Report: TR04/29

Author: Emily Wilton (Environet Ltd.)

Abstract

Air quality monitoring for PM10 (particles in the air less than 10 microns in diameter) has been carried out in both Tokoroa and Taupo since 2001. Concentrations measured at both sites have exceeded the national and Waikato Regional Council ambient air quality guideline for PM10 of 50 µg m-3 (24-hour average) each year. These PM10 particles are of concern because of their ability to penetrate the lungs and cause adverse health impacts.

In September 2004, the Ministry for the Environment introduced national environmental standards (NES) for air quality including an ambient air quality standard of 50 µg m-3 (24-hour average) for PM10. The NES comes into force in September 2005. The NES allows for one guideline exceedence per year. Should there be more than one exceedence, the NES expects that strategies will be put in place to ensure that there will be just one exceedence per year by 2013.

Air quality monitoring in Tokoroa shows guideline exceedences have occurred on around 15 to 41 days per year. The maximum measured PM10 concentration of 97 µg m3 occurred during 2004. In Taupo, monitoring has been based on a sampling regime of one day in six in 2001 and one day in three since August 2002. Measured guideline exceedences range from one day per year in 2001 and 2002 to four days in 2003. Because the monitoring is not continuous, actual exceedences are likely to be higher (e.g., 5-12 days). The magnitude of the PM10 concentrations was lower in Taupo with a maximum of 62 µg m-3 being measured during 2003.

The main source of PM10 emissions in the urban areas of Taupo and Tokoroa is solid fuel burning for domestic home heating. In Taupo the inventory indicates that domestic heating contributes around 88 per cent of the PM10 with motor vehicles contributing 9 per cent and outdoor burning 3 per cent. The inventory does not account for the potential contribution of natural sources such as dusts or industrial emissions from processes such as sanding.

In Tokoroa, the industrial emissions within the study area (which excludes Kinleith) are less than 2 per cent of the total PM10 discharges and domestic heating is dominant at around 83 per cent. While emissions from Kinleith and the Kinleith industrial park may be transported into the urban areas of Tokoroa under some meteorological conditions, it appears unlikely that they were a significant contributor on days when PM10 concentrations are highest during 2004. Outdoor burning also comprises around 9 per cent of the emissions from within the urban area.

Monitoring data suggest that reductions in PM10 concentrations of 19 per cent and 46 per cent are required in Taupo and Tokoroa respectively to meet the NES and 19 per cent and 48 per cent to meet a target of 50 µg m-3 with no exceedences. Reductions in the order of 47 per cent and 65 per cent are required to meet 66 per cent of the guideline, i.e. the level at which the Regional Plan considers air quality to be degraded. Analysis of the effectiveness of management measures indicates that the NES may be met in Taupo by natural attrition of old heating systems being replaced by woodburners that meet a new emission standard of 1.5 grams of particles per kilogram of fuel burnt. No additional management measures may be required achieve these reductions by 2013 in Taupo. However, there are a number of uncertainties in the analysis and additional measures may be considered to improve the probability of compliance with the NES. In Tokoroa, management options such as a prohibition on outdoor rubbish burning and the use of open fires are likely to be needed as well as additional measures such as an incentives programme to encourage household to replace solid fuel burners with cleaner heating methods.

Further investigations that would provide useful information relevant to this assessment include an assessment of the potential contribution of natural dusts in Taupo.

Management Options for Air Quality in Tokoroa and Taupo [PDF, 449 KB]