A dozen former Union Pacific workers have filed identical lawsuits in U.S. District Court in Omaha, saying they were exposed to cancer-causing materials in violation of federal law while working the trains, yards, shops and tracks of the Omaha-based freight railroad.

The lawsuits were filed by former employees, or the estates thereof, who worked in six states, including Iowa. The suits allege negligence via failure to use “ordinary care and caution” by not removing dangerous materials from the workplace and failure to monitor and test work sites for health hazards.

The company said Wednesday it is aware of the lawsuits that were filed this week but that it does not comment on active litigation. The former employees worked for Union Pacific for various lengths of time, one starting as far back as 1965 and finishing in 2006. Others started work in the 1970s, 1980s and 1990s.

Union Pacific, the second-largest freight railroad by ton-miles, operates about 32,000 miles of track in the western United States. Its operations include the trains, repair shops and yards where cars are organized into trains and vast miles of track with signaling equipment and other devices. All told, the company has about 43,000 employees in 23 states, including about 8,000 in Nebraska at various locations such as the Omaha headquarters and the vast Bailey Yard in North Platte.

“Railroads and their facilities are notorious for having been contaminated from years of transporting toxic substances and from the use of toxic substances and known carcinogens in the operation of the railroads themselves,” the suits say.

The suits say Union Pacific violated the Federal Employers Liability Act, a 1908 law that was the first aimed at protecting injured railroaders. It works somewhat like workers’ compensation insurance, but to collect, the aggrieved party must prove in court that the railroad in question was legally negligent.

The suits cite exposure to hazardous substances such as “diesel fuel/exhaust, benzene, creosote, manganese and rock/mineral dust and fibers.” The former workers contracted cancers including lymphoma, pancreatic and head and neck, according to the suits.