San Diego achieves cleanest air since 1955
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.
|Days over Standard - SD Air Basin||151||138||167||192||120||125||145||148||131||127||160||158||139||106||97||90||79||96||51||43|
|Stage 1 Episodes||10||11||8||2||4||4||4||4||0||1||2||2||1||1||0||0||0||0||0||0|
|Health Advisory Episodes||6||6||5||1||3||0||0|