Contaminated Shizuoka Tea Traced to Warashina District Factory

TOKYO, Japan

The Japanese government is testing 100 tea processing factories and has halted shipments from the Warashina district of Shizuoka City.

Dry tea from a Warashina factory exceeded cesium levels despite government safety assurances and on Thursday shipments were promptly banned by Japan's Ministry of Health, Labour and Welfare.

Masanori Den Shirakata owner of Den's Tea, who is in Shizuoka, had this report for World Tea News:

"The Tokyo mail order house that discovered the contaminated tea is Radish Boya (Radish Boy) which is certified to handle organics. The contaminated tea was produced in a factory in the Warashina district in Shizuoka City. Japanese government officials have asked 100 tea processing plants in the district not to ship any tea and also requested wholesalers refrain from distributing the teas locally. Officials of the prefecture are now testing to determine whether the contamination occured in the district, in a particular growing region or just that factory."

Last week the ministry greatly expanded restrictions on tea, adding portions of three northern prefectures to the leaf ban following additional testing. Tea grown in portions of five prefectures is now restricted.

The high reading was discovered by a mail order tea company in Tokoyo that carried out its own measurements, suggesting that contaminated teas may already have reached the market. The level of contamination was low enough that the U.S. Food an Drug Administration would have passed the sample as it has set an Intervention Level of 1200 bq/kg becquerels per kilogram for cesium. Japan imposes more restrictive limit of 500 bq/kg.

Neither fresh or processed tea can be shipped from Warashina and the ban extends to all of Ibaraki prefecture as well as tea from six towns in Chiba Prefecture, two in Fukushima Prefecture and six towns in Kanagawa Prefecture.

Northern Japan produces relatively little green tea and almost all is consumed locally. However Shizuoka is a major production region accounting for 40 percent of Japan's annual production of 95,000 tons. Much of the nation's tea exports originate in Shizuoka where picturesque gardens are framed byimages of Mt. Fuji.

Shortfalls are projected and the price of green tea is rising. Local shortages are anticipated and the bans may encourage customers to shift from green tea to cheaper alternatives such as oolong, according to the agricultural ministry's press office. Japanese tea production was valued at $1.3 billion in 2009. Shizuoka grows 39.3% of the nation's total production and processes and ships tea from nearby regions through the port at Yokohama. All prefectures where tea is grown have been asked to test leaf and dried tea where possible but a shortage of equipment and personnel leaves the task to growers and processors.

The discovery Thursday was by chance as not all of Shizuoka's consighments have been tested.

Shizuoka prefecture is located west of Tokyo and last year produced 42,000 metric tons of dried green tea. Governor Heita Kawakatsu told reporters this week that a shortage of manpower forced the prefecture to limit testing. Previously the prefecture reported safe levels in all regions. The dried leaves discovered by the Tokyo mail house had readings of 679 bq/kg of cesium. Warashina, the site of the contaminated tea is 360 kilometers (225 miles) from Fukushima.

Emissions from three partially melted reactor cores are now estimated at double the initial assessment, according to the Nuclear and Industrial Safety Agency, Japan’s nuclear regulatory agency. The pressure vessel at one of the plant’s reactors was compromised as soon as five hours after the quake, the agency told reporters.

The release of radioactive iodine and cesium peaked between March 14 and 16 following the March 11 quake and tsunami. It is now evident there were meltdowns in three reactors and that an estimated 770,000 terabecquerels of radioactive particles were released. A terabecquerel is a trillion becquerels, a measure of radiation. The release is between 20 and 40 percent of the 1986 fallout from Chernobyl, the world's worst nuclear disaster.

In fresh vegetables and leaves a residue of 500 bq/kg of cesium is Japan’s legal limit for transport and consumption. Yasuo Sasaki, senior press counselor at the Ministry of Agriculture, Forestry and Fisheries said radiation in tea leaves containing even small amounts of cesium is concentrated by four or five times in the tea making process and can reach levels well above the 1000 Bq/kg considered safe by international standards. 

Green tea leaves tested in Kanagawa prefecture in Mayexceeded Japan's legal limit. Authorities halted the ichibancha (first flush) harvest in the vicinity of Minamiashigara after tests at five municipalities in Kanagawa prefecture showed cesium readings greater than 500 Bq/kg. Additional tests showed readings from 200 to 900 Bq/kg in gardens northeast of Shizuoka towards Tokyo and in the northern most gardens in the vicinity of Fukushima 220 kilometres (135 miles) northeast of Tokyo and 280 kilometres from Minamiashigara.

The central government previously imposed a ban on a range of vegetables and dairy produce from parts of Fukushima prefecture and several neighbouring regions, and banned fishing in the vicinity of the plant. The ban was recently expanded to include plums.

