Lithium in drinking water, altitude, and suicide rates in rural areas of Argentinean Andes.

Abstract

The Lithium Triangle in the Andean plateau involves high altitude (>3,000 m asl) hydrological systems having high lithium graded waters. This research was carried-out in rural areas of north westernmost Argentinean Andes and was aimed: 1) to determine concentrations of lithium in drinking waters; 2) to calculate suicide mortality rates based on available official data (2003-2013); 3) to analyze bivariate differences between lithium concentrations in drinking water, mean rates of suicide mortality, altitude of sampling sites, and water sources; 4) to analyze bivariate correlations between lithium concentrations in drinking water, mean rates of suicide mortality, and altitude; 5) to test predictive models for mean rates of suicide mortality, when considering the predictors lithium concentrations in drinking water, altitude, and water sources. Lithium determinations in drinking waters were performed by Microwave Plasma-Atomic Emission Spectrometer. Nonparametric tests were applied to analyze differences and correlations. Generalized linear models (GLM) were used to fitting models for mean rates of suicide. Drinking waters contained up to 2.98 mg L-1 of lithium. Mean rates of suicide mortality (per 100,000 inhabitants) were high, ranging from 19.12 (± 19.83) to 30.22 (± 16.70). Lithium but not altitude was positively correlated with suicide mortality when analyzing bivariate correlations (Li: rho = 0.76, p-value < 0.001). However, when GLM were calculated, a significant interaction effect was found between lithium and altitude (p-value < 0.001). This interaction effect would act in some way restraining the suicide mortality rates.