Legal Framework and Policy Design - Stage 4

01  Define and establish a process for updating your Ambient Air Quality Standards

When reviewing and updating Ambient Air Quality Standards (AAQS), it is important to first plan out your timing, research and analyses to determine which policy and regulatory options will allow your jurisdiction to meet the updated standards. You should set a timeline for how often your government will go through this review process. Start by reviewing your current AAQS (referring to the latest WHO Guidelines) and new research from the scientific community on health and environmental effects, including risk and exposure information. Conduct quantitative analyses including cost-benefit analyses to support the review process (see Decision Support Guidance, Stage, 4 Step 1). This process should include the development of a summary assessment document with input from the scientific community and comments from the public, including peer review of published studies you may be relying on for your revision. You can then develop a policy paper that interprets the health, environmental and economic impacts data and identifies factors to consider in revising your standards. Conduct a proposal process as you did in Stage 1, have stakeholder consultations, and make a final decision on any updates or revisions.  

As part of quantitative analyses, it is important to assess updated information on emissions and monitoring data. In addition, the UNECE Air Convention’s Modelling and Mapping Manual includes approaches for health and environmental effects assessments, with approaches for quantifying specific pollutant/effect combinations discussed in the Health Impact Assessment Guidance and Environmental Impact Assessment Guidance. It is also important to consider transboundary air pollution out of the control of an individual country and whether additional international cooperation is necessary for updates to your AAQS (see Step 4 below for more information).  

Assessing social costs and benefits of air pollution rules and policies is necessary for a robust air quality management program. National and local officials will be weighing other important priorities and will need concrete data and information on the costs and benefits from updating standards and passing more stringent laws to reduce air pollution. Regulatory impact analyses contain descriptions of the potential social benefits and costs of a regulation. If you had resources to conduct your own impact analyses during the initial standard setting stage, this is a good time to update that analysis and present it to your governmental officials to obtain resources to continue with a more advanced air quality program.  

As you update your AAQS, your national or local government could set or update the legal requirements for alerting the public on bad air quality days and developing an emergency response framework (see Public Engagement & Communication Guidance, Stage 4, Step 3). You can also deploy low-cost sensors at public schools and implement local programs such as a school flag program for bad air quality days, education materials for schools and the health sector (doctor offices) and open burning bans and ordinances.  

02  Include additional pollutants, including super pollutants, in the legal and policy framework 

Adding new pollutants to your Air Quality Management Plan (AQMP) (and/or to your list of AAQS or source-based legislation) is important to ensure your legal and policy framework addresses the full range of health, environmental, and climate impacts.

Super pollutants such as black carbon, tropospheric ozone, and methane, are a group of pollutants that contribute both to climate change and poor air quality. Mitigating them can bring fast results both in terms of reducing the rate of near-term warming, and protecting public health and the environment.  

Black carbon, also known as soot, is a component of PM2.5 and has detrimental impacts on human health.  It is also a short-lived climate pollutant which remains in the atmosphere for days to weeks and impacts the cryosphere (ICCI, 2025) by reducing surface albedo and increasing glacier melt. Black carbon also influences cloud formation and impacts regional weather and rainfall patterns, with associated impacts on agricultural systems and food security.

Tropospheric ozone is a powerful greenhouse gas and an air pollutant, with harmful impacts on health and ecosystems (including crop yields). As a criteria pollutant, it is typically monitored and regulated early on, which means by Stage 4 you are probably already monitoring ozone concentrations and have adopted ozone standards. However, since tropospheric ozone is a secondary pollutant (it is not emitted directly into the atmosphere, but rather formed by the interaction of sunlight with precursors), mitigating these precursors (such as VOCs and methane) is essential to reduce ozone concentrations. Including methane in your AQMP, AAQS and source-based legislation can be a powerful way to mitigate ozone, in a context where global anthropogenic emissions of methane are increasing. Options for reducing methane emissions from agriculture are discussed in the Environmental Impact Assessment Guidance Stage 4, Step 3.

Additional pollutants could also include hazardous air pollutants (HAP) or “air toxics,” which include some VOC compounds. Hazardous air pollutants are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental effects. Certain areas have higher cancer risks from air toxics and tend to be in densely populated urban areas which generally are also addressing ozone and PM2.5. Air quality agencies responsible for ambient air quality can work with other agencies in their government on multi-pollutant goals for reducing health risks from air toxics or your institution can establish a program for addressing the risks from air toxics and coordinating regulations that get both HAP and criteria pollutant reductions.  

While regulated criteria pollutants are the focus for the AQMP, other examples of additional pollutants include ultrafine particulate matter (UFPs), microplastics and per-and polyfluoroalkyl (PFAS). These pollutants have significant health impacts and need to be addressed as part of an integrated environmental policy strategy.  

