RIFLE, Colo. — A two-year study has found no health crisis in Garfield County from a boom in natural gas drilling, but it said people close to gas operations may face higher rates of cancer and other illnesses.

The study by the Saccomanno Research Institute at St. Mary's Hospital in Grand Junction, Colo., said health risks could be lowered if energy companies recovered gas that is currently vented and wells were located farther from homes and schools.

The report, unveiled this week at a public meeting in Rifle, also recommends that Garfield County monitor trends, such as increases in respiratory problems, and make sure doctors are aware of potential issues.

The study, funded in part from a fine on the oil and gas industry, stemmed from concerns about possible health effects from increased gas operations in the western Colorado county.

Garfield County led the state last year in the number of drilling permits issued with 2,550, compared with 796 in 2004.

Some residents living near wells have complained of headaches, respiratory problems and other illnesses.

The Saccomanno Research Institute worked with Mesa State College on the study.

Although it found no health crisis related to the drilling boom, "that is not to say that some people haven't had health problems that could be related to the industry," said Teresa Coons, senior scientist at Saccomanno.

"There certainly are individual differences in susceptibility to exposure to toxic materials," she said.

An environmental risk assessment, based on mathematical modeling of emissions from a single well, found that people close to oil and gas operations may face higher health risks, including cancer, because of higher rates of benzene. Benzene, a byproduct of gas wells, causes cancer.

The modeling also found that people farther from gas operations may face lower health risks from potential benzene exposure.

Some of the proposed rules state regulators are considering as part of an overhaul of oil and gas rules address odors and other conditions that people living near gas fields have complained about.

Coons said the health assessment creates a base of information that didn't exist. "We have some trend data looking backward, but not a lot, and the industry hasn't been in the area for a real long time," she said. "So for some of the health effects that you might think of as more chronic results of exposure aren't going to show up for a number of years."

Donna Gray, a spokeswoman for Williams Production, a major gas producer in the county, declined to talk specifically about this week's presentation but said the company has hired a toxicologist to review the 250-page study.