Natural sources of pollution are difficult to control, although some actions can be effective (e.g. increasing groundcover to reduce dust, reducing fuel loads in bushfire-prone regions). Anthropogenic (human) sources can be controlled through strategic air quality policy. The management of air quality in Australia is a cooperative effort by all levels of government: The Australian Government sets emissions and fuel standards, and is responsible for the National Pollutant Inventory (NPI) and international obligations (see International agreements). State and territory governments are responsible for implementing the National Environment Protection Measures (NEPMs), state-based licensing of industrial facilities and legislation, and reporting progress on NEPM goals. Local governments are responsible for managing air pollution through their urban planning processes. National Environment Protection Measures The National Environment Protection Council Act 1994 is an agreement between the Australian Government, state and territory governments, and the Australian Local Government Association, to make joint legislative provision for the establishment of the National Environment Protection Council (NEPC). The NEPC is chaired by the Australian Government environment minister, and the environment ministers from each jurisdiction have a seat on the council. National Cabinet has endorsed the recommendations from the 2020 Conran Review of the COAG (Council of Australian Governments) Councils and Ministerial Forums to abolish the NEPC and have the environment ministers’ meeting (EMM) absorb its functions. However, this requires legislative change. The NEPC/EMM has 2 main tasks: to make NEPMs, and to assess and report on the implementation and effectiveness of NEPMs in participating jurisdictions. The NEPC publishes an annual report, which documents how the jurisdictions have implemented the relevant NEPMs. The most recent report published was for 2018–19 (NEPC 2021). The 4 NEPMs that are relevant to air quality are: Air Toxics – delivers a comprehensive information base (using nationally consistent approaches) for air toxic components (including formaldehyde, toluene, xylene and polycyclic aromatic hydrocarbons), which can be used in the development of standards to protect human health from exposure to these pollutants. Ambient Air Quality – delivers a national framework for monitoring and reporting on air pollutants including carbon monoxide, lead, particulates, nitrogen dioxide (NO2), sulfur dioxide (SO2) and ozone. A variation to the standards for particulates in this NEPM took effect in January 2016, and a variation for ozone, NO2 and SO2 was agreed in April 2021. Diesel Vehicle Emissions – promotes the reduction of pollution from diesel vehicles by providing guidelines to minimise deterioration in exhaust emissions performance or improve exhaust emissions performance. The NEPM is part of a suite of approaches, including programs operated by jurisdictions to reduce exhaust emissions from diesel vehicles, and to set emissions standards for new vehicles and fuel quality standards. National Pollutant Inventory – delivers a framework for collection and dissemination of information (amount, source and location) of 93 hazardous pollutants emitted to air, land or water by industry, commercial and domestic activities. National air quality standards Australia sets standards for concentrations of 7 pollutants in the ambient atmosphere for the protection of human health and wellbeing (Table 3), under the Ambient Air Quality NEPM. As part of the National Clean Air Agreement work plan, ministers proposed to decrease the standards for ozone, NO2 and SO2 in 2018, and, for ozone, replace the 1- and 4-hour limits with a rolling 8-hour average. Even more stringent goals have been set for 2025. These new NEPM variations were endorsed by the Minister for the Environment on 15 April 2021. Table 3 NEPMs for ambient air quality Pollutant Averaging period Maximum concentration (NEPM variationa) Maximum allowable exceedances (goal) Carbon monoxide 8 hours 9.0 ppm 1 day per year Lead 1 year 0.50 μg/m3 None Nitrogen dioxide 1 hour 1 year 0.12 ppm (0.09 ppma) 0.03 ppm (0.019 ppma) 1 day per year None PM10 1 day 1 year 50 μg/m3 25 μg/m3 Noneb PM2.5 1 day 1 year 25 μg/m3 8 μg/m3 Noneb (2025: 20 μg/m3) (7 μg/m3 2025 goal) Ozone 1 hour 4 hours 8 hoursa 0.10 ppm 0.08 ppm (0.065 ppma) 1 day per year 1 day per year (Nonea) Sulfur dioxide 1 hour 1 day 1 year 0.20 ppm (0.10 ppma) 0.08 ppm (0.02 ppma) 0.02 ppm 1 day per year (2025: 0.075 ppma) 1 day per year None μg/m3 = microgram per cubic metre; NEPM = National Environment Protection Measure; PM2.5 = fine particulate matter; PM10 = coarse particulate matter; ppm = parts per million New