During recent years, telomere length has been gaining the interest of researchers in the context of various pathological conditions, as well as due to its potential association with occupational and environmental exposure to xenobiotics. Metals are elements characterized by similar specific physicochemical properties. Toxic metals that require the most concern are as follows: lead, cadmium, mercury and arsenic. Tobacco smoke exposure, both in an active and in passive smoker, seems to decrease telomere length. Air pollution, both in environmental as well as occupational setting, is quite frequently assessed by exposure to particulate matter (PM). Persistent organic pollutants (POPs) constitute a heterogeneous group of lipid- soluble organic chemicals, which are resistant to degradation and prone to bioaccumulation. Pesticides are chemical compounds which exert biocide action mainly against insects, fungi, microbes, molluscs, rodents and others. They act as plant protection products. Psychosocial stress, traumatic experiences and social deprivation, however difficult for measurement, also may lead to telomere shortening.