Parts of SLO County could be in violation of new ozone-pollution rules

The southern entrance to the Carrizo Plain.
The southern entrance to the Carrizo Plain. jjohnston@thetribunenews.com

The federal Environmental Protection Agency has reduced the amount of allowable ozone air pollution, which comes substantially from vehicles. This move will mean that parts of eastern San Luis Obispo County, which have the highest levels of ozone pollution, will be in violation of the new federal standard.

However, the ozone readings above the federal standard are small, and the fact that the sources of the pollution are outside the county mean that area businesses and residents are unlikely to face mandatory emissions controls and other sanctions from the federal government, said Larry Allen, county air pollution control officer.

“In our county, there is not going to be a significant impact,” Allen said. “We have no major sources of ozone pollution in our county.”

In October, the EPA dropped the allowable ozone limit from 75 parts per billion to 70 ppb. Ozone is a pollutant that is formed when emissions typically associated with industry and cars and trucks, such as nitrogen oxides, are transformed into smog by exposure to heat and sunlight.

High levels of ozone are potent lung irritants and are associated with such respiratory ailments as asthma and cardiopulmonary disease.

The northeastern corner of the county is the only place that has the proper combination of precursor pollutants and heat and sunlight to create significant levels of ozone, Allen said.

The air district’s monitoring station in the Red Hills, near the Kern and Monterey County borders, typically records ozone levels of 73 ppb. Readings in the Carrizo Plain are 67 ppb.

Even one area of a county out of compliance means that the entire county could be classified as violating the new ozone rule, Allen said. However, the county air district plans to ask state and federal air regulators to divide the county into eastern and western halves in order to determine compliance. This split designation has been granted in the past, Allen said.

The western half of the county, which contains all of the cities and almost all the population, would be considered in compliance because ozone levels there are all well below 70 ppb.

County Supervisor Debbie Arnold, whose district includes parts of the eastern county, said Wednesday that the potential violation is frustrating because there is little county officials can do about high ozone levels because they are caused by precursor pollutants being blown into the county from the San Joaquin Valley and Southern California. She also noted that no one lives in the Red Hills area.

“It is ironic that we can be punished for a problem we did not create,” she said.

The lower ozone limit could become final in 2017.