The U.S. Environmental Protection Agency has agreed to re-examine the accuracy of its 33-year-old estimates of air pollution from flaring near refineries and at oil and gas drilling sites. The decision has health advocates and some people in South Texas hoping relief from the effects of foul air is coming.

The agreement comes in the wake of a lawsuit against the EPA by four environmental organizations. They claimed that air samples near oil refineries in Houston showed elevated levels of volatile organic compounds, chemicals associated with threats to public health and smog-forming pollution. Those levels, the plaintiffs said, were 10 to 100 times higher than being reported under outdated and inaccurate formulas that estimate levels of air pollution.

Although the lawsuit focused on refineries in Houston, the agreement could have consequences nationwide. Booming oil and gas drilling in Pennsylvania, Colorado, North Dakota and other states have been blamed for noxious emissions that residents say has sickened them.

The EPA said it will re-examine, and if necessary revise, the emissions formulas for flares at many of the estimated one million natural gas drilling and production sites across the country, according to the consent decree filed with the U.S. District Court for the District of Columbia.

The EPA has until February 2018 to complete its review and issue any revisions to the emissions equation.

The agency did not respond to a request for comment.

Flaring is used to burn off unwanted gas at drilling sites and refineries. It serves as a constant visual reminder that chemicals not consumed by the flames are being released into the air.

The environmental organizations contended that roughly 80 percent of industries do not monitor emissions from their flares and other facilities. Instead, they rely on estimates using formulas approved by EPA to comply with the reporting requirements of the federal Clean Air Act.

Those calculations have not been studied since 1983, the organizations found, although the law requires the EPA to review and if necessary revise these formulas every three years.

A more precise accounting of the compounds emitted during flaring will give a better understanding of potential health effects faced by people living nearby, according to Adrian Shelley, executive director of Air Alliance Houston, one of the four groups that sued the EPA.

"There has been want of information for people complaining of poor air quality and how it has been affecting their quality of life," he said. "We hope that this means that will change."

William Anaya, a Chicago-based attorney who represents the oil and gas industry in issues involving the EPA, cautioned that the agency must act fairly when evaluating its emissions formula.

"If the EPA is considering ratcheting up control of emissions, then it must consider that industry has built its infrastructure based on a formula that has been in place for years," he said.

Any new rules must be gradually implemented to allow the industry to comply, Anaya said, and the EPA should consider exempting or "grandfathering" existing flares that were designed to meet EPA standards at the time they built.

The environmentalists' lawsuit was filed in 2013 by Shelley's organization, the Community In-Power and Development Association, Louisiana Bucket Brigade, Texas Environmental Justice Advocacy Services and was represented by the Environmental Integrity Project.

The suit cited studies showing that smog-forming emissions can be 132 times greater than EPA estimates, which are based on data provided by the industry. The organizations claimed levels of carbon monoxide, nitrogen oxides and VOCs—including benzene, toluene and xylene—were underreported.

These chemicals have been proven to cause cancer and damage to the liver and kidneys. They also are a contributing factor in the formation of ozone known to be a major respiratory hazard.

A 2014 investigative series by InsideClimate News, the Center for Public Integrity and The Weather Channel explored the consequences to the health of people living in the Eagle Ford region of South Texas who were exposed to industry's pollutants.

Lynn Buehring and her husband, Shelby, have long suffered from the foul air that cloaks their small ranch house on the Texas prairie near Karnes City.

Their home is surrounded by dozens of oil and gas facilities that flare around the clock, generating emissions that Lynn Buehring says has exacerbated her breathing problems to a critical point.

So the news that tighter emission standards may be put in place elicited hope for stronger clean air protections. It also validated Buehring's contention— one embraced by her neighbors as well as many across the country —that the dirty air was caused by emissions wafting from these flares.

"Anything that will improve our quality of life will mean a lot," she said.