts per billion or ppb) Exceedance of standard occurs when the hourly average ozone levels measured at a monitor is 125 ppb or greater. St. Louis region was designated as being in attainment of the 1-hour ozone standard in May 2003 by USEPA

2003 Ozone Season Summary There were 12 exceedances of the 1- hour ozone standard on three days Exceedances occurred on July 17, July 31 and August 26

2003 Exceedances of 1-Hour Ozone Standard MonitorDate Max Value (ppb) Duration Arnold hours Breckenridge Hills hour 2 hours Ferguson hour Ladue hours Sunset Hills hour

2003 Exceedances of 1-Hour Ozone Standard – Cont’d MonitorDate Max Value (ppb)Duration Broadway hours Margaretta hour 2 hours Edwardsville hour East St. Louis hour 2 hours

Exceedances of 1- Hr Ozone Standard

8-Hour Ozone Standard Standard revised by USEPA in 1997 Protect public from adverse health effects resulting from longer periods of exposure to ozone Standard is 0.08 ppm, or 80 ppb, over 8 hour period

8-Hour Ozone Standard Excursion occurs whenever an 8-hour average of values is calculated to be 85 ppb or greater on any day. Attainment of standard is determined by averaging the 4 th highest annual maximum average by monitor over a 3 year period.

Hour Excursions On 11 days there were 64 excursions of the 8-hour ozone standard June 18, 23, 24 July 2, 17, 31 August 20, 21, 24, 25, 26

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