EPA works with industry, business and communities to reduce air pollution. A focus of this work in recent years has been in Melbourne’s inner west. This area experiences air pollution from a range of local sources, such as: 

• wood heaters 
• trucks 
• major roads 
• industry  
• shipping. 

By understanding the major sources of pollution in the inner west, we can better target efforts to prevent pollution and protect human health.  

What we measured 

The study focused on sources of PM2.5 particles.  

These tiny particles can enter the lungs and blood stream. They can cause adverse health effects over time, such as respiratory and cardiovascular disease. 
EPA has routinely monitored PM2.5 in the air for decades. While that monitoring tells us how much PM2.5 is present, it doesn’t tell us what those particles are made of, or where they come from. 

To assess sources of air pollution, this EPA study examined PM2.5 samples collected from 11 sites across the inner west of Melbourne between February 2021 and June 2022.  

To achieve the aims of the study, EPA worked with CSIRO and New Zealand scientists to: 

1. sample PM2.5 particles across inner west Melbourne 
2. test the particles to find out their chemical makeup, referred to as ‘chemical species’. We tested particle samples for 62 different chemical species, including trace metals  
3. determine the likely sources of these particles. 

What we found 

The major sources of PM2.5 in the inner west during the study period between May 2021 and May 2022 were found to be: 

• residential wood heaters (in winter) 
• bushfire fuel reduction burns (in autumn) 
• diesel vehicle emissions 
• undetermined sources of ‘secondary sulphate’. There are multiple sources of sulphur such as: 
  •  natural sources 
  • burning of fossil fuels 
  •  wood burning 
• sea salt from Port Philip Bay 
• motor vehicle emissions reacting with sea salt to form nitrous oxides – known as ‘secondary nitrate’. 

A single major pollution event comprising of elevated PM2.5 concentrations occurred on 10 July 2021. During this event, 3 main sources contributed to around 90% of the PM2.5 levels recorded: 

• residential wood heaters 
• secondary sulphate 
• ammonium nitrate particles, which likely formed when motor vehicle exhausts reacted with ammonia possibly from agricultural sources. 

Minor sources identified during the study period between May 2021 to May 2022 were: 

• petrol vehicle emissions 
• road dust 
• ship exhausts 
• industry. 

What this means  

The study has identified a range of human-related sources of PM2.5 in the inner west.  

The contribution to air pollution from these factors are highly variable over time.  

Other sources are natural, such as sea salts, cannot be managed and are not harmful to human health. 

EPA is focused on understanding sources and environmental conditions that may influence air pollution levels. 

We continue to work with community, industry and government to help protect human health and the environment. 

We also provide advice to community on managing exposure where necessary. 

It is important to note EPA encourages anyone with concerns about impacts to their health should contact their local GP for specific medical advice. This scientific information should not replace medical advice or guidance. 

What happens next 

The data is a baseline for assessing future air quality in inner west Melbourne and will help explore any future actions that may be needed.

EPA continues to work with the Department of Energy, Environment and Climate Action to implement the Victorian Air Quality Strategy.