See the Center for Public Integrity’s investigative report, Use of Toxic Acid Puts Millions at Risk, by Jim Morris and Chris Hanby

Oil industry documents filed with the federal government reveal that an accidental release of a lethal chemical used in 50 aging refineries across the country could prove devastating, with 16 million Americans living within range of toxic plumes that could spread for miles.

Los Angeles, Philadelphia, Minneapolis, New Orleans, and the stretch of Texas coastline known as “Refinery Row” are among the at-risk areas cited in the documents. Citing homeland security concerns, the government keeps the industry filings under close guard in Washington, D.C. They were reviewed as part of a joint investigation by ABC News and the Center for Public Integrity that airs tonight on World News with Diane Sawyer and Nightline.

There are safer alternatives for the chemical hydrofluoric acid, which is used to make high-grade gasoline, but the industry has resisted calls to stop using it. An industry spokesman told ABC News it would not be feasible to retrofit the refineries to use the safer approach. Federal officials tell ABC News, however, that the real impediment may be money– estimating it would cost about $50 million for the companies to upgrade each plant.

According to the industry’s worst-case scenario documents, a release of the chemical could endanger entire communities.

“Hydrofluoric acid is extremely toxic,” said Sen. Patty Murray, D-Washington. “It can be deadly immediately to workers around them, it can affect an entire community.”

Murray called the plants “a ticking time bomb.”Even though one-third of the oil refineries in the United States are using the chemical, Murray told ABC News that the industry has long avoided demands from safety advocates and from the union that represents refinery workers that it explore safer options.

“For three hours of revenue an oil company can change the use of hydrochloric acid to make it safer for the workers and the community,” Murray said. “Certainly that kind of investment assures people are safe when they go to work and the communities, the people who live around those refineries, are protected. It’s worth it.”