PORTLAND — Though cozy on a winter day, smoke from wood stoves and fireplaces presents a greater cancer risk to Oregonians that what is belched by cars and trucks, according to a U.S. Environmental Protection Agency analysis.

The EPA analysis ranked Oregon’s air high in cancer risk. The state placed third highest in the nation in the number of people living in census tracts with a cancer risk that reaches the EPA’s benchmark level of concern.

But Ted Palma, the scientist who led the National-Scale Air Toxics Assessment, released last month, said Oregon ranked high because it does a more thorough job documenting the generation of wood smoke.

“If the other 49 states did as good a job as Oregon,” Palma said, “Oregon wouldn’t be at the top.”

Pollution from wood burning helped push more than 40 census tracts in Clackamas, Jackson, Multnomah and Washington counties above the EPA’s overall risk benchmark, accounting for a third or more of the overall air cancer risk in those counties.

The EPA’s risk benchmark is based on 100 cancer incidents among 1 million people exposed continuously over a lifetime. The EPA says one out of three Americans — 330,000 in a million — will get cancer during their lives when all causes are taken into account.

The wood stove is a popular way to heat homes in southwest Oregon. It’s less common in the Portland area, but the smoke adds up there because of higher population and heavier use of fireplaces.

The statistics used in the assessment were from 2002. A bill since passed in the Legislature requires new wood stoves to get EPA certification. They would release roughly 70 percent less pollution than older models

The state Department of Environmental Quality estimates that more than 50 percent of the wood stoves used in about 420,000 Oregon homes are older than the EPA’s certification program.