AN off-the-scale dust spike at Stockton has officially been blamed on a sudden wind shift rather than an industrial pollution incident.
But irate residents dispute the explanation and believe the incident is symptomatic of declining air quality.
The spike of particulate matter of 10 microns or less (PM10) occurred in the early hours of yesterday.
It was recorded at the newly installed Fullerton Street air quality monitor as above 200 micrograms per cubic metre, the maximum the meter is capable of recording.
The National Environment Protection Measure for PM10 particles is less than 50 micrograms per cubic metre.
Acting Environment Protection Authority chairman and chief executive Mark Gifford said air monitoring sites in the Hunter registered spikes yesterday due to increasingly dry, hot and windy conditions.
Correct Planning for Mayfield group spokesman John Hayes disputed the explanation.
He said the community would not give up in its quest to determine the dust spike's origin.
"We need to be kept safe," he said.
"The authority [the Environment Protection Authority] that is tasked with protecting us is letting us down," he said.
"It seems to us that on the evidence we have seen their assertion [the spike was not caused by a local incident] can't be supported."
An Orica spokesman said no unusual activity had occurred at its Kooragang plant, which is directly opposite the monitoring station, that would have triggered the spike.
A Port Waratah Coal Services spokesman said the company's watering systems had been working at maximum capacity.
He said particle emissions at Carrington and Kooragang had remained within the annual daily averages.