Acknowledgements: scientific advisor Popova OS for introduction into work and assistance in the study; head of department of hygiene and ecology Nasybulina GM for possibility to implement scientific projects.

Author contribution: Bronskih NA — survey of students, statistical processing of results, review of literature on this issue; Sharenko EM — survey, statistical processing of results, searching the necessary literature; Popova OS — academic advisor, design development, organization of work, estimating quality of the obtained results, author’s criticism; Nasybulina GM — academic advisor, developing the study design, editing and editorial processing of the article.

Compliance with ethical standards: voluntary informed consent has been obtained from all those interviewed before the study.