The smoke from wildfires covered a lot of the West Coast last month, exposing millions of people to hazardous pollution.
According to a study by The Associated Press, the smoke caused an uptick in emergency room visits and potentially resulted in thousands of deaths among older Americans.
Major cities in Oregon were hit hard with record smoke pollution.
"So we saw during the peak of the smoke, we saw 1 in 10 people walking into our emergency departments and urgent care centers complaining of asthma-like symptoms, and that depending on the day, that could be up to, you know, double the number of people we would normally expect to see," Gabriela Goldfarb, with the Oregon Health Authority, said.
Researchers at Stanford University estimate that in California around 3,000 people over the age of 65 may have died prematurely due to the smoke.
That's based on previous studies.