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SPOKANE, Wash. — Washington's attorney general on Thursday asked a federal judge to immediately take steps to protect Hanford Nuclear Reservation workers from exposure to chemical vapors.

More than 50 workers have received medical evaluations after reporting exposure to vapors in recent months.

Attorney General Bob Ferguson, along with the watchdog group Hanford Challenge and a labor union, filed motions for a preliminary injunction in federal court in Eastern Washington. The injunction seeks to prevent further harm to Hanford workers by implementing certain protections now, instead of waiting for the outcome of a trial.

The state filed a lawsuit against the federal government over Hanford worker safety last September. Trial is set for next May, but Ferguson says workers cannot wait that long to have a safe workplace.

Hanford for decades made plutonium for nuclear weapons, and the site near Richland in southeastern Washington is now engaged in a massive cleanup of the resulting radioactive wastes.

The wastes are stored in 177 massive underground tanks, and it is vapors escaping from some of those tanks that are thought to be making workers sick. The vapors are invisible and are not radioactive. Their exact content is not known because the exact contents of the tanks, some dating back to World War II, are not known.

"How many sick Washington workers will it take before the federal government fixes this problem?" Ferguson said in a press release. "The federal government's culture of indifference to worker safety at Hanford must end. Now."

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Washington River Protection Solutions, the U.S. Department of Energy's contractor for the tanks, said it was committed to the safety of workers and disappointed by the actions of the attorney general.

"We believe the claims are not reflective of the safe work our team is accomplishing in the tank farms' challenging environment," WRPS said in a press release. "While we review the motion, we will work with the Department of Energy on an appropriate path forward."

All of the workers who recently reported exposure to chemical vapors were checked by medical personnel and cleared to return to work, WRPS has said.

But Hanford critics contend that this issue has been going on for decades.

"Too many workers have already gotten sick and even disabled by brain and lung diseases," said Tom Carpenter, executive director of Hanford Challenge. "Hanford's cleanup mission will last decades, and workers deserve a safe workplace now and into the future,"

By pursuing a preliminary injunction, Ferguson, Hanford Challenge and Plumbers and Steamfitters Local 598 seek to prevent further harm to workers by implementing certain protections now. They seek:

- Mandatory use of bottled air at all times for all personnel working within the perimeter fence lines of the tanks and those working inside the vapor control zone.

- When waste is disturbed, they seek an expanded vapor control zone not less than 200 feet outside the perimeter fence line, and barricading of all roads and access points to prevent entry into the expanded zone.

- Installation of additional monitoring and alarm equipment to warn workers when toxic vapors are being emitted.

Between late April and the end of June, 56 workers reported they were exposed to vapors, the attorney general's office said. Within minutes to hours after breathing the fumes, workers experienced nosebleeds, chest and lung pain, headaches, coughing, sore throats, irritated eyes, and difficulty breathing, the attorney general's office said.

Hundreds of workers have reported similar exposures since the early 1980s.