Government and independent experts last week gave a new round of reassurance that higher-than-normal radiation levels along the Surfer’s Beach were not from the Fukushima Daiichi reactors in Japan and nothing to be concerned about. In fact, the relatively high level of radioactivity has likely been around Half Moon Bay and other spots on the California coast for a long time.
Thomas Ward, a nuclear consultant with the U.S. Department of Energy, believes Surfer’s Beach is what is known as a “black sand” beach, a sandy spot that accumulates rare earth metals and other heavy elements. Last week, independent analysts confirmed that the main source for the heightened radiation at Surfer’s Beach was naturally occurring thorium and not cesium-137 released when the Fukushima plant melted down in 2011. Ward indicated that shouldn’t have come as a surprise.
“This beach has been known for the last 40 to 50 years to contain these radioactive sands,” he said. “It’s not considered a radiation hazard, so long as you’re not eating it, and you’re not living on it, 24/7.”
In 1962, researchers from the University of California, Berkeley, studying tidal drift noted radioactive thorium along the California coast. The study found thorium traces along the coast from the Russian River down to San Francisco. At the time, the study team didn’t try to pinpoint the source of the radioactive metal. Instead, its members concluded that it had to be coming from some regional source, likely a granite pocket somewhere along a river or beach.
Ward explained that he studied a similar stretch of black sand beaches that covered a large swath of Long Island in New York. He pointed out a black sand beach in Kerala, India, that shows natural radiation as high as 10 REM, a level that would make it nearly 100 times more radioactive than what has been measured off the San Mateo County coast. Yet Indian families have lived close to the Kerala beach for generations and have not shown genetic defects, he explained.
“It’s not a health hazard. It’s an anomaly, a geophysical anomaly,” Ward said.
Concern about local beach radiation exploded last month after a YouTube video was showing what some believed was the first major landing of radioactive material on the West Coast from the Japanese disaster. The video was viewed hundreds of thousands of times and sparked a regional health scare. Local health officials performed their own study a few days later.
Wendy Hopkins, a spokeswoman for the California Department of Public Health, said inspectors found no public health risks due to radioactivity in Half Moon Bay. The department is still analyzing sand samples from the area and will post its results on its website.
The radiation scare did have one interesting side effect. Biology teacher Barbara Lohman said the surge in interest in local radioactivity encouraged the Half Moon Bay High School science faculty to put in an order for new Geiger counters. She hoped that soon students would be able to do their own radiation surveys.
“We’d like to keep monitoring the radiation level as part of our environmental science and marine ecology classes,” she said. “The students are very interested.”