SALEM, Ore. — A plan intended to address Oregon air standards is advancing in the state legislature.

Along with the plan itself, lawmakers attached a set of changes Tuesday, stripping a protection for polluters and lowering a pollution limit that had been the subject of controversy, in a development some environmental advocates said amounted to a win.

The movement of the proposal comes as the latest development since regulators discovered significant levels of airborne pollutants including cadmium and hexavalent chromium in Portland neighborhoods in 2016. Many of the chemicals were suspected of being linked to manufacturers in the area, including glass manufacturer Bullseye Glass, and Oregon Gov. Kate Brown directed the state Department of Environmental Quality and the Oregon Health Authority to develop health-based rules for polluters.