The World Health Organisation has said people in the area worst contaminated after the Fukushima nuclear accident in Japan have a higher risk of developing certain cancers over their lifetime.
The nuclear plant was damaged two years ago after an earthquake and tsunami devastated northeast Japan.
Radiation leaked into the air, soil and sea and forced thousands of people to leave their homes.
The WHO said its risk assessment showed there is no discernible increase in health risks from the "Fukushima event" expected outside Japan.
However, with respect to Japan, the assessment "estimates that the lifetime risk for some cancers may be somewhat elevated above base-line rates in certain age and sex groups that were in the areas most affected".
In the most contaminated area, the WHO estimated that there was a 70% higher risk of females exposed as infants developing thyroid cancer over their lifetime.
The thyroid is the most exposed organ as radioactive iodine concentrates there. Children are deemed especially vulnerable.
The report concluded that for the general population inside Japan, the predicted health risks were low, but that one-third of emergency workers were estimated to have increased risk.
A 9.0 magnitude earthquake and tsunami on 11 March 2011 killed nearly 19,000 people.
It devastated the Fukushima Daiichi nuclear plant, triggering meltdowns, spewing radiation and forcing about 160,000 people to flee their homes.