Expanding Air Quality Monitoring with Low Cost Sensors: What Policymakers and Practitioners Need to Know

6 March 2026

The UN Environment Programme’s Global Environment Outlook 7 (GEO‑7) warns that “globally, six out of the top ten countries with the worst air pollution levels are from Asia and the Pacific, leading to respiratory diseases, poor health and lower agricultural productivity”. Against this global backdrop, EANET’s two new publications offer region‑specific guidance to help countries deploy Hybrid Air Quality Monitoring Networks (HAQMN) that combine reference‑grade monitors with Low‑Cost Sensors (LCS).

.

Guidelines for Establishing a Hybrid Air Quality Monitoring Network – Strategic direction for policymakers and planners

While reference-grade monitors have been traditionally used for air quality monitoring, based on their reliability and high accuracy, they also require a high investment and strong technical operation knowledge. Sensors refered to as ‘Low-Cost Sensors’ (LCS), on the other hand, have appeared in the recent years with improved technology related to the size and energy efficiency, lower cost and easier deployment, in particular in zones with limited infrastructures. However, LCS lack the same measurement precision and require maintenance and data analysis. The complementary use of LCSs and reference-grade monitors is referred to as Hybrid Air Quality Monitoring with Low-Cost Sensors (HAQMN), as described in these EANET Guidelines.

The Hybrid Air Quality Monitoring with Low-Cost Sensors Guidelines provide governments with a strategic framework for integrating LCS into existing reference‑grade networks. They emphasize that LCS should supplement, not replace,  reference-grade monitors, ensuring expanded coverage without compromising accuracy. They also lay out critical principles such as robust Quality Assurance and Quality Control practices, contextualized network planning, and clear differentiation from the EANET’s traditional monitoring practices and guidelines.

Aimed at senior government officials, these Guidelines describe institutional responsibilities, site selection criteria, and governance considerations. They serve as supporting documents to the EANET’s existing technical manuals, helping countries in the region and beyond expand monitoring capacity methodically and consistently.

.

Technical Manual for Hybrid Air Quality Monitoring with Low‑Cost Sensors – Operational guidance for technicians and practitioners

The Technical Manual provides detailed, operational instructions for implementing and maintaining LCS within hybrid networks. It includes step‑by‑step procedures for LCS assembly, installation, calibration, site preparation, communication systems, maintenance, and safety.

The document also incorporates expanded Quality Assurance and Quality Control procedures—such as data screening, bias correction, and performance evaluation—reflecting technical revisions made after expert review. It is designed for technicians, field operators, and analysts responsible for ensuring high‑quality, reliable data.

 .

/

 

.
How the Two Reports Work Together

.

.
A Regional Response to a Global Environmental Warning

Together, EANET’s Hybrid Air Quality Monitoring Guidelines and Technical Manual form a comprehensive, region‑tailored toolkit that intend to help countries modernize their monitoring systems, strengthen data quality, and better protect public health.

Adopted by the Twenty-seventh Intergovernmental Meeting on the EANET in November 2025, both publications reflect the increased interest to intergrate the use of new technologies for air quality monitoring in the EANET countries, in line with the EANET’s recently launched Medium-Term Plan (2026-2030).

.

Read the Guidelines for Establishing Hybrid Air Quality Monitoring Network (HAQMN) in the EANET region

Read the Technical Manual for Hybrid Air Quality Monitoring with Low-Cost Sensors: Implementation Guidelines in EANET

.

Photo credits: Ho Chi Minh by Andrei Miranchuk (2019).

EANET Monitoring Data Drives Scientific Research in 2024–2025

9 February 2026

EANET data continued to play an important role in international scientific research during 2024–2025, with over 135 peer-reviewed papers using the network’s long-term monitoring datasets to examine atmospheric chemistry, ecosystem impacts, and regional air-pollution trends. The number of research highlights the important scientific value of harmonized regional monitoring systems in addressing regional air-pollution challenges.

.

Advancing Understanding of Atmospheric Deposition and Air Pollution

A large share of recent publications used EANET observations to investigate wet and dry deposition of nitrogen, sulfur, and other atmospheric pollutants across East and Southeast Asia. Studies examined long-term deposition trends, spatial variability of precipitation chemistry, and seasonal patterns in pollutant concentrations (e.g., Temporal and seasonal variations in high-concentration precipitation samples at EANET sites in Japan: 20 years of wet-deposition data, 2025; Spatiotemporal distribution in chemical composition of wet atmospheric deposition in Bandung, Indonesia, 2024), contributing to improved understanding of how emission changes influence regional environmental conditions.

EANET datasets were also widely applied in atmospheric modelling research. Scientists incorporated the measurements to evaluate chemistry-climate models, refine emission inventories, and improve simulations of aerosol formation, transport, and deposition processes (e.g., Evaluation of atmospheric sulfur dioxide simulated with the EMAC chemistry-climate model using satellite and ground-based observations, 2025). Such work strengthens the reliability of regional and global air-quality projections used in policy and climate assessments.

.

