Trace element reference values in tissues from inhabitants of the European Union. VIII. Thallium in the Italian population

In order to establish reference values of thallium in tissues of the general population the element was determined in blood (TIB) and urine (TIU) of 123 healthy inhabitants living in the Marche region, Central Italy. The analysis was carried out by inductively coupled plasma-mass spectrometry (ICP-MS; detection limit in our experimental conditions, 0.001 μg Tl/I), which was validated by neutron activation analysis (NAA) and laser induced fluorecence (LIF) spectroscopy. The check of pre-analytical factors indicated a low risk of contamination and loss of Tl during sampling, handling and storage before the instrumental analysis (blank of the entire procedure less than the detection limit). Mean values of TIU and T1B were 0.066 μg Tl/1 and 0.063 μg Tl/1, respectively (median in both cases 0.057 μg Tl/1). No conclusive evidence concerning the distribution followed by our data set, normal or log-normal, were drawn, although Lilliefors test and Kolmogorovʹs D-test showed a tendency for T1B to follow both the normal and the log-normal while T1U followed a log-normal distribution. Overall correlations between T1U and T1B are rather weak. A significant, but not high, correlation (P < 0.0004, r = 0.44) was observed in females. Age, sex, smoking habits and alcohol consumption did not seem to play any role on T1U and T1B. Tentatively proposed reference intervals are 0.019–0.17 μg Tl/l (urine) and 0.014–0.19 μg Tl/l (blood).