water Article Carbamazepine Levels Related to the Demographic Indicators in Groundwater of Densely Populated Area Salma Ebrahimzadeh 1, * , Sara Castiglioni 2 , Francesco Riva 2 , Ettore Zuccato 2 and Arianna Azzellino 1   Citation: Ebrahimzadeh, S.; Castiglioni, S.; Riva, F.; Zuccato, E.; Azzellino, A. Carbamazepine Levels Related to the Demographic Indicators in Groundwater of Densely Populated Area. Water 2021, 13, 2539. https://doi.org/10.3390/w13182539 Academic Editor: Thomas M. Missimer Received: 30 July 2021 Accepted: 13 September 2021 Published: 16 September 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Civil and Environmental Engineering, Politecnico di Milano, 20133 Milan, Italy; arianna.azzellino@polimi.it 2 Department of Environmental Health Sciences, Institute di Ricerche Farmacologiche Mario Negri IRCCS, 20156 Milan, Italy; sara.castiglioni@marionegri.it (S.C.); francesco.riva@marionegri.it (F.R.); ettore.zuccato@marionegri.it (E.Z.) * Correspondence: salma.ebrahimzadeh@polimi.it; Tel.: +39-3279042372 Abstract: Consumption of pharmaceuticals by people is growing. Carbamazepine (CBZ) is an extensively used anti-epileptic drug that is recalcitrant to degradation. As a result, CBZ has been widely detected in the aquatic ecosystem due to its daily consumption and drainage in sewage systems. Leakages from sewage networks and septic tanks may represent one of the main sources of CBZ in groundwater. In this study, CBZ concentrations in groundwater and their correlations with the demographic structure of the population were investigated in the densely populated Milan urban area. Seventy-six demographic variables were retrieved from the Italian Population and Housing census. Twenty-one groundwater samples were collected from unconfined and semi-confined aquifers of the Milan area and the concentration of CBZ was measured. Groundwater CBZ levels in both aquifers were associated with the demographic data within a circular buffer with a radius of 1.5 km. All data were analyzed using a multivariate statistical approach. The results showed a significant association (p < 0.05) between CBZ concentrations and specific demographic segments of the population. Higher CBZ concentrations were found to be associated with the population aged 70 years and over (aging index), and with families having children aged under 5 years (family index). In addition, the divorce index was correlated with the high concentration of CBZ, whereas the educated and sexagenarian population showed a negative correlation. Our results indicated that the contamination of CBZ follows the same pattern in unconfined and semi-confined aquifers, which are used for drinking water purposes in Milan area. Therefore, changing the CBZ consumption pattern or replacing CBZ with other drugs may strongly influence groundwater contamination of the investigated area. Keywords: pharmaceutical pollution; carbamazepine; multivariate statistical analysis; demogra- phic information 1. Introduction Pollution from pharmaceuticals observed in the aquatic environment, and its potential risk for humans and the wider environment, have recently received significant attention among the global scientific community [1–3]. After pharmaceuticals are injected into the human body, they are excreted through the metabolism via urination [4,5], and then enter sewage networks or septic tanks. In many cases, wastewater treatment plans are not capable of effectively removing pharmaceuticals, and small concentrations of these compounds (ng/L) have been detected in the effluent of sewage treatment plants [6–8] or septic systems [9,10]. Pharmaceuticals mainly enter the groundwater through human activities such as sewage leakages [11,12]. Recently, several medical products from various classes have been found in groundwater [13–19]. Generally, pharmaceuticals in groundwater are regarded as emerging groundwater contaminants, and their long-term potential risk has been studied Water 2021, 13, 2539. https://doi.org/10.3390/w13182539 https://www.mdpi.com/journal/water