There are several international treaties that cover other pollutants that cause risks to human health. In 1998, parties to the UNECE’s Air Convention adopted the Heavy Metals Protocol and the Persistent Organic Pollutants (POPs) Protocol in Aarhus, Denmark. These regional agreements led to two global agreements – the Stockholm Convention on Persistent Organic Pollutants (POPs) in 2001 and the Minamata Convention on Mercury in 2013.  

Conduct an assessment for adding pollutants, adding those pollutants that need to be reduced in your area into your integrated AQMP. Identify and propose revised policies and measures in the area being addressed (hotspot, city, province, country, or airshed). Whilst incorporating these new pollutants into your legislative and policy framework will enable a more integrated, coordinated and effective response to all associated impacts (health, environment, climate), doing so does not come without challenges. Many of these pollutants are typically more complex and costly to measure in ambient air, and activity data and emission factors are often more fragmented, making the development of emission inventories complex. Mobilising the research community, and participating in regional or global cooperation networks can help to strengthen your capacity in these new areas. 

03 Define and establish a process for updating source-based legislation (emission standards)

For emissions standards, establish a similar process with a time period for when your agency will conduct the review (for instance, every 5-10 years), taking into account and prioritizing key source categories and activities. The review of each source category can be staggered to ease the workload for your institution, and there can be different review schedules for standards regulating new vs existing sources.

Determine if sources are complying with existing emission standards, then analyze the best available techniques to determine the appropriate level of ambition for the revised emission standards, and the timeline for industry to meet them. The objective is to evaluate if industry developments (including transport, heating, solvent use and agriculture), and new control technologies can achieve greater air pollution reductions than the current standards. Each update should have a public notice and comment period before final rule adoption.  

By Stage 4, a well-staffed compliance and enforcement program is very important as you move towards updating emission standards. As noted in Stage 1, Step 8 of the Legal Framework and Policy Design Guidance, effective enforcement mechanisms, including monitoring, inspections, and penalties for non-compliance are essential. Also consider establishing a permitting program with specific requirements for stationary sources. Determining compliance with emissions standards goes along with ensuring you are attaining your AAQS. In Stage 2, Step 10 and Stage 3, Step 10 of the Legal Framework and Policy Design Guidance it is recommended to design a monitoring and evaluation framework to determine if you are meeting your AAQS.  Everyone has a right to breathe clean air - it should not be dependent on where people live. Source-based legislation should be enforced to ensure a healthy environment for all.  

04 Establish a process for adopting and updating national emission reduction commitments  

Setting emission reduction commitments (or emission ceilings), whether nationally or locally, is an important component for an advanced air quality management framework. The emission standards already set are key to meet the overall emission ceilings (see Step 3 above). In the European Union context for instance, the National Emission Ceilings Directive provides limits for total emissions of certain air pollutants that have to be respected by Member States. These overall limits complement the emissions standards for key sources that are supported by the underpinning science, monitoring, modelling, reporting, enforcement, and capacity building efforts among Member States and the European Union.

Implementation of measures to meet emission ceilings for key pollutants in your AQMP will have the added benefit of reducing transboundary pollution, in addition to improving air quality locally. Emission ceilings can also further align with updated AAQS in your jurisdiction and/or WHO air quality guidelines. Emission inventories need to be of sufficient quality to serve as a basis for setting meaningful emission ceilings (preferably using Tier 2 for key categories). A Tier 2 or higher methodology for calculating emissions of identified key categories is a prerequisite for reflecting emission reduction efforts in emission inventories and for enabling an effective assessment of compliance with established emission ceilings as Tier 1 is only proportional to activity levels (see Emissions Inventory Guidance Stage 4, Step 4).  

Use integrated assessment modeling to set emission ceilings as described in the Decision Support Guidance (Stage 4, Step 4). Emission ceilings can be set for the whole country or for priority areas or cities.  Ideally, setting ceilings would be done within an airshed to take into account transboundary air pollution across administrative boundaries. It is also important to work with nearby countries if possible, to expand your goals to addressing regional air pollution (see Stage 4, Step 5 of the Legal Framework and Policy Design Guidance for more information on airsheds and transboundary air pollution).

As with setting and updating ambient air quality and emission standards, it is important to set clear timelines for the adoption process as well as for compliance. In order to better align your environmental policies, it will be important to coordinate air quality and climate goals in setting emission ceilings for specific pollutants or sectors. Updating the emission ceilings or emission reduction commitments should include a review of the existing commitments and their effectiveness.  

Considering economic markets and establishing an emissions trading program at the local, national or regional levels, can be an effective way to meet your emission reduction commitments. This provides flexibility to industry to achieve emission reductions cost-effectively while also supporting economic growth. 

