(TNS) - SAN JOSE, Calif. — The heavy smoke from wildfires that choked much of California in recent weeks was more than an inconvenience.

It was deadly. And it almost certainly killed more people than the flames from the massive fires themselves, health experts say.

Between Aug. 1 and Sept. 10, the historically bad concentrations of wildfire smoke were responsible for at least 1,200 and possibly up to 3,000 deaths in California that otherwise would not have occurred, according to an estimate by researchers at Stanford University. Those fatalities were among people age 65 and over, most of whom were living with pre-existing medical conditions like heart disease, diabetes and respiratory ailments.

By comparison, through Wednesday, 26 people have died directly in wildfires this year statewide.

“Clean air is much more important than we realize,” said Marshall Burke, an associate professor of earth system science at Stanford who calculated the impacts. “When you look at it on a population level, you can see very clearly that breathing clean air has huge public health benefits, and breathing dirty air has disastrous consequences.”

Decades of medical research has shown that soot is among the most dangerous types of air pollution to human health. Known as “PM 2.5,” for particulate matter that is smaller than 2.5 microns in size, the microscopic soot particles are so small that 30 or more of them can line up along the width of a human hair.

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