CHICAGO—A worker in the chemical-flavoring industry who needs a lung transplant after exposure to an ingredient used in butter flavoring for popcorn has been awarded $30.4 million, which a law firm said is the largest U.S. award to an individual in a case involving diacetyl.

A Cook County, Ill., jury last week sided with Gerardo Solis, who worked for several flavoring companies over 17 years and developed a rare lung disease, and against Mr. Solis' former employers and suppliers of the chemical used to produce the butter flavoring.

Several companies were named in Mr. Solis' lawsuit, including BASF Corp. and Flavorchem Corp., Mr. Solis' most recent employer. Each would bear a share of the liability.

The award is the highest to date in U.S. worker lawsuits involving popcorn and butter flavoring, according to Independence, Mo.-based Humphrey Farrington & McClain P.C., the firm that represented Mr. Solis.

The highest amount previously granted by a jury in cases like Mr. Solis' was $20 million against food flavor manufacturers Bush Boake Allen Inc. and International Flavors & Fragrances Inc. in 2004. Both companies also were named in Mr. Solis' lawsuit.

BASF, with North American headquarters in Florham Park, N.J., said in a statement that it was “disappointed” with the jury's verdict and was confident its position will be vindicated on appeal if not corrected by the trial judge.

Meanwhile, Kenneth McClain, lead attorney in Mr. Solis' case, said he hopes this jury award will pressure the flavoring industry to make safer products.

“We would hope the flavoring industry would stop using the blue collar worker as guinea pigs,” Mr. McClain said. “No one knows the effects of the chemicals these workers are working with...and some of them are very dangerous.”

Mr. McClain said he offered to settle Mr. Solis' claim with BASF for $3 million, but the company rebuffed the proposal and offered to settle for $350,000. Mr. McClain said the case then went to trial, resulting in the $30.4 million award last week.

It's estimated there are more than 300 cases pertaining to diacetyl in the litigation pipeline nationwide.

According to the Centers for Disease Control & Prevention, studies have demonstrated that butter flavoring vapors are capable of causing severe airway injury in laboratory animals, but the causal relationship between diacetyl exposure and development of bronchiolitis obliterans—a condition that Mr. Solis' attorneys contended he developed from working with diacetyl—has not been firmly established.

According to court documents, BASF's diacetyl, which was sold to Downers Grove, Ill.-based Flavorchem, was known to have the propensity to cause respiratory illnesses, including bronchiolitis obliterans, but provided no warning of that possibility.

As a result, Mr. Solis, who worked for Flavorchem from 1998 to 2006, developed the rare lung disease, now has only 25% lung capacity and is in need of a lung transplant.

“Even if there is no liability connection between the chemical and the injury, if the injury (the plaintiff) has is a serious one like bronchiolitis obliterans, it's trouble for the defendant,” said William G. Passannante, a New York-based attorney with Anderson Kill & Olick P.C. who was not involved in the case.

Mr. Passannante said cases involving lead paint and asbestos had some similarity to those associated with diacetyl, but cases involving the chemical are not as widespread and don't have the same potential for insured losses.