LONDON — People exposed to the highest doses of radiation during Japan’s Fukushima nuclear plant disaster in 2011 may have a slightly higher risk of cancer but one so small it probably won’t be detectable, the World Health Organization said in a report released Thursday.
A group of specialists convened by the agency assessed the risk of various cancers based on estimates of how much radiation people at the epicenter of the nuclear disaster received, namely those directly under the plumes of radiation in the most affected communities in Fukushima, a rural agricultural area about 150 miles north of Tokyo.
Some 110,000 people living around the Fukushima Daiichi nuclear plant were evacuated after the massive earthquake and tsunami on March 11, 2011, knocked out the plant’s power and cooling systems, causing meltdowns in three reactors and spewing radiation into the surrounding air, soil, and water.
In the new report, the highest increases in risk appeared for people exposed as infants to radiation in the most heavily affected areas. Normally in Japan, the lifetime risk of developing cancer of an organ is about 41 percent for men and 29 percent for women. The new report said that for infants in the most heavily exposed areas, the radiation from Fukushima would add about 1 percentage point to those numbers.
‘‘These are pretty small proportional increases,’’ said Richard Wakeford of the University of Manchester, one of the authors of the report.
‘‘The additional risk is quite small and will probably be hidden by the noise” of other cancer risks, he said.
Specialists had been worried about a spike in thyroid cancer, since iodine released in nuclear accidents is absorbed by the thyroid, especially in children. After the Chernobyl disaster, about 6,000 children exposed to radiation later developed thyroid cancer because many drank contaminated milk after the accident.