The document summarizes a study measuring radioactivity in Japanese green tea from Shizuoka prefecture after the Fukushima Daiichi nuclear disaster. High resolution gamma spectroscopy was used to measure levels of Cesium-134, Cesium-137, Potassium-40, and natural uranium and thorium isotopes in raw tea leaves. Tea preparation methods were tested to determine radiochemical extraction yields, finding they did not significantly impact yields. Residual radioactivity in used tea leaves was low, under 10%. While the tea studied was below Japanese limits for radiocesium, the study notes issues with how limits have been applied to tea and recommendations for standardizing tea preparation methods and using extraction yields in assessments.

1. NRC8 - International Conference on Nuclear
and Radiochemistry
Session 13: radioactive elements in the environmental
Japanese Green Tea - radioactivity measurments,
radiochemical extraction yield determination and some
radioprotection considerations
21st september, 2012
Authors: S.Manera1, M.Oddone2, A.Salvini1, L.Strada2
1LENA University of Pavia, 2Chemical Dept. University of Pavia
Dr. Sergio Manera - Radioprotection Adviser LENA (UniPv) - manera@unipv.it
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2. Why Japanese Green Tea ?
Of course because of the Fukushima Dai-ichi nuclear crisis.
Everyone knows about Tea and how to prepare it, our context is well
known.
The consumption of tea is widespread in Japan (4th world top consumer,
2nd largest producer) with about 1kg of leaves per person per year.
Shizuoka Prefecture accounts for about 45% of Japan Green Tea
production. Our green tea sample is from Shizuoka.
MHLW selected Tea as a matrix of interest for monitoring radioactivity in
the environmental in Japan after the FD nuclear crisis for both domestic
consumption and export.
Turkish tea analysis in the aftermath of Chernobyl accident are well
known and we wanted to replicate those investigations for some “fresh”
data. 2

3. Why Japanese Green Tea ?
On June 17th, 2011, 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 137Cs. The
official government statement indicated: “tea would be destroyed”.
The radioactive releases and relative fallout over Japan started on
march 12th 2011. Tea usually grows in soil from early April to mid-
may (first harversting). There was the chance this matrix avoided
totally the fallout and was exposed only the root uptake of Cesium in
the plant.
Measurements of tea leaves started appearing early in 2011 but there
have been some misunderstandings about the measures.
3

4. A few informations about Green Tea
The classification of tea takes place on the basis of the processing of the
leaves which is a key factor for the finished product.
Tea may be fermented (Black Tea) where the oxidation of the leaves causes
the characteristic brown color or unfermented (Green Tea) in which there
are treatments with heat to prevent the oxidation of the leaves. There are
also semi-fermented tea. 4

5. A few informations about Green Tea
Green tea: tea is stabilized after harvest without being subjected to oxidation
by means of dry heat, moist heat or roasting (Japanese common procedure).
In Japan Tea means Green Tea, it’s the most common tea in the country
and green Tea is the most natural, undisturbed and interesting matrix to
investigate the behavior of radioactivity such as Cesium and Potassium.
…
Black tea: tea made completely oxidize after harvest, tea fully fermented, typical
brown color.
Oolong tea: tea stabilized after partial oxidation.
White tea: tea that undergoes whitering in dry air after harvest, silvery-white color.
Yellow tea: tea stabilized and allowed to stand with the heat and moisture. It is more
like a green tea slightly post-fermented.
Postfermeted Tea: tea stabilized and subsequently subjected to fermentation.
5

6. Material and methods: codex 2011 radionuclides
For all the measurements we made a large use of high resolution
and low background gamma spectroscopy.
FAO: “Codex Alimentarius Guideline Levels for radionuclides in
food contaminated following a nuclear or radiological
emergency” (may 2nd, 2011).
The new Codex list of 20 (6) radionuclides:
• 3H, 14C, 99Tc, 35S, 89Sr, 90Sr;
• 60Co, 134Cs, 137Cs, 192Ir;
• 129I, 131I, 103Ru, 106Ru, 144Ce;
• 235U 238Pu, 239Pu, 240Pu, 241Am;
• (in capitol our gamma investigation).
• We added 40K (Potassium has the same behaviour as
Cesium) and 238U, 232Th natural series to the list of the
nuclides to be investigated. 6

7. Results: raw Green Tea gamma analysis
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8. Results: ratio 134Cs/137Cs
The activity ratio (134Cs/137Cs) is about 0.75, which is in good
agreement, within the uncertainty of measure, with the initial ratio
(scaled backwards to march 2011) of about 1:1 for the two
isotopes which has already been world-wide assessed.
Whole of LENA
measures on the
FD crisis
8

9. Results: raw material homogeneity test
To investigate homogeneity we mixed the sample and randomly
divided it in 3 sub-samples of about 60-70 g each, then we
counted them separately using the 100 ml bottle geometry.
The sample dishomogeneity index is calculated as the simple
dispersion from the mean value reported in column 4;
The results show the raw material is actually well homogeneus.
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10. Tea preparation and extraction Yield
To investigate the extraction Yield of Cesium and Potassium we
preparated Tea beverage in 4 different ways:
8-10g/100ml, 5min extraction time
8-10g/100ml, 10min extraction time
8-10g/100ml, 15min extraction time
8-10g/100ml, 5+5min extraction time (2 extractions)
The extraction yield is the ratio (or the percentage) of
Cesium/Potassium in the prepared beverage in respect to the
ammount of Cesium/Potassium in the dryed tea leaves.
We used boiling deionizated water instead of tap water to
achieve more reproducibility.
All the prepared beverage have been stabilized in 100ml bottle
geometry adding 1ml of diluted technical grade hydrochloric
acid. 10

