**5.10. Honey**

β-emitter with a half-life of 23 years and acts as a reservoir for 210Po. Activity concentrations

Our own investigations on imported seafood in 1998 resulted in 12 objections in mussels and 2 objections in sardines concerning too high levels of 210Po. For food producers and food distribution agents, this was surprising. 210Po was never seen as a problem. One consumes sardines as a whole fish, the intestinal tract included [65, 66]. This explains the higher con‐ tamination level of sardines and anchovies. A second survey in 2010 showed values equal to those in 1998. Since 1990, the limit value for 210Po in fish was raised from 10 to 150 Bq/kg (the rate of fish and seafood consumed in Switzerland is of minor relevance). Therefore, since 1998, no more objections had to be raised [56]. A survey of the 210Pb and 210Po contamination of seafood in France over the last 15 years reports the same contamination levels [67]. Even higher 210Po levels were found in anchovy from local fishers at the Turkish coast of the Aegean Sea. The annual dose by ingestion was calculated to be 15 μSv [68]. Low activity concentrations were found in fish caught in Swiss lakes. A mean value of 87 samples was 0.4±0.3 mBq/kg 210Po. Such low values are not astonishing. Only the edible parts of the fish, without the intestinal tract and entrails, were analysed. Measurements of entrails of 34 fish samples showed

Baby food is infant follow-on formula that is industrially produced from cow's milk or soybeans. It is given to children up to 4 months after birth. For this kind of food, more restricted limit values are regulated concerning radionuclides. The given limit values are calculated to the final reconstructed constitution of the food (**table 1**). Radioactive contaminants are introduced through the milk into the products. Therefore, radiostrontium and radium are of

In 1987, an investigation of 56 samples of follow-on formulas showed a severe contamination with radiocaesium. Four samples exceeded the limit value of 400 Bq/kg; the highest value was more than 5.000 Bq/kg. Ten further samples contained radiocaesium in amounts greater than today's tolerance limit of 10 Bq/kg. However, no radiostrontium was analysed, so it is unknown how more violations were present concerning too high activities of 90Sr. In 2007 and 2012, we analysed baby food for both radionuclides. Whereas radiocaesium levels were quite low (<0.05 up to 0.5 Bq/kg), the radiostrontium contamination reached almost the same values (0.3 Bq/kg). Radium belongs to the same element group of the earth alkaline metals as calcium and strontium. Therefore, it is not surprising to find contaminations with radium (226Ra and

In 1986/1987, spices were of no special concern. They figure as a food of minor relevance, because the consumption rate of spices is relatively low in Switzerland. A second reason is the fact that spices are imported from the Middle and Far East, where they were not at all affected by the fallout from Chernobyl. Over the last 10 years, the radiocaesium content in spices was

range from 20 to 100 Bq/kg. In fish, the 210Po level is much lower (1–20 Bq/kg) [64].

a mean activity concentration of 25 Bq/kg [69].

228Ra) in infant formulas ( 0.1–0.8 Bq/kg) [70, 71].

**5.8. Baby food**

146 Radiation Effects in Materials

special interest.

**5.9. Spices and salt**

In 1986, 40 Swiss honey samples were investigated with γ-spectrometry. They contained 131I with a mean of 40.3 Bq/kg (6 samples) and radiocaesium with 54±47 Bq/kg (35 samples). The highest value was 192 Bq/kg of 137Cs. Six samples contained radioiodine over the tolerance limit of 10 Bq/kg, and six samples were over the tolerance level for radiocaesium of 10 Bq/kg. No violation of the limit values was observed [74].

Honey is considered as food of minor importance. Therefore, its survey was stopped in 2004. From 2005 on, we analysed more than 150 honey samples. They can be divided into two groups: honey from flowers and forest honeys (included chestnut honeys). Honey from flowers show only small amounts of contamination: 0.2 to 5 Bq/kg radiocaesium. In forest honey, one can find up to 25 Bq/kg 137Cs. Sporadically, we found violation of the tolerance values for radio‐ caesium and radiostrontium. One honey from Austria contained 1.6 Bq/kg 90Sr and 176 Bq/kg 137Cs. These products, and especially products from East European countries, contain elevated contaminations even 30 years after the accident at Chernobyl [75, 76].

### **5.11. Tea**

After the Chernobyl accident, we analysed tea with γ-ray spectrometry. From 21 samples, 12 teas exceeded the tolerance value of 500 Bq/kg. The mean activity found was 12.4±10 kBq/kg radiocaesium. One tea showed 429 Bq/kg, a clearly elevated contamination. In the following year, no sample exceeded 500 Bq/kg radiocaesium. After some years, the contamination levels were reduced to below 5 Bq Cs/kg with one exception. Contamination in black tea from Turkey was only slowly declining. Even in 2015, almost 30 years after the Chernobyl accident, the radiocaesium level reached 50 Bq/kg, and we found radiostrontium in amounts of 38 Bq/kg maximum. In 2011, our focus was set on imported tea from Japan. Until the end of 2015, we analysed more than 150 tea samples coming from different prefectures in Japan. The γ-analyses proved the contamination of green tea from the Fukushima-Daiji NPP's accident. At least, part of the measured radiocaesium originates from the fallout of the NPP's accident. This is proven by the presence of the short-lived radionuclide 134Cs (2.1 years). In 30 of 157 investigated tea samples, 134Cs was present in amounts of 13.4±24.8 Bq/kg. Besides tea, other food categories that are imported from Japan were analysed. Over the last 5 years, we analysed more than 350 food samples (**Table 2**). As can be noticed, the radiostrontium level of tea is approximately 5±7 Bq/kg and could be found in every tea sample analysed. This contamination mainly comes from the bomb's fallout. Teas from other countries of the Far East also contain radiostrontium [77, 78].


All values in Bq/kg. First line: mean ± standard deviation of the activity concentrations; the number of samples with values over the detection limit is bracketed. The total of analysed samples per food category is set in brackets after the food category name. Second line: activity concentration range of all samples. N/A, not analysed.

**Table 2.** Overview of investigated food imports from Japan from 2011 to 2015.

### **5.12. Mineral and tap waters**

#### *5.12.1. Artificial radionuclides*

1981, when our laboratory started with the radioactivity survey of food, water, besides milk, was the first food category to be monitored. Before 1986, no bomb fallout was detectable in the drinking water of Basel (<0.01 Bq/L radiocaesium). Just after the accident at Chernobyl, radioiodine and radiocaesium were detectable in small amounts of 59±77 and 9±9 Bq/L in some drinking water reservoirs of the state of Jura. The production of drinking water of the city of Basel was never affected.
