A federal appeals court has declined to reconsider its decision upholding the dismissal of a toxic substance exposure lawsuit brought by a group of employees who sought establishment of a medical monitoring trust fund.

In 2006, the 5th U.S. Circuit Court of Appeals withheld a final decision in the case until the Mississippi Supreme Court certified whether a medical monitoring cause of action is allowed under state law.

A cause of action is a specific legal claim — such as for negligence or medical malpractice — for which a plaintiff seeks compensation. Each cause of action is divided into elements, all of which must be proved to present a winning case.

Earlier this year, the Mississippi Supreme Court ruled that state law does not recognize a cause of action for medical monitoring. The justices said the “possibility of a future injury is insufficient to maintain a tort claim,” according to court papers.

In March, the 5th Circuit upheld U.S. District Court Judge Louis Guirola Jr.’s 2005 dismissal of the lawsuit. On Monday, the 5th Circuit denied a motion from the employees to rehear the case.

The workers in 2004 sued the Boeing Company, now based in Chicago; Brush Engineered Materials Inc., based in Cleveland, Ohio; and Wess-Del Inc., based in Santa Clara, Calif. The employees said they were exposed to products containing beryllium while employed at Boeing’s facilities at the Stennis Space Center in Hancock County and at Canoga Park in California.

In the lawsuit, which represents only one side of a legal argument, the plaintiffs did not claim any present physical injury. Rather, they sought to have future medical examinations paid for by the defendants through a medical monitoring fund.

The issue of medical monitoring has been raised in several states, with mixed results.

Organizations such as the American Tort Reform Association have argued the theory of medical monitoring would hold defendants responsible for an injury that the plaintiff has not developed and may never develop.

Others, including trial lawyers, claim that a plaintiff’s fear of developing an injury constitutes an injury in itself.

Fifth Circuit Judge James Dennis, writing in a dissent Monday, said the court ought to let the workers amend their lawsuit so that their claims are in accord with the Mississippi Supreme Court opinion. Dennis said while the workers could file a new lawsuit, an amended complaint would save time.

Two other members of the panel — Judges Eugene Davis and Jerry Smith — declined to rehear the case.

Beryllium is a metallic element used in aerospace and defense industries. It’s not dangerous in solid form, but inhalation of beryllium dust can cause a scarring lung disease that can be fatal.

Boeing used the material in manufacturing parts for a space shuttle. Brush Engineered Materials sold Boeing many of the beryllium-containing products, according to the court record.

Wess-Del allegedly sold the products to Boeing with the knowledge that they would be used in space shuttle construction in Boeing’s Mississippi facility, according to the workers’ lawsuit.