Japanese Tea and Radiation

By Christine Banks


A Shizuoka Tea Farm

Following the March 11th earthquake and subsequent problems at the Fukushima Daiichi nuclear power plant, reports surfaced of radiation in the Japanese food supply. After immediate concern for the Japanese people, many people began to wonder: how will this affect tea?

Tea is a $1.3 billion (2009) industry for Japan. Beyond the tea leaves used for brewing a fresh cup, green tea is also used in flavoring for many Japanese products. Ground dried tea leaves are processed into seasonings for foods like cookies and ice cream, leaving the potential for further radiation exposure in the food supply.

Early Days

The disaster at the Fukushima Daiichi nuclear power plant led to the release of radioactive isotopes into the air (predominantly cesium-137 and iodine-131, and some cesium-134). The exact amount of radioactivity sent into the air is unknown, but is estimated to be 770,000 trillion Becquerels (a unit of measure - Bq) of radioactive particles. This formed a large plume that generally followed the major wind patterns and moved most of the radiation east, over the Pacific Ocean. However, some radioactive contamination moved into other areas of Japan, since atmospheric events like rain, low pressure systems, wind changes and the altitude of the plume affect movement. Cesium-137 is more of a long-term concern than iodine-131, as the cesium isotope’s half-life (the length of time required for the amount of the substance to reduce by half) is about 30 years vs. iodine-131’s half-life of 8 days. There is a short-term risk of thyroid damage if radioactive iodine in food is absorbed into the body and accumulates.

Within days of the earthquake, the International Atomic Energy Agency (IAEA) began regularly receiving radiation dose rate information from all 47 Japanese prefectures. Initially, radiation levels were only elevated in the immediate vicinity of the Daiichi plant, but by March 19th, it was reported that radioactive iodine was found in food products from the Fukushima prefecture. Radiation levels that exceeded acceptable limits had been detected in milk produced in the Fukushima area and in some vegetables in Ibaraki. The IAEA’s monitoring team also found contamination on the ground at a location 50 to 70 km from the Fukushima site. Then several more prefectures surrounding Fukushima reported iodine-131 in a variety of foods above the regulation values set by the Japanese authorities. Elevated iodine-131 was found in drinking water in 12 prefectures, though levels were considered to be below the safe limit for everyone except infants.

By the end of March, no cesium or iodine isotopes were detected or were below levels considered safe in most foods. And by mid-April, nearly all of the restrictions on food produced in certain areas were lifted.

Not So Fast…

Things began to change in May, especially for tea producers. Officials in Kanagawa prefecture, south of Tokyo, reported that elevated cesium levels were detected in a sample of tea leaves collected May 9 from the city of Minamiashigara. Then, according to the IAEA, eighteen samples of unprocessed raw tea leaves collected from Chiba, Gunma, Ibaraki and Tochigi prefectures on 17, 19, 24 and 26 May also tested above the regulation values for radioactive cesium. Those prefectures suspended shipments of tea leaves in response to the contamination concerns.

The World Health Organization (WHO) and the Food and Agricultural Organization (FAO) jointly set standards for radiation in food products, called the Codex General Standard for Contaminants and Toxins in Food and Feed, which contain Codex Guideline Levels. The Codex Guideline level for food products is a maximum of 1000 Bq/kg for cesium-137 and 100 Bq/kg for iodine-131. In comparison, the U.S. Food and Drug Administration has a border intervention level of 1200 Bq/kg of cesium for imported goods.

In early June, the Japanese government ordered a halt in shipments from the eastern prefectures of Ibaraki, Chiba, Kanagawa and Tochigi, which are not major tea producing areas of the country and decided to ban shipments of dried tea leaves containing more than 500 Bq/kg of radioactive cesium. The Japanese government exercised caution by setting the level at half the Codex accepted maximum, which should be reassuring to tea drinkers.

Spread to Shizouka

Tea connoisseurs’ concern began when radioactive cesium was detected in tea from the Shizuoka prefecture, 350 km from the Daiichi nuclear power plant. Shizuoka produces 40% of Japan’s green tea, and had initially declared its teas safe; most people thought it was far enough away to avoid the impacts of the Daiichi distaster. A recall of dried tea had to be initiated after leaves from a tea factory in the city of Shizuoka measured about 179 Bq/kg over the government’s limit, officials said. Although the cesium was at a level unlikely to affect human health according to Codex guidelines, Shizuoka prefecture decided to carry out sampling tests at nearly 100 other tea factories in the area. As of June 15th, five processing plants of the 20 tested thus far were asked to stop shipping tea due to cesium levels above the limit. There have been unsubstantiated rumors that the Japanese government has tried to censor the release of unfavorable test results.

