DENVER - Colorado lawmakers on the House Health, Insurance and Environment Committee did not vote Thursday on a bill proposing a study on possible health effects of oil and natural-gas development on the Front Range.

House Bill 1297, sponsored by Rep. Joann Ginal, D-Fort Collins, and Sen. Irene Aguilar, D-Denver, would examine data from Adams, Boulder, Larimer and Weld counties. The study would cost nearly $570,000 through fiscal 2017.

When exactly lawmakers planned to revisit the bill remained unclear Friday. Aides for Ginal and Aguilar did not return phone messages left at the Capitol.

Wendy Highby, founder of activist group Weld Air and Water, said she was surprised that lawmakers did not vote on the measure, which was discussed into Thursday night. Activists like Highby have concerns about oil and gas activity in urban areas such as Greeley.

"We're going to be impacting a lot of people's lives with as close as these wells are going to be sited to densely populated areas," Highby said.

Legislators introduced a similar measure last year, which was defeated.

The study proposed by this year's bill would be conducted by the Colorado Department of Health and Environment with input from a "scientific oversight committee" consisting of nine voting members. Those members would include the chief medical officer for the state health department as well as four members appointed by legislative leadership and four others selected by Gov. John Hickenlooper.

The final report would be due Jan. 1, 2017, and would be submitted for review for publication in a scientific journal.