Coloradans living within 500 feet of an oil and gas operation have a risk of getting cancer that is eight times the upper threshold set by California’s Environmental Protection Agency, according to a new study released Monday.

The study — from the Colorado School of Public Health, Boulder County Public Health, the University of Colorado, NASA and the University of California Irvine — concluded that the cancer risk estimate for individuals within those areas to be 8.3 per 10,000.

The upper threshold of California environmental standards — which are more stringent than federal guidelines — is 1 in 10,000.

The Colorado Oil & Gas Association disputed the study, saying its author, Lisa McKenzie, “has participated in other inflammatory analysis that has been disavowed by state health officials and has even been described as misleading.”

The industry group also noted that the study looked within Colorado’s mandated 500-foot setback from occupied buildings, which grows to 1,000 feet from high-occupancy buildings such as schools or hospitals.

More than a quarter of the state’s wells, about 2,464, are within 1,000 feet of occupied buildings, according to Colorado Oil and Gas Conservation Commission data. Nine percent — 825 — are within 500 feet.

The figure in the study is a measure of additional cancer risk, on top of the baseline likelihood that all Americans have of developing cancer over their lifetimes, said McKenzie, of the Colorado School of Public Health.

On average, Americans have between a 30 percent and 40 percent chance of cancer over a lifetime. This adds less than a tenth of a percentage point to that risk, McKenzie said.

The takeaway, she said, is that “people living near oil and natural gas sites might be exposed to hazardous air pollutants at levels that could impact their health.”

The study analyzed more than 660 air samples taken during the summer of 2014 along Colorado’s Front Range; 29 samples were taken from within 500 feet of an active operations.

Concentrations of potentially harmful hydrocarbons were highest near active oil and gas sites. For example, concentrations of benzene were 41 times higher in samples collected within 500 feet of an oil and gas operation than in samples collected more than a mile away.

Samples taken in Boulder County

Included in the study were samples taken at five sites in Boulder County: Boulder County offices on Broadway and Iris Avenue in Boulder; Alexander Dawson School in Lafayette; the Lafayette Fire Department; St. Luke Orthodox Christian Church in Erie; and Stephen Day Park in Longmont.

The sampling, undertaken by the county in 2014, found that although levels of harmful compounds were higher in eastern Boulder County — the epicenter of local oil and gas activity — they did not exceed federal or California health standards. None of the samples in Boulder County were within 500 feet; the average distance of the sample sites was 1,400 feet from oil and gas operations.

Study co-author Pam Milmoe, coordinator of Boulder County Public Health’s Air Quality Program, did note that most of Boulder County’s wells are older and lower-producing, and therefore putting out fewer emissions. But two companies do have plans for new operations that could put wells close to homes.

Crestone Peak Resources’ plans for a 10-acre site between Lafayette and Erie maintain at least 1,000 feet from homes in that area. Extraction Oil & Gas is still planning locations for surface operations in its plans to develop 52 wells on 4,000 acres in eastern Boulder County; wells in its Broomfied development are 1,000 feet or more from homes, according to spokesman Brian Cain.

Boulder County Commissioner Deb Gardner, in a statement, said the 500-foot setback “is clearly not adequate to protect the health and safety of our residents.”

She called for “immediate action” from the state’s top industry regulatory authority, the COGCC and lawmakers to “safeguard the lives of Colorado residents against the devastating health effects of oil and gas.”

‘Substantial uncertainties’

Dr. Larry Wolk, executive director and chief medical officer at the Colorado Department of Public Health and Environment, said in a prepared statement that McKenzie’s study “confirms our 2017 findings of low risk for cancer and non-cancer health effects at distances 500 feet and greater.”

Wolk noted his agency’s ongoing collection of air samples near oil and gas activities. “So far, we have not found any elevated short- or long-term risks from the same substances evaluated in the McKenzie study.”

However, Wolk did say the report “underscores the potential public health importance of the 500-foot setback and the need to collect more comprehensive air quality data in communities in close proximity to oil and gas operations.”

The study’s authors acknowledged that more research was needed, noting “substantial uncertainties.” For instance, McKenzie said, the study’s authors don’t know the actual exposure levels for residents near oil and gas operations.

“We measured this concentration in the air, but we don’t know exactly what someone was exposed to,” she said. “The study is saying if someone was to be exposed to this level of air pollutant, this is what the health risk would be.”

For those opposed to oil and gas development, there is already more than enough evidence that the industry is harmful.

“The health effects of drilling are well documented,” said Cliff Willmeng, a Lafayette-based activist. “The industry will fight it to the bitter end, just like the tobacco industry did.”

Shay Castle: 303.473.1626, castles@dailycamera.com or twitter.com/shayshinecastle.