Measured Ozone concentrations in outdoor air.

Crude accidental hourly values of ozone (O3) at ground level in the outdoor air measured in the National Air Quality Monitoring Network (LML). Ozone is a colourless to light blue gas and has a typical pungent odor. Ozone is not emitted directly, but is formed from other air pollutants, such as nitrogen oxides (NOx) and volatile organic compounds (VOCs). Ozone plays a role as a filter of UV light in the ozone layer and as a greenhouse gas in the lower layer of the atmosphere. At ground level, however, ozone also has harmful effects on human health (airway complaints and worsening of cardiovascular diseases) and vegetation (leaf damage and decrease in agricultural crop yields).