Regional Data Supporting Global Science and linking Air Pollution, Ecosystems, and Climate

Beyond atmospheric science, researchers increasingly used EANET data to explore environmental impacts of deposition on ecosystems. Recent studies analysed nitrogen inputs to lakes and forested watersheds, relationships between acid deposition and vegetation changes, and long-term variations in stream and precipitation chemistry (e.g., Wet and dry deposition of atmospheric nitrogen to Lake Erhai Basin: Composition, spatiotemporal patterns and implications, 2025). These findings help clarify how atmospheric pollution interacts with climate variability and ecosystem health across the region.

In addition, several global-scale investigations incorporated EANET measurements to evaluate worldwide nitrogen-deposition trends and to assess future scenarios under changing socio-economic and climate conditions (e.g., Changing patterns of global nitrogen deposition driven by socio-economic development, 2025), demonstrating the EANET’s contribution to global environmental assessments.

.

Strengthening Evidence-Based Regional Cooperation

The increasing number of publications using EANET data reflects both the growing accessibility of standardized monitoring datasets and the importance of long-term observations for regional cooperation. By providing comparable measurements across multiple Participating Countries, EANET enables cross-country analyses that support scientific collaboration, policy evaluation, and improved understanding of regional air pollution.

.

Useful Resources:

.

Photo credits: a house on a hill with mountains in the background (2023) by Charles MingZ.

Acid deposition in East and Southeast Asia – EANET Researchers look at the science and policy over the last 30 years

3 June 2022 – Niigata, Japan

The well-renowned researcher Prof. Hajime Akimoto and co-authors recently published the article Development of science and policy related to acid deposition in East Asia over 30 years on the occasion of the celebration of the twentieth anniversary of the EANET. 

.

Acid Deposition and its Impacts

Acid deposition is a scientific phenomenon in which air pollutants, mainly sulfur dioxide (SO2) and oxides of nitrogen (NOX), and other air pollutants are emitted into the atmosphere from the combustion of fossil fuels and forest fires. They are transformed via long-range transport and chemical reactions with water, oxygen, and other atmospheric chemicals, which produce nitric acid, sulfuric acid, and other acids in the atmosphere and come down on the earth’s surface. The deposition of acids on the surface causes detrimental impacts on the ecosystem, water bodies, soil, forests, and infrastructures.

.

Evaluation of Policy Development

Based on three decades of knowledge on acid deposition in East Asia, Professor Akimoto and co-authors in EANET summarized the development of science and policy on acid deposition in East Asia over the period of 30 years.

In this article, the authors reviewed the state of acid deposition in East Asia since the 1980s and early 1990s and report important information on acidification of inland water, forest soil, and forest decline in the East Asia region.

In the context of broadening the scope of the EANET to include wider air pollution issues, Akimoto et al. also analyzed the past successes and future challenges the EANET will face in the coming years.

.

Read the full article on the following link: Akimoto et al. (2022), Development of science and policy related to acid deposition in East Asia over 30 years, Ambio, https://doi.org/10.1007/s13280-022-01702-6

.

Continue the discussion on science, policy, and acid deposition in East Asia and ask questions to Professor Akimoto during The State of Acid Deposition in East Asia, from data to policy online awareness workshop on 20 June 2022.

.

Photo credits: Indonesia by Ali Burhan (2021), free of the copyright license.

Updated EANET Monitoring Site Information Accessible Online

29 July 2021 – Niigata, Japan

To provide useful inputs for decision-making at the local, national, and regional levels, the Acid Deposition Monitoring Network in East Asia (EANET) has been monitoring acid deposition in East Asia for over 20 years. Recently, an updated version of the Site Information page has been released, displaying detailed information on each monitoring site.

.

Monitoring Acid Deposition across East Asia

With a coverage expanded through Cambodia, China, Indonesia, Japan, Lao PDR, Malaysia, Mongolia, Myanmar, Republic of Korea, Russia, Thailand, Philippines, and Viet Nam, EANET has assisted over the years in the deployment of monitoring stations in very diverse urban, rural and remote locations.

These monitoring sites gather high-quality data related to the deposition of major acidifying species and related chemical substances such as SO42-, NO3, H+ in precipitation, SO2, NO2 ozone, and particulate matter (PM) in ambient air.

.

Figure 1 – Location of acid deposition monitoring sites in 2019 (access the most recent sites’ information on the EANET Site Information page)

.

Dry and Wet Deposition Monitoring

Among the EANET’s major activities, acid deposition monitoring consists mainly in the review and revision or establishment of national monitoring plans, as well as the deployment of monitoring equipment, using common methodologies, to measure wet deposition, dry deposition, analyze the impacts of these depositions on soil and vegetation as well as on the inland aquatic environment.

.

Comprehensive Monitoring Site Information Available Online

Recently updated in June 2021, the Site Information webpage displays detailed information about the current 66 EANET monitoring sites, including, among others, each site’s address and location, characteristics, the monitoring period and items, and monitoring instrument name.

To find out more about the results and data on each site, visitors can also access the sites’ data reports on the Monitoring System Data Report page.

.

Contact the Network Center if you wish to update any data from your monitoring site.

.

Photo credits: all rights reserved to EANET.