SPOKANE — Federal health officials will conduct a short-term evaluation related to the exposure of workers to chemical vapors on the Hanford Nuclear Reservation.

The probe by the National Institute for Occupational Safety and Health is expected to focus on several areas including medical response, safety and health program management, and exposure control.

“Having an agency entirely separate from the Department of Energy conducting oversight into the safety of working conditions at Hanford is critical to protecting workers,” said U.S. Sen. Ron Wyden, D-Ore., who met recently with Hanford workers concerned about exposure to the vapors.

For decades, Hanford made plutonium for nuclear weapons. Much of the waste from that work is stored in 177 giant underground tanks that are the focus of cleanup efforts at the site near Richland. Clean up is expected to take decades and cost billions of dollars. “I will be closely following this process to ensure this evaluation provides the guidance necessary to keep workers safe,” said U.S. Sen. Patty Murray, D-Wash.

Hanford workers have long raised issues of chemical vapors associated with waste held in the underground tanks.

More than 50 workers in recent months have received medical evaluations for possible exposure to chemical vapors, after reporting suspicious odors. Most were cleared to return to work.

The federal institute has been working with Hanford officials on the vapors issue. The agency will review current policies and procedures for evaluating worker health concerns.

The study will consider how worker exposures are assessed by reviewing samplings of possible vapors, response to concerns regarding possible exposure and how data is analyzed to identify trends.

No schedule has been set for the review.

Stacy Charboneau and Kevin Smith, the top Department of Energy managers at Hanford, said in a letter that they will ensure investigators have full access to information and workers to interview.