Photo: The Canadian Press

Smoke and haze from wildfires obscures the Embarcadero Thursday, Nov. 15, 2018, in San Francisco.

Smoke masks. Eye drops. No outdoor exercise. This is how Californians are trying to cope with wildfires choking the state, but experts say an increase in serious health problems may be almost inevitable for vulnerable residents as the disasters become more commonplace.

Research suggests children, the elderly and those with existing health problems are most at risk.

Short-term exposure to wildfire smoke can worsen existing asthma and lung disease, leading to emergency room treatment or hospitalization, studies have shown.

Increases in doctor visits or hospital treatment for respiratory infections, bronchitis and pneumonia in otherwise healthy people also have been found during and after wildfires.

Some studies also have found increases in ER visits for heart attacks and strokes in people with existing heart disease on heavy smoke days during previous California wildfires, echoing research on potential risks from urban air pollution.

For most healthy people, exposure to wildfire smoke is just an annoyance, causing burning eyes, scratchy throats or chest discomfort that all disappear when the smoke clears.

But doctors, scientists and public health officials are concerned that the changing face of wildfires will pose a much broader health hazard.

"Wildfire season used to be June to late September. Now it seems to be happening all year round. We need to be adapting to that," Dr. Wayne Cascio, a U.S. Environmental Protection Agency cardiologist, said this week.

In an overview published earlier this year, Cascio wrote that the increasing frequency of large wildland fires, urban expansion into wooded areas and an aging population are all increasing the number of people at risk for health problems from fires.

Wood smoke contains some of the same toxic chemicals as urban air pollution, along with tiny particles of vapour and soot 30 times thinner than a human hair. These can infiltrate the bloodstream, potentially causing inflammation and blood vessel damage even in healthy people, research on urban air pollution has shown. Studies have linked heart attacks and cancer with long-term exposure to air pollution.

Whether exposure to wildfire smoke carries the same risks is uncertain, and determining harm from smog versus wildfire smoke can be tricky, especially with wind-swept California wildfires spreading thick smoke hundreds of miles away into smoggy big cities.