Can integrated behavioral models explain the PM2.5 preventive measure adoption gap? Structural equation modeling of PADM-TPB pathways in urban Thailand

Abstract

Fine particulate matter (PM 2.5 ) poses a significant health risk to residents of Bangkok and its surrounding provinces, yet many do not consistently adopt protective behaviors, such as wearing masks or limiting outdoor activities, even when pollution levels are high. This “adoption gap” between awareness of a risk and acting on it is not well understood. This study examined this gap by developing and testing an integrated behavioral model combining the Protective Action Decision Model (PADM), which explains how people come to recognize and appraise an environmental hazard, and the Theory of Planned Behavior (TPB), which explains how attitudes, social pressures, and perceived control shape behavior. A cross-sectional study was conducted among 1214 adults across Bangkok, Nonthaburi, and Samut Prakan provinces from April to May 2025. Structural Equation Modeling (SEM) was used to examine the pathways among knowledge, perceived threat, attitudes, subjective norms, perceived behavioral control, and preventive behaviors. The integrated model showed excellent fit to the data (CFI = 0.955, TLI = 0.947, RMSEA = 0.056) and explained 21.3% of the variance in preventive behavior. Three findings stood out. First, perceived behavioral control was the strongest correlate of preventive behavior (β = 0.386, p < .001), more important than attitudes or social norms. Second, while perceived threat was positively associated with attitudes (β = 0.857) and subjective norms (β = 0.424), perceived threat itself showed a negative direct association with behavior (β = −0.209, p = .005), suggesting that fear about a health risk, without a corresponding sense that protective action will help, can be associated with avoidance rather than action. Third, knowledge about PM 2.5 showed a positive direct association with behavior (β = 0.106, p < .001) but a negative association with perceived threat (β = −0.121, p < .001), indicating knowledge operates through multiple pathways. These findings suggest that public health messaging that emphasizes PM 2.5 dangers without building residents' confidence and practical capacity to protect themselves may be insufficient and, in some cases, counterproductive for closing the gap between awareness and protective action in urban Southeast Asia.

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