This story has been updated.

The Senate has passed a much-anticipated bill proposing broad reforms to an existing chemical safety law — one which environmentalists have long argued puts the American public at unnecessary risk of exposure to toxic substances.

The bill, dubbed the Frank R. Lautenberg Chemical Safety for the 21st Century Act, has been in negotiations for more than two years and finally went to a vote Thursday night, where it passed with bipartisan support. It proposes a major overhaul of the 1976 Toxic Substances Control Act (TSCA), which gives the Environmental Protection Agency authority to regulate chemicals in the U.S.

In recent years, however, environmentalists have called for major changes to the existing law, which they’ve argued does not give the EPA enough power when it comes to restricting toxic substances.

“This law is about 40 years old, and it simply hasn’t kept up with the new science that is showing how chemicals can affect our health,” said Richard Denison, lead senior scientist with the Environmental Defense Fund.

A major problem with the existing TSCA, according to Denison, is that it requires the EPA to demonstrate such a high burden of proof that a chemical is dangerous to human health as to make it nearly impossible to restrict a substance’s use. The “poster child” for this issue is the EPA’s failed attempts to ban asbestos — a substance known for its cancer-causing qualities — in the 1980s.

As a result of restrictions in the current law, Denison said, the EPA has not been able to generate adequate information on many chemicals still commonly used in the U.S., and there are also many restrictions on the information it’s permitted to share with the public, so as not to divulge confidential trade information.

“Most people assume that the chemicals in the products and materials they encounter every day have been thoroughly tested and shown to be safe,” Denison said. “In fact, only a handful of chemicals have ever been reviewed for safety.”

The new bill would grant greater authority to the EPA to study the effects of chemicals and regulate their use and has received wide support from both Democrats and Republicans. The bipartisan support is a reflection of the amount of time senators have spent negotiating the bill, a process that has required “careful balancing of the interests on both sides in this debate,” Denison said.

While the bill grants much greater regulatory authority to the EPA, which supporters hope will lead to more uniform, national health-based standards, it also includes some protections for the industry from state regulations.

The bill has also received support from members of the chemical industry. Cal Dooley, CEO of the American Chemistry Council — a trade association representing chemical manufacturers — issued a statement Thursday calling the new bill “a watershed moment in the history of U.S. environmental legislation.”

And the president of the National Association of Chemical Distributors, Eric Byer, also issued a statement Thursday saying, “Today’s vote puts us on the doorstep of finally reforming an outdated law in a way that will build confidence in the U.S. chemical regulatory system, protect human health and the environment from significant risks, and meet the commercial and competitive interests of the U.S. chemical industry and the national economy.”

However, the bill has its critics in the environmental world. Representatives of a coalition of more than 450 organizations and businesses, known as Safer Chemicals, Healthy Families, have pointed out what they consider to be key flaws in the bill.

For instance, while the bill gives the EPA greater power to review and regulate chemicals, it includes a prioritization system — which essentially classifies chemicals as “high priority” or “low priority” for further investigation — that some have argued might allow certain dangerous chemicals to slip through the cracks, said Andy Igrejas, national director of Safer Chemicals, Healthy Families.

Additionally, the coalition’s communications director, Tony Iallonardo, suggested that the bill could make it harder for the EPA to intercept imported products inappropriately containing toxic chemicals. And the coalition also opposes the aspects of the bill that would weaken states’ abilities to independently regulate chemicals while they’re undergoing review by the EPA.

As the bill has only passed in the Senate for now, it will need to be subjected to a vote in both chambers before being enacted into law. For its part, the House of Representatives passed a similar, although much more limited, bill earlier in 2015 proposing some smaller-scale reforms to the TSCA.

The House and Senate bills have to be reconciled in order to get a bill done and to the president and signed,” Denison said. “We hope it ends up with the kind of comprehensive reform that the Senate bill outlines in order to really overhaul the law.”

But while Safer Chemicals, Healthy Families doesn’t endorse either bill at the moment, Iallonardo and Igrejas noted that the House bill doesn’t contain some of the provisions they oppose in the Senate bill. And since the House bill also passed with bipartisan support, they’ve argued that it’s possible to remove some of these provisions in future negotiations without losing the support necessary to pass a final bill in both chambers. At the same time, there are aspects of the Senate bill — such as an increase in dedicated funding to the EPA’s chemical reviews — that the coalition supports.

When it comes time to reconcile the two bills, Igrejas said, “We’re urging Congress to really focus on just the basics of making this law work, empowering EPA to identify and restrict where necessary the chemicals that causing a problem and really having the authority to sling through and make those restrictions stick and be meaningful for the public.”

Such negotiations between the House and the Senate could be complete, and a final bill sent to a vote, by early 2016. And while disagreement continues over which provisions should remain in the final product, most have agreed that the moves toward reform are a much-needed step in fixing a badly outdated, and even detrimental, law.

“For the first time ever, we have both parties in both houses of Congress recognizing the need for reform and committed to getting it done,” Denison said. “Hopefully it will provide Americans the protection they need from exposure to toxic chemicals.”

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