Antero's plan came at the tail end of a huge drilling boom. When Brandon moved to Battlement Mesa in 2004, there were no rigs in sight, she says. By 2008, the nearby I-70 corridor was an industrial zone. After a game of golf, Brandon says, the dust from drilling was so pervasive, "I felt like I had pancake makeup on." Oil and gas workers flooded in, and many retirees left, forced out by sharply rising rents. Then in 2009, amid an international gas glut, gas prices plummeted. Battlement Mesa emptied once again, and is now a third vacant. Against this backdrop, Antero's plans are, to some, particularly galling.

"We've endured the industry in this part of the state for the last few years. But we know that our country needs the energy, and this is where it is, and so we tolerated the inconvenience," says Dave Devanney, co-president of the Battlement Concerned Citizens. "But now they are not satisfied with drilling in the countryside around us; now they're drilling in our backyard."

Drilling can release a range of pollutants. Fracking a well can require hundreds of truck trips, and the associated dust and diesel exhaust can cause respiratory problems. Emissions can combine to form ground-level ozone, a major cardiac and pulmonary toxin. Companies usually keep their fracking-fluid recipes secret, but they can include everything from diesel to methanol. Both fracking fluids and the natural gas itself can contain volatile organic compounds like benzene, a carcinogen that can also damage the nervous system. Those compounds have turned up in drinking water, raising worries that they are migrating to water wells. Fluids stored in open waste pits can contaminate the soil or surface water, or evaporate into the air.

But while researchers may know some of the chemicals being used, and some of their health impacts, they seldom know exactly what is being released into the environment, how much, or at what concentrations. They don't know exactly what people living nearby are exposed to, or for how long. In many cases, they know the health impacts of chemicals at high levels, but not at lower levels. They may know the impacts of one chemical in isolation, but not in combination with the others used in natural gas production. The only way to find out, says Judy Jordan, Garfield County's oil and gas liaison, is to "go in there and start studying people."

In 2004, the county used the fine levied in the Divide Creek incident to fund a broad health survey. The study only found some evidence, "not definitive," of increased respiratory conditions, says Teresa Coons, the epidemiologist who headed the study. But it recommended ongoing health monitoring, especially of vulnerable populations, like children and the elderly. Battlement Mesa's mix of retirees and young families fits the bill.

Not all the residents are worried. Keith Lammey, president of the Battlement Mesa Service Committee, the community's homeowners' association, spent years working in finance in the oil and gas industry before retiring. "No, I'm absolutely not concerned about the drilling," Lammey says, adding that it's heavily regulated.

And Antero, which has a history of operating in residential areas, has proposed what it calls unprecedented mitigation efforts to shield residents. Antero plans to use one centralized and covered wastewater pit, so that volatile organic compounds and odors don't escape into the air. It also plans to use pipes to transport wastewater,  in order to limit truck traffic -- "leading edge" measures, according to Jordan. Even the plan to drill 500 feet from homes is well above the state's minimum of 150 feet.

Many residents remain unconvinced. Last fall, the newly formed Battlement Concerned Citizens collected over 400 signatures on a petition requesting that any drilling be postponed until a health study could be completed.

The BCC met with a sympathetic county commission, ready to get to the bottom of questions that had dogged the drilling boom. "There's so much misinformation, fear, as well as accusation. We said, ‘Let's do it right,' " says Commissioner John Martin.

"I receive calls from people that get constant nosebleeds and headaches," says Commissioner Trési Houpt, who also sits on the Colorado Oil and Gas Conservation Commission. Houpt helped write new regulations for the state, effective in 2009, which, among other things, require operators to disclose fracking chemicals to Colorado's public health department in the event of an emergency. "The industry has the intellect and the resources to be able to respond if they're impacting peoples' health," she says. "If we can identify concerns through this study, I have the confidence and expectation that they'll come up with a better process for extracting natural gas near residential areas."

In mid-February, the county commission voted to pay for two studies: a health impact assessment (HIA), to be completed this summer, and the first phase of a longer-term, more in-depth community health study. Both will be conducted by the Colorado School of Public Health.

For the HIA, researchers are restricted to gathering existing health and environmental data. The goal, says Roxana Witter, the lead investigator, is to assess the current health of residents, determine whether they might be particularly vulnerable to industry activities, and then present regulators with recommendations about modifying Antero's plans. The HIA will also identify gaps in current data, which will be used to design the longer-term study. Because it needs to be done in time to be included in the permitting process, the researchers won't be able to address questions about exposure levels and pathways. Witter hopes the longer-term study will tackle these.

Neither Antero nor the state are required to use the HIA's recommendations, but so far, both have cautiously embraced the idea. Antero has said it will most likely wait for the recommendations before submitting its permit applications to the county and the Colorado Oil and Gas Conservation Commission. COGCC Director Dave Neslin, in turn, has committed to considering the HIA, and both the county and the commission could attach health stipulations to Antero's permit. But Neslin said he could not recall the commission ever denying a permit for health reasons.

The Battlement Mesa health study is part of a growing national trend. New York state was so alarmed by the potential impacts of fracking on water supplies that this spring it imposed regulations effectively blocking all drilling in New York City's watershed. This month, the Wyoming Oil and Gas Conservation Commission voted to require operators to disclose the chemicals used in fracking. And most significantly, in March the Environmental Protection Agency announced that it would launch a new national study on fracking's health and environmental impacts, to be completed in 2012.

But for some Battlement Mesa residents, the health assessment is only a partial victory. A long-term study simply makes them guinea pigs in their own homes, they say.

"The jury is still out," says Devanney. "My hope is that the HIA will show that natural gas drilling and a residential community are incompatible activities." He hopes, at a minimum, that wells will be pushed back 1,000 feet from homes.

"It doesn't seem like rocket science, it seems like common sense. But common sense has fallen victim to business sense in some areas."