Particle levels in air

Methods - how we monitor

• Where and how we collect the data

  The Waikato region has 20 gazetted urban airsheds: Cambridge, Hamilton, Huntly, Matamata, Morrinsville, Ngāruawahia, Ōtorohanga, Paeroa, Putaruru, Taupō, Te Aroha, Te Awamutu-Kihikihi, Te Kūiti, Thames, Tokoroa, Tuakau, Turangi, Waihi, Whangamatā and Whitianga. The seven airsheds identified in bold are currently monitored by Waikato Regional Council for PM_10. We suspect these areas are at risk because they are susceptible to build of PM₁₀ during periods of calm, settled weather.

  Monitoring sites

  • Hamilton (1) - Peachgrove Road (not current)
  • Hamilton (2) - Corner of Ohaupo Road and Lorne Street.
  • Hamilton (3) - Claudelands Event Centre, Heaphy Terrace
  • Taupō - Taupō District Council pumping station, Gillies Street Reserve
  • Te Kūiti - Waitomo District Council offices, Queen Street
  • Tokoroa – Billah Street reserve
  • Putaruru – Bowling Club on Arapuni Street
  • Matamata - Matamata Playcentre on Farmers Road (not current)
  • Ngāruawahia - Herschel Street (not current)
  • Turangi – Ohuanga Road (not current)
  • Waihi – Grey Street (not current)
  • Cambridge – Leamington Domain (not current)
  • Te Awamutu – Albert Park (not current)
  • Morrinsville - Morrinsville College
  • Thames - Thames High School

  Monitoring frequency

  PM₁₀ data are collected daily at all sites and reported as an average level for each 24-hour period, with the exception of Taupō prior to 2006 where data were collected on a one-in-six day (prior to 2002) or one-in-three day (2002 to 2006) monitoring regime. This 24-hour period is significant in determining adverse effects on human health. We also analyse hourly average data so that we can assess variations in concentrations during the day.

  PM_2.5 data are collected daily at Hamilton (Claudelands), Taupō, Te Kūiti and Tokoroa sites and reported as an average level for each 24-hour period. This 24-hour period is significant in determining adverse effects on human health. We also analyse hourly average data so that we can assess variations in concentrations during the day.

  Monitoring history

  Daily PM₁₀ measurements have been collected during the following years for each location:

  • 1998 to 2013 in Hamilton (1)
  • 2012 to current in Hamilton (2)
  • 2014 to current in Hamilton (3)
  • 2001 to current in Taupō and Tokoroa
  • 2003 to current in Te Kūiti
  • 2005 to 2012 in Matamata
  • 2006 to current in Putaruru
  • 2008 to 2012 in Ngāruawahia
  • 2008 to 2011 in Waihi
  • 2009 to 2018 in Turangi
  • 2013 to 2016 in Cambridge and Te Awamutu
  • 2015 to current in Morrinsville
  • 2016 to current in Thames

  Daily PM_2.5 measurements have been collected during the following years for each location: 

  • 2019 to current in Hamilton (3)
  • 2021 to current in Taupō
  • 2019 to current in Te Kūiti
  • 2015 to current in Tokoroa

  Measurement technique

  There are many different ways of measuring particulate concentrations in air and each method can provide varying levels of accuracy.

  One of the most common methods used by regional councils has been the Beta Attenuation Monitor (BAM). In the Waikato region, the Thermo-Scientific FH62 BAM has been the main instrument used for monitoring particulate concentrations in addition to Thermo-Scientific Sequential Partisols. A tapered element oscillating microbalance (TEOM) was also used for a period in Hamilton. However, the more recent development and availability of optical based particulate monitoring instruments that have US-EPA equivalent status has resulted in a recent shift to use of Teledyne API T640x monitors.

