June 1998 Air Quality Report

Here you will find information about:

• Weather patterns affecting air quality
• Highest monitored levels of air pollution
• Highest levels of particulate matter (PM₁₀), carbon monoxide (CO) and ozone (O₃)

Air Quality Report - June 1998

Weather was typical for the month of June with excellent dispersion and good air quality throughout the month. Precipitation was slightly below normal with Sea-Tac airport receiving 74% of normal rainfall for June. The airport average monthly temperature of 59.9 degrees F was -1.0 degrees from normal for June with a maximum temperature of 82º F on the 21st and 29th and a minimum temperature of 48º F on the 14th, 15th and 16th.

• Preliminary data shows that none of the air quality measured values exceeded a federal standard (NAAQS) or reached the Unhealthful category on the national Pollutant Standards Index (PSI). The highest pollutant reading was in the moderate category (PSI of 61) and occurred on Sunday, the 21st caused by ozone. Four days of the month were in the moderate category and caused by ozone.
• The highest PM10 value of 34 µg/m³ (PSI of 34) was measured on Wednesday the 3rd at the Duwamish site in Seattle and on Monday the 22nd at the Alexander Avenue site in the Tacoma Tideflats. The highest PM2.5 of 17 µg/m³ (proposed PSI of 51) was measured on Tuesday the 2nd at the Kent site and on Monday the 29th at the Duwamish site in Seattle.
• The highest 8-hour average for carbon monoxide was 3.2 ppm (PSI of 32) and occurred the afternoon of Thursday the 4th at the University district in Seattle.
• The highest 1-hour average for ozone was 0.073 ppm (PSI of 61) and occurred the afternoon of Sunday the 21st at the site 2 miles east of Enumclaw. The highest 8-hour average for ozone was 0.065 ppm (proposed PSI of 53) the same afternoon of Sunday the 21st.

Puget Sound Air Pollution Control Agency