A recording of a dangerous level of air pollution near the coast of Hawke’s Bay turned out to be salty sea air.

A combination of onshore winds and a high swell contributed to the breach of the National Environmental Standard (NES) for air quality at the industrial area of Awatoto, near Napier.

Hawke’s Bay Regional Council monitors the air quality with regular testing in three airsheds.

Air quality scientist Jeremy Kidd said the Awatoto industrial area and the air quality monitoring site within the area were very close to the coast, so there were often a lot of sea salt particles in the air.

“High particulate matter concentrations occurred on the morning of December 21, 2024, and we suspect this was mainly because of large amounts of sea salt particles in the air,” Kidd said.

“Winds were blowing onshore from a northeasterly direction, and the swell height was around 2m, meaning that wave action would create more airborne sea salt particles, which would be blown onshore towards Awatoto.”

The NES for air quality is designed to provide a minimum level of protection for human health. A breach of the NES means that this minimum level of protection was not achieved.

Hawke’s Bay Regional Council’s air quality scientist Jeremy Kidd checks air quality data. Photo / Supplied

“An area (known as an airshed) that has regular breaches of the NES is considered ‘polluted’. In a polluted airshed, resource consent applicants must limit or offset their emissions of PM10 to have a consent application accepted.”

Particulate matter (PM) is small airborne particles composed of solid and/or liquid matter.

“When we talk about particulate matter, we refer to PM10, which means particles that are 10 micrometres or less in diameter,” Kidd said.

“These particles are small enough to penetrate deep into your lungs and have consequences for human health.”

He said breaches of the NES happen most often in the colder months (May to August) in Napier and Hastings, but can occur any time of year in Awatoto.

An airshed is a defined geographic area where air pollution is monitored. The monitoring sites are located at Marewa Park in the Napier airshed, St John’s College in the Hastings airshed and Waitangi Rd in the Awatoto airshed.

Kidd said the highest number of breaches in a year was in 2008 when there were 27 alone in Hastings, while in Awatoto it was in 2024 with eight.

Hawke’s Bay Regional Council targets no more than one exceedance per year.

“Emissions in the Napier and Hastings airsheds are predominantly from residential heating sources, while those in the Awatoto airshed are predominantly from industrial and natural sources,” Kidd said.

The limit is a measure of particulate matter (PM10) of 50 μg/m3 (micrograms per cubic metre) in a 24-hour average. The reading on December 21, 2024, was (PM10) of 52 μg/m3

Measures industrial companies can take to prevent exceeding the limit

• Keeping yards tidy and suppressing dirt/dust so that it’s not blown into the air under windy conditions or when trucks drive through.
• Make sure all equipment is working and regularly maintained to limit any fugitive emissions from industrial premises.
• Compliance with consent conditions designed to reduce particulate matter emissions.
• Switching from coal-fired boilers to cleaner forms of energy production.

For households

• Households can make sure they’re using a compliant wood burner and burning properly seasoned, dry wood in fireplaces. People can switch to cleaner forms of home heating (i.e. a heat pump).
• From May 1 to August 31, it’s prohibited to burn outdoors on any property within the Hastings airsheds.