The Muswellbrook monitor, which measures levels of particular matter less than 2.5microns in diameter, forms part of the Upper Hunter air quality monitoring network.

The monitor recorded daily levels between 61.2 and 118.2micrograms per cubic metre on five occasions between August 20 and August 30.

Although daily PM2.5 averages for the period fell within ‘‘very good’’ to ‘‘poor’’ National Environment Protection standards, poor air quality alerts were issued on August 27 and28.

No alerts were issued for the larger PM10 particles, which are also measured at Muswellbrook.

‘‘The high readings occurred overnight during cool and calm conditions which is conducive to particulate build-up and characteristic of the type of particle matter expected from fuel combustion, including woodsmoke,’’ a spokeswoman from the Office of Environment and Heritage said.

But Upper Hunter Air Quality Monitoring Network advisory committee member Carol Russell, said she had serious reservations about the explanation.

‘‘If woodsmoke is contributing to dust problems it means the government has a major problem that needs to be addressed,’’ she said.

‘‘The health implications are obvious to anyone with a basic understanding of the relationship between dust levels and health impacts.’’

Singleton-based GP Dr Twan Au, who plans to conduct an independent health study into the impacts of Upper Hunter dust pollution, said high particulate matter levels were reflected in the symptoms of many patients.

‘‘I can certainly confirm we have seen an increase in the numbers of people with sinus and asthma problems recently,’’ Dr Au said.

The department spokeswoman said a preliminary report from the Upper Hunter Air Quality Monitoring Network would be published on the Office of Environment and Heritage’s website by the end of the year.