Radioprotection, vol. 46,n ◦ 6 (2011) S151–S159 C  EDP Sciences, 2011 DOI: 10.1051 / radiopro / 20116969s Radionuclides in south Indian seafoods: A special focus on major contributing species S.G. Wesley and M.F. Khan ∗ Department of Zoology and Research Centre, Scott Christian College (Autonomous), Nagercoil – 629 003, Kanniyakumari District, Tamil Nadu, India Abstract. Concentrations of natural radionuclides 238 U, 208 Tl ( 232 Th), 226 Ra, 210 Po, 210 Pb and 40 K, and fallout 137 Cs were determined in pelagic and demersal fishes which are of economic importance. Pelagic fishes concentrated more radionuclides in the muscle tissue when compared to benthic species. Similarly, teleosts registered more activity than elasmobranchs. Based on the activity levels in muscle, the intake, effective dose and lifetime risks to humans were estimated. The internal radiation doses received by fishes and human beings seem to be mainly due to 210 Po and 40 K. The fishes were found to be safe for consumption. 1. INTRODUCTION Fish production is very significant for global food trade and food security, as fish provides more than 15% of total animal protein supplies. About 38% of world fish production enters international trade and around 50% (in value terms) of this trade originates in developing countries. Recent growth in the demand for seafood throughout the world has led to a considerable increase in interest in the safety of marine organisms as food sources [1]. In order to determine seafood safety, many countries have carried out research programmes on various kinds of pollutants in marine organisms [2]. Naturally occurring U and Th series radionuclides, singly occurring 40 K and fallout 137 Cs in marine ecosystem have attracted special interest due to their chemical and radioactive properties. The naturally occurring radionuclides, 238 U, 208 Tl, 226 Ra, 210 Po, 210 Pb and 40 K, and fallout 137 Cs are important contributors to radiation dose received by human beings via seafood consumption, because of their high accumulation rates in the edible parts (especially 210 Po) of marine organism [3, 4]. Data pertaining to the above-mentioned radionuclides remain scanty in the southern coastal regions of India, one of the high background radiation areas (HBRA) of the world. Among the seafoods, fishes are the most important species, representing more than 200 edible species alone from the southern coast of India [5]. No guideline values have been calculated for radionuclide levels in Indian seafoods till date. Based on the above scenario, the present study was carried out to find out the distribution of natural radionuclides in the economically important edible pelagic and demersal fish species of the southeastern coast of India and to estimate the radiation dose to humans in terms of seafood safety. 2. MATERIALS AND METHODS 2.1 Collection of samples Thirty-four species of edible pelagic and demersal fishes were collected at the major fish-landing centres (Chinnamuttom and Idinthakarai) and were also caught by trawling at 10 nautical miles offshore between Kanniyakumari and Uvari (Fig. 1). Samples were collected during January 2009 to March ∗ Present Address: Department of Advanced Zoology and Biotechnology, Sadakathullah Appa College (Autonomous), Rahmath Nagar, Tirunelveli-627 011. Tamil Nadu, India. Corresponding author Email: godwinwesley@yahoo.com, Tel.: +91 9443607998