Sydney has made it on to a list of global air pollution "hotspots" in a study that uses new satellite data to measure nitrogen dioxide levels in the atmosphere.
The Greenpeace East Asia analysis, published on Monday, suggests the Sydney hotspot is ranked 40th globally.
The world's biggest hotspot is Mpumalanga in South Africa which is home to a dozen coal-fired power plants.
The list includes areas with power plants in India, South Africa and Germany; industrial clusters in China; and so-called megacities with high transport-related emissions including Dubai, London and Paris.
Vehicles, especially those that run on diesel, and coal-fired power stations are the main source of Australia's NO2 emissions.
The data, collected by the European Space Agency's Sentinel satellite, has been available since June and tracks emissions from the ground up through several kilometres of the atmosphere.
A fisherman casts his line as smoke is seen blanketing the Sydney city skyline as a result of Rural Fire Service hazard reduction burn. Source: AAP
The satellite data isn't directly comparable to ground-level pollution. World Health Organization figures show Australia generally has good air quality.
But Newcastle GP and clean-air campaigner Ben Ewald says high NO2 emissions are linked to ozone formation which can cause asthma attacks in sensitive people and chronic lung disease.
The Greenpeace analysis suggests levels of the hazardous gas averaged 0.25 parts per million in parts of Sydney over the three-month study period.
Nitrogen dioxide levels also averaged 0.25ppm over the three months near the Hunter Valley's Liddell Power Station and Bayswater Power Station.
Pollutant levels averaged 0.15ppm in Victoria's La Trobe Valley and Gladstone and Biloela in Queensland - all of which are home to coal-fired power stations.
Greenpeace air pollution campaigner Lauri Myllyvirta says governments need to act.
"This new satellite is our 'eye in the sky' from which the culprits - coal-burning industry and oil guzzling transport - cannot escape," Ms Myllyvirta said in a statement on Monday.
NO2 is formed whenever fuel is burned at a high temperature or if the fuel itself contains nitrogen. Coal, oil, gas and biomass burning all contribute to NO2 emissions.
