LANDER - Pinedale-area scientists and health professionals are calling on Gov. Dave Freudenthal and state and federal agencies to complete a more scrupulous investigation into the potential human health impacts of expanded natural gas drilling in Sublette County.

Amid a series of ozone warnings for the Pinedale area this winter, more than 40 people - including scientists, several doctors and nurses, and two Sublette County Public Health officials - are requesting that an independent agency complete a comprehensive assessment of the Bureau of Land Management's proposed plan to expand gas drilling in the Pinedale Anticline.

The 42 signatories sent an official letter of request addressed to Freudenthal, the BLM, the Wyoming Department of Environmental Quality, the Wyoming Department of Health, as well as to oil and gas industry officials.

The BLM's latest draft assessment of the potential environmental impacts of drilling about 4,400 additional natural gas wells just outside of Pinedale "did nothing to address the potential human health consequences of ongoing and proposed federally permitted natural gas development activities in our county," the letter states.

The letter reminds recipients that the Environmental Protection Agency recently slammed the BLM's proposed plan for new development, giving it what amounts to a failing grade, citing concerns about elevated ozone levels, groundwater contamination and decreased visibility, among other things.

Area residents are fortunate to know about the pollution that has already been documented, the letter says, but the signatories are also concerned about the yet "undiscovered" and thus "undisclosed" human health risks associated with local energy activity.

"Health impact assessments are designed to address exactly this critical knowledge gap," the letter asserts.

Dr. Thomas Johnston, Sublette County's public health officer and one of signatories, said he hopes the recipients take the letter seriously, because current and future gas drilling in the area creates potentially severe health risks for people.

"We need to re-evaluate the (BLM's) environmental impact statement, because there's nothing in it that deals with public health," Johnston said.

Leslie Rozier, a nurse practitioner who works at the Pinedale Medical Clinic, also signed the letter. Born and raised in Sublette County, Rozier said, she is "acutely" aware that the air quality in the region has gotten worse in her lifetime.

The technology exists, she said, to do the gas extraction more cleanly, and it's time for either the state or the federal government to require the industry to clean up existing operations before allowing those operations to expand.

"When you hike into the Wind River Mountains, you can no longer see the valley floor," Rozier said. "In the language of Wyoming, we need to say, 'Whoa, slow down.' You have to rein in the horses because they're out of control."

Her husband, Rod Rozier, a former teacher, atmospheric scientist and engineer who participated in notable stratospheric ozone research at the earth's polar regions, also signed the letter.

The elevated ozone levels recorded in the region since 2005 have already been harmful to some residents, Rozier said, but the locals who are most affected by the pollution have the least influence over the development process.

"These are dangerous levels of ozone," he said. "My question for Governor Freudenthal is, 'Can you help us here?' The BLM is not listening to the residents of Pinedale, Wyoming. Can we bring other responsible agencies to the table to make certain that minimal impacts are going to occur?"

For his part, Freudenthal is aware of the petition, Cara Eastwood, his press secretary, said Monday. And both the DEQ and the state Department of Health are in the process of evaluating it, she said.

"The state is considering the possibility of conducting an air quality study that is more focused in scope that could be designed by both the Air Quality Division of DEQ and the Department of Health," Eastwood said.

The public will have a chance to discuss these issues in detail with state officials from DEQ and other agencies, she said, at a public meeting April 21 in Pinedale.

Chuck Otto, director of the BLM's Pinedale office, said he has read the letter, and his agency plans to address the concerns of the signatories.

"I'm taking it seriously," Otto said. "Anything that may impact human health is one of the paramount issues that we have to deal with. It's a serious concern."

The BLM has been working with the EPA on resolving air quality issues in Sublette County, Otto said, but until his office receives a response from the EPA to a recent letter sent by the BLM last week, he cannot offer any specifics regarding what steps the agencies might take.

Gregory Keeley, communications director for U.S. Sen. John Barrasso, R-Wyo. - who also received the letter - said the senator is "attuned" to the recent ozone warnings. And while he believes more study is needed regarding wintertime ozone formation, Barrasso also believes the time is right for "scientific experts to address these issues," Keeley said.

Oil and gas industry companies with interests in current and proposed drilling in the Jonah and Pinedale Anticline fields also received a copy of the letter.

Deena McMullen, spokeswoman for Shell Exploration and Production Co., said her company received a copy, but wasn't prepared Monday to comment on it publicly.

"We're taking it seriously," McMullen said. "We're looking at their concerns, but we're still in the process of determining how to respond to the letter. The industry is working with the DEQ to look at things we can in Sublette County now. We're trying to educate ourselves further on the issue. I think a lot of education has to happen for folks, including for ourselves."

McMullen said Shell plans to do its part to lessen emissions.

Environment reporter Chris Merrill can be reached at chris.merrill@trib.com or at (307) 267-6722.