Assessing Influential Variables Affecting Outdoor Levels of Formaldehyde (HCHO)

Formaldehyde (HCHO) is a hazardous air pollutant that poses significant risks to human health. Despite its importance, limited studies on HCHO levels in urban settings exist. This study aims to analyse outdoor HCHO levels in the city centre of Vilnius, focusing on how environmental variables (e.g., temperature) and urban morphology factors (e.g., proximity to forest areas) influence HCHO concentrations. To assess the relevance of each independent variable in explaining the spatial variations of HCHO, we utilised a Multiscale Geographically Weighted Regression (MGWR) technique to evaluate the role of several variables, namely distance to buildings, viewshed size, distance to railways, road density, dew temperature, distance to water, distance to urban green spaces (UGS), CO₂, and volatile organic compounds (VOCs). The results showed that HCHO concentration levels in Vilnius city centre are influenced by natural and human-induced variables, emphasising the complex dynamics of urban air quality. Among the numerous valuable relationships analysed for HCHO in this study, the most influential variables were distance to buildings, viewshed size, distance to railways, road density, distance to water, and distance to UGS, alongside weather factors such as dew temperature and CO₂. The results showed spatial variations in HCHO concentrations in Vilnius city centre, where levels are influenced by environmental factors such as the proximity to buildings, water, railways, and road density. Viewshed size also plays a role in HCHO levels across all locations. Additionally, CO2 and dew temperature show a positive correlation with HCHO concentrations. These findings provide valuable insights for decision-makers, enabling the development of targeted management strategies.