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Lead is one of the important pollutants in our industrial society. The toxic effects has been extensively studied by different stand point of views; such as inhibitory pathway enzymes in hemoglobin biosynthesis that also disturbes the nevous systems. In the present study, the thermodynarnic aspect of Human Serium Albumin (HSA) destabilization by lead, has been studied with various experimental techniques sutCh as equilibrium dialysis, thermal denaturation and titration spectrophotometer at pH 3.2 and different temperatures. The number of binding sites, the strength of binding and the magnitude of binding cooperativity of lead to HSA were determined at two temperatures of 27°C and 37°C. The binding process is endothermic. So, heat increases the toxic effect of lead. Moreover, the melting temperature of protein, as a thermodynamic stability parameter, is decreased by increasing environmertal concentration of lead