The article shows that an effective indicator of the level of pollution of air, water and soil with toxic compounds of anthropogenic origin is a health of the population in different age groups. As eco-indicators, it is proposed to use diseases of the respiratory system for people under 18 years old, the circulatory and digestive systems - 18-56 years old, the musculoskeletal system - over 56 years old. To carry out ecological diagnostics of negative changes in the natural environment of urbanized areas of small towns, we propose to assess the response (reaction) - hospitalization rate in different age groups of the population: under 18 years old, 19-55 years old, and over 56 years old.