NEPM standards for ozone, nitrogen dioxide and sulfur dioxide were ratified in April 2021. There are allowable exceedances for particulate matter for exceptional events under Clause 18 of the Ambient Air Quality NEPM: ‘fire or dust occurrence that adversely affects air quality at a particular location and causes an exceedance of 1-day average standards in excess of normal historical fluctuations and background levels, and is directly related to: bushfire; jurisdiction authorised hazard reduction burning; or continental scale windblown dust’. Share on Twitter Share on Facebook Share on Linkedin Share this link Under the NEPM, jurisdictions are required to report annually on their compliance with the air quality standards (see case study: Air quality monitoring by the states and territories). For this task, air quality monitoring stations operate in populated areas and in areas where there is an air pollution concern, such as within the industrial regions of the Hunter Valley in New South Wales and Brooklyn in Victoria (Figure 44). Each monitoring station aims to capture ambient air quality measurements that are representative of a local area. Stations are generally not sited in hotspot areas such as next to a busy road or in the path of a chimney effluent. There are 211 fixed air quality monitoring stations in operation around Australia, not all of which are NEPM-compliant (e.g. due to airflow interference from nearby trees). Large parts of inland Australia, particularly in the north and west, have little to no monitoring coverage. There are also pollutants, such as mercury, that are not covered by the NEPM and are monitored by research teams in Australia. Mercury is only continuously monitored at Kennaook/Cape Grim (Tasmania) and Gunn Point (Northern Territory), which are baseline atmospheric monitoring stations operated by the Bureau of Meteorology. Figure 44 Locations of air quality monitoring stations in Australia, 2019–20 Expand View Figure 44 Locations of air quality monitoring stations in Australia, 2019–20 Source: Christy Geromboux, Centre for Air pollution, energy and health Research Share on Twitter Share on Facebook Share on Linkedin Share this link Case Study Air quality monitoring by the states and territories Air quality monitoring is undertaken by the states and territories 365 days a year. This requires significant effort and resourcing, in terms of siting and setting up the station, instrument calibration and maintenance, and quality control of measured data before they are released to the public. Not all the 211 stations (Figure 45) are compliant with the National Environment Protection Measures (NEPMs). NEPM compliance requires the monitoring station to have a clear sky angle of 120°, and to be sited more than 50 m from a main road and 10 m from the nearest tree. Trees and buildings limit the flow of air to the monitoring site, and pollution may also deposit onto the trees before reaching the station. Having clear sky access should provide an unrestricted measurement. Existing NEPM stations are re-evaluated for compliance every 5 years. Noncompliant stations still provide useful data, and some are industry funded, or use lower-cost instruments for indicative measurements – for example, those in regional New South Wales that contribute to the dust measurements (see Dust storms), and stations in Tasmania outside Hobart, Launceston and Devonport that measure particulate matter. An air quality monitoring station will typically measure the NEPM criteria pollutants, alongside meteorological variables, such as temperature, wind speed and direction, rainfall and humidity (Table 4). Table 4 Measurement techniques used to monitor air quality pollutants at state and territory monitoring stations Pollutant Measurement technique Carbon monoxide Infrared spectrometry Ozone Ultraviolet spectroscopy Nitrogen dioxide Chemiluminescence Fine particulate matter (PM2.5) Beta attenuation monitor Coarse particulate matter (PM10) Tapered element oscillating microbalance Sulfur dioxide Pulsed fluorescent spectrophotometry Recommendations from New South Wales on the design of an air quality monitoring network are to be adopted nationally (OEH 2019). This includes the need to increase the number of monitoring stations as the population of a region expands beyond 25,000 people. This is so that the recent NEPM requirement to assess population exposure to air pollutants can be adequately met. Once the measurements have been checked, they are processed to their required NEPM averaging time (e.g. hourly) before they are released to the public. The measurements are usually displayed with a colour representing the air quality category (see Approach), which shows the health impact of that measured value. Share