Smoke advisories were in place Monday due to smoke from the Sand Fire burning in the Santa Clarita Valley.
The blaze had scorched 51-square-miles Monday morning, threatening more than 1,500 homes.
The South Coast Air Quality Management District noted in its advisory Sunday that air quality might reach unhealthy levels in areas directly affected by smoke. Areas were expected to include portions of the Santa Clarita Valley and San Gabriel Mountains.
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Updated smoke advisories Monday morning included Victorville, the Antelope Valley, and from the LA County mountains to the Santa Clarita Valley, said meteorologist Crystal Egger.
"What we have seen since yesterday is a change of the wind direction, an onshore wind," Egger said. She added that the wind flow originating from the south, southwest direction blew smoke to the north.
Doctors in the region have reported an uptick in patients with allergies, asthma and chronic obstructive pulmonary disease resulting from the fire's effect on air quality.
People are advised to limit outdoor activity, keep windows and doors closed, and to run air conditioners in their homes.