JEFFERSON CITY, Mo. It may not be the language that either side wanted, but after a four-hour filibuster Tuesday, the Senate gave first-round approval to a bill that would make significant changes to the state's workers' compensation system.

As the bill stands, it would prohibit employees from bringing lawsuits against co-workers in most on the job injuries. A hard-fought-for amendment would also prevent employers from recouping workers' compensation costs from civil lawsuits filed by employees against a third party.

"They're not my first set of options, or my second set of options, or my third set of options or my fourth," said Sen. Jack Goodman, R-Mt. Vernon, who sponsored the bill. "But we are in a deliberative body with 34 members who all are entitled to work their own consciousness."

Limiting the liability of co-workers was the main provision of the bill, a key piece of the state GOP's pro-business agenda this session. But when it first came to the floor two weeks ago it was held up by the objections of two senior senators, Sen. Jason Crowell, R-Cape Girardeau, and Sen. Kevin Engler, R-Farmington. They each objected to a provision that would take illnesses stemming from on-the-job toxic exposure out of the workers' compensation system and place it in the courts.

Goodman and other supporters of this original measure said that the unique nature of toxic exposure illnesses which develop over time and are harder to pinpoint the cause of make them better suited for court where there is a higher threshold of evidence required to prove negligibility. Supporters said this would help protect business from false toxic exposure claims.

But due to the increased burden of proof compared with workers' compensation claims, Engler and Crowell said that it would become more difficult for affected workers to receive benefits. After a proposal by Crowell to keep toxic exposure cases in the workers' compensation system and double the amount that companies could pay to more than 800 weeks was rejected, he proposed an amendment that more narrowly focused on the issue of preventing companies' ability to recoup workers' compensation payments through a practice known as subrogation.

Because toxic exposure cases frequently involve civil suits against third parties in addition to workers' compensation claims, Crowell said employers frequently are able to recapture some of the money they've paid from the third party through subrogation.

"If an employer can just subrogate from any third party actions out there, then they have no skin in the game at all to make any kind of changes," Crowell said.

The amendment was ultimately added to the bill, drastically altering it from similar legislation currently working its way through the House of Representatives. Crowell and Engler both noted that their amendment could face a challenge if the bill makes it to a conference committee, where legislative differences are reconciled. But Engler said that even if that is the case, it was worth fighting for in the Senate.

"You have an opportunity as a senator to right an injustice that a company has no financial interest when they've harmed somebody," he said. "This makes them have some financial interest."

The bill faces one final vote in the Senate, likely to occur later this week.