SILT, Colo. (AP) - As they drove home from Rifle after an area natural-gas operator was presented a good-corporate-citizen award recently, Carol and Orlyn Bell encountered a "terrible" smell when they neared their Dry Hollow ranch, south of Silt.

"It was the strongest odor we've smelled in the last four years," Carol Bell said.

The Bells said the odor came from nearby gas wells and production facilities, something they've seen surround their 110-acre ranch in those four years.

Odor complaints and air pollution concerns are on the rise in Garfield County, where longtime residents often wake up to hazy skies in the Colorado River valley. Many believe the gas industry is responsible, and figures from the Colorado Air Quality Control Commission may back up that claim.

Haze, or smog, forms when air pollutants such as nitrogen oxides, carbon monoxide and volatile organic compounds, or VOCs, react with sunlight to form ozone. VOCs include benzene, toluene, ethylbenzene and xylene.

In the lower atmosphere, ozone can pose serious health risks. Ozone has been linked to low birth weights, makes it hard for children to breathe, causes asthma attacks and increases emergency-room visits. Children and the elderly are most susceptible to ozone-related problems, health officials said.

Garfield County, the most active county in the state in terms of drilling permits, gets 95 percent of its stationary VOC emissions from gas industry facilities, according to the Colorado Air Pollution Control Division. Of the 7,522 tons of VOC emissions per year, 7,173 tons came from those sources, division numbers show.

Oil and gas facilities are the single largest source of formaldehyde, benzene, acetaldehyde, acrolein, hexane, toluene and xylenes among stationary pollution sources in Colorado, the division said. The National Cancer Institute identifies formaldehyde as a known carcinogen.

Jeremy Nichols, director of Rocky Mountain Clean Air Action, a Denver nonprofit group pushing for lower emissions from the industry, said the "out-of-control" emissions show a "rape and pillage" philosophy.

"It's really sad and unfortunate, too," he said. "It's so easy to do it right."

Orlyn Bell said odors were almost constant when he inspected area irrigation ditches last Monday. This summer, he had headaches "dozens of times" while he reroofed a workshop.

"It seemed to be while I was on the roof, because when I came down, I couldn't smell it," he said.

The Bells have lived on their ranch for 26 years, and four gas wells were drilled on their property. They do not own the mineral rights to the gas under their land.

Complaints are often of odors, toxic smells or "it stinks real bad," Western Colorado Congress organizer Patrick Barker told Rifle City Council this week.

He gained the council's support for tougher emission regulations to be considered by the Colorado Air Quality Control Commission in November. Rifle and Glenwood Springs both endorsed the move.

Beth Dardynski also lives south of Silt and said she spent nearly all of July battling gas-related odors from nearby condensate tanks.

"The springs on the lids on top of the tanks didn't work," she said, "so the air would bring the fumes down into our homes each night. It smelled like I had an open diesel can next to my bed."