Human biomonitoring to assess exposure to thallium following the contamination of drinking water

In 2014, in some parts of the water distribution system of the municipality of Pietrasanta (Tuscany, Italy), thallium (Tl) levels above the recommended limits were measured and some restrictions to water usage for drinking and food preparation were imposed. The study aimed to assess Tl exposure and possible health effects by means of a human biomonitoring survey. In the 2014–2016 time frame, 2154 urine and 254 hair samples were taken from different population groups and from a control group. The levels of Tl found in urine and hair were statistically higher in exposed groups than in controls and compared to the reference values for the general population. Concentrations in urine were significantly associated with the geographical origin of the sample, the consumption of drinking water and food grown in local gardens. A significant association was found between urine and hair. No positive associations were found between the Tl levels in hair or urine and several self-reported symptoms and health effects, except for sleep disturbance. The study indicates that the concentration of Tl in drinking water can be traced by urine analysis. Urine and hair have proven to be biological matrices that can be effectively used for the evaluation of Tl exposure. To date, the study represents the most extensive human biomonitoring campaign for the evaluation of the Tl exposure available at international level.