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The United States is in the middle of a natural gas boom. These days, a community can find itself not simply with one or two new wells, but suddenly surrounded by them. And that has some locals worried. Their biggest concern is that the chemicals used in gas production are causing everything from nosebleeds to cancer. But scientists see it differently. They say the evidence of harm just isn't convincing.
To find out why there's such a disconnect, NPR's Jon Hamilton visited the small town of DISH, Texas.
JON HAMILTON, BYLINE: Look at a satellite image of DISH and you'll see an odd patchwork. There are ranch-style homes and green pastures but there are also rectangles of gray-blue gravel. Zoom in a bit and you can see they're filled with gas wells, compressors, storage tanks and metering stations.
Bill Sciscoe is the mayor of DISH. And he has a message for anyone who expects to see gas drilling in their town.
MAYOR BILL SCISCOE: Run. Run as fast as you can. Grab up your family and your belongings and get out.
HAMILTON: Sciscoe says he can't leave. He owns too much property here that no one wants to buy. So he took over as mayor last year after the previous mayor and his family left to get away from the drilling. Sciscoe is an imposing guy: black boots, black sport coat, aviator sunglasses. He shows me around town. About 225 people live here among the gas wells.
In some areas there's the sulfurous odor of escaping gas. In others, you can feel the rumble of compressor engines big enough to power a locomotive.
(SOUNDBITE OF MACHINERY)
HAMILTON: Sciscoe says things were very different when he moved here in 1987.
SCISCOE: This place was absolutely beautiful. It was serene. It was very quiet, very clean. I raised five children here.
HAMILTON: Then around 2005, two things happened to the town which was named Clark at the time. First, Clark became DISH as part of a deal to get free satellite TV service from the DISH network. Second, energy companies arrived and began drilling lots of gas wells. The wells were made possible by a technique known as hydraulic fracturing or fracking, which released natural gas trapped in the hard shale a mile underground.
SCISCOE: We're going to take a left on this dirt road right here, in front of the truck.
HAMILTON: Sciscoe has brought me to the biggest thing in DISH.
SCISCOE: We can just pull right up to the gate here.
(SOUNDBITE OF MACHINERY)
HAMILTON: It's a swath of gas wells and heavy equipment that stretches for a quarter mile. Sciscoe says emissions from this site aren't safe to breathe.
SCISCOE: It's just a who's who toxic chemical mix; pretty much all of those items that you get from petroleum products are spewing into the air in this area.
HAMILTON: A few years ago, the town spent $15,000 on an air quality study. It found elevated levels of several chemicals, including benzene. But since then, energy companies have fixed some problems. And the state installed a device that constantly sniffs the air for pollution. It shows levels are generally within government limits. And when state health officials came to check for toxins in residents' blood and urine, they found no cause for concern.
Even so, Sciscoe firmly believes that people in DISH have been hurt.
SCISCOE: There's not a lot of residents right around this facility. But within a quarter of a mile, half a mile of this facility, there's been six people die of cancer here. And so, do I think that this is a concern? Yes, I do.
HAMILTON: Sciscoe is pretty convincing. And even scientists who are skeptical about his claims say they understand why he's concerned. But they also say the scientific evidence that gas production around DISH has made anyone sick is pretty weak.
To understand why, I go see Brian Schwartz, an environmental epidemiologist at Johns Hopkins in Baltimore. I ask him: what would it take to figure out whether there really is a link between gas operations around DISH and those people with cancer.
DR. BRIAN SCHWARTZ: My answer to that would be you can't. You can't study that right now because it takes about 20 years, let's say, for solid tumors to develop after exposure to a chemical. So if the drilling has happened in the last five years, I cannot answer the cancer question right now.
HAMILTON: Schwartz says even if more time had passed, a half-dozen cancer cases probably wouldn't mean much unless they were all the same type of cancer.
SCHWARTZ: Cancer is not one disease. Cancer is a hundred different diseases. So if that person has leukemia, that person has lung cancer and that person has ovarian cancer, it's not a cancer cluster. Those three cancers all have very, very different causes.
HAMILTON: Health officials in the U.S. check out more than a thousand suspected cancer clusters each year. They almost never find anything.
Of course, cancer is just one of the concerns in DISH. The previous mayor - the guy who left town last year - is Calvin Tillman. Tillman says he got worried when his two sons began getting nosebleeds. Then one night, he says, his younger son had a nosebleed that got really bad.
CALVIN TILLMAN: Our house literally looked like a murder scene. There was blood down the wall in the hallway. And I got up the next morning to go to work and my wife said, that is it. And at that moment, we decided we've got to move out of here.
HAMILTON: Tillman moved his family off the shale, to a town called Aubrey. He says back when he was still mayor, he realized that scientists wouldn't pay attention to just one story like his. So he had residents fill out a health survey.
TILLMAN: Do you have itchy eyes, bloody nose, runny nose, scratchy throat - things like that. And it came back that about half the people that were polled had a symptom that could be related to one of the chemicals that we found in our air study.
HAMILTON: But scientists say the mere presence of a chemical isn't enough. You have to know how much people were exposed to and for how long.
Tom La Point is a toxicologist at the University of North Texas in Denton, about 15 miles east of DISH. He's also part of a task force looking at the impact of fracking. La Point says modern testing equipment can detect chemicals at levels far, far below those known to hurt anyone.
TOM LA POINT: I've had people get quite upset, saying we can measure benzene. Well, yes, we can measure benzene but the concentrations are below the effect level. And that really means something. That really does.
HAMILTON: La Point says even if tests do find enough of a chemical to cause health effects, there's another scientific hurdle. Researchers need to know whether the pollutant is coming from local gas operations or some other source, like cars and trucks. La Point says that's hard to figure out in a place like DISH, because it gets so much of its air pollution from the Dallas-Fort Worth area.
POINT: So ironically, even though we're not by any means the largest county in the metroplex, we have the worst air quality because the general winds bring it up from Dallas and Fort Worth over Denton County.
HAMILTON: Where it mixes with the pollutants from gas production.
So you've got two mayors from one small town making some big claims. And you've got scientists who say those claims aren't backed by solid evidence. But are the mayors wrong to say that gas production is a hazard?
Brian Schwartz, the epidemiologist from Johns Hopkins, says no one knows. And he says that's a big problem.
SCHWARTZ: When these areas are developed, thousands to tens of thousands of wells are drilled and fracked. So the magnitude is huge. And frankly, the development is way out ahead of public health evaluations of any kind to date.
HAMILTON: Schwartz says that's not fair to DISH or any other place where people are worried about the health effects of drilling and fracking.
Jon Hamilton, NPR News.