on Twitter Share on Facebook Share on Linkedin Share this link Air Quality Index Australia has an Air Quality Index (AQI) system that is designed to communicate air pollution levels in an easy-to-understand way to the general public, and quickly show the associated level of health hazard. Often, reporting concentrations of air pollutants is meaningless to the public unless they are accompanied by a description of whether the concentration might be harmful to health. In addition, the NEPM standards are different for each pollutant, making comparison difficult. It is more helpful to place each measurement on an ‘even footing’ by calculating an AQI value. For each pollutant monitored at a given site, an AQI number is calculated as a percentage of the pollutant’s Ambient Air Quality NEPM standard. The ‘national standard’ is defined as the maximum recommended limit that a pollutant should reach. An AQI number of 100 indicates that the pollutant has been measured at a level equal to the national standard; an AQI of 200 shows that the level of the pollutant is double the recommended limit. Lower AQI numbers represent better air quality, from 0–33 (representing ‘very good’) up to ≥150 (representing ‘very poor’). The AQI also allows an easy comparison of levels of different pollutants across different locations. However, the use of different descriptions for the AQIs among the jurisdictions has been confusing. AQI standardisation Australian jurisdictions are now working towards unifying how they report air quality levels for clearer public messaging. During the summer 2019–20 bushfires, jurisdictions that maintain an air quality website found that the 24-hourly average measurements of fine particulate matter (PM2.5), which are usually reported in line with NEPM requirements, were not sufficient for members of the public looking for real-time information. The Royal Commission into the bushfires recommended that a standard hourly reporting system be designed and used in Australia (Binskin et al. 2020). Global air quality websites (e.g. Air pollution in Australia: real-time Air Quality Index visual map) take hourly measurements from air quality stations around the world and report them as a rolling average AQI. However, as these websites are not Australian based, the AQIs provided are calculated using the United States (US) air quality standards, which are generally more lenient than in Australia. The US 24-hour standard for PM2.5 is 35 micrograms per cubic metre (μg/m3), compared with the Australian 25 μg/m3 limit (US EPA 2020). Therefore, the AQI values displayed by overseas websites are lower than would be reported by Australian websites, implying that air quality is better than it really is by Australian standards. Note that some states and territories also set their own air quality standards (e.g. see case study: Management of dust and odour at Brooklyn Industrial Precinct, Victoria). Different messaging used by the jurisdictions also causes confusion during periods when the air quality is compromised. A report commissioned by the National Air Technical Advisory Group (NATAG) through the New South Wales Environment Protection Authority discovered that different AQI category definitions were in use nationally and internationally (DPIE 2020). For example, Queensland, South Australia and the 2016 state of the environment report (Keywood et al. 2017) used a 5-category system in which the highest band is ≥150. The Australian Capital Territory, the Northern Territory and Western Australia used a 6-category AQI system with an additional category representing an AQI above 200. New South Wales was the only jurisdiction to have moved to a 1-hour AQI for PM10and PM2.5, using 80.1 μg/m3 and 62.1 μg/m3, respectively, as 1-hour limits. Tasmania and Victoria did not report an AQI and gave the measured concentrations with an indication of the health impact. There were also differences in naming the 6th and worst category AQI: it was described as ‘hazardous’ by the Australian Capital Territory and New South Wales, ‘extreme’ by Western Australia, and ‘severe’ by the Northern Territory. The system now used by New South Wales has been recommended for adoption by the other jurisdictions in 2021. This combines the ‘very good’ and ‘good’ categories into a single ‘good’ category (coloured green), and adds an ‘extremely poor’ category (coloured maroon) when pollutant levels exceed twice the NEPM limits (see Approach). Instead of reporting AQI values, the pollutant concentration will be listed. Inventories An emissions inventory is a key input to chemical transport models that predict levels of pollutants in the atmosphere. The models use emissions inventories to calculate how much of a pollutant is released by different