Three more Hanford workers reported symptoms Thursday morning consistent with those caused by exposure to chemical vapors.
Few incidents have been reported since workers have been required to wear supplied air respirators for much of the work at the Hanford tank farms over the last five months while improvements are made to better protect workers from vapors.
The three workers who reported symptoms — plus two other workers who reported an odor but had no symptoms — were doing work that was assessed as not requiring the supplied air respirators.
The three workers with symptoms were checked by the Hanford medical provider and released to return to work. The two workers with no symptoms declined medical evaluations, according to Hanford officials.
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The Thursday incident brings the number of workers medically evaluated for possible vapor exposure since last spring to about 56.
There also have been some cases of workers reporting unusual smells, which are not included in that number.
At a recent Hanford Advisory Board committee meeting, officials said some reports of smells had been traced to fumes from fuel transferred and sewage emptied from porta-potties. However, the number does include some earlier cases that may have been linked to spraying of weeds.
The five workers involved in the Thursday incident were in the AY Tank Farm, where preparations are being made to empty Tank AY-102, a double-shell tank with waste leaking between its shells.
Unlike single-shell tanks, the AY tanks are not passively vented to the atmosphere and no work was being done that would disturb waste. Disturbing waste and passive venting both are a risk for vapor releases.
However, a cover block had been removed from at least one concrete-lined pit in the farm to allow work to be done in the pit. The pits may contain pumps or valves for waste lines.
Three of the five workers were wearing full-face respirators to protect themselves from potential radiation. The other two workers were in an area where work did not require a respirator for radiation protection.
One of the employees who reported symptoms worked for Washington River Protection Solutions, the Hanford tank farm contractor, and the other four were subcontractor employees.
Although symptoms were not disclosed because of healthcare privacy laws, workers typically report nosebleeds, headaches, watery eyes, increased heart rate, coughing, sore throats or dizziness. Some workers believe their long-term neurological or lung diseases were caused by exposure to the vapors.
Washington River Protection Solutions is collecting and analyzing data to attempt to identify a source of the possible vapors reported Thursday.
The contractor also is implementing 47 recommendations made in an independent review that looked at the vapor issue and how workers could be better protected.