Abstract
This research project, funded by the Health Systems Research Institute (HSRI), aimed to
evaluate and strengthen the surveillance system for diseases associated with fine particulate
matter (PM2.5) exposure in Health Region 8 comprising Nong Khai, Nakhon Phanom, Loei, and
Bueng Kan provinces. PM2.5 is a growing environmental threat that poses significant risks to public
health, especially among vulnerable populations, and may cause both acute and chronic
conditions such as respiratory and cardiovascular diseases. A major issue identified is the limited
number of disease diagnoses coded as resulting from air pollution exposure (ICD-10: Z58.1 and
Y97). Therefore, the project sought to test approaches to improve the surveillance system and
develop a passive patient screening form for hospitals in pilot areas. Both quantitative and
qualitative evaluations were conducted to generate evidence-based policy recommendations.
A mixed-methods design was applied, consisting of: (1) a quasi-experimental design to test
the passive patient screening form in Nakhon Phanom and Nong Khai hospitals during periods
when PM2.5 concentrations exceeded the national standard (37.5 µg/m³), comparing the coding
frequency of Z58.1 before and after implementation; and (2) a descriptive study to assess the
current status and performance of the surveillance system in Loei and Bueng Kan provinces. The
research team conducted in-depth interviews with 28 health personnel and relevant stakeholders
and reviewed 971 medical records of suspected PM2.5-related patients from November 1, 2024,
to October 31, 2025.
Qualitative results showed that both administrators and practitioners were aware of the
importance of and accepted the surveillance system. Implementation was relatively
straightforward due to the existence of compatible hospital information systems such as HOSxP
and the presence of command mechanisms through provincial health meetings. The system
demonstrated flexibility and responsiveness to central-level directives. However, its main
limitation lies in the absence of standardized diagnostic criteria and clear case definitions for PM2.5-
related diseases, leading to incomplete and unreliable data analysis. In terms of resources, most
provincial public health offices lack sufficient funding and specialized staff for PM2.5-related health
work. Furthermore, personnel training on PM2.5 health impacts remains limited, and the use of
surveillance data is largely confined to situation reporting rather than being applied in health risk
assessments.
Quantitative analysis revealed that the surveillance system in Loei and Bueng Kan showed
full coverage (100% sensitivity) but low accuracy. In Loei, the positive predictive value (PPV) was
30.39% (134 out of 441 records met the definition), while in Bueng Kan, the PPV was 58.8% (311
out of 530 records met the definition). The low PPV indicates that a large number of reported
cases in the Health Data Center (HDC) system did not meet the diagnostic criteria, and no clear
relationship was observed between PM2.5 concentration and reported case numbers, possibly due
to underreporting.
Regarding the pilot test of the screening form in Nakhon Phanom and Nong Khai, only one
of four hospitals used the official Department of Disease Control (DDC) screening form, while
others used online “Pollution Clinic” forms or locally developed tools. Nakhon Phanom Hospital
integrated air-quality alerts into its HOSxP system; however, the number of Z58.1 codes in 2025
(Jan–May) decreased (38 cases) compared to 2024 (94 cases), a 59.57% reduction. As for Nong
Khai Hospital, the number of Z58.1 code entries increased to 11 cases in January–May 2025, up
from 8 cases during the same period in 2024 — an increase of 37.5%. This increase may be
attributed to higher average PM2.5 levels in 2025 compared to 2024 and the implementation of
screening tools.
Policy recommendations to enhance the surveillance system’s efficiency include: (1)
strengthening central-level academic leadership and standardization, including unified
surveillance formats, diagnostic criteria (particularly Z58.1), database management, indicators, and
clear “clean-air room” policies; (2) organizing national-level training and capacity-building
programs on technical, management, and investigation standards to ensure consistent
understanding among personnel; (3) enhancing awareness and improving passive screening
systems by encouraging health workers to recognize environmentally related diseases during
diagnosis; and (4) expanding environmental health services and enforcing environmental laws by
increasing the number of air-quality monitoring stations, establishing additional Pollution Clinics
in community hospitals, and strengthening legal measures to effectively control air pollution.