sources, at what height, and how emissions might vary over a typical day (e.g. by motor vehicles at peak hour). The pollutants are dispersed in the model atmosphere based on actual hourly weather data. Pollutants are then removed from the atmosphere model by dry deposition (falling to the ground) and wet deposition (removal by rainfall), or transformed into other substances by chemical reaction. The NPI collates information on emissions from industries (not Australia’s total emissions). The NPI is an online database that provides information about the emissions of 93 substances in Australia. The NPI requires Australian industries to self-report their annual emissions to air, water and land. The NPI was first established in 1998 and has undergone reforms to streamline processes and reduce the burden for businesses reporting to the NPI. In 2017, public accessibility was improved when the NPI data became available on data.gov.au. A discussion paper aimed at reviewing the NPI was released in 2018, encompassing whether the pollutants reported on are the right ones, whether the right information is collected and how cost-effective the data collection is (NPI 2018). The paper received 374 submissions in response, but no recommendations have been released. The NPI covers industry but does not detail other emissions (e.g. domestic emissions, traffic emissions), and how they might vary in time and space. Australia does not have a consistent emissions inventory that covers all emissions from the whole country, but development of such an inventory is a priority under the 2018–20 National Clean Air Agreement work plan. Jurisdictions such as New South Wales and Victoria have produced well-developed inventories, although the time taken to develop them means that there is a 5-year lag between the release date and the period the emissions are based upon. Other states produced inventories in the early 2000s for key pollutant sources such as motor vehicles, but these are now out of date because of changes to vehicle numbers and types, and the growth of cities. Consistent methods are needed for estimating key pollutant sources and strengths. These need to be applied by each state and territory to achieve a national inventory. National Clean Air Agreement work plan The National Clean Air Agreement, agreed to by all Australian environment ministers in 2015, is a framework to help governments identify and prioritise actions required to maintain and improve air quality. Under the agreement, work plans are implemented and reviewed every 3 years. The agreement acknowledges the role of all levels of government, business and the community in ensuring good air quality for all Australians. The agreement includes a focus on developing partnerships with business and nongovernment sectors to achieve and sustain improved air quality outcomes. It recognises the need for robust, reliable data and information to support decision-making and to satisfy community needs. The initial work plan of the agreement (DAWE 2015) was carried out between 2015 and 2017; it was reviewed in 2018 (Table 5). Table 5 Progress in delivering actions in priority areas in the National Clean Air Agreement 2015–17 work plan Priority areas Actions Status Standards Vary the Ambient Air Quality NEPM to strengthen particle reporting standards Complete Review the Ambient Air Quality NEPM for sulfur dioxide, nitrogen dioxide and ozone towards strengthening the standards Complete Review the Fuel Quality Standards Act 2000 Complete Review Air Toxics and Diesel Vehicle Emissions NEPMs Ongoing Emissions reduction measures Reduce emissions from nonroad spark-ignition engines and equipment (decision RIS completed 2015) Complete Reduce emissions from wood heaters Ongoing Manage nonroad diesel engine and marine engine emissions Ongoing Partnerships and cooperation Explore partnerships with nongovernment stakeholders to positively influence air quality outcomes Ongoing Improve exchange of information and experiences in implementing air quality management and monitoring tools across jurisdictions Complete Better knowledge, education and awareness Improve access to reliable air quality information for researchers, policy-makers and the community: National Air Quality Data Service National Environmental Science Program Clean Air and Urban Landscapes hub Complete Undertake National Pollutant Inventory reforms Ongoing Priority setting Establish and implement a priority-setting process and work plan Complete NEPM = National Environment Protection Measure; RIS = regulation impact statement Share on Twitter Share on Facebook Share on Linkedin Share this link Standards The 2015–17 work plan included actions to review and vary standards in the Ambient Air Quality NEPM, including