The testicles and the sperm counts in bulls abandoned in the evacuation zone around the battered Fukushima No. 1 nuclear plant have so far not been affected by chronic exposure to radiation, an academic study has found.
The finding provides crucial data to scientists and public policy advisers on the possible impact of the reactor meltdowns on humans.
A team of researchers examined two bulls, found in September 2011 and January 2012, within 20 km of the plant, an area that was completely evacuated because of fears to public health.
They also looked at a bull fetus from the area to help determine the effects of prolonged radiation exposure associated with the world’s worst nuclear calamity since Chernobyl in 1986.
“Since the testes are 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 notes.
Researchers from Tohoku University and other schools found concentrations of cesium-134 and cesium-137, substances of concern because of their relatively slow rates of decay, were broadly similar in all organs, but were sharply higher in muscles.
“Radioactivity concentration of cesium in the testes was about more than half of that in the skeletal muscle and the level was the same as in other organs,” the researchers said.
Examination of the bulls’ sperm found that their count, structure and size were normal.
“Adverse radiation-induced effects were not observed” following radiation exposure of up to 10 months, the study says.
The researchers expect that the study will shed light on the risks posed by the radiation to reproductive health, but said the small size of their sample means further investigation will be required before any definitive conclusions can be reached.
The study was published online Tuesday in Scientific Reports, a peer-reviewed journal from the publishers of the respected Nature.
Cesium levels found in the organs of the bulls and the fetus were mostly well above the official limit for consumption, currently set at 100 becquerels per kilogram.