The use of statistical methods for censored data to evaluate the activity concentration of Pb-210 in beans (Phaseolus vulgaris L.)

A survey of 210Pb activity concentration, one of the major internal natural radiation sources to man, has been carried in the most common species of beans (Phaseolus vulgaris L.) grown and consumed in Brazil. The representative bean types chosen, Carioca beans and black type sown in the Brazilian Midwestern and Southern regions, have been collected in this study and 210Pb determined by liquid scintillation spectrometry after separation with chromatographic extraction using Sr-resin. Available values in data set of radioactivity in Brazil (GEORAD) on the 210Pb activity concentration in black beans grown in Southeastern region have been added to the results of this study with the purpose of to amplify the population considered. Concerning the multiple detection limits and due to the high level of censored observations, a robust semi-parametric statistical method called regression on order statistics (ROS) has been employed to provide a reference value of the 210Pb in Brazilian beans, which amounted to 41 mBq kg−1 fresh wt. The results suggest that the 210Pb activity concentration in carioca beans is lower than in black beans. Also evaluated was the 210Pb activity concentration in vegetable component of a typical diet, which displays lower values than those shown in the literature for food consumed in Europe.