Emissions from oil and natural gas operations account for more than half of the pollutants — such as propane and butane — that contribute to ozone formation in Erie, according to a new scientific study published this week.

The study, the work of scientists at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado, concluded that oil and gas activity contributed about 55 percent of the volatile organic compounds linked to unhealthy ground-level ozone in Erie.

Key to the findings was the recent discovery of a “chemical signature” that differentiates emissions from oil and gas activity from those given off by automobiles, cow manure or other sources of volatile organic compounds.

“There were very, very few data points that did not fall on the natural gas line,” Jessica Gilman, research scientist at CIRES and lead author of the study, said Wednesday. “We had a very strong signature from the raw natural gas.”

CIRES is a joint institute of CU and the National Oceanic and Atmospheric Administration. Its study was published online Monday in the journal Environmental Science and Technology.

Emissions detected in Boulder

The air quality monitoring effort, dubbed the Boulder Atmospheric Observatory, was conducted in February and March of 2011 on a tower set up a couple of miles east of downtown Erie.

It showed that, on average, Erie had highly elevated levels of propane in its air — 10 times the levels found in famously smoggy Pasadena, Calif., and four times those in Houston. The results prompted town leaders last year to place a six-month moratorium on new drilling applications while they gathered additional information on the fast-growing industry.

But trying to determine exactly how much of Erie’s propane was due to the thousands of gas wells located in and around town, and how much was due to the effects of being part of a major metropolitan area, was inexact at best.

Until now.

“What we saw at the Boulder Atmospheric Observatory was the mixing of two sources — oil and gas and vehicles,” Joost de Gouw, research physicist at CIRES, said. “For each compound, we can separate how much came from oil and gas and how much came from vehicles.”

The researchers arrived at the unique chemical signature by analyzing the chemical makeup of all their air samples, characterizing 53 different types of volatile organic compounds and comparing the results to the composition of raw natural gas.

“We estimate 55 percent of the compounds contributing to ozone formation in Erie are from oil and gas,” de Gouw said.

And it’s not just Erie that is affected by oil and gas activity, which has exploded in recent years in the gigantic Wattenberg Gas Field northeast of Denver. The study showed that scientists found the telltale signs of drilling emissions in air samples taken in Fort Collins and Boulder, albeit in lesser amounts.

“Air pollution can travel many, many miles downwind from the source,” Gilman said. “Air doesn’t stop at any border.”

Health effects in dispute

But whether emissions from oil and gas activity are endangering human health on a wide scale continues to be fiercely debated. Multiple families in Erie and around the state have complained that living so close to wells has made them sick, with nosebleeds, asthma and headaches as common symptoms.

But two studies commissioned by the town last year concluded that the levels of propane in Erie weren’t concerning.

One environmental consulting firm concluded that even a lifetime exposure to the concentrations cited in the CIRES study would have a “low” risk of causing adverse health effects. A second firm stated that the town’s propane levels were “1,000-fold or more below those considered to be of health concern.”

Doug Flanders, spokesman for the Colorado Oil and Gas Association, wrote in an email Wednesday that Denver’s air quality is “much better” than that of Houston or Los Angeles.

“December 2012 EPA data show Denver-area smog levels are well below those of Houston or Los Angeles,” he wrote.

Gordon Pierce, technical services program manager for the Colorado Department of Public Health and Environment’s air pollution control division, said the state put in place stricter ozone controls in 2006 and 2008 for the oil and gas industry.

New control requirements were established for condensate tanks and new reporting and record-keeping requirements were also implemented. Late last year, Pierce said, the state adopted new EPA rules regarding emissions at gas wells. But he said his agency will continue to monitor the effects of the industry in Colorado, which now has more than 50,000 active wells.

There may not be proven health effects from individual volatile organic compounds, Pierce said, but when those compounds are combined with nitrogen oxides from vehicle tailpipes and baked in the sun, they form ozone. At ground level, ozone can cause breathing difficulties and eye irritations, especially among the young and elderly.

He said it’s possible that if a strong enough link is established between oil and gas operations and high levels of ozone, the state could pursue stronger regulatory measures.

“We’re always looking at different strategies for reducing ozone,” Pierce said.

Pointing to Weld County

In the meantime, anti-drilling activists such as Jen Palazzolo plan to use the CIRES study’s findings to once again put pressure on Erie’s elected leaders to be tougher on oil and gas operators in town. Palazzolo is a leader of Erie Rising, a group that has strongly resisted oil and gas drilling in Erie.

“The study supports information that we’ve been trying to put out and that the industry has been trying to shoot down,” she said. “There’s no way you can argue against the fact that oil and gas contributes to ozone precursors.”

After its drilling moratorium expired in September, Erie entered into memoranda of understanding with two operators that require them to use steel-rim berms around tanks and separators, closed-loop systems for drilling and completion operations, and a more effective vapor recovery unit for new wells. The companies also agreed not to use hydraulic fracturing fluid products that contain diesel, 2-Butoxyethanol or benzene.

But Palazzolo and others opposed to the industry say those agreements don’t do nearly enough to protect the public health.

“It’s time for us to re-address this with the Erie Board of Trustees and ask them if they are going to continue approving the number of oil and gas operations that are planned in town,” she said.

Erie Trustee Mark Gruber said the town has done just about all it can on the issue, given the reality that control over the industry rests with the state and not local communities. Furthermore, he wonders how effective additional restrictions would be given the fact that the science indicates that volatile organic compounds are windborne and travel long distances.

“By and large, the contamination we see — if it’s in Erie, I’m going to point to Weld County,” he said. “We’re between a rock and a hard place. We’ve got 300 wells, they’ve got 19,000. We can’t build a wall to stop the emissions coming from Weld County.”

The county had 19,799 active wells as of last week, and in 2012 saw 1,826 well permits approved, representing 48 percent of all permits approved statewide that year.

Weld County Commissioner Sean Conway said his county works closely with state health authorities on ensuring the cleanest footprint from oil and gas operations. Ninety-five to 98 percent of emissions are being captured by the industry now, he said, and ozone levels have actually decreased in his county over the last few years.

Still, he said he welcomes the news this week that emissions from the oil and gas industry can be specifically traced by their chemical makeup. He said it could serve as a powerful tool for dealing with the industry from a factual standpoint, rather than an emotional one.

“If they are able to identify this now, it will give us a good starting point in identifying what are the actual impacts of this and how we go about ensuring public health and safety,” Conway said.