A jury has awarded a former popcorn-plant worker $15m after finding that his exposure to butter-flavouring fumes led to his severe respiratory problems, according to a report by the Kansas City Star newspaper.

The verdict brings to nearly $53m the total amount awarded in the last two years against the makers of the popcorn flavouring, International Flavors & Fragrances Inc. of New York and a subsidiary, Bush Boake Allen Inc, the paper said.

Four other plaintiffs reached confidential settlements with the defendants last year.

The plant where the plaintiffs worked, the Gilster-Mary Lee Corp. microwave popcorn factory in Jasper Missouri, has paid the employees workers' compensation and has not been named as a defendant in any of the actions.

The latest case was filed by Stephen McNeely a machine operator who filled popcorn bags with salt and butter flavouring. McNeely, who worked at the plant from 1989 to 2001, developed bronchiolitis obliterans, a rare, progressive lung disease that may require him to get a lung transplant.

Independence lawyer Ken McClain, who represents McNeely and other popcorn workers, declined to comment on the case, citing a gag order entered by the judge. Attorneys for International Flavors could not be reached for comment.

McNeely is one of about 30 former and current workers at the Jasper plant who have sued International Flavors and Bush Boake Allen and are represented by McClain. At least 20 more cases are awaiting trial.