Seasonality of PM10 exceedances

  • Image, seasonality of pm10.

    We compare the daily concentrations of particulate matter 10 micrometres or less in diameter (PM10) in the air with the national short-term standard. This highlights the pattern of daily PM10 exceedances over a one-year period.

    We classified Seasonality of PM10 exceedances as supporting information.

    Key findings

    From 2011 to 2013, 95 percent of exceedances of the PM10 national short-term (daily) standard occurred during the cooler months of May to August.

    • These exceedances are largely due to home-heating emissions. They are exacerbated by relatively settled winter weather conditions that slow their dispersal.


    Note: PM10 – particulate matter 10 micrometres or less in diameter. Exceedances relate to the national daily standard. Data from regional councils of Northland, Bay of Plenty, Waikato, Hawke’s Bay, Manawatu-Wanganui, Wellington, Canterbury, West Coast, Otago, Southland; district councils of Marlborough and Tasman; Nelson City Council; Auckland Council.

    Definition and methodology

    Particulate matter 10 micrometres or less in diameter (PM10) can be emitted from the combustion of fuels, such as wood and coal (eg from home heating and industry), and petrol and diesel (from vehicles). Natural sources of PM10 include sea salt, dust, pollen, smoke (from bush fires), and volcanic ash. It is also formed from reactions between gases or between gases and other particles.

    The four main human-made sources of key pollutants in New Zealand are burning wood or coal for home heating, road motor vehicle use, industry, and household outdoor burning.

    See Relative contribution of key human-made emissions for more details on emission rates for each source.

    PM10 concentrations exceed the national short-term standard when they are above 50 micrograms per cubic metre (µg/m3).

    The national standard provides a set level of protection against health risks from exposure to PM10. It does not provide complete protection from adverse health effects as there is no threshold concentration below which health effects do not occur.


    Data quality

    We classified Seasonality of PM10 exceedances as supporting information.


     This supporting information is a partial measure of the ‘Airborne particles of concern to human health’ topic.


     The accuracy of the data source is of high quality.

    See Data quality information for more detail.


    Published 21 October 2015

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