In the study, University of Texas at Arlington biochemists measured 100 wells across the Barnett Shale, believed to hold one of the largest natural gas reserves in the U.S.
FORT WORTH, TEXAS (AP) - North Texas water wells within two miles of active gas drilling sites contain higher concentrations of arsenic and other carcinogens, according to a study published in the journal Environmental Science and Technology.
In the study, University of Texas at Arlington biochemists measured 100 wells across the Barnett Shale, believed to hold one of the largest natural gas reserves in the U.S., and compared the results to a similar study undertaken before hydraulic fracturing technology and higher natural gas prices opened the area to drilling.
Some 30 percent of the wells within 1.8 miles of gas drilling sites showed an increased amount of arsenic and other heavy metals, the study said, and 29 wells exceeded the Environmental Protection Agency's maximum arsenic limits of 10 parts per billion.
One of the researchers, UTA biochemist Zacariah Hildenbrand, told The Denton Record-Chronicle that "to find that high of arsenic concentrations was alarming."
"This is indirect evidence that drilling does affect the water," he said.
Researchers believe the wells were contaminated when shaking caused by fracking knocked rust off old pipes and into fresh water. But Texas Alliance of Energy Producers spokesman Alex Mills called the theory "a little farfetched."
An industry veteran, Mills said natural gas wells are drilled so deep that vibrations from drilling would never reach far shallower water wells.
Researchers also said in the study that higher concentrations of heavy metals could alternatively be the result of the lowering of the water table or faulty casings around gas drilling operations, which would allow contaminants to flow up through the well bore and into aquifers and other supplies of drinking water.
A team of researchers at Southern Methodist University are also studying the Barnett Shale, trying to determine whether fracking - which involves blasting water, sand and chemicals deep into underground rock formations to free oil and gas - and the disposal of vast amounts of wastewater into injection wells has caused an unprecedented series of earthquakes.
Fracking produces millions of gallons of chemical-laced wastewater.
The liquid, called brine, is a mix of chemicals, saltwater, naturally occurring radioactive material and mud, and is considered unsafe for ground water and aquifers.