AIR QUALITY

What Was Measured?
The Bay Area Air Quality Management District (BAAQMD) measures five air pollutants in San Mateo County at a Redwood City test site.  These are: ozone (triatomic oxygen); carbon monoxide; nitrogen dioxide; sulfur  dioxide; and suspended particulate matter, most commonly measured as PM 10 (particulate matter larger than 10 microns).  Ozone results from a chemical reaction which takes place in the atmosphere between nitrogen dioxide and reactive organic gases under the photochemical influence of sunlight. While ozone in the upper atmosphere is beneficial and helps reflect radiation away from the Earth's surface, it is an irritant to people's eyes and lungs when it exists in the lower atmosphere.  Suspended particulate matter is composed of dust, ash, and smoke.  Smoke, composed of carbon and other products of incomplete combustion, is the most obvious form of particulate pollution.  "Days Over Standard" (DOS) figures are the number of days per year on which a specific California air quality standard was exceeded.

What Was Found?
From 1988 to 1994, nitrogen dioxide, carbon monoxide, and sulfur dioxide air concentrations did not exceed the state standards.  DOS for suspended particulate matter rose from 5 in 1988 to 12 in 1991.  DOS for TPM dropped to 7 in 1992 and again to 5 in 1993, but rose to 8 in 1994.  From 1988 to 1994, the highest number of days per year exceeding the state ozone standard has been 2. In 1990, 1991, 1992, and 1994 the state standard for ozone was not exceeded.

As a result of the phase-out of leaded gasoline, airborne lead levels in the Bay Area, which once exceeded both federal and state standards, have dropped dramatically over the past few years and now border on being nondetectable.

What Is The Trend?
California's standards for ozone and suspended particulate matter are more stringent than federal standards. (California standard for ozone is 9 pphm compared to the federal standard of 12 pphm; California standard for suspended particulate matter is 30 g/ M3 compared to the federal standard of 50 g/m3).

The concentrations of carbon monoxide, nitrogen dioxide, and sulfur dioxide in the air from 1988 to 1994 have been sufficiently low to allow San Mateo County to meet state and federal air quality standards.  The concentration of total particulate matter in the air increased from 1988 to 1991, dropped the next two years, but rose again in 1994, exceeding the state standards for 8 days that year. The concentration of ozone in the air has decreased significantly and San Mateo County's air quality exceeded state ozone standards only 4 days from 1988 to 1994.

Why Is This Important?
Air quality standards are set to protect health.  Air pollution poses a threat to every resident in a community, particularly the very young, the elderly, and people with respiratory ailments.  Air pollution can also negatively affect plant and animal life.  Air quality is an indicator of the overall health and desirability of a community.  Clean air is an attractive attribute for residents as well as businesses.

Source: Bay Area Air Quality Management District

Researcher: W. Goertz (Green Environment, Inc.)