Exposure to thallium contamination in drinking water: first results of human biomonitoring in Pietrasanta (Lucca, Italy).

Abstract

Introduction: since the end of 2014 in Pietrasanta (Lucca, Italy) several bans on the use of drinking water have been established by the municipality because of high thallium levels (above EPA guidelines of 2 µg/l) detected in some areas of the drinking water system. Population exposure stopped when pollution sources were excluded, and some pipes were replaced or cleared. The main objective of this study was to assess the degree of thallium exposure in a population living in areas of Pietrasanta involved in contamination of drinking water. Methods: various human bio-monitoring campaigns have been carried-out, by detecting urinary thallium levels. The first set of samples was collected within 30 days from water usage ban (samples A). The second set was collected after 2 months (samples B). 86% of participants provided both samples. Urine thallium levels were compared with reference values provided by the Italian Society for Reference Values (SIVR). Results: 637 samples A and 700 samples B were analysed, accounting for 20% of total population from contaminated area. Geometric mean (GM) of samples A was 0.42 µg/l (min-max: 0.005-8.96 µg/l). At cessation of exposure, samples B showed a significant decrease of thallium levels (GM: 0.29 µg/l; min-max: 0.005-5.44 µg/l). 42,5% of samples A and 20,9% of samples B showed thallium levels above 0.5 µg/l, which is 95° percentile of SIVR reference population. Conclusion: population in Pietrasanta exposed to thallium contamination showed average urinary thallium levels higher than reference values. According to WHO, exposure causing urinary thallium concentrations below 5 g/L is unlikely to cause adverse health effects. Even though Pietrasanta samples showed urinary levels far below this value, poor epidemiological evidence on chronic exposure to thallium imposes strong caution on evaluation of health effects.