*5.7.2. Natural radionuclides*

Natural radionuclides cause the main radiocontamination of fish and seafood. Mussels and molluscs are known to enrich 210Po in the intestinal tract, whereas the mother nuclide lead-210 ( 210Pb) is not enriched. Cherry and Shannon [63] published an excellent review. Both radionu‐ clides are part of the natural decay series of uranium and are built at the end of the decay chain. <sup>210</sup>Po is a powerful α-emitter with an energy of 5,500 keV and a half-life of 183 days. 210Pb is a β-emitter with a half-life of 23 years and acts as a reservoir for 210Po. Activity concentrations range from 20 to 100 Bq/kg. In fish, the 210Po level is much lower (1–20 Bq/kg) [64].

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

### **5.8. Baby food**

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 special interest.

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

#### **5.9. Spices and salt**

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 stable: 1 to 5 Bq/kg for 200 samples analysed. Higher activity concentrations were found for natural radionuclides from the uranium and thorium decay series. For example, white and black pepper and cinnamon contain considerable amounts of thorium and radium (up to 40 Bq/ kg). This is near the Swiss limit value of 50 Bq/kg [72].

Salts belong to the spices. Either they are produced from evaporation of seawater or are yielded from mines or salt fields. A survey of 23 products gave the following results: artificial radio‐ nuclides, such as radiocaesium, are not present. A major contaminant of salts is potassium chloride. Therefore, it is not surprising that 40K activity concentrations are relatively high in salts: 330±30 Bq/kg. One salt from Persia contained 6 kBq/kg 40K. Some radionuclides from the decay series, such as radium, are present in small amounts: 1.2±1.1 Bq/kg 226+228Ra [73].
