Sen. Rand Paul (R-Ky.) takes questions during an interview with the Associated Press in his Capitol Hill office in Washington on Tuesday, Feb. 10, 2015. (AP Photo/J. Scott Applewhite)

A bipartisan measure that would overhaul the nation’s chemical safety laws seemed destined for the president’s desk this week — until Sen. Rand Paul (R-Ky.) put a hold on it Thursday.

The Frank R. Lautenberg Chemical Safety for the 21st Century Act, which passed the House easily Tuesday and was slated for a vote Thursday in the Senate, had been hailed as a rare example of Republicans and Democrats reaching consensus on a critical public policy question. Both industry officials and public health activists say the 40-year-old law governing the regulation of thousands of chemicals, the Toxic Substances Control Act, does not work.

But Paul said the measure, which will provide the industry with greater certainty while giving the Environmental Protection Agency the right to obtain more information about a chemical before approving its commercial use, had not been subject to enough scrutiny. The legislation is a compromise between House and Senate measures, and reflects additional changes that were made in negotiations this month.

Speaking on the Senate floor, Paul said the bill was 180 pages long and needed more review. “I told people, everybody involved in this, I just want to read the bill,” he said.

Paul said he was concerns about provisions that would prevent states from acting unilaterally on chemical regulation, and higher fines or imprisonment for anyone who “places an individual in imminent danger of death or serious bodily injury.”

As a result of that provision and another one increasing fines for knowingly violating the law, Paul said, “it involves new criminalization, new crimes that will be created at the federal level.”

In an interview Wednesday one of the bill’s authors, Sen. Jeff Merkley (D-Ore.), spoke as if he had a sneaking suspicion something was going to go wrong.

“It’s been like we’ve been running a marathon and we can see the tape at the end of the block,” Merkley said, less than 24 hours before Paul raised his objection. “We want to get across the finish line before something untoward happens.”

Advocates of the reform — including Donelle Harder, spokeswoman for Sen. James M. Inhofe (R-Okla.) — could barely contain their frustration. The bill passed the House 403 to 12, and in an email to reporters, Harder observed that Paul tacitly approved the measure when it passed unanimously in December.

“All that to say, I couldn’t help but realize today that I have personally carried and birthed a child in the same amount of time in which Rand Paul could have raised objections to the few lines in this bill that he is now calling ‘rushed,'” Harder wrote.

Richard Denison of the Environmental Defense Fund was equally critical. “Well, it looks like American families will have to wait a bit longer for better protection from toxic chemicals” given Rand’s decision, Denison wrote in a blog post.

The bill is likely to come up for a Senate vote in June, after the Memorial Day recess.