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

Abstract

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.

Thallium Contamination of Drinking Water: Health Implications in a Residential Cohort Study in Tuscany (Italy)

“…The low number of residents in the hamlet of Valdicastello, i.e., the hamlet where the highest values of thallium in drinking water were recorded, considerably reduced the statistical power, although analyses of the major groups of pathologies (all-cause mortality, mortality and hospitalizations for cancer, and cardiovascular diseases) seem to confirm this trend. These results seem to be consistent with the results of the human biomonitoring campaigns carried out in the study area [40]. Urinary thallium values had a geometric mean of 0.467 µg/L (95th percentile equal to 1.89 µg/L) for the most exposed group (samples of residents in the hamlet of Valdicastello within two weeks of the drinking water prohibition ordinance), compared to 0.186 µg/L (95th percentile 0.563 µg/L) in the control group.…”

“…However, above all, the level of contamination of the pipes, which has in fact necessitated the total replacement of the distribution network where possible, or alternatively the use of innovative cleaning techniques, supports the hypothesis of chronic exposure of the resident population. Biomonitoring data from hair samples, which reflect a longer duration of exposure than urine samples, also show higher levels in the three exposure areas than observed in the control group [40,41].…”

“…In 2014-2015, concentrations of Tl above the recommended reference value (EPA: 2 µg/L) were measured in some parts of the drinking water distribution system in the municipality of Pietrasanta (Tuscany, Italy) [40,41]. Due to its rarity in nature, Tl is not included in the list of parameters for monitoring drinking water quality under European and Italian legislation.…”

“…In this context, in addition to a comprehensive water sampling campaign in the affected area and a large neighboring area, a series of human biomonitoring campaigns were also initiated to assess the impact of contamination on the exposure levels of the resident population [40]. A total of 2154 urine samples and 254 hair samples were analyzed in different areas affected by the contamination and at different times following the issuing/lifting of the ordinances.…”

“…Moreover, individual information on lifestyle, occupation, risk factors, and symptomatology potentially related to thallium exposure was also collected. The sample selection criteria and the results of the biomonitoring campaigns are described elsewhere [40].…”