Beverage concentrations unknown

An unknown factor is whether high readings in fresh leaves will lead to harmful levels in the drink itself. Drying four pounds of fresh leaves to produce one pound of dried leaves concentrates the radioactive material between four and five times. Dried leaves (ara cha) tested in Minamiashigara were found to contain 3000 Bq/kg of cesium isotopes. Cesium-137 has a half-life of 30 years and Cesium-134 is radioactive for two years. However many of these radioactive particles are never ingested as they remain in the leaves after steeping.

Agricultural ministryofficials estimate tea brewed from contaminated leaves contains between 30 and 45 times less cesium (60 grams of green tea, brewed 60 seconds, in 2580 ml of 90-degree C water).

Japan’s radiation limits are set below the 1000 Bq/kg threshold for cesium listed in the Food and Agricultural Organization and World Health Organization’s Codex Alimentarius. The food safety guidelines were updated May 2 for nuclear emergencies.

The international safety standard for radioactive cesium in water is 200 Bq/l (5 milisieverts). Agriculture ministry officials maintain that radioactive materials are diluted between 1-to-30 and 1-to-45 using minimally processed leaves and by one-sixth to one-ninth in tea made from fresh leaves. Tea drinkers typically use 4 grams to make 160 militers of tea.

"Early data in cup suggests less than 10 percent is getting into the tea, but that is a hypothesis, not necessarily a like-for-like analysis," advises Dr. Andrew Scott, a British tea expert. He notes that it is common practice in Asia to drink tea leaves brewed more than once."

Virtually all the Kanagawa region’s tea, collectively known as Ashigara, is consumed domestically. As a precaution the prefecture halted all shipments of tea leaves within its boundaries. Private sector and public testing has been ongoing across Japan since the discovery of radioactive iodine and cesium in vegetables but this is the first instance where tea has been contaminated.

The Ashigara region borders Shizuoka. The discovery of Cesium-137 on May 9 has been traced to the earlier explosion at the Fukushima-Diiachi powerplant. The Minamiashigara area gardens tested 570 Bq/kg with subsequent tea readings of 780 Bq/kg reported in tea leaves sampled in Odawara and 740 Bq/kg in Kiyokawa tea leaves. Samples from Yugawa gardens were tested at 680 Bq/kg. Kanagawa officials say the gardens will be tested again next month just prior to the nibancha harvest. Until then the harvest of green tea is suspended. In late May tests near Izu city revealed tea with 98 bq/kg of cesium. The tea was banned.

In a similar situation following the 1986 explosion and meltdown of the Chernobyl reactors in the Soviet Union, samples from tea gardens in Turkey and Georgia tested at 25,000 bq/kg to 89,000 bq/kg. Cay-Kur, Turkey’s national tea company, buried 58,000 tons of the most contaminated teas and simply blended the remainder with the previous year's crop to arrive at an average 12,500 bq/kg reading. At that time less was known about the hazards of food borne radionuclides. Subsequent experiments showed that 60 percent of the radiation was transferred to the liquor from contaminated leaves.

The concern among Japanese tea professionals is over reaction. Kotaro Tanimoto, President of the Tea Import/Export Association prepared the attached report primarily for the European market. It provides a general overview useful when explaining the situation to customers that are predictably alarmed. Click here to view the presentation from the Japan Tea Exporter’s Association.

On learning of the contamination retailer Steven Sartini at La Teiera Eclettica in Milan, Italy expressed frustration that “I now have no arguments to use when the ever increasing numbers of customers declare they will stop consuming any tea from Japan. Some have even stated concern for Chinese teas that, as far as they're concerned (due to total ignorance of geography), is close enough to Japan for radioactive contamination…”

Monitoring the Situation

Several very useful websites are updated frequently regarding the situation in Japan. Real time radiological monitoring is available from the Ministry of Education, Culture, Sports, Science and Technology (MEXT).

Click here to download readings of radioactivity in Japan.

Click here to download readings of radioactivity by prefecture.

Click here for a interactive map that indicates the level of radioactivity in Japan's 47 prefectures.

The International Atomic Energy Agency provides daily briefings on the situation in Japan. The IAEA's Fukushima Nuclear Accident Update Log closely follows progress as the Japanese strive to contain radiation leaking from the stricken power facility.

The United States Department of Energy maintains a helpful blog called "The Situation in Japan" that is updated frequently. The department also produced a very informative slide presentation that you can download here.

The World Health Organization issued this guidance on food safety useful to tea retailers, importers of Japanese tea and wholesalers answering questions from their clients and the public.

Dan Bolton