March 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 - March 1998

Weather during March was typical for a spring month except for above normal rainfall. Dispersion was very good and resulted in good air quality for most of the month.

• Precipitation was well above normal for the Puget Sound region during March. Sea-Tac airport received 232% of normal rainfall for March. The airport average monthly temperature of 46.6 degrees F was 1.0 degrees above normal for March with a maximum temperature of 68 degrees F on the 12th and a minimum temperature of 28 degrees F on the 5th.
• 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 56) and occurred on Friday, the 20th caused by particulate (PM10). Three days of the month was in the moderate category.
• The highest PM10 value of 62 µg/m³ (PSI of 56) was measured on Friday the 20th at the Duwamish industrial site in Seattle.
• The highest 8-hour average for carbon monoxide was 4.2 ppm (PSI of 47) and occurred the early evening of Friday the 20th at the Broadway & Hewitt Ave site in Everett.

Puget Sound Air Pollution Control Agency