New research results showed that tiny amount of radioactive sulfur leaked from the Fukushima nuclear meltdown in March reached California within days, but researchers now say that the amount was not dangerous to health.
Atmospheric chemists at the University of California, San Diego, said they observed the highest levels ever detected of radioactive sulfur in the atmosphere and is believed to have traveled by wind across the Pacific Ocean from the Fukushima Daiichi nuclear plant, according to a study published in online edition of the Proceedings of the National Academy of Sciences.
The amount of radioactive sulfur that arrived on the wind in California between March 22 and April 1 was tiny, and in fact "almost nothing," said study co-author Mark Thiemens, a professor of chemistry at the University of California, San Diego.
"It took me three years to figure out the chemistry, to be able to measure things that low," he said.
The California chemists were able to get their estimate based on air sampling. Thiemens and his team were measuring the levels of sulfur-35 as part of climate research they were doing, and collected the readings between March 22 and April 1.
Researchers observed the highest levels ever detected of radioactive sulfur in the atmosphere. Their readings indicated that there were 1,500 atoms of sulfur-35 per square meter in the air in La Jolla, Calif., which was an increase above normal levels.
The incident fascinated scientists because while reactors don't make sulfur, the radioactive isotopes of sulfur were found to be originated from the reactors of the damaged Fukushima Daiichi nuclear plant.
As the reactors in Fukushima started to heat up, sea water was used in order to cool down the reactors. At that point of time, the operators of the plant didn't have any other choice but to use sea water.
As a result, some of the chlorine atoms in the sea water captured neutrons from the reactor and produced radioactive sulfur called sulfur 35, which is usually generated by cosmic rays striking argon atoms in the atmosphere. The sulfur then escaped the reactor in both gas and aerosol form, traveling across the ocean by strong westerly winds.
A few weeks after the Fukushima Daiichi nuclear plant was damaged in the March 11 tsunami, low amounts of radioactive iodine were detected in milk samples in different cities around the U.S., including in California, Colorado, Connecticut and Massachusetts.