Ground-level ozone concentrations, Auckland, 2001–16

Ground-level (tropospheric) ozone (O3) exists at a natural background level but is also produced when nitrogen oxides (NOx) and volatile organic compounds from vehicle emissions, petrol fumes, industrial processes solvents, and other human-made sources react in the presence of sunlight. It is the primary component of photochemical smog.
Ozone also occurs naturally in the stratosphere, where it protects us from ultraviolet radiation – this ozone occasionally can mix downwards to ground level.
Because sunlight and warmth are required for the chemical reactions that form ground-level ozone, peak concentrations often occur in summer when daylight hours are longer and temperatures are higher. Since the precursors for ozone can travel downwind from their sources before they react with sunlight, ozone concentrations can be high many kilometres from the precursor emissions’ sources.
Exposure to high concentrations of ozone can cause respiratory health problems and is linked to cardiovascular health problems and mortality. It can also damage vegetation.
More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.