strengthening the particle reporting standards, which came into effect in 2016. Most jurisdictions have formally included the updated standards in their legislation or policies, and all jurisdictions are reporting against the strengthened standards. The review of the Air Toxics NEPM showed that it has been valuable in aiding the investigation of available data to identify locations where high concentrations of these compounds may occur. Monitoring to date has shown that air toxic concentrations are significantly lower than concentrations that require further monitoring under the Air Toxics NEPM. The 2017–18 NEPC annual report stated that most jurisdictions agreed that the ‘NEPM has been effective in providing an impetus to investigate available data and in identifying locations most likely to experience significant population exposure to elevated levels of air toxics’ (NEPC 2019b). The review of the reporting standards for ozone, NO2 and SO2was not completed in the 2015–17 work plan. This was because the NEPC decision to vary the NEPM under the National Environment Protection Council Act 1994 (NEPC Act) required additional actions (e.g. public consultation) that could not be completed in the work plan timeframe. This priority was carried over to the 2018–20 work plan, and agreed on 15 April 2021. Because a significant source of air toxics is diesel emissions, the Diesel Vehicle Emissions NEPM is an important tool in an integrated approach to reducing the emission of air toxics. The 2013 review of the NEPC Act found that both NEPMs are close to achieving their goals, and an initial assessment presented in the 2015–17 mid-term review report suggested that a full review of both NEPMs should be carried out in the 2018–20 work plan (DEE 2016). The review would consider variations or revoking of the NEPMs. However, these actions depend on the streamlining of the NEPC Act provisions governing these processes. Emissions reduction measures The 2015–17 work plan included actions relevant to managing emissions from nonroad spark-ignition engines and equipment, nonroad diesel engines and wood heaters (see Management of specific pressures). Partnerships and cooperation The 2015–17 work plan included actions to explore partnerships with nongovernment stakeholders that will lead to improvements in air quality. The 1-year Clean Air Champion initiative, designed to raise industry and community awareness of clean air issues, was completed in mid-2016. Actions to support ongoing engagement to identify nonregulatory ways to manage air quality and to better integrate air quality management in new infrastructure developments and upgrades have included: Australian Government support for the upgrade to cleaner outboard engines by surf lifesaving clubs in 2017 Environment Protection Authority Tasmania involvement in the Coordinated Smoke Management Strategy Environment Protection Authority Tasmania partnering in the collaborative AirRater project to monitor air quality and to create a smartphone application to report air pollution Queensland’s discussions with coal transporters to reduce coal dust emissions and share monitoring data Western Australian Government involvement in the Air Quality Coordinating Committee. The priority area to improve exchange of information across jurisdictions was removed from the work plan because a number of business-as-usual avenues of information exchange already exist across jurisdictions and with other stakeholders (e.g. Clean Air Society of Australia, New Zealand biennial conference). Better knowledge, education and awareness The 2015–17 work plan included actions to improve access to air quality information for policy-makers, researchers and the community. The proposed National Air Quality Data Service was affected by resourcing constraints and therefore not pursued. Instead, efforts will be made to include air quality monitoring stations from some jurisdictions in the National Environmental Monitoring Sites Register being implemented by the Bureau of Meteorology. Research carried out in the Clean Air and Urban Landscapes hub, funded under the Australian Government’s National Environmental Science Program, contributed to improved knowledge to develop tools and evidence to support a Clean Air Plan for Western Sydney, and extend nationally lessons learned under the Air Quality in Australia project (Forehead et al. 2021). Priority setting An Air Management Group was established to set priorities for future work plans under the National Clean Air Agreement (Table 6). The 2 new priorities set by the group in the 2015–17 work plan, to be implemented in the 2018–20 work plan, were to develop a national approach to emissions inventories for air quality management and to implement an air