Ozone is toxic because of his high oxidating capability. Tropospheric ozone is one of the most concerning air pollutants in cities, producing lung irritation.
A statistical study of 95 large urban communities in the United States found significant association between ozone levels and premature death. The study estimated that a one-third reduction in urban ozone concentrations would save roughly 4000 lives per year (Bell et al., 2004). Tropospheric Ozone causes approximately 22,000 premature deaths per year in 25 countries in the European Union. (WHO, 2008)
Breathing ozone is toxic. There are many applications of ozone that do not have the same negative effects as inhalation. This is addressed in the first video.