05 Work bilaterally, regionally and globally to address transboundary air pollution 

Work with neighboring countries on transboundary air pollution by sharing data, coordinating air quality management programs, and harmonizing standards and policies. Gather and assess additional data on regional and global background levels of transboundary air pollution, including PM2.5 and ozone and its precursors. Engage in the specific cooperation network(s) relevant for your region. Examples include UNEP’s Intergovernmental Network of Air Quality in Latin America and the Caribbean adopted a Regional Action Plan on Air Quality (2026-2029), the UNESCAP’s Asia-Pacific Regional Action Programme on Air Pollution, and the West Asia Air Quality Network. Pairing this regional cooperation network with country-driven projects for reducing emissions is the best case for progress in addressing air pollution. As part of this network, it is important to work with non-governmental organizations (NGOs) and other Civil Society Organizations (CSOs).  Regional action plans can address sustained financing, monitoring coverage, updated emission inventories integrating air pollutants, GHG and SLCPs, linkage with climate and health agendas, and operational readiness for emergency episodes such as wildfires and dust storms.  

Regional cooperation networks can also set up platforms or committees for consultations and input for national and local governments to use when working on their AQMPs. Bilateral agreements can also be a useful tool to encourage reductions in a neighboring country with a shared airshed.  

Participate in global negotiations at UNEA as well as other regional conferences (e.g., Better Air Quality Conference in Asia, Africa Clean Air Forum). These meetings are valuable for sharing information and are an effective approach for making aspirational commitments (e.g., UNEA resolution 6/10) for air pollution and in some cases, for negotiating binding commitments to ensure air pollution improvement (e.g., UNECE’s Gothenburg Protocol), Lusaka Agreement,  Malé Declaration, and the ASEAN Haze Agreement).

Working to harmonize standards and sector policies across countries in your region gives key activity sectors (such as industry, transport, agriculture) certainty and ensures a more level playing field by preventing the distortion of competition between countries, as well as between different sectors, that occurs when some jurisdictions have less stringent standards than others nearby. Other regional issues to consider are increased access to data, sustained financing, monitoring coverage with a quality assurance protocol, updated emission inventories integrated with GHG inventories, procuring equipment, sharing model legislation and AQMP frameworks, filling data gaps with satellite data, coordination of NGO funded projects, and operational readiness and joint early warning systems in the region for wildfire smoke episodes, sand and dust storms, or other source events such as industrial accidents.

A prominent example of a regional scientific and technical data exchange effort for air pollution is the UNECE Air Convention’s Cooperative Programme for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe (EMEP). This data sharing programme is the underpinning for legal and policy frameworks to achieve emission reductions and improvement of air quality within the UNECE.  

06 Develop and coordinate an airshed approach

As part of a successful regional cooperation network, governments within the region or sub-regions can work together on an airshed approach - looking at geographic boundaries instead of political boundaries as noted in Stage 3, Step 8 of the Legal Framework and Policy Design Guidance. An airshed approach takes into account transboundary air pollution within a given area, including areas in the same country. It can be helpful to work together on shared scientific and technical analysis and data exchange to better determine how to address air pollution in the airshed.  

There are many ways to define an airshed depending on the scope of analysis. The World Bank defines an airshed as “an area defined by geographic, topographical, and meteorological boundaries rather than political or administrative lines. Within an airshed, air pollution is freely and routinely transported and influenced by shared sources of pollutants, weather, and terrain.” (World Bank, 2024).  In other words, an airshed is a geographical area frequently affected by the same air mass (CEEW, 2026).

The airshed approach has been applied by the Mexico City Metropolitan Area (MCMA), among other examples. Persistent air quality issues led local authorities to establish an airshed management mechanism which has operated since 1992 (CEEW, 2026). This approach is most successful if the local and national governments coordinate with key stakeholders and activity sectors. Harmonising the legal and regulatory framework within an airshed can also help reduce different interpretations and approaches between neighboring countries. Establishing shared monitoring and data exchange protocols will help underpin successful analyses and ensure the data is comparable. Ideally, regional cooperation networks will facilitate transboundary consultations and information exchange where the implementation of national laws and programs could affect the air quality in another country.  

07 Link your Air Quality Management Plan to greenhouse gases and hazardous air pollutants reduction objectives 

In Step 2 above, you have assessed and included new pollutants, including super pollutants and Hazardous Air Pollutants (HAPs), into your legal and policy framework. Applying a multi-pollutant approach into your Air Quality Management Plan (AQMP) and including multi-pollutant objectives can help ensure you address the whole range of impacts on health, ecosystems, and climate. A comprehensive AQMP programmatic framework takes into account analysis, planning, implementation of air quality management programs and measures to meet multi-pollutant objectives.  

