Due to their therapeutic and pharmacologic properties, medicinal herbs have a long history of use around the world. The objective of this study is to determine the activity concentration of natural (⁴⁰K, ²²⁶Ra, ²³²Th, and ²³⁸U) and artificial (¹³⁷Cs) radionuclides in samples of herbal teas from Serbia. The samples of the following commercially available teas: dandelion leaf (Taraxaci folium), mulberry leaf (Mori nigrae folium), ground ivy (Glechoma hederacea), sweet wormwood (Artemisia annua), rose hip (Cynosbati fructus), wall germander (Teucrium chamaedrys), and thyme (Thymus vulgaris), were collected in Serbia in 2021. The radionuclides’ activity concentrations were determined using gamma spectrometry. The results show that among the natural radionuclides, ⁴⁰K is dominant (320–1600 Bq/kg), while the activity concentration of ²²⁶Ra and ²³²Th ranges from below the minimum detectable activity (MDA) to 12 Bq/kg, and below the MDA to 13 Bq/kg, respectively. In all investigated samples, the ²³⁸U activity concentration is below the MDA. Cesium-137 is detected in five out of seven analysed samples (MDA–2.9 Bq/kg). The results indicate that ¹³⁷Cs, released into the atmosphere after the Chernobyl accident in 1986, is still present in the environment of Serbia. Nevertheless, according to the Serbian legislation regulating the maximum permitted levels of radionuclides in foodstuffs, all of the investigated samples of herbal teas are safe for human consumption.

1. L. Tettey-Larbi, E. O. Darko, C. Schandorf, A. A. Appiah, “Natural radioactivity levels of some medicinal plants commonly used in Ghana,” Springerplus, vol. 2, no. 1, 157, Apr. 2013.
   DOI: 10.1186/2193-1801-2-157
   PMid: 23641323
   PMCid: PMC3639363
2. F. K. Görür, R. Keser, N. Akçay, S. Dizman, N. T. Okumuşoğlu, “Radionuclides and heavy metals concentrations in Turkish market tea,” Food Control, vol. 22, no. 12, pp. 2065 – 2070, Dec. 2011.
   DOI: 10.1016/j.foodcont.2011.06.005
3. Ö. Kiliç, M. Belivermiş, S. Topcuoğlu, Y. Çotuk “²³²Th, ²³⁸U, ⁴⁰K, ¹³⁷Cs radioactivity concentrations and ¹³⁷Cs dose rate in Turkish market tea,” Radiat. Eff. Defects Solids, vol. 164, no. 2, pp. 138 – 143, Feb. 2009.
   DOI: 10.1080/10420150802681530
4. L. Petrović, “Nuklearna havarija u Černobilu 1986. godine: Prilog istraživanju ekoloških problema 20. veka,” Istorija 20. veka, tom 28, br. 2, str. 101 – 116, 2010.
   (L. Petrović, “Nuclear incident in Chernobyl 1986: An addition to the research of the environmental problems of the 20th century,” History of the 20th Century, vol. 28, no. 2, pp. 101 – 116, 2010.)
5. G. Vitorović i dr., “Radioaktivnost mleka u Srbiji od Černobilja 1986. do Fukušime 2011. godine,” Veterinarski Glasnik, tom 67, br. 3 – 4, str. 237 – 244, 2013.
   (G. Vitorović et al., “Milk radioactivity in Serbia from Chernobyl nuclear disaster in 1986 to Fukushima accident in 2011,” Vet. Gaz., vol. 67, no. 3 – 4, pp. 237 – 244, 2013.)
   DOI: 10.2298/VETGL1304237V
6. M. Greger, Uptake of nuclides by plants, Rep. TR-04-14, Stockholm University, Stockholm, Sweden, 2004.
   Retrieved from: https://skb.se/upload/publications/pdf/TR-04-14.pdf
   Retrieved on: Sep. 18, 2021
7. I. Kandić, A. Kandić, I. Čeliković, M. Gavrilović, P. Janaćković, “Activity concentrations of ¹³⁷Cs, ⁴⁰ K, and ²¹⁰Pb radionuclides in selected medicinal herbs from Central Serbia and their effective dose due to ingestion,” Sci. Total Environ., vol. 701, 134554, Jan. 2020.
   DOI: 10.1016/j.scitotenv.2019.134554
   PMid: 31753500
8. A. Y. Ahmad, M. A. Al-Ghouti, I. AlSadig, M. Abu-Dieyeh, “Vertical distribution and radiological risk assessment of 137Cs and natural radionuclides in soil samples,” Sci. Rep., vol. 9, no. 1, 12196, Aug. 2019.
   DOI: 10.1038/s41598-019-48500-x
   PMid: 31434929
   PMCid: PMC6704082
9. A. M. Abd El-Aty et al., “Residues and contaminants in tea and tea infusions: a review,” Food Addit. Contam. Part A, Chem. Anal. Control Expo. Risk Assess., vol. 31, no. 11, pp. 1794 – 1804, 2014.
   DOI: 10.1080/19440049.2014.958575
   PMid: 25164107
10. B. M. Mitrović et al., “¹³⁷Cs and ⁴⁰K in some traditional herbal teas collected in the mountain regions of Serbia,” Isotopes Environ. Health Stud., vol. 50, no. 4, pp. 538 – 545, 2014.
    DOI: 10.1080/10256016.2014.964233
    PMid: 25322769
11. GammaVision®-32, AMETEK Inc. (ORTEC), Oak Ridge (TN), USA, 2006.
12. M. Jevremovic, N. Lazarevic, S. Pavlovic, M. Orlic, “Radionuclide concentrations in samples of medicinal herbs and effective dose from ingestion of ¹³⁷Cs and natural radionuclides in herbal tea products from Serbian market,” Isotopes Environ. Health Stud., vol. 47, no. 1, pp. 87 – 92, Mar. 2011.
    DOI: 10.1080/10256016.2011.556723
    PMid: 21390990
13. K. Chandrashekara, H. M. Somashekarappa, “Estimation of radionuclides concentration and average annual committed effective dose due to ingestion for some selected medicinal plants of South India,” J. Radiat. Res. Appl. Sci., vol. 9, no. 1, pp. 68 – 77, Jan. 2016.
    DOI: 10.1016/j.jrras.2015.09.005