 ast year, San Diego County achieved
its cleanest air since air quality moni toring began more than 40 years
ago. The federal clean air standard was exceeded on just one day in 1997,
compared to two days in 1996 and 12 days in 1995. Twenty years ago, federal
clean air standards were violated on 90 days. Motor vehicles produce 60
percent of smog-forming emissions.
 The one violation in 1997 occurred
at the mountain slopes station in Alpine on the Fourth of July, when vehicular
traffic was very heavy.
This was the second straight year
that locally-generated pollution was not primarily responsible for a federal
violation. Pollution transported here from the Los Angeles air basin contributed
significantly to the violation of the federal standard.
"Cleaner-burning gasoline introduced
in 1996 significantly reduced vehicle emissions. Also, the meteorological
influence from the current El Nino likely contributed to the reduced number
of violations last year," said Greg Cox, chairman of the San Diego
Air Pollution Control Board. "While our air quality has significantly
improved, continued progress is necessary to meet the more stringent revised
federal standard and California standard."
The more stringent California standard
was exceeded on 43 days in 1997. This is down from the 51 days in 1996,
96 days in 1995, and a high of 192 days in 1981.
Clinical studies show that chronic
exposure to smog reduces lung capacity, lowers stamina and leaves people
vulnerable to long-term respiratory problems. Smog is especially harmful
for children whose lungs are still developing, senior citizens whose immune
systems are weakening, and those who suffer from asthma and chronic lung
disease.
Clean air standards are set by the
state and federal governments to provide an adequate margin of safety in
protecting public health. Measured as ozone, the current federal standard
is 12 parts per hundred million (pphm) or 100 on the Pollutant Standards
Index (PSI). The state standard is 9 pphm or 75 PSI.
San Diego has not had a Stage 1 smog
alert since 1991 and no Stage 2 alerts since 1979. A Stage 1 alert occurs
when smog levels reach 20 pphm or 200 PSI. A Stage 2 alert is called when
smog levels reach 35 pphm or 275 PSI.
No health advisories were issued
in the county during the past two years. Three were issued in 1995. A health
advisory is issued when smog levels reach 15 pphm (138 PSI), and the community
is advised to reduce vigorous outdoor activity.
With the exception of ozone (smog),
San Diego met federal air quality standards for all other criteria pollutants:
carbon monoxide, nitrogen dioxide, sulfur dioxide, inhalable particulates,
and lead.
Additionally, this was the seventh
straight year that San Diego County did not exceed the state 8-hour standard
for carbon monoxide. State standards were also met for nitrogen dioxide,
sulfur dioxide and lead; but not for ozone and inhalable particulates.  | 
