New Zealand's indoor pollution levels exceed WHO safety guidelines 91 pct of the year - study

A first of its kind global study on air quality has found New Zealand's average indoor pollution levels exceed the World Health Organization's long-term exposure guidance in 11 out of 12 months.
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A first of its kind global study on air quality has found New Zealand's average indoor pollution levels exceed the World Health Organization's long-term exposure guidance in 11 out of 12 months.

The data has been released by Dyson after being collected January - December 2022 from 3.4 million air purifiers connected to the internet around the world, 11,844 of which were in Aotearoa.

The Global Air Quality Connected Data project focused on two types of pollutants: PM2.5, which refers to particles smaller than 2.5 microns in diameter; and Volatile Organic Compounds (VOCs), which are gas pollutants released from a wide range of sources like aerosol sprays, candles and furniture.

PM2.5 particles are smaller than dust and pollen, which is generally categorised as PM10 - particles with a diameter of 10 microns or less. Experts say PM10 particles can be inhaled and deposited deep into the lungs.

To give an idea of how small this is, an average human hair has a diameter of around 50-70 microns.

WHO's 2021 air quality guidelines recommend PM2.5 exposure levels be kept to an annual average of level of less than 5 micrograms per cubic metre (μg/m³). New Zealand's annual indoor average for 2022, according to Dyson, was 6.85μg/m³.

The highest average levels of indoor PM2.5 pollution were detected in the colder months with the worst month being May (8.46μg/m³), which was almost double that of the best month, February (4.46μg/m³), Dyson said.

As was the case with most of the 39 countries in the study, Aotearoa's most polluted indoor time of day fell between 6pm and 1am. The indoor PM2.5 average levels were highest at 10pm (6.885μg/m³) and lowest at 5am (3.215μg/m³), while the VOCs were highest at 11pm on average. 

Air pollution is a serious issue. Research has shown long-term exposure significantly increases the risk of developing respiratory disease, while acute exposure to elevated levels of air pollution can exacerbate existing respiratory conditions, leading to hospitalisations and death.

In New Zealand, respiratory disease is the third most common cause of death after cardiovascular disease and cancer. It accounts for one in 10 hospital stays, with hospitalisation rates higher among Pacific peoples (2.6 times higher) and Māori (2.2 times higher) than other ethnic groups.

"Fine particulate matter (PM2.5) can penetrate through the lungs and further enter the body through the bloodstream, affecting all major organs," the WHO states on its website.

"Exposure to PM2.5 can cause diseases both to our cardiovascular and respiratory system, provoking, for example stroke, lung cancer and chronic obstructive pulmonary disease (COPD).

"New research has also shown an association between prenatal exposure to high levels of air pollution and developmental delay at age three, as well as psychological and behavioural problems later on, including symptoms of attention deficit hyperactivity disorder (ADHD), anxiety and depression."

There are several actions New Zealanders can take to improve the air quality in their homes. Not smoking or vaping inside is perhaps the most obvious, but there are various other steps one can take around cooking, cleaning, heating and furnishing.

Simple ventilation is one of the best ways to combat causes of indoor pollution including mould and dampness, which is "by far the biggest threat to indoor air quality", according to Dr Guy Coulson, an air quality scientist with NIWA.

"Opening windows is remarkably effective, even just a 10-minute blast to flush out pollutants will make a big difference," Dr Coulson said last year.

"However, if you live in an area with a lot of outdoor air pollution or if you are highly sensitive to pollutants, you might want to consider using a ventilation system or an air cleaner with a HEPA filter."

Air purifiers from the likes of Dyson, Breville and Samsung have HEPA filtration, and some have an auto mode that means they will automatically turn on and clean the air when pollutants are detected. However, in New Zealand, only 3 percent of Dyson purifiers spend more than three-quarters of the time in auto mode, the company said, with most owners changing the settings manually.

Asthma and Respiratory Foundation New Zealand (ARFNZ) advises that in a home where you can't easily open windows for ventilation, Kiwis should get advice on what size purifiers would be best and where they should be placed.