The Texas Commission on Environmental Quality (TCEQ) said it had reviewed air quality test results in the Barnett Shale that found trace amounts of a chemical compound once used widely as a pesticide, but said there is no danger to the public health and the chemical is unlikely to have come from oil and gas activities.
TCEQ spokesman Terry Clawson told NGI's Shale Daily that the agency evaluated three samples taken in April and May from sites near Argyle, TX, "out of an abundance of caution," but added that none of the tests had definitively detected the presence of ethylene dibromide (EDB), a known carcinogen.
"Since the sample detection limits -- the levels at which modern technology can say for certain that this chemical is definitely even present -- for EDB for these three samples are 0.40 ppb [parts per billion], we cannot confidently say that the EDB was actually present in these samples," Clawson said Wednesday. "The concentrations indicated in these three samples may be due to the sampling and analytical procedure itself instead of actually being present in the ambient air."
TCEQ reportedly detected trace amounts of EDB on April 11 and May 13 -- totaling 0.12 ppb and 0.08 ppb, respectively -- at a well pad owned by Gulftex Operating Inc. in Bartonville, TX. The agency recorded a 0.11 ppb reading of the compound on May 13 near a gas compression facility run by Williams Production Co., near Argyle.
Clawson said trace amounts of EDB have been detected across the state for years. He said the TCEQ found the compound at very low levels in about 2.5% of more than 30,000 air quality samples taken statewide since 2000. In the Barnett Shale, the agency found EDB in 2% of the air samples it has taken since 2003, "all of which have been at concentrations that would not be of health concern."
"Monitored concentrations of EDB are typically reported at concentrations so low that they are less than values that can be confidently measured by laboratory instruments," Clawson said. "[But] despite these analytical limitations, the TCEQ evaluates the limited detections as a worst-case scenario in order to evaluate them from a health and welfare perspective."
Clawson indicated that he took issue with the notion set forth by the Denton Record-Chronicle that the test results warranted an investigation by the TCEQ.
"It is not scientifically appropriate to compare a concentration in a short-term sample to a long-term [one]," Clawson said. "EDB has never been detected above the method detection limit at any stationary monitor analyzing for EDB in TCEQ Region 4 in the last 10 years. Based on monitoring data and what we know about the levels that actually cause health effects, we do not believe EDB poses a short-term or a long-term health concern."
EDB was once used as an additive in leaded gasoline and as a pesticide and fungicide for crops and soil, but the EPA banned its usage in most cases by 1984. The compound is still used by the pharmaceutical industry, and also as a pesticide to treat logs for termites, bark beetles and wax moths. Other uses include the manufacture of dyes, waxes, resins and gums.
Clawson said the agency's data does not identify the source of the EDB, but suggested some possible explanations for its presence.
"Theoretically, possible sources of EDB at an oil and gas production facility could include vehicular traffic and compressor engines," Clawson said. "However, because of the reduced usage of leaded gasoline in vehicles and the fact that testing for EDB emissions from compressor engines has only measured trace amounts in some instances, it is unlikely that oil and gas facilities are sources of the EDB observed in air in the Barnett Shale region."
Officials with Gulftex and Williams did not return calls seeking comment.
EPA spokesman Joe Hubbard told NGI's Shale Daily that it would coordinate with the TCEQ to address air quality concerns in Argyle.
"Currently, we are not aware of any link between EDB and oil and gas production," Hubbard said Wednesday. "The Clean Air Act does not provide air emission limits for EDB, however NIOSH [the National Institute for Occupational Safety and Health] and OSHA [the Occupational Safety and Health Administration] do have restrictions for worker safety."
Drilling activity in the Barnett has been on the decline over the last year, according to NGI's Shale Daily Unconventional Rig Count. While the play only saw a 2% decline in drilling from 66 rigs to 65 rigs from the week ending Aug. 12 to the week ending Aug. 19, the Barnett has seen a 24% decline from the 85 rigs in operation one year ago.