Washington (CNN) -- A flight attendants' group is distributing radiation dosimeters to a sampling of its members as assurance that they are not being exposed to harmful radiation levels on trips to and from Japan.
Association of Flight Attendants President Veda Shook said the group believes that sufficient measures are in place to ensure the health and safety of flight attendants but said the dosimeters will give flight attendants "an added level of comfort."
The small, passive devices will be carried by flight attendants and read after trips; they do not "alert" or sound an alarm if radiation is detected. Some flight attendants could begin carrying the devices as soon as Monday.
Japanese civil aviation authorities have imposed flying restrictions for a 30-kilometer (18.6-mile) radius centered on the Fukushima Daiichi nuclear power plant, and U.S. officials say they have not found harmful levels of radiation on planes flying out of Japan.
The plant was damaged in a magnitude-9.0 earthquake and subsequent tsunami last week.
A "handful" of flight attendants have opted out of flights to Japan, Shook said, but others have volunteered for flights to the country.
"Our membership has been terrific in helping to provide services and aid to the people of Japan," said Chris Witkowski, the association's director of air safety, health and security.
The association said that about 500 of its flight attendants are based at Narita International Airport, the main airport serving Tokyo, and hundreds more layover there on a daily basis. Although the association has accounted for all of its flight attendants, it cannot confirm the status of family members, the group said.
The association has started collecting donations for its members and families and is delivering it to members at Narita.
The association said its flight attendants work for three U.S.-based airlines with regular flights to Japan: United, Hawaiian and Ryan International, a charter airline based out of Rockford, Illinois.