Annual Smog Season Is Off to a Slow Start

Smog season began Thursday in Ventura County with low to moderate levels throughout the county.

The slow start to the season is normal, officials said.

“Officially, smog season runs from May 1 to the end of October, but in actuality, our worst months are June through the second week of October,” said Kent Field, meteorologist with the Ventura County Air Pollution Control District. “People ask, ‘Is it going to be a smog year or not this year?’ And the answer is, ‘No one knows.’ ”

Warm weather, stagnant air and increased solar radiation conspire to cause ground-level ozone concentrations, the major component of smog, to increase in the summer.

However, the county’s air has been getting cleaner in recent years, thanks largely to stricter emission controls, Field said. The county’s air is about four times cleaner than it was 10 years ago, with fewer violations of federal health standards being reported, he said.

Last year, the county exceeded the state ozone standard of 79 on the pollutant standards index 80 times. The higher federal standard of 100 on the pollutant standards index was reached 17 times, with 13 of those instances in Simi Valley, Field said.

Simi Valley has the county’s worst air quality because of the local topography and its proximity to the Los Angeles Basin.

The county has exceeded state standards twice so far this year.

The frequency of federal violations is expected to increase this year, Field said, because the government is expected in July to lower the figure at which air quality is considered unhealthful. That would be the first time that has occurred in about a decade.

“So instead of 13 exceedences, maybe we’ll jump back up to 50,” Field said.

Breathing ozone can cause a variety of respiratory problems, including shortness of breath and chest discomfort.

Last year, only one ozone health advisory was issued in the county. During an advisory, which is issued when ozone measurements reach 138 on the pollutant standards index, people in schools, convalescent homes and other institutions are advised to take precautions.

However, Field recommends that everyone schedule vigorous activities in the morning or late evening, when ozone levels are lower.