SALEM, Ore. (AP) — A plan intended to address Oregon air standards following the discovery of airborne pollutants in Portland neighborhoods advanced Tuesday in the Legislature.

Along with the plan itself lawmakers attached a set of changes stripping a protection for polluters and lowering a pollution limit that had been the subject of controversy. Lawmakers in a joint subcommittee unanimously approved the proposal and amendments and sent it forward for further consideration.

The movement of the proposal was 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 and Oregon Gov. Kate Brown directed the state Department of Environmental Quality and the Oregon Health Authority to develop health-based rules for polluters.

The proposal that advanced Tuesday was one of three introduced to fund the program - but controversy arose over rules the proposal added along with the funding. Environmental advocates charged that the bill set thresholds for toxin emissions too high.

Businesses and manufacturing industry lobby groups including the Northwest Pulp and Paper Association, Boise Cascade wood products company, and Ash Grove Cement Company submitted remarks in favor of the proposal at an earlier public hearing.

But amendments to the bill, approved Tuesday, changed it enough to win support from some environmental groups.

One change was to the threshold for cancer-causing chemicals. Brown had proposed regulating companies whose emissions risked sickening 25 people for every million exposed, but the original Senate bill had called for doubling that limit. An amendment Tuesday eliminated the increase.

Another change was to liability: the original proposal had included language shielding corporations from being sued for breaking the rules set by the state. But another amendment adopted Tuesday eliminated the protection.

"This bill is a massive breakthrough," said Mary Peveto, head of Neighbors for Clean Air, a Portland nonprofit group that before the amendments had been against the bill.

The Oregon Environmental Council likewise changed their position after the amendments.