Radioactive particles from Fukushima detected in Napa wine

Researchers found trace amounts of radiation in California wines grown after 2011. Researchers found trace amounts of radiation in California wines grown after 2011. Photo: Instants, Contributor Photo: Instants, Contributor Image 1 of / 60 Caption Close Radioactive particles from Fukushima detected in Napa wine 1 / 60 Back to Gallery

It's been more than seven years since the meltdown at Fukushima Daiichi Nuclear Power Plant in Japan, but the effects of such a disaster can linger for decades, often in subtle, unseen ways.

One such side effect has been growing on vines — and aging in barrels — in Northern California, according to a team of French researchers, unbeknownst to the wine lovers who drink it.

The 2011 Fukushima meltdown, triggered by a 9.0-magnitude earthquake and subsequent tsunami, released radioactive materials into the ocean and the air. The World Health Organization said that while some radioactivity was detected in food products from Japan following the disaster, it was below a safe threshold. As the radiation was carried by currents and atmospheric patterns, food from other countries was also found to have even smaller traces of radiation.

That includes the treasured wines of Napa Valley, according to the newly released study.

The researchers examined California cabernet sauvignon vintages between 2009-12, wondering if they would see a jump in radioactive particles after 2011, when the Fukushima disaster occurred.

At first, they weren't able to detect any cesium-137 (a radioactive isotope) without opening the bottle and using a gamma detector. But then they vaporized the wine, reducing it to ashes. Among the ashes of the vintages after 2011, they found about twice as much cesium-137 compared to those from before the nuclear meltdown.

The contamination detected was still "extremely low."

Interestingly, the amount of cesium-137 was higher in red wine as compared to rosé, as it was in French wines tested after Chernobyl.

One of the pharmacologists behind the study, Philippe Hubert, came up with this method of testing wines in 2001, according to the MIT Technology Review. Hubert invented the technique not to determine if they were safe to drink, but rather to test if rare vintages were legitimate or frauds.

Any French wines claiming to be produced before 1952 should have no trace of cesium-137 whatsoever because it would predate atmospheric nuclear tests and explosions. After an international ban on atmospheric tests was passed in 1963, the amount of radioactive particles in wines steadily decreases, with a small spike after Chernobyl.

Using this logic and a gamma detector, you can determine if a vintage is a fraud when the amount of cesium-137 in the bottle doesn't match the normal range of the year it purports to be from.

Read Alix Martichoux's latest stories and send her news tips at amartichoux@sfchronicle.com.