Samples from 110 industrial waste disposal facilities in 16 prefectures from east to northeast Japan have revealed cesium readings ranging from 10,800 to 144,200 becquerels at four incinerators in Fukushima Prefecture, 23,000 becquerels at a facility in Iwate Prefecture and 11,500 becquerels at an incinerator in Chiba Prefecture, the ministry said.
Similar tests in late August found that ashes from nonindustrial incinerators contained more than 8,000 becquerels of cesium per kilogram in Tokyo and six other prefectures.
A worker exposed to 8,000 becquerels of cesium a day for some amount of time would still come in below the annual radiation limit of 1 millisievert.
At the end of August, the ministry issued a guideline advising local authorities to solidify incinerated dust and ashes containing between 8,000 to 100,000 becquerels of cesium per kilogram with cement, wrap it in watertight sheeting and bury it in landfills.
The ministry earlier decided to allow waste containing up to 8,000 becquerels per kilogram to be buried in waste disposal sites, provided that no residences are built at the sites in the future.