This paper presents findings from a recent study of a tropical river (Cacalotenango) in the important mining area of Taxco, México, where runoff from tailings and an active mine could be threatenig the environment. This study sought to evaluate the actual threat of lead contamination using an holistic approach. In this study, total concentration of lead in sediments, geochemical sediment characteristics such as organic matter and carbonates, and the physicochemical parameters of the river water were measured. Finally a kinetic study under controlled conditions (pH,T) was performed in situ in order to obtain the concentration (highest value 72 µg L^-1 at the station near the active mine) and the velocity rates (fitted curves change from linear at pH 8.0 to polynomial at pH 6.0) at which lead releases from sediments to the water column. The results indicate that, although the total lead concentrations on sediments are 7 to 30 times (from 860 to 5820 mg Kg^-1) above the natural background value for the area (mean value 150 mg Kg^-1) and could be potentially hazardous, the natural physicochemical and geochemical features of the river such as high alkalinity (295 mg L^-1), near neutral pH (mean value 7.2), high organic matter (mean value 3.5%) and carbonates content (mean value 12%), prevent the release of lead from sediments and into one of the water supplies of the inhabitants of the area. Therefore, current river conditions buffer against potentially dangerous lead release and, thereby, limit its environmental threat.