The 2011 Fukushima Daiichi reactor meltdown in Japan is not the cause of abnormally high radiation levels discovered recently along Surfer's Beach, according to an analysis by independent experts. But exactly why a swath of the local coastline is showing about 14 times the baseline radiation level remains a curious mystery.

San Mateo County health officials reiterated on Tuesday that the beach radiation did not pose a public hazard.

People across the country expressed an interest in radiation on the Coastside in recent days after an online video shot at Surfer's Beach led some to believe what they were seeing was the first major landing of radioactive material on the West Coast attributable to the Japanese disaster. First posted on Dec. 23 on YouTube, the seven-minute video shows the meter of a Geiger counter as an unidentified man off-camera measures different spots on the beach south of Pillar Point Harbor. The gadget’s alarm rings as its radiation reading ratchets up to about 150 counts per minute, or roughly five times the typical amount found in the environment.

The amateur video went viral, drawing more than half a million views to date, and spurring government inspectors to conduct their own surveys.

After watching the clip, El Granada electrical engineer Steven Weiss grabbed his own radiation measurement equipment to test the radiation reports for himself.

On Monday, Weiss carried a Geiger counter in each hand for a second survey of Surfer's Beach. As he descended to the waterline, the readings on his gadgets climbed. He tested various spots: the side of the bluffs and the white sand closest to the waterline, both registering levels that were high but not suspiciously so as far as he was concerned. But when he placed the sensors down near a line of black silt along the back of the beach, the meters on both his gadgets spiked. The counters registered about 415 counts per minute. A cpm of 30 is considered the baseline for radioactivity typically found in the air.

“It's not normal. I've never seen 400 cpm when I just wave my Geiger around.” he said. “There has to be something radioactive for it to do that.”

Weiss is no amateur; for 40 years he has made a living designing Geiger counters, most recently for International Medcom Inc. After he verified the hotspot, he took a sample of the dark sediment and sent it to his company's main offices in Sebastopol for analysis.

International Medcom CEO Dan Sythe later put the dirt sample in a spectrum analyzer to view the radioactive “signature” of the particles, the photon energy associated with each isotope. What he found was different from cesium-137, the fissile material used in the Fukushima reactors. He would know – since the 2011 meltdown, Sythe has visited Japan nine times to help map the cesium fallout.

Instead he was seeing radium and thorium, naturally occurring radioactive elements.

“It doesn’t mean that it‘s OK. It's not something you'd want your baby playing in,” Sythe said. “All we’re saying is this radiation is not from Fukushima.”

Sythe summarized his findings on his blog in the hopes that it would dispel a sense of panic spreading on the Internet that Fukushima radiation was hitting U.S. shores. People were posting online claiming that the West Coast would soon be “toast,” he said, so it was vital to get better information online.

The radiation scare followed a constellation of other alarming news in recent months. Last month, marine biologists announced that starfish were mysteriously disintegrating along the West Coast, a trend that has not been linked yet to any cause. Past computer simulations had indicated that radioactive cesium-137 from the Fukushima reactors could begin appearing on West Coast shores by early 2014. Those findings, published in August by the Institute for Cross-Disciplinary Physics and Complex Systems in Spain, also noted that any radioactive material that crossed the Pacific would likely be diluted and fall below international safety levels.

Public fear and paranoia has clouded the Fukushima issue since the start of the disaster, said Dan Hirsch, a nuclear policy lecturer at the University of California, Santa Cruz. He believes the problem stems from a vacuum of data from the government, prompting amateur sleuths with Geiger counters to seek their own answers. He pointed out that the Environmental Protection Agency gave assurances to the public in 2011 that the Fukushima radiation posed no public health risk. But later a 2012 audit revealed that many of the EPA’s radiation monitors were out of service at the time of the Fukushima disaster. For some, that fed the perception that the government had something to hide, he said.

“I'm frustrated because the government should be doing a better job, and the people who are fearmongering are just fanning the flames,” Hirsch said.

The viral video posted last month began spreading on the Internet before government officials took notice. County health officials first learned of the video four days after was uploaded, and they sent their own inspector out to the beach the next day. Using a different unit, the county inspector measured the beach to have a radiation level of about 100 micro-REM per hour, or about five times the normal amount. REM stands for “Roentgen equivalent man,” a measurement of the dosage and statistical biological effects presented by radiation.

Although the radiation levels were clearly higher than is typical, San Mateo County Health Officer Dean Peterson emphasized that it was still not a dangerous level for humans. A person would need to be exposed to 100 microREMs of radiation for 50,000 hours before it surpassed safety guidelines by the Occupational Safety and Health Administration, he explained.

Peterson forwarded the matter to the U.S. Environmental Protection Agency and state Department of Public Health, agencies with more expertise on analyzing radioactivity. Both of those agencies were contacted by the Review this week, but officials said they were still investigating the situation. Peterson said he thought it was important to go forward with his information to assure the public that local beaches were still safe.

“I’m completely confident that what we have on the beach is not a public health threat,” he said.

Nonetheless, the presence and concentration of natural thorium and radium at Surfer’s Beach left experts puzzled. Both elements are actually common at beaches. In fact, a 2008 study by the Journal of the Serbian Chemical Society found similar concentrations at Southern California beaches.

Sythe offered a couple possible explanations. A vein of thorium could be spilling out from the nearby coastal bluffs, he suggested. Alternatively, he heard mention of an old oil pipe running nearby the beach. Oil pipelines had a tendency to collect heavy radioactive minerals, he said.

Peterson thought the minerals could be just washing up with the salt water from the shores. The radioactive materials all were just past the high tide line, so it made sense that would be where the minerals would build up, he said.

“The conditions that are out on the beach could be the same conditions that have been out there for millennia,” he said.

Update: Tests by government health inspectors have found no connection between the elevated radiation levels at Coastside beaches and the Fukushima Daiichi disaster, according to a statement by the California Public Health Department released late on Tuesday evening. An analysis by county and state officials found the radiation was the result of naturally occurring minerals, a conclusion similar to reports by independent experts.

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