DENVER (AP) — Colorado officials committed to cleaner air and reducing reliance on fossil fuels have reached a turning point on whether to tolerate the hulking oil refinery north of Denver that ranks among the state's major polluters and regularly malfunctions.

They must approve or deny Suncor Energy's applications to renew its operating permits, which serve as contracts governing the emission levels of toxic pollutants that can cause cancer and serious heart, lung and other health problems.

This is oversight power Colorado air pollution regulators have declined to use over nearly a decade of...