11. Tea preparation and extraction Yield
Used tea leaves are usually disposed to urban waste on common
use of the product.
Tea leaves after preparation of the beverage have been packed up
(still partially wet) and pressed in multifilter geometry to be
measured again to investigate the eventual loss of
Cesium/Potassium.
The last step was required because of the very low specific
radioactivity of the sample and we wanted to account for all the
radioactivity processed step by step.
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12. Results: the extraction Yield measurements (1)
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13. Results: the extraction Yield measurements (2)
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14. Results: the extraction Yield determination (3)
The extraction Yield doesn’t seem to be affected by the extraction
time. The 3 radionuclides show a very similar behavior in the
process.
The 2 in-sequence extractions do seem to add-up lineary.
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15. Results: residual radioactivity in used Tea leaves
The percentage of residual activity in the used Tea leaves seem
stable for all the 3 measured radionculides.
The 2 in-sequence extractions do seem to add-up lineary again on
all the 3 measured radionuclides.
The total lost of Cesium/Potassium was less than 10%, considering
the uncertainty.
15

16. Food limits and food safety in Japan
In Japan food safety is checked by means of a direct comparison
between measured values and “limits”. Limits are shown above.
Based on the results of the comparison Japanese authorities issue food
restrictions. Ordinances usually concern Prefectures or municipalities
of origin and prohibit the sale and consumption of the product.
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17. Saitama and Shizuoka - Tea Contamination
Saitama Prefecture Shizuoka Prefecture
1826 measures before 31.03.2012 200 measures before 31.03.2012
6,9% 3,5%
> limits > limits
< limits < limits
93,1% 96,5%
before 31.03.2012 N°measures < limits > limits
Saitama 1826 1708 127 (118)
Shizuoka 200 193 7 (7)
Note: (118) is the number of dryed Tea samples positive to checks.
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18. Some radioprotection considerations
In many cases in Japan and during the first year of monitoring the nuclear
crisis of FD lacked the indication “fresh or dried food”. Mushrooms and Tea
are particularly affected (ratio dryed/fresh of 5-7 ).
In many cases Tea leaves measures were compared with the limit of 500
Bq/kg (category general food) for food restrictions. This is wrong because
FAO Codex Alimentarius - 2011 edition reccomends to evaluate the risk for
food “ready for consumption” and so Tea must be prepared. The limits of
the category “Drinking water” should be applied to Tea beverages.
For Tea it’s easy to standardize the laboratory preparation using the ISO
Guide 3103:1980 issued for “flavor test of Tea”. It’s requirements are easy:
2g-100ml-6min extraction time.
Extraction yields are very easy to be determined and so why not using
them? It’s a cut of 60% of the raw-material radioactivity content. Not using
EY can be considered a bad conservative approach.
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19. Results: our tea?
Our Tea contamination level:
Raw measure of Cs-tot: 420 Bq/kg.
Tea beverage: 8.4 Bq/kg. (using ISO standard).
Adding the extraction yield to the tea beverage: 3.4 Bq/kg.
Comparison with Provisional limits (till 31.03.2012):
< 500 Bq/kg OK (wrong use of limits for vegetables)
< 200 Bq/kg OK (correct use of limits for drinking water)
Comparison with New limits (from 1.04.2012):
< 100 Bq/kg NO (wrong use of limits for general foods)
< 10 Bq/kg OK (correct use of limits for drinking water)
Our Tea is fit for human consumption and may be lawfully sold.
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20. Committed Effective Dose
Based on tea consumption of about 1 kg/y of tea leaves per
person in Japan, the correspondent intake of radioactivity is easy
calculated using the extraction rate measured above:
ACs-tot = 1 kg/y * 420 Bq/kg * 0.4 = 168 Bq/y
therefore using the ingestion dose coefficients for 134Cs and 137Cs
in the weight ratio, the committed effective dose is:
DAdults = (96 Bq * 1.3*10-08 Sv/Bq) + (72 Bq * 1.9*10-08 Sv/Bq)
= 0.0026 mSv/y
DInfants = (96 Bq * 2.1*10-08 Sv/Bq) + (72 Bq * 2.6*10-08 Sv/Bq)
= 0.0039 mSv/y
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21. Future tasks
It’s our aim to further and more widely investigate both the
concentration of radioactive Cesium and the extraction yields in
green tea samples produced in Japan, including other prefectures
of origin.
The goal is to confirm the extraction yields calculated with this
work and to promote it’s application in dose assessment.
It’s also important to assess the extraction yields starting from
the first year after the nuclear accident and keep monitoring it for
stability purposes.
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22. Japanese Green Tea - radioactivity measurments,
radiochemical extraction yield determination and some
radioprotection considerations
21st september, 2012
THANK YOU FOR YOUR ATTENTION !!
22
Dr. Sergio Manera - Radioprotection Adviser LENA (UniPv) - manera@unipv.it