Comprehensive profiling of phthalic acid esters (PAEs) in air-conditioning filters from diverse indoor environments across 12 major cities in China.

Phthalic acid esters (PAEs), commonly used as plasticizers, primarily through airborne exposure. Unlike settling dust, air conditioning filters can effectively capture suspended particles and are an important source of indoor pollutants. This study analyzed 94 air-conditioning filter samples collected from five room types: bedrooms, living rooms, kitchens, mahjong rooms, and cloakrooms, across summer, autumn, and winter in 12 major Chinese cities. Using target LC-MS/MS combined with custom database, 22 PAEs were identified, and the detection rate of 19 PAEs was 100 %. Principal component analysis showed that season had more influence on the distribution of indoor PAEs than room type, and there were obvious differences between summer and winter samples. Among PAEs, dioctyl phthalate (DOP) dominates (44.28 %-96.22 %), and the toxic metabolites it generates through lipase activity cause serious health problems. The chemical composition analysis showed that the DBE value of 81.82 % PAEs was 6, the H/C value of 45.45 % PAEs was 1.35-1.65, and the O/C value was 0.15-0.25, including several PAEs with the highest peak force ratio. This finding suggests that many PAEs have similar properties and may have similar chemical behavior. Correlation analysis showed that there was more positive correlation among PAEs, and the correlation increased in autumn. Spatial-temporal analysis revealed that peak PAE intensities varied significantly, by over 15-fold geographically and 1.53-fold seasonally. These findings underscore the pronounced spatial and temporal variability in PAE concentrations, highlighting the complexity of exposure patterns across different environments and time frames.