debbiehelbing / Getty Images

Adam hasn't been able to get a good night's sleep for days. While it's already rare for him to sleep through the night undisturbed—since he often sleeps outside on a downtown Portland sidewalk—the thick smoke that's plagued the city air has only exacerbated the problem.

"I wake myself up coughing and I've been getting terrible headaches," says Adam, who asked the Mercury only identify him by his first name. "It's like I started smoking again."

Adam says he avoids local shelters for a number of reasons and doesn't feel welcome in other public indoor spaces, leaving him with no other option than to breathe the hazy air. It's the same smoky air that researchers say could cause long-term health problems—and in some cases, cancer—if exposed to for extended period of time.

Some homeless advocacy groups like Right 2 Survive and Street Roots have been collecting and distributing respiratory masks to people who live outside. But the Oregon Health Authority says the most effective way to protect yourself from smoke inhalation is to stay inside.

Dr. Brianna Sustersic, senior medical director of primary care at Central City Concern's Old Town Clinic, says she's been telling her patients—who are mostly houseless—to spend time in public libraries, malls, or Multnomah County cooling shelters. The options are limited. She does see a few patients who have housing, but when temperatures hit the 80s, its hard for them to keep their windows shut.

In the past few days, Sustersic says the Old Town Clinic has seen a significant uptick in patients coming in with respiratory issues, many without appointments seeking immediate help.

"People with chronic issues like asthma or emphysema are having trouble breathing," Sustersic says. "I've been writing medical notes for air condition for people in [housing] units."

Support The Portland Mercury

While the smoke has begun to lift, Sustersic says the problem's not evaporating with it. As wildfires become a regular feature of Oregon summers, she predicts air quality issues among the houseless will become a chronic problem.

"I certainly expect these issues to continue," she says. "We're trying to be more proactive by reaching out and warning people we already know have respiratory problems before smoke hits the city. And, hopefully they can get indoors."