Air pollution in the Wollongong region has steadily decreased despite the growing population, the state's environment watchdog says.
Air quality improved significantly between 2003 and 2008 with reductions in the city's six most common pollutants, according to a study just released by the NSW Environment Protection Authority.
The study examined more than 850 pollutants in the greater metropolitan region of Sydney, Newcastle and Wollongong, which covers about 75 per cent of the state's population.
In Wollongong, it showed a 5 per cent drop in nitrogen oxides, a 15 per cent drop in toxic sulfur dioxide and a 19 per cent drop in pollutants known as volatile organic compounds.
There was a 1 per cent fall in carbon monoxide emissions plus decreases in particulate matter such as dust.
EPA chairman Barry Buffier said air quality improvements across metropolitan centres were linked to better regulation.
"This latest report will help to support the development of new programs, targeting new and emerging air quality issues in NSW, such as mining and other relatively unregulated emission sources," he said.
The NSW Air Inventory included natural emissions, such as those from bushfires, and man-made emissions, including those from cars and trucks.
An EPA spokeswoman said it would help to identify who and where the state's biggest emitters were.
The inventory would be updated for 2013, which in Wollongong would "help us to understand if the [partial] closure of the BlueScope steelworks has had an impact over a long period", she said.
Man-made emissions in Sydney were also steadily decreasing, although there was a rise in industrial emissions in the Hunter, especially dust from coalmines, the EPA said.