You should show how your AQMP makes the most efficient use of available resources by looking at different future control scenarios based on emission inventory improvements, modeling for local and regional issues and risk exposure and benefits assessment of predicted air quality changes. Carefully target emission controls on high emitting sources of PM2.5 and black carbon, as well as ozone and its precursors, particularly those located near population centers. A primary goal of multi-pollutant planning is to develop a national and local control strategy that maximizes air quality, health and environmental benefits while reducing costs. For GHG and integrated air quality and climate planning, it is also important to consider the potential negative impacts of certain climate and energy policy measures on air quality, such as the use of biomass and biofuels in the residential and transport sectors.

For local areas, use multi-pollutant assessments to update the AQMP to refine local area needs and better address specific health and ecosystem risks. Present local officials with modeling results that show the economic benefits for taking a holistic approach to air quality management. At this point, showing the costs of inaction is important to ensure implementation of the AQMP is on the horizon and emission reductions will occur according to the timelines established in your plans and laws (UNECE, 2022; IIASA, 2023). 

Use integrated assessment modeling at the local or national level to conduct integrated assessments and refine your policy options (see Decision Support Guidance, Stage 4, Step 3). Create a feedback loop between the available data assessed in Stage 1, the additional data gathered from further development of the AQMP and assessment of transboundary air pollution.   

08 Link with sector-based approaches 

By Stage 4, you will have already identified which activities are responsible for air pollution in your area. Depending on what sources are the most important, additional action could be needed in the agriculture (including crop residue burning), energy (including gas flaring), transport (including road transport and shipping), industry (including solvent use), household energy (including biomass cooking) and waste management (including open waste burning) sectors. Ensure all sector-based programs are aligned with the Air Quality Management Plan (AQMP). It will be important for continued progress to continually update your emissions inventories, improve the data collected, and use integrated assessment modeling and tools to focus on key sectors. Integrated assessment models (such as GAINS, LEAP-IBC, or ABaCAS) provide information on the sectors where potential for further reduction exists and on which reduction techniques can be applied (see Decision Support, Stage 4, Step 3).  

To ensure appropriate institutional arrangements to address all needed sectors, you will need to coordinate across ministries (health, finance, energy, transport, agriculture…), work to integrate environmental policies, and cooperate on finance, technology exchange and mitigation efforts. Ensure you are sharing relevant information to each of these stakeholders on health risks of air pollution, ecosystems and agricultural impacts, as well as costs and benefits, so they can adopt informed policies and regulations and have consistency in those policies across sectors. Weak or absent coordination mechanisms between ministries or institutions with different policy responsibilities is a barrier that will delay effective implementation of your AQMP (UNEP/CCAC, 2026). A good example of cross-sectoral implementation is China’s co-control strategy for air pollution and climate change (UNEP/CCAC, 2026).  

09 Implement control measures in the Air Quality Management Plan

Monitor your jurisdiction’s progress in meeting the Ambient Air Quality Standards (AAQS) and the timelines and fixed deadlines in the Air Quality Management Plan (AQMP), following a defined planning process, reporting progress on set schedules, and justifying any delays. Adjust the AQMP based on new information and repeat the stakeholder engagement process and national or local adoption process.  Ensure you have implementation capabilities for both local control strategies as well as national regulations and policies to achieve measurable emission reductions.  

Work on the ground to ensure the control measures in the AQMP are being implemented and reductions from the mitigation measures and new technologies are being realized. You may need to hire experts at this stage to install technologies, provide guidance on BAT, and work to implement specific projects. Early implementation is essential, since foregone near-term emissions reductions cannot be fully recovered later (UNEP/CCAC 2026). This will also be important for planning to move to Stage 5 where additional local projects will need to be implemented and additional practical on-the-ground work will need to be funded and completed. Include advanced training for your team into your annual planning process, review compliance and enforcement procedures, include a stakeholder engagement and review process for transparency and gather inputs for continued improvement of control measures and technologies.

Ensure that your local officials have access to information on how reduced air pollution improves health and environmental outcomes. Use clear and engaging communication material and work with academia on health and ecosystem effects of air pollution. Successful communication of risks and costs of inaction will enable better implementation of your AQMP (see Public Engagement & Communication Guidance Stage 4, Step 8).  

If your annual budget is not enough for full implementation of your AQMP and to continue advancement to Stage 5, you may need to work with bilateral and multilateral development banks and philanthropies (e.g., World Bank, Asian Development Bank, African Development Bank, South-African Development Bank, Clean Air Fund), and apply for resources to fund projects for successful implementation of control measures and strategies.