State of Air in Nepal with focus in Kathmandu Valley

This report provides an assessment of the current air pollution situation in Nepal, with a focus on Kathmandu Valley, using information from multiple data sources. The report offers science-based evidence to policymakers of Nepal to tackle air pollution issues. The report also includes a brief review of the existing policy landscape related to air quality management covering the policies and regulations that directly and/or indirectly affect air quality to identify needs for improvement.

This “State of Air” (SoAR) report, produced under USAID Clean Air (2021–2026) and led by FHI 360 with technical authors from AIT and partners, compiles multiple evidence streams—ground monitoring, satellite products, chemical transport modeling, and reanalysis—to give Nepal’s policymakers a science-based baseline on air quality, especially PM₂.₅. It applies a DPSIR (Drivers–Pressures–State–Impacts–Responses) lens, reviews the policy landscape, and sets out data-driven priorities for Kathmandu Valley (KV) and nationwide action.

Where air quality stands: levels, patterns, hotspots

Across 2010–2022, measured and modeled data show extremely high PM₂.₅ in much of Nepal, with the Terai plains (central–western, along the India border) carrying the heaviest exposure. Most annual PM₂.₅ levels at Department of Environment (DoE) stations during 2017–2021 exceeded WHO Interim Target-1 (35 μg/m³); the KV annual averages sat roughly 25–60 μg/m³—5–12× the 2021 WHO guideline (5 μg/m³). Spatial products (satellite, reanalysis) corroborate this gradient and identify seasonal accumulation over population corridors.

Seasonality is pronounced. In KV, daily (24-h) PM₂.₅ can fall <10 μg/m³ during the monsoon, then surge >300 μg/m³ in winter episodes, consistent with bowl-shaped topography, low mixing heights, and stagnant high-pressure conditions. Using high-coverage U.S. Embassy and Phora Durbar monitors (2017–2022), the report shows winter maxima, monsoon minima, and frequent exceedances of the Nepal NAAQS 24-h PM₂.₅ = 40 μg/m³ through the dry months; at the roadside-influenced Phora Durbar site, >50% of days breached the standard over the study period.

The COVID-19 lockdowns (2020 and parts of 2021) created a natural experiment: 24-h exceedances dropped in lockdown months; annual means in 2020 at the two USEK sites fell ~20% vs 2019, before rebounding in 2021—evidence that mobile/industrial activity reductions can materially lower PM₂.₅, but gains are fragile without structural change.

What’s emitting: sources and their fingerprints

At the national scale, the dominant PM₂.₅ source is residential combustion (solid fuels), followed by industry & power, fugitive/road dust, agriculture, transport, garbage burning, and open biomass burning. Within KV, multiple lines of evidence—receptor modeling, emissions inventories, roadside vs urban-background contrasts—point to motor vehicles, soil/road dust, biomass and garbage burning, and brick kilns as priority local contributors. Measured black carbon (BC) concentrations in KV (~4.5–16.7 μg/m³, highest in winter) reinforce the importance of combustion sources; controlling BC offers air-quality + climate co-benefits (reducing glacier-darkening deposition in the Himalaya).

The report also flags transboundary and regional transport as material drivers during episodes, urging quantitative attribution across source regions and coordinated controls across the airshed, not just the municipal boundary.

Health and wider impacts—why urgency is warranted

In 2019, Nepal’s air-pollution-attributable premature death rate reached ~222 per 100,000—highest in South Asia—with total deaths ~42,100. While household air pollution (HAP) deaths fell ~42% since 1990, the combined burden changed little because ambient PM₂.₅ and ozone deaths tripled over the same period. Average life expectancy loss from air pollution is ~3 years nationwide, and ~4.1 years in KV (2019). Beyond health, the report cites crop losses, ecosystem harm, and tourism & welfare costs (e.g., World Bank’s earlier estimate: ~4.7% of GDP in 2013).

