The smoke contains fine particulate matter, which can pose serious health risks, especially for people with preexisting conditions.
"You breathe them, they can get really deep into your lungs," said Dr. David Lo, a professor at UC Riverside and researcher who studies air pollution at the university's BREATHE Center.
"Any of the toxic effects of the particles themselves getting deep into your lungs, as well as any toxic chemicals they carry with them, are going to get into your lungs really easily and have all their negative effects," Lo added.
The Environmental Protection Agency's Air Quality Index measures pollution levels on a scale from 0 to 500. Readings below 50 are considered healthy. Scores between 51 and 100 are categorized as "moderate," while anything over 100 can pose risks to sensitive groups. Levels above 150 are considered unhealthy for everyone.
"Typically, this actually involves those such as children, elderly, pregnant women, those with respiratory conditions such as asthma or COPD, and even those with heart disease," said Dr. Laren Tan, a pulmonary disease specialist at Loma Linda University Medical Center. "These are the sensitive or most vulnerable population of patients to bad air quality."
Tan added that common symptoms from poor air include wheezing, chest pain, tightness, cough, sometimes throat pain and eye irritation.
Health officials recommend that residents in affected areas stay indoors, keep windows closed, run air conditioners on recirculation mode, and use air purifiers if available. If outdoor activity is unavoidable, wearing an N95 mask can help reduce exposure to fine particles.
"While inside, you can use an air filter, that would be very helpful, avoid strenuous activity outside when the air quality is horrible," Tan said.
The smoke advisory remains in effect through midnight.