Oct. 4--WESTWORTH VILLAGE -- On 20 acres all but hidden between the flows of both Texas 183 and Farmers Branch Creek, Deborah Rogers runs a farm, complete with dozens of goats, a few chickens, dogs, even peacocks, all of whom live peaceably in the shade of giant oak stands.

It has been an idyllic existence for her.

Until this year.

The change came in the form of two laboratory reports she commissioned this spring and summer showing toxic and irritant pollutants on her property.

Carbon disulfide. Dimethyl disulfide. Methyl ethyl disulfide. Methyl propyl disulfide.

In a lengthy lab report that also detailed the presence of toxins such as benzene, chloroform and toluene, nine specific disulfides stood out because they far exceeded the state's levels for investigating adverse effects, both for short-term and long-term exposure.

"This didn't mean anything to me in the beginning," Rogers said. "I didn't know exactly what I was looking at."

Rogers, along with some air-quality experts, now question whether those disulfide compounds are a byproduct of nearby natural gas drilling operations, such as when gas is released into the air through processes known as flaring or venting.

Coincidentally, one of her air-quality tests was conducted May 25, the same day a Chesapeake Energy well was flaring, or burning off natural gas, about three-quarters of a mile away from her house off Texas 183.

Disulfide compounds turned up again, in greater concentrations, less than two weeks ago in a study done by the same firm in the city of Dish in Denton County, site of numerous natural gas compressor stations. That air sampling study showed elevated levels of pollutants and toxics, such as benzene, xylene, carbon disulfide and dimethyl disulfide.

Chesapeake strongly denies that it could have been the source of the pollutants detected on Rogers' property and questions the conclusions and objectivity of the report. An attorney for the Texas Pipeline Association also raised concerns about the methodology of the Dish report and whether any conclusions can be drawn from the data.

Chesapeake officials said the presence of benzene, toluene and xylene could have come from multiple sources, identifying Lockheed Martin, Naval Air Station Fort Worth and vehicle traffic as likelier sources, and they reject that disulfide compounds are part of the Barnett Shale.

Chesapeake also disavowed any responsibility for toxins found in Dish, saying that its compressor station has no air toxic content. Several other companies, including Crosstex, Atmos, Energy Transfer Partners and Enbridge, also have gas-handling facilities in Dish, and the town has numerous gas wells.

However, the U.S. Environmental Protection Agency considers carbon disulfide to be associated with natural gas production.

And the reports commissioned by Rogers and the city of Dish are generating questions from some residents about the volume and variety of pollutants emitted by the natural gas industry and whether more testing should be done.

Not regularly monitored

In Tarrant County alone, there are 2,093 active gas wells, as of September, plus 2,368 in Johnson County and 3,998 in Wise County.

For different reasons, though, neither the Texas Commission on Environmental Quality, the EPA nor the Texas Railroad Commission, which has regulatory authority over the natural gas industry, regularly monitors emissions, which has made the Rogers and Dish studies all the more controversial.

Because the Dallas-Fort Worth area is in nonattainment status for ozone pollution, the state environmental agency concentrates its air-quality monitoring on ozone-specific compounds. The EPA said its authority is limited on gas drilling, and the state railroad commission said it has no jurisdiction over air.

Unlike ozone and some industrial pollutants, the low-level presence of disulfides in the air has not been studied well enough to know what effects they might have on human health, experts said.

The environmental quality commission performed its own air-sampling tests this summer at gas drilling sites in Tarrant, Wise, Denton and Johnson counties and is awaiting the results. Regional Director Tony Walker said he has not seen anything that alarms him, although he has not drawn any conclusions until more is known.

However, violations of the screening levels set by the state do not mean the disulfide compounds are unhealthy, Walker said.

"Right now, the reports are not saying anything that would not already be expected from that industry," Walker said. "The information gained so far has not generated an automatic change in [our] path. We're in the process of gathering new information. We'd like to see that too. If there is a reason to be concerned, we'll address that concern."

Dr. Roxana Witter, a physician and clinical instructor in the Colorado School of Public Health in Denver, was a principal investigator on a study published in 2008 that found elevated levels of pollutants in one Western Slope county with thousands of gas wells.

But carbon disulfide and related compounds were not part of her study, and like Texas, the state of Colorado does not regularly monitor emissions from gas wells.