Monitoring, modeling, and data infrastructure

Nepal’s government monitoring network has expanded since 2016 to roughly 30 stations (28 DoE + 2 USEK) with PM measurements (PM₁/PM₂.₅/PM₁₀/TSP) and basic meteorology, complemented by satellite AOD, regional inventories, and CTM outputs. The report recommends QA/QC upgrades, uniform data standards, and policy-linked indicators so that monitoring underpins enforcement and public communication. It also highlights the need for National Emissions Inventory practices (referencing USEPA NEI), regular source apportionment, and episode-forecasting to manage winter PM and spring–summer ozone.

Policy landscape—what exists, what’s missing

Nepal’s NAAQS (2003; 2012 update) sets a 24-h PM₂.₅ limit of 40 μg/m³ (no annual value). The Kathmandu Valley Air Quality Management Action Plan (KVAQMAP, 2020) defines eight objectives (transport & construction dust; industries; solid-waste; household energy; awareness; decision-support; emergency management; and governance/finance). Multiple national and local policies touch air quality, but the report finds enforcement gaps, capacity constraints, and limited resources. It calls for periodic SoAR updates, a data-driven AQMP/CAAP with measurable targets, and resourced enforcement across agencies.

What to do—prioritized, practical actions

1) Target KV’s biggest local sources with proven, scalable controls.

Transport: tighten in-use compliance (I/M, roadside/remote sensing), retire high emitters, pave and clean dusty corridors, and accelerate clean public transport & last-mile logistics.

Construction & road dust: enclosures, watering/paving, wheel-wash, haul route management, and real-time yard sensors.

Brick kilns: expand zig-zag/VSBK upgrades, enforce stack & fugitive controls, and track fuel switching.

Waste burning: ban and replace with managed collection, composting/AD, and enforce no-burn campaigns.

Household energy: scale clean fuels/stoves, electrification where feasible, and address coal/biomass retail quality.

2) Build a modern AQM system for Nepal.

Inventories: institutionalize a national EI (methods, QA/QC, update cycles), harmonized with regional databases.

Monitoring: maintain and expand the DoE network, standardize QA/QC, and publish open, validated datasets.

Modeling & forecasting: operationalize episodes forecasting; deploy source apportionment (PMF/CMB; PSAT/OSAT) to target measures efficiently.

3) Plan for co-benefits—PM₂.₅ + O₃ + climate.

Prioritize measures with health + climate value (e.g., BC control, energy efficiency, electrification).

Develop multi-benefit assessments (health, crop loss, glacier impacts) to rank projects for finance.

4) Make the DPSIR engine work.

Align drivers/pressures (urbanization, motorization, construction) with responses: integrated land-use & transport, low-emission zones, freight routing, and green public procurement (low-VOC coatings, dust-controlled sites).

Coordinate transboundary dialogues for IGP–Himalaya transport and seasonal smoke management.

5) Enforcement & participation.

Resource inspection, laboratories, and case management; clarify agency roles.

Backstop with citizen engagement and private-sector participation (AAQ data displays; clean-fleet commitments; brick-sector coalitions).

Bottom line

The evidence is consistent and compelling: Nepal’s PM₂.₅ exposures are among the highest in South Asia, with KV facing severe wintertime accumulations and year-round exceedances. Yet the report also shows fast wins are possible—lockdown-era drops, source-specific successes (e.g., brick kiln upgrades), and demonstrated benefits from vehicle and dust management. Building a credible AQM system—inventories, monitoring with QA/QC, modeling, and enforcement—while focusing on KV’s top sources and transboundary context will deliver near-term health gains and long-term climate co-benefits.

Keywords

Kathmandu Valley; DPSIR; PM₂.₅ seasonality; Terai hotspot; U.S. Embassy & Phora Durbar monitors; NAAQS (24-h PM₂.₅ = 40 μg/m³); residential combustion; motor vehicles; road/construction dust; brick kilns; garbage burning; black carbon (4.5–16.7 μg/m³); COVID-19 reductions; life-expectancy loss; inventories; source apportionment; transboundary transport; AQMP/CAAP; enforcement and QA/QC.