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Sulphur dioxide levels in air

Why we monitor sulphur dioxide in air

Sulphur dioxide (SO2) was measured in Hamilton from 1 March 2012 to 31 August 2012 and in Tokoroa from 1 December 2017 to 31 May 2018. 

Sulphur dioxide is a potent respiratory irritant, and has been associated with increased hospital admissions for respiratory and cardiovascular disease, as well as mortality. People most sensitive to sulphur dioxide include asthmatics and those with chronic obstructive lung disease. The main source of sulphur oxides in urban areas is from combustion of fossil fuels such as coal and oil. Domestic home heating is typically the main contributor to sulphur oxides in urban areas in the Waikato region. In comparison, industry and transport are minor contributors. There has also been a decreasing contribution from transport because of the introduction of low sulphur petrol and diesel from around 2006 onwards. Waikato Regional Council aims to measure sulphur dioxide levels in the Waikato region about once every 5 years.

Highest concentrations of sulphur dioxide are likely to occur in or near urban areas where there is a high density of domestic home heating and adjacent to industrial sources. The Waikato Hospital was considered to be a significant source of sulphur dioxide in the airshed as a result of combustion of coal in the hospital’s boilers. The coal fired boilers were replaced with gas fired boilers over a staged period in 2012 ending around May 2012 not long after monitoring of sulphur dioxide began in Hamilton.

What's happening?

Results show levels of sulphur dioxide were very low and fall entirely within the excellent air quality category in both Hamilton and Tokoroa.

The Waikato Regional Plan sets guideline concentrations for sulphur dioxide at 350 µg/m3 for a one hour average and 120 µg/m3 for a 24 hour average.

In 2005 the Government set National Environmental Standards (NES) for air quality including a standard for sulphur dioxide of 350 µg/m3 for a one hour average. It allows nine hours per year when concentrations can be greater than 350 µg/m3 with an upper limit of 570 µg/m3 with no allowable exceedances.

We separate sulphur dioxide levels into categories relative to the regional or national guideline.

>>Find out more about these data and trends

More information

More detail on this indicator, including how and where Waikato Regional Council collects this information, is available on the methods page.

Useful links

When this indicator is updated

This indicator will be updated in 2023. 

Contact at Waikato Regional Council

Air quality scientist - Science and Strategy Directorate

Last updated June 2018