Fukushima radiation sperm tests given 'all clear' by study

The testes and sperm count of bulls abandoned in the evacuation zone around the battered Fukushima nuclear plant were not affected by chronic exposure to radiation, according to a Japanese academic study.

The results came after a team of researchers examined two bulls found in September 2011 and January 2012 within a 20-kilometre radius of the plant, an area that was evacuated amid fears of threats to public health.

They also looked at a male foetus from the area to help determine the effects of prolonged radiation exposure associated with the disaster, the world's worst since Chernobyl in 1986.

"Since the testis is a relatively radio-sensitive organ, we considered that radiation exposure would lead to changes in the morphology or the function of this organ," the study noted.

An examination by researchers from Tohoku University and other schools of the bull's sperm showed their number, structure and size were normal.

"Adverse radiation-induced effects were not observed" following radiation exposure of up to 10 months, the study said.

Researchers also found concentrations of caesium 134 and caesium 137, substances of concern because of their slow rates of decay, were similar in all organs, but sharply higher in muscles.

Researchers said the size of their sample meant further investigation would be required before any definitive conclusions could be reached.

The study was published online in the peer-reviewed journal Scientific Reports.