Eighteen Democratic state legislators in Colorado earlier this month sent a letter to the state’s top public health and environmental scientist, questioning a report released in February that concluded there are few health risks for people living near oil and natural gas drilling sites.

At a time when some residents and activist groups are questioning the state’s requirements for minimum distances for oil and gas activity from populations, the lawmakers’ concerns about the report, “Assessment of Potential Public Health Effects from Oil and Gas Extraction in Colorado,” take on added significance in a state whose economy is heavily dependent on the growth of natural resource development.

Lawmakers wrote to Larry Wolk, chief medical officer of the Department of Public Health and Environment (DPHE), who produced the report in response to a recommendation from Gov. John Hickenlooper’s statewide oil/gas task force convened in 2014-2015 related to oil/gas development.

The lawmakers urged DPHE to be “precautionary in protecting the health and safety of Coloradans” as opposed to “acting like there is no significant problem.” They also faulted the study for not using air quality data or considering oil/gas effects on the state climate plan.

Depending on how hard the lawmakers push their concerns, they could end up challenging Hickenlooper, a Democrat and trained geologist who has supported oil and gas development and environmental protections.

DPHE’s study that prompted the report combined more than 10,000 air quality samples to evaluate how 62 substances in the samples compared to identified safe levels for human exposure. Among the conclusions were:

Wolk pointed out at the time that DPHE reviewed 12 previous epidemiological studies that looked at potential health effects from living near oil and gas operations. The previous studies provided “limited evidence” of the possibility for harmful health effects, the latest work concluded.

The lawmakers’ letter referred to the latest report as “dismissive of public health risks,” and questioned its “in-house” origin by DPHE instead an independent research team.

When the results was released, Wolk said it was an evaluation based on existing science and that “going forward, we will continue to evaluate health risks using more comprehensive, relevant data currently being collected.”

Ultimately, the state legislators told Wolk they would like to see a “new, transparent, peer-reviewed” study of people living and working near oil/gas operations.