Background/Aim. Air pollution outside and inside is still one of the most
sensitive issues. The aim of this study was to assess the ozone level in
ambient air and working premises in terms of its possible influence on human
health. Methods. The study was based on the results obtained in Lithuanian
conditions. Continuous ozone measurement data from the rural monitoring
station in Preila over the period 1995-2011 were analyzed. More than 180,000
hourly values were examined according to the requirements in the Directive
2008/50/EC. The World Health Organization (WHO) and European Union indicators
the Sum of Ozone Means Over 35 ppb (SOMO 35), the maximum daily 8-hour mean
concentration of ozone higher than 100 and 120 ?g/m3 were estimated. Indoor
ozone concentrations in copying and welding rooms were evaluated. The ozone
concentration was measured with the ozone analyzer O341M. Results. The
frequency distribution of ozone hourly concentrations at the Preila station
showed that less than 1% of the data were higher than 120 ?g/m3 and 6% of
them higher than 100 ?g/m3, that could have the adverse effect on human
health, during 1995-2011. The investigations made in working premises showed
that near a copying machine the ozone concentration can reach 330 ?g/m3,
however in the room, i.e. 0.5 m from the machine, the average ozone
concentration during automatic copying was 165 ?g/m? and during manual
copying it was 50 ?g/m?. Measurements in a welding room showed that the ozone
concentration was in the range of 380-1,850 ?g/m3 at the distance of 25 cm
from the electrode and at the distance of 1 m from the source the ozone
concentration decreased 2.5 times. Conclusion. The danger of the ambient
ozone level to human health practically was not observed in Lithuanian
conditions. However, almost 6% of the data exceed the new WHO guideline of
100 ?g/m3 during the measurement time. Indoor ozone during welding reached a
higher level than during copying that can cause human health problems.