PCBs are persistent, human-made chemicals that the Environmental Protection Agency has linked to cancer and adverse immune and neurological effects.

Regulations promulgated by the EPA in 1979 largely banned production and use of PCBs, which were used in products such as electrical equipment and paints.

From 1929 until 1977, Monsanto manufactured and sold nearly all PCBs used in the United States, according to the Commonwealth Court opinion.

Monsanto acknowledged the adverse health effects of PCBs as early as 1937 but continued to market and sell products containing the chemicals until 1977 without warning the public about potential hazards, the suit says.

In December 2020 Pennsylvania sued Monsanto, Solutia and Pharmacia in the Commonwealth Court, which is generally an appeals court but serves as trial court in lawsuits filed by or against the state.

The suit alleges that Monsanto's PCB products have contributed to widespread and persistent contamination of air, soil and water, including more than 1,300 miles of streams and over 3,600 acres of lakes in the commonwealth.

The defendants filed preliminary objections in April, seeking dismissal of the suit for lack of standing and legally insufficient claims.

Writing for the court, Judge Anne E. Covey said Pennsylvania has standing to pursue its claims under the parens patriae doctrine, which allows the commonwealth to pursue legal action on behalf of citizens to preserve public natural resources and protect public health.

Additionally, Pennsylvania has standing as a trustee of the commonwealth's natural resources under the environmental rights amendment of the Pennsylvania Constitution, Pa. Const. art. 1, § 27, according to the court.

The court overruled the defendants' preliminary objections to the public nuisance, design-defect, failure-to-warn, negligence and damage claims, saying they had not shown with certainty that the law does not permit recovery by the plaintiffs.

However, the court dismissed the trespass and unjust-enrichment claims, saying Pennsylvania and its environmental agencies had failed to plead all necessary elements.

The trespass claim is legally insufficient because Pennsylvania failed to adequately allege that the defendants intentionally released PCBs onto state lands or directed a third party to do so, the court said.

Similarly, the commonwealth did not sufficiently plead it had conferred a benefit on the defendants when it investigated and responded to the PCBs' effects, which is required to sustain an unjust-enrichment claim, according to the court.

"The doctrine does not apply simply because the defendant may have benefited as a result of the actions of the plaintiff," the court said, quoting Lackner v. Glosser, 892 A.2d 21 (Pa. Super. Ct. 2006).

Finally, the court dismissed in part the suit's continuing tort claim, saying Pennsylvania could only pursue its allegations that the defendants had a continuing duty to warn, correct and remediate damage caused by their conduct.

In a concurring opinion, Judge P. Kevin Brobson said affording the state broad access to common law pollution remedies "would make dead letters out of our environmental laws."

In a Dec. 30 statement, current Monsanto parent Bayer AG, which is not a named party, said it will continue to challenge the suit's legal merits.

"Monsanto voluntarily stopped its lawful production of PCBs more than 40 years ago and never manufactured, used or disposed of PCBs into Pennsylvania's waters, and therefore should not be held liable for the contamination alleged by the plaintiffs," Bayer said.

Leslie M. Greenspan of the Tucker Law Group LLC represented Pennsylvania. Thomas M. Goutman of Shook Hardy & Bacon LLP represented the defendants.