quality smartphone app nationally. Table 6 National Clean Air Agreement work plan for 2018–20 Priority areas Actions Standards Review latest scientific evidence of health impacts in relation to annual average PM10 standards in the Ambient Air Quality NEPM Complete review of the Ambient Air Quality NEPM standards for sulfur dioxide, nitrogen dioxide and ozone Review legislative instruments made under the Fuel Quality Standards Act 2000 Reduce emissions from nonroad spark-ignition engines and equipment (decision RIS completed 2015) Review the need for the Air Toxics and Diesel Vehicle Emissions NEPMs Emissions reduction measures Reduce emissions from wood heaters Manage nonroad diesel engine emissions Partnerships and cooperation Engage and explore opportunities with nongovernment stakeholders to positively influence air quality outcomes Better knowledge, education and awareness Improve access to reliable air quality information for researchers, policy-makers and the community Undertake National Pollutant Inventory reforms NEPM = National Environment Protection Measure; PM10 = coarse particulate matter; RIS = regulation impact statement Share on Twitter Share on Facebook Share on Linkedin Share this link At the time of writing, the 2018–20 work plan was reaching completion. However, the mid-term review was delayed in 2020, and we are unable to assess the effectiveness of the 2018–20 work plan, or report on what the ongoing actions will be for the 2021–23 work plan. National Air Technical Advisory Group The National Air Technical Advisory Group (NATAG) was established in 2018, comprising representatives from the Australian and state and territory governments. NATAG provides technical advice to the Meeting of Environment Ministers and the senior officials who support ministers, and supports the Air Project Management Group (established under the National Clean Air Agreement to set priorities). NATAG’s tasks include providing technical advice on the development and implementation of air quality standards, providing advice in line with the National Clean Air Agreement and its work plans, developing consistent methods for national air quality policies and programs, developing the air quality evidence base, identifying knowledge gaps, and recommending and informing research. Current priorities of NATAG include development of consistent air emissions inventories across Australia to support air quality modelling and policy development, and to improve population exposure and health impact assessments. The review of the Ambient Air Quality NEPM in 2011 identified advantages of an integrated, risk-based approach to air quality management. However, improvements in exposure assessment and changes in design of the monitoring network would be required to achieve this new approach. NATAG, through the New South Wales Office of Environment and Heritage, reviewed the design of the air quality monitoring network in 2019 (OEH 2019). The review made recommendations that will form the basis for updating the guidance on designing air monitoring networks, including changes to the frequency of network reviews, and approaches to ensure that network design guidelines remain current, are sufficiently flexible to incorporate technical advances in air quality assessment and improved understanding of air quality impacts, and provide independent expert review of implementation of the monitoring network. A final recommendation concerns a change to Clause 14 of the NEPM, which addresses review of performance monitoring requirements – in particular, basing the number of performance monitoring stations on the potential risk to the region’s population from pollutant exposure, flexibility to add performance stations in regions with high risk, and changes to the methodology used to determine the minimum number of performance monitoring stations in a region. Another important recommendation was for jurisdictions to reassess ozone monitoring requirements based on the updated 2007 screening procedures, focusing on large inland and coastal centres. New South Wales Clean Air Strategy 2021–30 New South Wales has drafted a 10-year strategy to improve air quality statewide (DPIE 2021a). The strategy is currently undergoing consultation. It lists actions in 5 categories: Better preparedness for pollution events – improve information and how it is communicated to help reduce health impacts of pollution on New South Wales communities, including impacts from bushfires, hazard reduction burns and dust storms. Cleaner industry – drive improved management of air emissions by industry. Cleaner transport, engines and fuels – further reduce air emissions and impacts from vehicles, fuels and nonroad diesel sources. Healthier households – support reducing