In accordance with Act 123/1998 Coll. on free access to environmental information, as amended, the CHMI has provided verified primary and aggregated data on outdoor air pollutants. These are the main pollutants with limit values according to current legislation: arsenic (As), benzene, benzo[a]pyrene, cadmium (Cd), carbon monoxide (CO), nickel (Ni), nitrogen dioxide (NO2), nitrogen oxides (NOX), ground-level ozone (O3), lead (Pb), particulate matter (PM10), particulate matter (PM2.5), sulphur dioxide (SO2). The data are based on measurements at stations owned by the CHMI for the period 1969-2022. The primary data are presented in measurement intervals of 30 min, 1 h or 24 h, depending on the type of measurement. Aggregated data are calculated from the above primary data. These data are: daily mean values, monthly mean values, annual mean values and the number of exceedances of the limit values for the protection of human health. Verified data for subsequent calendar years from 2020 will always be available by 1 July of the following year.