The article presents results of hygienic, clin. and laboratory studies concerning dependence of mieloperoxidase level in males residing in ecol. unfavorable area of Kazakhstan (Taraz town) on polycholrbiphenols content of air.Polycholrbiphenols content appeared to be 2-3 times exceeded among suspended particles of ambient air.The enzyme activity appeared to be changed in the examinees group (p < 0,05), statistically significant decrease of the enzyme was seen in 48% of the examinees.Reliable invert correlation was seen between lower mieloperoxydase activity and polychlorbiphenol concentration - that was at r = - 0,82 (p < 0.05).Mieloperoxidase activity indicates its sensitivity to xenobiotics influence in dependence on the exposure duration.Studies of mieloperoxidase activity in neutrophils can serve as a screening method and prenosol. diagnosis of ecol. dependent disorders in population.