Aim of the study:
Air pollution remains a pressing environmental concern in Thailand’s industrialized regions, particularly within the Rayong Industrial Pollution Control Zone a hub of petrochemical and heavy industries under the Eastern Economic Corridor (EEC). This study investigates the temporal trends and interrelationships of major air pollutants, including PM10, PM2.5, CO, NO2, SO2, and selected volatile organic compounds (VOCs), from 2017 to 2023 using Air Quality Index (AQI) based evaluations and correlation analyses.

Material and methods:
Data from continuous air monitoring stations operated by the Pollution Control Department (PCD) were statistically analyzed through SPSS to identify annual and seasonal variations.

Results and conclusions:
The results revealed that PM10 concentrations exhibited a steady decline after 2019, whereas PM2.5 demonstrated an increasing trend, implying a shift toward finer particulate pollution. NO2 and SO2 levels also decreased notably during the same period, suggesting effective emission control policies and technological improvements. Correlation analyses indicated strong positive associations between PM10 and combustion related gases such as NO2 (r = 0.853) and SO2 (r = 0.760), while PM2.5 showed negative relationships with several gaseous pollutants, reflecting differences in source origins and atmospheric behaviors. The AQI values ranged from 20.47 to 41.69 throughout the study period consistently below the “Clean” threshold (AQI = 50) indicating generally acceptable air quality. However, higher AQI levels during 2019–2020 were associated with increased industrial and vehicular emissions. Overall, the findings highlight a positive trajectory in Rayong’s air quality improvement, particularly after 2019, which is likely attributable to enhanced pollution control measures and environmental governance.