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Leukemia, for example, might be caused by exposure to benzene. Butbreast cancer isn't. Another problem is that most so-called cancer clusters are randomevents, Schwartz says. They're not caused by anything in theenvironment. "If I take a shotgun and I blast it against that wall, there willbe a random pattern of holes in the wall, right?" he says. "And Icould draw a circle around three or four or five that look to be abit more densely packed than all the other ones." But it would still be a cluster caused purely by chance. Of course, cancer is just one of the concerns in Dish. Residentsare also worried about immune diseases, reproductive problems and awide range of symptoms. The town's previous mayor, Calvin Tillman, became alarmed when histwo boys started getting nosebleeds. They seemed to occur when theodors of gas were strongest and air quality monitoring showedhigher levels of chemicals, Tillman says. Then one night his younger son had a really bad nosebleed. "Our house literally looked like a murder scene," Tillman says."There was blood down the wall and in the hallway. And I got up thenext morning to go to work, and my wife said, 'That is it.' And atthat moment we decided we've got to move out of here." Tillman and his family moved off the shale, to a town calledAubrey, Texas. Tillman knows that's just one family's story. But hesays he documented others several years earlier when he had Dishresidents take a health survey asking whether they had experiencedsymptoms such as itchy eyes, a bloody nose or a scratchy throat. "It came back that about half of the people that were polled had asymptom that could be related to one of the chemicals that we foundin our air study," Tillman says. Better Studies Are Needed But the mere presence of a chemical isn't enough to show it causeda symptom, scientists say. You have to show that a person wasexposed to a high enough concentration for a long enough period tocause itchy eyes or a scratchy throat. And the Dish survey didn't do that, says Tom La Point, atoxicologist at the University of North Texas in Denton, about 15miles east of Dish, and a member of a task force looking at theimpact of gas drilling. La Point says test results can be confusing because modernequipment is able to detect chemicals at levels far, far belowthose known to produce symptoms. "I've had people get quite upset saying we can measure benzene," hesays. "Well, yes we can measure benzene. But the concentrations arebelow the effect level. And that really means something. It reallydoes." Even if tests in Dish had shown enough of certain pollutants tocause health effects, there would still be another scientifichurdle, La Point says. Researchers would need to know whether thepollutant was coming from local gas operations or some other source like vehicle tailpipes. And that's hard to figure out in a place like Dish, which is inDenton County and gets a lot of air pollution from the Dallas-FortWorth metroplex, La Point says. "Ironically," La Point says, "even though we're not by any meansthe largest county in the metroplex, we have the worst air qualitybecause the general winds bring it up from Dallas and Fort Worth,"where the pollution from cars mixes with the pollution from gasoperations. Scientists are quick to caution that the problems with evidencefrom Dish do not show that gas drilling is safe for people who livenear it. What the caveats show is that there is a pressing need forrigorous scientific studies, Schwartz says. "When these areas are developed, thousands to tens of thousands ofwells are drilled and fracked. So the magnitude is huge," he says."And frankly, the development is way out ahead of public healthevaluations of any kind to date." That's not fair to the people in Dish or any other place in thecountry where drilling and fracking have got people worried, hesays. We are high quality suppliers, our products such as Flat Panel LED Light , T8 LED Tube Lights Manufacturer for oversee buyer. To know more, please visits Round LED Panel Light.
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