4 days ago
New Zealand's air quality improving, but winter smoke still an issue
Smoke from wood burners and coal fires builds up in calm, cold conditions.
Photo:
Dave Allen / NIWA CC BY-NC-ND 4.0
Air quality is improving across many parts of the country, but the use of fires as heating creates a spike in pollutants during winter.
Air pollution has detrimental health impacts, with older adults, children, and other vulnerable groups most at risk.
Dr Chris Daughney, chief science advisor for the collective of regional and unitary councils, Te Uru Kahika, said there was generally a spike in pollutants during winter, as smoke from wood burners and coal fires built up in calm, cold conditions, and affected the health of whole communities.
However, the LAWA data showed improvements overall, with air quality trends improving for 30 of the 44 long-term PM10 monitoring sites over the past 10, and only 4 sites seeing a decline.
But when it came to guidelines for smaller particles, most places exceeded international guidelines.
Particulate matter is tiny airborne particles - naturally occurring like dust, pollen or sea salt, or human-made through the burning of fuels - and their health impact depends on particle size.
PM10 refers to particles less than 10 micrometres in size which can enter human airways. PM2.5 refers to finer particles, less than 2.5 micrometres in size, which can penetrate deep into human lungs, even the bloodstream.
LAWA chairperson Dr Tim Davie explained it was not yet mandatory to monitor PM2.5 under the National Environmental Standards for Air Quality (NES-AQ), and the science on its effects was relatively recent.
But 13 regions were already actively monitoring it anyway, and the number of monitored sites had increased in recent years.
Davie said the overall improvement in air quality was thanks to individuals making good decisions about how they heated their homes or travelled around their cities.
"It's not councils investing, it's people investing - buying low emissions wood burners and changing their heating to electric and buying electric cars.
"Councils set policies around that that encourages it, but it's actual people out there who are making those investments and making the changes, and that's really great to see."
Thirty of 44 monitored towns and cities show improving air quality over the past ten years - between 2015 and 2024.
Ten sites had an indeterminate trend, which meant there was not enough statistical certainty to determine if air quality had been improving or degrading.
Howeever, in 2024, only three monitoring sites met both the daily and annual World Health Organisation (WHO) guidelines for PM2.5 - Whareroa Marae in Mount Maunganui, Whangārei, and central Wellington.
The highest PM2.5 annual average concentrations were seen in Tokoroa, Pūtāruru, Kaiapoi, and Timaru, where winter woodsmoke from home heating was trapped by local topography and weather conditions.
LAWA air quality science lead Teresa Aberkane explained air quality responded to human behaviour.
"Many places like Timaru, Tokoroa, and Kaiapoi have taken active steps to reduce winter emissions, and we're seeing those actions reflected in the data."
* It's important to note not everywhere is monitored, and these levels include industrial and rural activities as well as natural sources (such as salt spray) in addition to particles caused by home heating.
The 10 most polluted, in order
(Most polluted)
Washdyke, Canterbury
Mount Maunganui (Totara St Rail Crossing), Bay of Plenty
Awatoto, Hawke's Bay
Gore (Main Street), Southland
Penrose, Auckland
Gisborne central
Tokoroa, Waikato
Putaruru, Waikato
Mount Maunganui (Ranch Rd), Bay of Plenty
Timaru (Anzac Square), Canterbury
The 10 least polluted
Rotorua (Edmund), Bay of Plenty
Lower Hutt (Birch Lane), Wellington
Wainuiomata (Bowling Club), Wellington
Thames, Waikato
Patumahoe, Auckland
Morrinsville, Waikato
Tauranga (Otumoetai), Bay of Plenty
Upper Hutt (Savage Park), Wellington
Taumarunui, King Country
(Least polluted)
Reefton (school), West Coast
