From benefit to burden: Assessing the full range of health impacts in urban green spaces using a threshold model

Urban residents increasingly value the health benefits of natural exposure, highlighting the role of green spaces in early disease prevention. While the positive health impacts of green space exposure are well-documented, the negative physiological effects remain less understood. This study introduces an advanced threshold model designed to capture both the positive and negative physiological impacts of green space exposure. In a comparative experiment, participants were virtually exposed to images of Healthy Urban Greenery (HUG) and Distressed Urban Greenery (DUG), with continuous electroencephalogram (EEG) monitoring as the physiological measure. The results showed that: (1) physiological responses to both HUG and DUG closely aligned with the proposed threshold model; (2) DUG exposure negatively impacts health, beyond merely reducing the positive effects typically associated with green spaces; (3) women are more susceptible to the negative effects of DUG than men; and (4) restorative effects are stronger after prolonged DUG exposure, with greater initial negative impacts leading to more significant recovery in HUG. These findings demonstrate the threshold model's effectiveness in capturing the complex interactions between humans and their environments, offering a nuanced understanding of the health impacts of green space exposure.