Breathing in Denton County is risky business — not as risky as in some parts of Dallas and Tarrant counties, federal researchers found — but riskier than the national average and far riskier than the target levels set by the Environmental Protection Agency.

A recent EPA analysis of the region’s air quality showed Denton County residents faced the same risk of developing neurological conditions as the national average. But the risk posed for cancer and respiratory diseases is nearly 25 percent higher in Denton County than the national average and 41 times the EPA’s target of 1 person per million, according to its Web site.

DRC/Barron Ludlum

Readings taken by state environmental officials at this natural gas facility just west of Dish found benzene levels well over the state limit. Benzene is a known carcinogen.

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In some parts of Dallas and Tarrant counties, as in several other highest-risk areas of the country, residents face the risk of 100 people per million developing cancer.

Where the numbers come from

State and federal legislation aimed at reducing air pollution has made progress in recent years. Officials with the Texas Commission on Environmental Quality have pointed to decreasing levels of ozone in the region’s ambient air quality over the past decade, even though critics say the agency’s plan to reduce pollution still fails to meet federal requirements.

In addition, the Environmental Protection Agency has found decreasing numbers reported to its Toxics Release Inventory in recent years. The EPA released the raw data for 2008 earlier this year and released its own analysis and research tools this month.

Toxic releases reported by Denton County manufacturers have also decreased in recent years, though largely from improvements made at Acme Brick. That company reduced its self-reported releases by 96 percent by installing scrubbers on its smokestacks.

However, the natural gas industry has not reported toxic releases in Denton County. The industry went from almost nonexistent 10 years ago to producing millions of cubic feet of natural gas out of the Barnett Shale each day.

A Rice University study, commissioned by the Environmental Defense Fund, found a strong correlation between the amount of condensate produced at Barnett Shale gas wells and the amount of certain pollutants showing up in Denton’s ambient air quality readings.

In addition, preliminary studies have found high levels of toxic chemicals at and around these facilities. For example, at natural gas compression facilities, state and private inspectors have found carbonyl sulfide, carbon disulfide and the known carcinogens — benzene, toluene, ethylbenzene, xylene and napthalene.

Additional data from several TCEQ studies is scheduled to be released at the end of this month, and the agency’s report is scheduled to be released in January.

Assessing the impact

To measure the potential impact on communities of both the ambient air quality and toxic releases inventory, the EPA released the National-Scale Air Toxics Assessment for 2002 in June.

That was the latest year federal scientists had comprehensive data available on toxic air.

The EPA conducted similar assessments in 1996 and 1999.

According to the assessment, benzene presents the primary source of Denton County’s cancer risk, which is 41 people in a million, versus the national average of 33, and the EPA’s target of 1 person in a million.

The chemicals presenting the biggest risk for neurological and respiratory diseases were xlyenes, which come from both industrial sources and auto exhaust, and acrolein, which is formed by the breakdown of pollutants in outside air, according to the assessment.

Local health officials do not monitor those numbers, Denton County Health Depart­ment spokeswoman Betsy Haggard said.

No one knows how many compression facilities are operating in Denton County or elsewhere in the Barnett Shale because not all facilities are required to get a permit before operating, according to Tony Walker, TCEQ’s director of Region 4.

Industry representatives have said their compression engines have catalytic converters, just like cars, to reduce their emissions.

However, recent inspections by the TCEQ have found substantial emissions elsewhere at gas plants and wellheads, near condensate tanks, vent stacks and even unlit flares.

Preliminary readings at some sites could present health problems to workers, according to David Sterling, a public health expert at the University of North Texas Health Science Center.

“At 15 parts per million, benzene becomes a risk to workers in 10 to 15 minutes,” Sterling said of a reading found at the fence line of a wellhead west of Dish in August.

A 2004 National Cancer Institute study of workers in a shoe manufacturing plant showed that exposure as low as one part per million of benzene in the air was enough to change the workers’ white blood cell counts.

According to the National Institutes of Health, people who are regularly exposed to low levels of benzene can develop severe anemia, leukemia and lymphoma.

The risk for the general population is less clear, Sterling said.

Future studies need to show whether preliminary readings are just a one-time thing. If not, if emissions are close to children and older people, “it’s quite a different tune,” Sterling said.

He called for state regulators to make a plan that protects public health, and to let the public see and review that plan, enforce it and show the plan is working.

There’s no reason to close down plants, Sterling said.

“They can be run in a manner that we can have the industry and health. It doesn’t have to be an either-or situation,” Sterling said.

PEGGY HEINKEL-WOLFE can be reached at 940-566-6881. Her e-mail address is pheinkel-wolfe@dentonrc.com.

MORE ON THE WEB

Explore the Environmental Protection Agency’s Toxics Release Inventory: www.epa.gov/triexplorer

Read more about lead exposure: www.epa.gov/lead

Read more about hydrochloric acid exposure: www.epa.gov/ttn/atw/hlthef/hydrochl.html

Read more about how a child’s IQ can be affected by the mother’s exposure to air pollutants: www.cumc.columbia.edu/dept/mailman/ccceh/pdf-papers/PereraPediatrics2009.pdf

Read more about how magnetic resonance imaging found brain damage from lead exposure: www.cincinnatichildrens.org/about/news/release/2009/lead-exposure-12-2-2009.htm

Look up your school on USA Today’s report “The Smokestack Effect”: http://content.usatoday.com/news/nation/environment/smokestack/index

Read more about a Rice University study linking natural gas production and Denton’s air quality: www.edf.org/pressrelease.cfm?contentID=10489

Read a summary of reports from the National Institute for Health about benzene exposure and a study from the National Cancer Institute: www.cancer.gov/cancertopics/factsheet/risk/benzene