Lead isotopes in biological matrices to identify potential sources of contamination: the case study of Sulcis-Iglesiente district (SW Sardinia, Italy)

Abstract

The Sulcis-Iglesiente district has been, until recently, one of the most important Italian polymetallic mining areas for the extraction of lead. Located close to the town of Iglesias, the San Giorgio area constitutes a dramatic example of an area affected by intense mine pollution. Epidemiological studies regarding the mining areas of Sardinia have indicated the Sulcis-Iglesiente as a typical example of how dispersion of metal can affect human health. We have chosen this peculiar area to evaluate whether a supposed prolonged and continuous exposure to high lead concentration can be detected by means of a bio-monitoring procedure that uses the analysis of human scalp hair and the measurement of lead isotope ratios. Total lead concentrations in 144 human scalp hair samples from adolescents (11–13 years old) belonging to both genders, along with 23 lead isotope analyses in hair samples from Sant’Antioco (10 samples), Iglesias (10 samples) and roadway dust (3 samples) are discussed here. The hair database consisted of two groups of samples: 1) Iglesias group (IG) consisting of 59 subjects (32 females and 27 males). The town of Iglesias is located near the mining–waste of San Giorgio area. Other potential local pollutants are limited to emissions from vehicular traffic. 2) Sant’Antioco group (SAN) containing 85 cases (52 females and 33 males). The area of Sant’Antioco Island is not affected by intense mine activity and the pyroclastic volcanic rocks, outcropping in this site, are not characterised by metal mineralisation events. Three road dust samples were collected; two close to the mining area, more precisely one at Monteponi (RDMT), and another one within the urban area of Iglesias (RDIG) and a third sample was collected at Sant’Antioco, an area affected by industrial activities. Pb concentrations of adolescents living at Iglesias resulted higher than those of adolescents living at Sant’Antioco (median values PbIG: 1.56 μg/g and PbSAN: 0.30 μg/g, respectively). The influence of gender did not play any significant role. Hair from children living in Sant’Antioco exhibited lead isotope ratios in the ranges 1.152 – 1.165 for 206Pb/207Pb and 2.101 – 2.108 for 208Pb/206Pb, while hair samples from Iglesias resulted less radiogenic: 206Pb/207Pb ~ 1.147–1.154 and 208Pb/206Pb ~ 2.106 – 2.118. These values pointed to a multi-source mixing between the less radiogenic sources, corresponding to the Pb ore deposits, and the more radiogenic sources identified in local background. These data confirm the real danger of mine wastes in relation to lead exposure of subjects living near the mining sites of Sardinia. We suggest a continuous control of the level of Pb and other metals in the inhabitants of the cities of Iglesiente. Finally, although in the past some doubts have been raised about the use of lead isotopes to identify potential sources of contamination in biological matrices, the data obtained confirm that the lead isotope method remains a powerful technique.