Small concentrations of radioactive sulphur from the Fukushima nuclear plant in Japan were detected in California between March 22 and April 1, 2011.

The results published in the week's edition of the journal Proceedings of the National Academy of Sciences mention that the amounts found were almost negligible.

The amounts were not dangerous, in fact they were "almost nothing," USA Today quoted Mark Thiemens, a professor of chemistry at the University California, San Diego, as stating. "It took me three years to figure out the chemistry, to be able to measure things that low," he said.

When nuclear reactors melt, there is a leakage of Neutrons and other products of the nuclear reaction. When seawater is pumped into the reactor, they absorb the neutrons which collide with chloride ions in the saltwater.

Each collision knocked a proton out of the nucleus of a chloride atom, transforming the atom to a radioactive form of sulphur.

According to Irish Weather online, "when the water hit the hot reactors, nearly all of it vaporized into steam. To prevent explosions of the accumulating hydrogen, operators vented the steam, along with the radioactive sulphur, into the atmosphere. In air, sulphur reacts with oxygen to form sulphur dioxide gas and then sulphate particles."

Both the particles then blew across the Pacific Ocean on prevailing westerly winds to an instrument at the end of the pier at UC San Diego's Scripps Institution of Oceanography. This is where Thiemens' group recorded the findings.