After three straight days of unhealthful air in Simi Valley, county officials expect pollution levels to return to normal today.
Ozone pollutant levels registered 131 Saturday, up from 113 on Thursday and 114 on Friday, according to the Ventura County Air Pollution Control District.
Smog levels of 101 to 199 are considered unhealthful, and county officials issued an advisory Saturday urging people to avoid strenuous outdoor activity.
Ozone, a colorless gas that forms when hydrocarbons and nitrogen oxides bake in sunlight, can impair respiratory function and prematurely age lungs, experts say.
Authorities predict smog levels in Simi Valley will return to 70 today, which they consider moderate air quality.