The region's three coal-fired power stations all saw an increase in toxic pollution during the most recent financial year, environmental activists say.
Despite the year-on-year increase, energy providers say they've stayed within the legal pollution concentration limits, labelling the data "selective" and "misleading".
Environmental Justice Australia analysed the latest data from the National Pollution Inventory, which requires big polluters such as power stations, mines and manufacturing to provide information about their toxic substances emissions.
Eraring, on the western shore of Lake Macquarie, recorded an increase in five toxic pollutants, including a 130 per cent increase in mercury pollution.
The Origin Energy power station also had a 6 percent increase in nitrous oxides, 16 per cent increase in PM10 fine particle pollution, an 88 per cent increase in PM2.5 fine particle pollution, and a 15 per cent increase in sulfur dioxide.
AGL's Bayswater Power Station, near Muswellbrook, was the worst in Australia for nitrous oxides pollution and second in the nation for sulfur dioxide pollution. It also recorded a 48 per cent increase in mercury pollution and a 32 per cent increase in PM2.5 fine particle pollution.
At Vales Point Power Station, operated by Delta Electricity on the southern banks of Lake Macquarie, there was a 10 per cent increase in mercury and a 47 per cent jump in sulfur dioxide.
EJA lawyer Isabella Farrell-Hallegraeff said despite NSW power stations producing less power overall, dropping almost 3 per cent, they were among the worst emitters of some of the most toxic pollution.
"Coal-fired power stations in NSW are pumping out some of the most toxic chemicals for our health, leading to serious health problems like cancer, respiratory illnesses and severe asthma," she said.
"We know there is no safe level of air pollution and while coal-fired power stations continue to operate, the NSW government and the Environment Protection Authority have a responsibility to protect the health of our community."
Delta Electricity company secretary Steve Gurney said anti-coal activist groups made the same "highly selective" claim every time the National Pollution Inventory data was released.
"Once again we see activist groups seeking to create community fear based on selective and misrepresented data, which is then related to conclusions in discredited reports," Mr Gurney said.
"The actual data and air quality monitoring do not support these sensationalist and misleading claims by the EJA."
An AGL spokesperson said the Bayswater Power Station had not exceeded the air emission concentration limits, which were set by the EPA.
"Year to year changes in our NPI data is the result of increases or decreases in fuel usage and electricity generation, plant performance and maintenance operations," the AGL spokesperson said.
An Origin spokesperson said the energy provider was committed to minimising its impact on the environment and communities.
"We closely monitor emissions performance and Eraring continues to remain well beneath its emissions licence limits, with many changes documented in the National Pollution Inventory during 2022/23 reflecting an increase in Eraring's output in order to meet the power needs of the market," they said.
