Publications·August 21, 2025
This NEACAP Policy Analysis Report reviews recent progress and persistent challenges in managing air pollution across North-East Asia, focusing on China, Japan, Mongolia, and the Republic of Korea. It credits notable air quality gains to stronger domestic legal and regulatory frameworks—especially controls on power plants, large industry, transport, and household fuels—while also noting the constructive role of information-sharing through regional platforms. Yet it stresses that keeping momentum requires tackling stubborn and emerging problems: urban pollution, agricultural emissions (ammonia), ozone (O₃) driven by NMVOCs and methane (CH₄), barriers to implementation, and the air–climate nexus. The report calls for integrated policies and deeper regional collaboration to convert these hurdles into opportunities with clear co-benefits for health, ecosystems, and development.
Achievements. Measured concentrations of several pollutants have fallen markedly over the last decade. PM2.5 and NO₂ decreased due to robust sectoral policies; the biggest PM2.5 reductions (over 60%) occurred in China and in Ulaanbaatar, Mongolia, with Japan and the Republic of Korea also posting sizable declines (~45% and 30%, respectively). Emissions of key PM2.5 and O₃ precursors (especially SO₂, NOₓ, primary PM2.5) declined with tighter standards and enforcement, while national monitoring and remote-sensing capacity expanded. These gains were enabled by well-designed legislation, progressively updated standards (aiming toward WHO guidelines), and strengthened governance. In parallel, bilateral and trilateral cooperation channels have supported joint research, monitoring, and capacity building.
Where progress is uneven. Despite the above, the report highlights three persistent patterns: (1) Ozone trends have not improved—and in many urban areas have worsened—because NMVOCs continue to rise and global CH₄ concentrations have increased; (2) Ammonia (NH₃) from agriculture is flat or rising, with limited targeted policies; and (3) large shares of urban populations still breathe PM2.5 above guideline levels. The report recommends stronger controls on NMVOCs and methane, development of dedicated agriculture measures (e.g., nitrogen use efficiency, composting and biogas, emission regulation for large livestock farms), and sustained investment in monitoring—especially outside major cities—to give a more complete picture and underpin effective interventions.
Trends and drivers. Region-wide, NO₂ concentrations show a consistent downward trend; SO₂ has also declined in most places with notable exceptions (e.g., Ulaanbaatar). But O₃ increased over the last decade, particularly in cities where chemistry is often VOC-limited (observed during COVID-19 lockdowns). These dynamics underscore the need to re-balance precursor controls, move beyond a sole focus on NOₓ, and confront solvent and fugitive VOCs as well as methane.
Air–climate linkages. Improvements in air quality can interact with climate forcing (e.g., removing cooling sulfate/nitrate aerosols can “unmask” warming). Climate change, in turn, intensifies heatwaves and stagnation events, raising the frequency and severity of pollution episodes and urban O₃ exceedances. The report also notes sandstorms affecting northern China, linked to desertification processes in Mongolia, as a transboundary particulate challenge. It advocates integrated air quality–climate–development policies and closer collaboration between air-quality and climate communities for modeling and policy design.
Monitoring, remote sensing, and modeling. The region has expanded ground networks and made use of remote sensing—including the Geostationary Environment Monitoring Spectrometer (GEMS)—to observe pollutants in near-real time, and it has strengthened emission inventories and modeling capacity. The report urges harmonized common formats and methodologies across countries to build comparable time series for emissions and impacts, with links to greenhouse-gas reporting where appropriate. Platforms such as EANET and GEMS-PAN are cited as partial repositories, but much data remain national and heterogeneous, pointing to the value of a NEACAP-facilitated data architecture.
Barriers and implementation gaps. The report inventories economic, technological, institutional, and social barriers—financing shortfalls, fragmented responsibilities, and difficulty scaling innovations—that slow the translation of policy into sustained air quality gains. It recommends reinforcing legal frameworks, enforcement, and tailored measures for ammonia and fugitive NMVOCs, alongside urban planning that integrates air quality objectives (green space, active mobility) and cooperation across jurisdictions that share airsheds.
Health, ecosystems, and crops. Beyond mortality reductions from lower PM2.5 and NO₂, the report summarizes ecosystem benefits from reduced sulfur and nitrogen deposition and flags crop-yield losses from ozone exposure. These cross-sector impacts support the case for integrated strategies that jointly advance SDG3 (Health), SDG11 (Cities), and SDG13 (Climate)—areas where progress could be hampered without decisive action on ozone, urban–rural interactions, climate extremes, and institutional challenges.
What NEACAP and partners can do next. The report proposes two complementary tracks: national actions (expand monitoring in urban and rural areas; update standards toward WHO; tighten sector rules with state-of-the-art technologies; target agriculture and fugitive VOCs; embed air quality in urban planning; integrate air and climate; and incentivize clean technologies), and (sub)regional actions through NEACAP (strengthen policy collaboration, best-practice exchange, and scientific/technical cooperation, including technology transfer and capacity building). A conceptual framework illustrates how national and regional roles fit together.
Bottom line. The four countries have shown that ambitious, science-based regulation and sustained monitoring can cut PM2.5 and NO₂ substantially. The unfinished agenda centers on ozone, agriculture (NH₃), and data harmonization, all under the shadow of climate change. Integrating policies across air quality, climate, and development and deepening NEACAP-enabled cooperation are presented as the region’s best levers for durable gains—with co-benefits that reduce overall societal costs and build public support for long-term climate ambition.
Keywords (from the report)
NEACAP; NEASPEC; PM2.5; PM10; O₃/ozone; NO₂; SO₂; NH₃; NMVOCs; methane (CH₄); primary PM; WHO air quality guidelines; SDG3/SDG11/SDG13; monitoring networks; remote sensing (GEMS); emission inventories; modeling; data harmonization; EANET; GEMS-PAN; CAPSS (ROK inventory); enforcement; legal frameworks; urban pollution; agricultural emissions; urban–rural interactions; sandstorms/desertification; climate–air quality linkages; co-benefits; best-practice exchange; capacity building; multilateral cooperation; policy integration.