emissions from household activities, with the main priority being wood heater emissions. Better places – reduce impacts of air pollution on communities through better planning and design of places and buildings. International agreements Australia is party to several international agreements that aim to reduce exposure to harmful chemicals in the atmosphere. Stockholm Convention on Persistent Organic Pollutants The Stockholm Convention on Persistent Organic Pollutants, which Australia ratified in 2004, is a global treaty to restrict and reduce unintentional production of 27 compounds that are known to bioaccumulate in humans and other animals. Exposure to these compounds, which have been used in pesticides, fire retardants and lubricants, leads to serious health effects, including cancers, decreased neurological function and increased risk of chronic diseases (Carpenter 2011).The convention includes a requirement to evaluate its effectiveness (Article 16), which is assessed using information from monitoring of persistent organic pollutants (POPs) in a number of compartments, including air. As reported in the 2016 state of the environment report (Box ATM12), data from 2 Australian air monitoring networks (including a nationwide passive air network) (Wang et al. 2015) were used in the second evaluation of the convention. The third evaluation is currently underway and will also use data from the national passive air sampling network. Rauert et al. (2018) found that many types of POP were still increasing globally in the atmosphere in 2015. Minamata Convention The Minamata Convention describes the controls that countries should put in place to protect human health and the environment from mercury and mercury compounds. Australia became a signatory to the convention in 2013. The Australian Government published a regulation impact statement report on the benefits of ratification in March 2021, required in Australia’s domestic treaty-making process, and expects to ratify the convention later in 2021. The convention includes effectiveness evaluation (Article 22) by tracking the progress of implementation and change. Draft indicators and monitoring guidance include monitoring of gaseous elemental mercury in air. Long-term measurements are critical to monitoring how effective the Minamata Convention has been in reducing mercury emissions globally. Australia’s longest records of atmospheric mercury are located in the far north and far south coastal areas. Measurements at Gunn Point in the Northern Territory since 2014 and Cape Grim in Tasmania since 2011 show average elemental mercury concentrations at 0.9–1.0 nanograms per cubic metre (ng/m3). This is considered to be at background levels (Slemr et al. 2015, Howard et al. 2017). Measurements at Oakdale in New South Wales in 2017–18 showed much lower elemental mercury levels (mean 0.68 ng/m3) compared with the coastal sites (MacSween et al. 2020a). Slightly higher mercury levels were found close to a power station in Victoria (Schofield et al. 2021). Technology is available to filter mercury from power station emissions (Pacyna et al. 2010), but these technologies have not been implemented in Australia. International Convention for the Prevention of Pollution from Ships The International Convention for the Prevention of Pollution from Ships (MARPOL) includes regulations aimed at preventing both accidental pollution and pollution from routine vessel operations, including air pollution. Annex VI (which came into force in 2005) sets limits on SO2 and nitrogen oxide (NOx) emissions from ship exhausts, and prohibits deliberate emissions of ozone-depleting substances; designated emission control areas set more stringent standards for NOx, sulfur oxides and particulate matter. Australia implements MARPOL through the Protection of the Sea (Prevention of Pollution from Ships) Act 1983. The Commonwealth legislation giving effect to MARPOL includes Marine Order 97 (Marine pollution prevention – air pollution) 2013. Globally, the cap on the sulfur content of ships’ fuel decreased from 3.5% to 0.5% from 1 January 2020. The Australian Government introduced specific requirements in December 2016 for cruise ships to use fuel with 0.1% or less sulfur while at berth in Sydney Harbour. Aviation emissions Australia is pledging to reduce the carbon footprint of its aviation emissions under the 2010 International Civil Aviation Organization Assembly Resolution (DIRD 2017). By implementing best practice, the industry can reduce overall emissions by improving air traffic control, encouraging airlines to use better-quality fuels and improving aircraft technologies. Reducing the carbon footprint in this way will also reduce the emissions of pollutants of concern to air quality.