The effect of ecological factors on a cardiovascular system of children Sultan Tuleukhanov, Zhanna Abdrassulova, Nurdana Salybekova, Gulzhaina Alpamyssova and Arina Kenshilik E3S Web Conf., 159 (2020) 01001 Published online: 24 March 2020 DOI: 10.1051/e3sconf/202015901001