The Impact of Environmental Contaminants on Telomere Length

Introduction & Objective: Nowadays, numerous studies have been conducted to evaluate the different effects of environmental pollutants on fetal intrauterine conditions at birth and the results indicate that these factors have a negative effect. Heavy metals including arsenic, lead, cadmium, selenium etc. are distributed in the environment due to anthropogenic activities such as mining, coal burning, industrial gas emissions, household waste and the use and disposal of products. Polycyclic aromatic hydrocarbons (PAHs) caused by incomplete combustion of fossilsfuels, tobacco and other organic matters. Polychlorinated biphenyls (PCBs), and phthalates are used in plastics, solvents or goods such as cosmetics, toys, and food packaging and construction materials.Organophosphorus pesticides are used in agriculture, home and garden. These pollutants are produced in industry, commerce agriculture, municipal and household activities. Most of these pollutants have the ability to cross the placental barrier and thus have effects on the fetus. Therefore, exposure to them during pregnancy may eventually affect the baby. Telomeres are duplicate DNA sequences (TTAGGGs) located at the ends of eukaryotic chromosomes that, after each cell division, are shorter in normal somatic cells to prevent chromosomal fusion. When the telomere reaches a certain length, cell division stops and cell apoptosis occurs. Changes in telomere length among individuals largely depend on natural changes at birth, so early telomere length is important throughout life. It is considered as a marker of cellular aging and is associated with an increased risk of age-related diseases including cardiovascular disease as well as mortality. Because telomeres are highly sensitive to oxidative stress, exposure to environmental contaminants may be directly affected by oxidative stress.The purpose of this study is to review the effects of environmental pollutants on telomere length reduction.Materials & Methods:The search process was performed on valid electronic citation databases including Google Scholar, Scopus, PubMed and Web of Science using the keywords Telomere length, Environmental Contaminants, pregnancy, pregnancy outcome.Results:Results showed that exposure to phthalate metabolites in the first trimester of pregnancy was inversely related to telomere length. No difference observedbetween these metabolites in the first trimester of pregnancy and telomere length of cord blood in both sexes. Also, in relation to polycyclic aromatic hydrocarbons, there was an inverse relationship between PAHs metabolites and telomere length and neurobehavioral growth in children, with a decrease in telomere length and growth as metabolites increased. In another study on the effects of cadmium and a brief review of leukocyte telomere length in newborn infants in China, the results also showed that maternal exposure to cadmium decreased cord blood telomere length. Long and short-term exposure to PM2.5 and polychlorinated biphenyls, indicated an inverse relationship between telomere length and long-term exposure and a direct relationship to short-term exposure to contaminants and telomere length, respectively. Perfluoroalkyl and polyfluoroalkyl also as stable organic matters and constituents crossing the maternal and fetal barrier during pregnancy had an effect on telomere length, which resulted in a decrease in telomere length due to the reaction of these contaminants and the effects of neonatal sex. Reactive chemicals containing oxygen (ROS), increased oxidative stress.Conclusions:Given the adverse effects of environmental pollutants on the health of pregnant mothers and newborns as a vulnerable and vulnerable group of society, and the inadequacy of studies on some diseases and abnormalities, researchers are advised to pay more attention to this issue. They are focused. managers also plan and adopt health policies and applications to prevent the development of environmental pollutants and implement effective remedies.