As some may have noticed, health officials issuing air quality advisories that highlight three communities — the East San Gabriel Valley, the San Gabriel Mountains and the Santa Clarita Valley — is an unhealthy summer tradition, an air quality expert said Thursday.

Another such alert was issued for Friday for the SCV several other areas in the region.

These types of warnings associated with poor air quality happen regularly around this time of year for the SCV, according to Philip Fine, the deputy executive officer for planning, rule development and area sources for the South Coast Air Quality Management District.

“For this time of year, our main pollutant of concern is ground-level ozone,” said Fine. “And that is what drives those advisories and announcements.”

The Southern California Basin, of which the Santa Clarita Valley is a part, does not have high levels of ground-level ozone because of emissions made directly from a car or truck or a power plant, Fine said.

“There’s other pollutants that are emitted by those sources, and they undergo chemical reactions in the atmosphere in the presence of sunlight,” Fine said. “And then the ground-level ozone is formed.”

This pollutant, according to public health officials, is harmful to sensitive groups, such as the elderly, young children and those with underlying conditions.

The pollutants are pushed inland, Fine said, by onshore winds in the summer. Santa Clarita is a downwind valley, he added.

“You have the San Gabriel Valley and Santa Clarita, where we get transport of the pollution that’s emitted down in the Basin and in the (San Fernando) Valley and gets transported up through the (Newhall) Pass up toward Santa Clarita,” Fine said. “Over time, a lot of heat and a lot of sunlight form ground-level ozone.”

Santa Clarita usually is not the Basin community with the highest levels of ground-level ozone, but it is one of the highest in Los Angeles County, Fine said.

“It’s been like that for many years.”

Fine said the South Coast AQMD expects the unhealthy air quality to dissipate by roughly October when the winter season makes ground-level ozone less of an issue.

For more information on current air quality in the Santa Clarita Valley, visit http://www.aqmd.gov/.