“Our future work depends on striking the right balance to strengthen the U.S. Environmental Protection Agency’s abilities and funding, without limiting state powers in creating and enforcing needed protections,” said a letter, obtained by The New York Times, sent by the top environmental regulators in California, Connecticut, Minnesota, New Hampshire, New York, Oregon, Washington and West Virginia.

Some of the most vociferous objections relate to the so-called Monsanto Clause. The provision does not mention the company by name, but between the early 1930s and 1977, Monsanto manufactured almost all of the 1.25 billion pounds of PCBs sold in the United States.

The chemicals were initially admired for their ability to prevent fires and explosions in electrical transformers and other equipment. But as the use of PCBs skyrocketed nationwide in products as varied as paints, pesticides and even carbonless copy paper, evidence mounted that they were contaminating the environment and potentially causing health problems including cancer and immune-system complications. The E.P.A. banned their production in 1979.

PCB litigation has surged in the last year as cities and school systems struggle to comply with directives from federal and state regulators to reduce PCB levels in sewer discharge and in caulk once used to construct schools. Separately, a group of individuals who received diagnoses of a form of cancer known as non-Hodgkin’s lymphoma sued Monsanto last year, claiming the company should pay damages.

The Senate Environment and Public Works Committee, in a June report accompanying its version of the legislation, asserted that neither existing toxic chemical law nor any revisions pending in Congress should be seen as a way to “pre-empt, displace or supplant” the right to sue for damages in lawsuits like the ones filed against Monsanto.

The House also voted to preserve the right to sue if individuals or local governments believe they have been harmed by a chemical, regardless of future federal regulations of the substance. But a critical paragraph added to the House bill in late May made sure past regulatory requirements by the E.P.A. would continue to disqualify legal claims, and it specifically referred to the section of the 1976 toxic chemical law governing PCBs, giving Monsanto clearer authority in the future to ask judges to dismiss lawsuits filed against it.