People living near Barnett Shale gas production facilities could be at risk for immune system damage from toxic air emissions, and the risk is likely understated by an air quality study completed for the city of Fort Worth earlier this year, a state lawmaker warned Mayor Betsy Price in a letter.

In his letter to Price, State Rep. Lon Burnam (D-Fort Worth) said he asked the Texas Commission on Environmental Quality (TCEQ) to compile air quality monitoring findings for benzene in the Barnett gas patch. The findings Burnam reported to Price:

"While most of these exceedances occurred outside Fort Worth city limits, comparing TCEQ's sample concentrations to the ATSDR comparison values raises important questions about the city of Fort Worth's air quality study (AQS) conducted by ERG [Eastern Research Group Inc.] earlier this year," Burnam wrote.

Results of the million-dollar ERG study were released last summer and were purported to indicate little for Barnett area residents to worry about (see Shale Daily, July 19). While a handful of sites were found to have emissions exceeding regulatory allowances, setback requirements for natural gas facilities were generally said to be adequate. "Based on the emission rates that ERG calculated for this project, five sites -- a processing facility, three compressor stations and one well pad -- had overall emission rates that exceed regulatory thresholds that are supposed to trigger certain permitting requirements," the report said.

"Comparing TCEQ's results to ATSDR's MRLs for non-cancerous (particularly immunological) health effects indicates that residents living near natural gas production facilities in the Barnett Shale could be at risk of damage to their immune systems," Burnam wrote. "Because the Fort Worth AQS fails to use the more conservative (and thus more protective) health-based comparison values (such as those published by the ATSDR) in its health evaluation, the AQS' conclusions regarding the health effects of emissions from natural gas production facilities could be misleading."

Burnam said the benzene concentrations in ERG's samples were below both TCEQ and ATSDR comparison values. But the ERG AQS only sampled air around eight sites and "'ambient air monitoring stations were not close to some of the highest-emitting well pads,'" Burnam wrote, quoting from the AQS.

"Three out of four ERG dispersion modeling scenarios, however, yield benzene concentrations significantly above the ATSDR's comparison values deemed safe for acute and intermediate exposure."

Burnam called for the city to direct ERG to "reanalyze its dispersion modeling data" and its implications for public health. He wants the firm to use "the most conservative published comparison values, such as those published by the ATSDR." The city should also reevaluate its well setback requirements using the most conservative values.

TCEQ has seven air monitoring stations in the Barnett Shale and plans to add nine more within the next 18 months, a toxicologist with the agency told the Fort Worth Star-Telegram.

Price, in a statement, acknowledged Burnam's letter and and asserted the city's commitment to the health and safety of citizens. In October Fort Worth City Council voted down gas drilling ordinance changes that were based on the AQS findings (see Shale Daily, Oct. 20).

An early report from the AQS before results were finalized overstated volatile organic compound emissions at one site and was later corrected (see Shale Daily, March 2).