Monday, June 20, 2011

Guest Post: Facts About Japanese Tea in the Wake of the Fukushima Disaster

I recently read what sounded like bad news about Japanese tea and radiation. To help us understand what's going on and separate fact from fearmongering, I've called upon a scientist to explain!


First, a quick word about who I am: my name is Marc, and I’m a physicist. I’ve been working in the research and development industry for about ten years now, and my work allows me to deal with scientists from a huge array of fields, from astrophysicists to zoologists and everything in between. And, as many scientists before me, I have been horrified by the Fukushima Reactor crisis: not so much the crisis itself, but more so the absolutely shameful job of the media in reporting on the situation. The information they have given the public swings between wildly inaccurate conjecture all the way to outright lying, all designed to sensationalize and horrify without a scrap of truth anywhere to be found. Radiation and radioactive fallout are scary topics, at least in part by how poorly they’re understood, and situations like the media response to Fukushima don’t help matters.

Thankfully, greater minds than mine are devoted to educating the public about the truth of the situation, and those with the intelligence to question the drivel being fed to them can read up on the topic here:
But it is time to add my own small contribution to the voices of reason out there, specifically on the topic of tea. The question as to whether my favourite soothing drink has been transformed into a radiation-laced toxin capable of giving me cancer is one that is close to my heart and probably beneath the notice of other scientists.

A report of the potentially radioactive nature of Japan’s greatest export (besides anime and giant transforming robots) can be found here. The story comments on the fact that ‘higher than normal’ levels of radiation have been found; specifically, 679 becquerel (Bq) per kilogram of tea, which is above the permitted maximum of 500 Bq/kg. For those of you who are not physicists, a Bq is defined as the number of radioactive decays per second, as opposed to cpm (counts per minute), or a Curie (the radioactivity compared to Radium) or Gray (absorbed dose of radiation in tissue), or Sieverts (dose equivalent radiation), or Roentgen (radiation to produce a charge in a unit of blah blah you get the idea). The fact of the matter is that there are dozens of ways to measure radioactivity, and very few people actually understand the way they are all interconnected and related.

But back to the core issue: is this hazardous to people looking to consume green tea? Well, yes and no. Mostly no, though. In fact, overwhelmingly no, but not completely no.

The problem is that radioactive cesium-137 has deposited on the leaves. Unlike most of the radioactive material from the Fukushima fallout, cesium-137 has a long half-life of 30 years (so if there are 20 particles of it left today, in 30 years there will be 10 left, and 30 years after that there will be 5 left, etc...). Most of the radiation reported in the media is either Iodine-131 or radioactive isotopes of water, with half-lives ranging from a few days to a few seconds. The stuff everyone on the West Coast was so scared would be coming over from Japan in the initial days and weeks of the accident was actually less radioactive than standing next to a smoker for a few minutes (smoking generates very low doses of radiation, about 15 mSv/year) by the time it reached the coast. But radioactive cesium is long lasting, so there is some risk that it will still be on the tea when you consume it. But again, is this a risk?

Thankfully, the answer is still mostly no. See, in order for radiation to inflict damage, a bundle of radiation (either a particle or quantum of high energy light) has to smash into something vulnerable, like a strand of your DNA. If it smashes into something that absorbs it harmlessly, then there’s no risk. And it just turns out that water is a great harmless absorber. So when you steep your pot of tea, you’re effectively surrounding any potential radioactive particles with a very healthy measure of shielding, reducing the effectiveness of any radiation by 30 to 40 times!

Furthermore, there is almost no risk that your body will absorb the radioactive cesium, since unlike radioactive iodine, your body doesn’t pick up or use it in any fashion. It’s not stored or used, and so any cesium you swallow is going to be purged back out, harmlessly away from your body.

Now, there is a risk if you happen to enjoy eating dry tea, but I’m pretty sure not many people have a sudden urge to munch on a handful of dried tea leaves. But even that risk is minimal: there is a huge amount of research that points towards the health benefits of slightly higher-than-average doses of radiation, since people in Tibet or other high-altitude areas are already receiving significantly more radiation than people who live near the ocean shore. And to be clear, the ‘standard safe levels of radiation’ listed by most organizations fall way, way below any possible risk level to alleviate the public’s concerns (and lack of understanding) about radiation.

So, at the end of the day, there is very little reason to not sit back and enjoy that cup of Japanese green tea... assuming tea growers manage to convince the Japanese government to let them ship it and tea drinkers ask the Canadian government to accept it.

Will this affect your purchase of tea from Japan? What about other products, like fish?

Photo of Fukushima nuclear power plant used under Creative Commons from Beacon (Beacon Radio/flickr).
Photo of tea plantation used under Creative Commons from ajari (flickr).
Photo of tea set used under Creative Commons from Shigemi J. (pen3ya/flickr).


  1. Thank you for breaking down the science for us! I'm relieved - I don't want anything getting between me and one of my favourite teas. :)

    So I guess I'd say no, this won't affect my purchase of tea. As for fish, I mainly buy local varieties, so I can't say that this really impacts my diet. I don't know what I'd do if the roles were reversed and we couldn't touch the food we grow here. That would be devastating.

  2. A lot of the scare from the reaction is psychological at this stage... which isn't saying the same thing as "there's no risk". There IS some risk, but the trick is to not blow it way out of proportion.

    As for Japanese fish... well, I didn't support importing it BEFORE the Fukushima crisis, and I see no reason to change my stance now. There's plenty of fish in the sea! No need to ship their stuff here while we're shipping our stuff there... that's just silly.

  3. Thanks, Marc for this informative post.

  4. Oh, absolutely my pleasure. I'm glad people could get some use of my physics degree!

  5. very interesting post - I'm sure alot of people are wondering so really informative!

  6. I hope I can shed a little light... radiation is a complicated, messy subject, but it's better to have a little knowledge than... well, whatever you call what the media had been spewing.

  7. What a great post-thank you. I drink Japanese green tea constantly and was actually very concerned about radiation. Thanks for easing my mind.

  8. My pleasure. The world is scary enough without adding unnecessary stress to your life, so I'm glad I could help a little!

    Brew a pot for me!

  9. Great post! Thank you for clearing up all the smoke and mirrors. My tea ball isn't working properly, so I actually did end up eating some tiny bits of tea today, but I'm not terribly concerned. I do try to avoid imports from Japan (and all other far far away places) on grounds that local equivalents are lower impact, but I'm happy to support Japan the next time I need tea.

  10. A perfectly reasonable stance... and don't worry about eating the tea leaves wet. As long as they've soaked in the water, you're fine (again, even if you ate them dry, you'd be fine, but once they're wet you're MORE fine!).

    I also try to support local products whenever I can, but in this global economy there are somethings that simply cannot be found locally... at which point we must do our best to make ethical decisions with our hard earned space bucks. Supporting Japan at a time like this probably is a good decision.

    But I still won't order tuna. What they're doing to the tuna stockpiles worldwide is almost criminal.