Spatial Assessment of Allergenic Pollen Risk in Urban Green Infrastructure: A Systematic Review and an Integrated Hazard-Exposure-Risk-Planning Framework

Urban green infrastructure (UGI) serves as a core pillar of sustainable urban development, delivering multiple benefits including urban heat island mitigation, stormwater regulation, and health promotion. However, allergenic pollen released by urban vegetation represents a typical ecosystem disservice, creating a prominent sustainability trade-off between greening benefits and residents’ allergy risk. For a long time, research in this field has evolved along two largely independent lines: vegetation allergenic hazard assessment and atmospheric pollen exposure analysis. Marked disconnections persist in indicator systems, spatial scales, and outcome translation, and an integrated spatial assessment framework remains lacking. Based on a systematic review of 127 publications from the Web of Science Core Collection (2000~2025) using framework synthesis methods, this study constructs a hazard–exposure–risk–planning (HERP) framework for the spatial assessment of allergenic pollen risk in UGI. This paper systematically synthesizes the core indicators, technical approaches and inherent limitations of each framework layer and identifies five key barriers: inconsistent indicator definitions, lack of cross-validation between surface vegetation and atmospheric pollen data, missing population vulnerability layer, insufficient multi-scale coupling, and weak translation of research into planning practice. The proposed framework provides a potential comparable and reproducible standardized pathway for cross-regional allergenic risk assessment and offers methodological support for healthy urban planning that balances ecosystem services and residents’ respiratory health.