Producing nearly 90% of the nation’s wine, California makes up the lion’s share of the wine industry in the USA. However, this Californian supremacy may now have to be reconsidered following a discovery made by French researchers. A team at the Centre of Nuclear Studies located in Bordeaux-Gradignan has just announced a discovery concerning wines produced from various grape varieties of the Napa Valley- a famous wine region north of San Francisco. Shockingly, they have found traces of radioactivity…
According to information released in a prepublication published on the site arXiv.org, the researchers have found very weak traces of caesium 137, a radioactive isotope which poses little risk to human beings when consumed in such small doses, yet which draws public attention once again to an infamous event: the explosion of the Fukushima nuclear power plant.
The 2011 disaster resulted in the contamination of a vast amount of land spanning up to 20km around the plant, and the area has now been rendered a no-go zone. However, even beyond the borders of the town, and even Japan, radioactive pollution has infiltrated the atmosphere and hence has spread all over the world by the wind.
A new illustration of the powers of serendipity
Randomly coming across a number of bottles of Californian Cabernet Sauvignon in a supermarket, Michael Pravikoff, a physician at the Centre of Nuclear Studies in Bordeaux-Gradignan, had the idea of studying the radioactivity of the wine in order to evaluate the extent of the consequences of the Fukushima disaster.
'I bought them just to see', recalls Michael Pravikoff.
With the intention of quantifying the caesium 137 levels of the Californian wines, the scientists began to analyse the wines produced between 2009 and 2012. In order to do this, Michael Pravikoff and his team developed a particular technique of measuring radioactivity: gamma-ray spectrometry. The main advantage of this method is that by measuring the energy of the gamma-rays emitted by a substance, scientists are able to identify the nature of the radioactive source.
A proven method
A little earlier in history, gamma-ray spectrometry was already used as a means of detecting the increase of some isotopes in wines, notably after the nuclear tests carried out during the Cold War, and after the Tchernobyl disaster. Aside from being used in connection to these terrible events, the technique can also be used to precisely confirm the year of production of a wine. In this case, the French researchers used the method to judge the scale of the consequences of the Fukushima disaster.
'It was more from a purely scientific view that we started to measure the levels of the wine,' acknowledges Michael Pravikoff. And the challenge was a big one, to say the least.
After their first attempts, the scientists could only ascertain very weak levels of radioactivity being emitted by the wines. In fact, the levels were so insignificant that it was impossible to utilise the results. Nevertheless, in order to succeed in obtaining answers to their questions, the scientists thought outside of the box…
A method adapted to the very weak radioactivity of the Californian wine
In order to maximise the weak isotopic traces, the scientists heated the wine to a temperature of 500°C for several hours. The result: the liquid ultimately turned into a small mass of ashes weighing only several grams. Analysis of the substance revealed contamination linked to the release of radioactive particles following the explosion at the Fukushima power station.
In comparison with levels naturally present in the environment, the Californian wines produced after the Japanese disaster were found to actually have concentrations of caesium 137 up to twice as high as what is considered normal. At first glance, this appears rather worrying, but in reality, it poses no real danger, stresses Michael Pravikoff.
'These levels are only slightly raised, well below the levels of radioactivity naturally present all across the world,' assures the scientist, writing for a column of the New York Times. A reassuring point of view confirmed by the opinion publishedshortly after the catastrophe by the World Health Organisation on its website:
'Small amounts of radioactive caesium and iodine can indeed be traced by using very sensitive detection methods, but this shouldn’t affect foods produced in other countries (excluding Japan), considering that the amounts are well below acceptable levels, and ought to not pose a health issue for those who eat this food.'
So, we don't need to worry about foodstuffs produced outside of Japan, nor about wines produced from Californian grapes. Who knows, maybe the increased levels of caesium 137 give it an original flavour?