Air, water and soil samples taken from the places where U.S. troops worked during Operation Tomodachi did not contain harmful levels of toxic substances, Stars and Stripes reported Wednesday.
Maj. Neal Fisher, spokesman for U.S. Forces Japan, said samples collected from areas where troops deployed near Sendai were analyzed for hundreds of environmental contaminants.
"Preliminary results show that troops were not exposed to harmful levels of any substance," Fisher said in an e-mail.
He added that the initial test results were being reviewed and would be shared with family members of U.S. troops as soon as possible.
Health organizations have been concerned about toxic chemicals like asbestos since cleanup operations began after the March earthquake, tsunami and subsequent explosion at the Fukushima nuclear plant.
Fisher said more than 5,000 personnel who worked in the disaster zone or had contact with potentially contaminated materials were monitored for potential radiation exposure.
"Exposure assessment is still ongoing, but the levels of radiation seen so far have been negligible," he said.
Fisher said there were slightly higher radiation readings for U.S. personnel working closer to the Fukushima plant.