  Waikato Regional Council currently uses two types of PM₁₀ and PM_2.5 monitoring equipment:

  • Thermo-Scientific FH62 and 5014i BAMs (Beta Attenuation Monitors) for continuous monitoring in Hamilton (2), Tokoroa, Taupō, Te Kūiti, Putaruru, Matamata, Ngāruawahia, Turangi, Cambridge, Te Awamutu, Morrinsville and Thames.
  • Teledyne AP T640x (optical) monitors for continuous monitoring in Hamilton (3), Tokoroa, Te Kūiti and Taupō.
• How this indicator is compiled

  The National Environmental Standards for Air Quality (NESAQ) sets an ambient air quality standard in New Zealand for PM₁₀ of 50 µg/m³ (micrograms per cubic metre of air) averaged over a 24-hour period with 1 allowable exceedance of this concentration per 12-month period. More than 1 exceedance is classified as a breach of the standard.

  There is currently no New Zealand based guideline or standard applicable to PM_2.5 and consequently the 2021 World Health Organisation (WHO) guidelines have been used for reporting PM_2.5 concentrations against. The WHO guidelines for PM_2.5 includes a 24-hour average guideline of 15 µg/m³ with 3 allowable exceedances per 12-month period.

  Annual average concentrations of PM₁₀ and PM_2.5 are compared against the 2021 WHO annual average guidelines of 15 µg/m³ and 5 µg/m³ respectively.

  The method used for trend analysis for PM₁₀ is consistent with the method used by Statistics NZ and Ministry for the Environment for Air Quality Domain and synthesis reporting. The method utilises the Theil-Sen function in the OpenAir R-Statistics package which is based on the Seasonal Mann-Kendall test for monotonic trends. It detects underlying trends in variable environmental time-series data sets and may suggest presence of an underlying trend which is not evident from visual inspection of the air quality record or summary statistics. This method generates probability (p) values from an analysis of monthly averages that are used to assess the likelihood that the apparent relationship is real or a result of chance. The conventional threshold for deciding whether a relationship is likely to be genuine is at a probability value of p = 0.05 or lower, which corresponds to a 95% confidence level and greater.

  At least six years of data is required with an optimal requirement of the most recent 10-year period to be used where available. The Theil-Sen function with the deseason option is used.

  Trend analysis for PM_2.5 is not possible due to unavailability of long-term datasets.
• Limitations

  Waikato Regional Council has limited PM₁₀ data in some areas. We need data from several years at each site to adequately determine annual and seasonal PM₁₀ concentrations. Equipment malfunction means there can be periods of missing data on occasions.

  In Tokoroa, monitoring of PM₁₀ was carried out during 1999 from 19 February to 30 November at the South Waikato District Council Offices. The method of measurement used during the 1999 monitoring was a light scattering technique and is subject to limitations, such that it does not hold USEPA reference or equivalency status. Subsequent monitoring from 2001 to September 2005 was conducted with a MET One BAM which meets USEPA equivalency status. However, subsequent analysis suggests this method may not have been accurately recording PM₁₀ concentrations.

  Prior to 2006, in Taupō there was limited data available due to the one-in-six and subsequent one in three day monitoring regime.

  Quality control procedures

  Environment Waikato, 2009: Environmental Monitoring Air Quality Manual. Environment Waikato, Hamilton. (WRC Doc#1534207).

  Environment Waikato, 2003: Quality Assurance Procedures Manual for ambient air quality monitoring at Environment Waikato. Environment Waikato, Hamilton. (WRC Doc#937636).

  Ministry for the Environment Good Practice Guide for Air Quality Monitoring and Data Management 2009 (GPG air quality monitoring and data management)

  NEMS Air Quality – Continuous Particulate Monitoring v1.0.0 (Air Quality - Continuous Particulate Monitoring » National Environmental Monitoring Standards (NEMS)), November 2022.

  NEMS Processing of Environmental Time-series Data v1.1.0 (Processing of Environmental Time-series Data » National Environmental Monitoring Standards (NEMS)), March 2023.