"Ozone levels improved compared with 2017, meeting the national standards on 98 per cent of all days," the report noted, adding that air-bourne particle levels increased.

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Measures of particulates of 2.5 microns size or smaller (PM2.5) - which can enter the bloodstream - were notably high last year. About two-thirds of monitoring sites recorded daily levels above the national standard and about half breached the annual goal.

"[This increase from 2017 was] mainly due to increased hazard-reduction burns around Sydney and the Illawarra, and the increase in particles throughout the state due to the intense drought," the report said.

Wood smoke from heaters also contributed to the elevated PM2.5 levels in places such as Muswellbrook and Singleton, it said.

Comment was sought from Environment Minister Matt Kean, the Office of Environment & Heritage.

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James Whelan, a researcher with the Environmental Justice Australia said his group had met Mr Kean and Planning Minister Rob Stokes to press them to finalise and implement a statewide pollution strategy.

"By its own account, the NSW government is failing to protect the state’s communities from harmful levels of air pollution," Mr Whelan said.

"Pollution controls are readily available to reduce Sydney’s sulfur dioxide and oxides of nitrogen, and to control particle pollution in the Hunter Valley," he said, adding that hundreds of premature deaths could be prevented.

The NSW government monitors air quality at 83 monitoring stations throughout the state.

The Environment Protection Authority said 2018 was "an unusual year for hazard-reduction burns and bushfires".

"The EPA focuses on emission and exposure reduction actions on the basis that they target emission sources that have large impacts on air quality and human health, based on the evidence," a spokesman said.

"Broader issues relating to addressing air pollution including sulfur dioxide are being considered in the National Environment Protection Council review, which is proposing to change the National Environment Protection (Ambient Air Quality) Measure relating to the standards for ozone, nitrogen dioxide and sulfur dioxide," he said.

That review is being led by EPA Victoria on behalf of the Commonwealth, states and territories, and it is currently undertaking public consultations this month and next, he said.