On June 17th, the French press reported that Shizuoka tea with double the accepted level of cesium was intercepted in Paris. EU rules on acceptable levels of radiation are the same as Japan’s for cesium-137. The official government statement indicated the tea would be destroyed.

The Ministry of Health has been continually testing different food products, and posts the results every day (see the link below). On June 21, their posting contained samples of Shizuoka teas from 4 different areas, but they were all second flush teas. These samples of unrefined tea leaved and raw leaves were found to have low levels of cesium, ranging from 13 to 138 Bq/kg. On June 22, one tea sample (“refined tea leaf – first flush”) from the Ihara area of Shizuoka had results that were 22 Bq/kg above the government’s acceptable levels. Another sample from the same area, simply listed as “tea” only had 12 Bq/kg. The June 27 samples were from the Warashina area of Shizuoka, and these second flush raw tea leaves and unrefined tea leaves ranged from 14-39 Bq/kg and 115-161 Bq/kg, respectively.

The Japanese Tea Exporters’ Association has been closely monitoring iodine-131 and cesium-137 found on tea leaves in major tea producing areas of Japan. In information sent to Adagio by the Japanese Tea Exporters’ Association, tests showed that no cesium-137 was found on first flush fresh leaves in the major tea growing regions except for Shizuoka, and Shizuoka’s levels were below Codex guidelines. However, the concern is that drying and processing the tea leaves could concentrate the cesium.

Other major tea producing areas in Japan don’t seem to have been similarly affected due to their distance from Fukushima. Japan’s second largest tea growing region is Kagoshima on the island of Kyushu, which thousands of kilometers away from Fukushima – a similar distance separates New York and Denver.

Around 90% of Japan’s tea is used domestically. Consumers there are fearful of shortages since a sizeable proportion of their domestic tea has been contaminated. Prices are expected to rise for tea from uncontaminated regions. On the other hand, export orders for the other 10% have nearly dried up, affecting Japan’s economic recovery in the aftermath of the March earthquake. This has led to Japanese tea producers’ biggest concern: over-reaction. Many people are opting to just avoid Japanese teas altogether rather than researching the different growing regions and making an informed decision.

But How Much Is In Your Tea?

Another variable is how much of the radioactive material actually enters the liquid when the leaves are steeped. The tests the Japanese Tea Exporters’ Association conducted (10g leaves/430 ml water/90C/60 seconds) with leaves sampled in May found that steeped tea from Shizuoka is safe to drink. But the elevated cesium-137 was not found in Shizuoka tea until June, so it is unclear what percentage of Shizuoka’s tea violates the government rules and whether these were included in the tests. There is little conclusive information on how much radioactive material could get into the tea liquid, since there are so many factors involved in both processing and brewing tea, and some teas are steeped multiple times; estimates have ranged anywhere from 2% to 16%.

Many farmers and processors have been upset about the levels set by the government. Since tea is not generally a product that is consumed in the same manner as say, spinach would be, they feel that it is unfair to apply the regulations for food to a product like tea. Some tea drinkers do consume the brewed leaves of certain green teas, but this is not an overly common practice. The Japanese Health Ministry has heard their concerns and plans to make revisions to food safety standards over the summer, though producers feel that will be too late for this year’s crop of tea. A few media outlets are reporting that the Health Minister will announce the safety of Shizuoka tea on the Ministry website very soon, based on the revised standards for tea.

So Is It Safe Or Not?

Yes, most of Japan’s tea is safe. Tea from the Uji region, and the Yame, Kumamoto, Miyazaki and Kagoshima prefectures have not been found to have any radiation to date; they are all west of areas where radiation has been found. There technically is detectable cesium in all Shizuoka’s tea, though it seems that most does not exceed government standards. The jury is still out on how much of Shizuoka’s teas have been affected and whether it is localized to certain areas of the prefecture or certain processors. For what it’s worth, the acceptable radiation levels being used by the Japanese government are far more stringent than both United States and WHO standards, which can only benefit tea consumers. Obviously, pregnant women and children need to be extra cautious about radiation exposure in general. We should all consistently make informed decisions about what we put in our bodies – not just tea.

Adagio Teas' 2011 crop

Adagio Teas shares your concern about radiation in Japanese teas. We expect to be getting samples in from this year's harvest soon. Shizuoka is the only area we buy from that has the potential of being affected and we will proceed cautiously by sending all teas for independent testing to U.S. based labs.

Some links for further investigation:

Japanese Ministry of Health, Labor and Welfare – daily updates with testing levels in various food products

Maps of radioactivity dispersion/predictions – loop them for interesting views

IAEA Update Log