The European target value for the protection of human health is based on the daily maximum 8-hour mean ozone concentration. Averaged over 3 years, this daily maximum 8-hour mean should not exceed 120 µg/m³ more than 25 times a year. This European target value is a medium-term objective (MTO) and applies since 2010 (average 2010-2012). The long-term objective (LTO) is not a single day with maximum 8-hour means above 120 µg/m³. This indicator is expressed as the NET60 indicator.