Phthalates in window films of university dormitories: Distribution characteristics, accumulation patterns, and...

Organic film naturally accumulated on indoor glass (window films) can serve as passive samplers of semi-volatile organic compounds; however, the time-resolved accumulation of phthalates in dormitory environments remains poorly understood. This study collected window film samples from 20 university dormitories in Beijing, China, and quantified 14 phthalates over five consecutive accumulation cycles following pre-cleaning. Correlation analysis and generalized linear mixed models evaluated temporal accumulation patterns, film growth characteristics, and the influence of environmental and behavioral variables. Although the detection frequencies of several individual phthalates fluctuated over time, the detection frequencies across target compounds generally increased during the accumulation period, indicating progressive enrichment in window films. As the film grew, phthalate composition shifted from compounds with relatively low octanol-air partition coefficients (K_oa) to those with higher K_oa values. Film mass and thickness increased significantly over time, while the film growth rate decreased significantly. Phthalate concentrations were positively correlated with accumulation time and film thickness, and their contribution to total film mass increased over time. Temperature, relative humidity, room orientation, occupancy-related variables, ventilation status, cleaning frequency, humidifier use, and selected personal care product variables were identified as significant correlates of specific phthalates. Associations with personal care products exhibited compound specificity and did not apply to all target phthalates. These findings indicate that window films in dormitories serve as dynamic reservoirs for phthalates, reflecting the combined effects of film growth, indoor environmental conditions, and occupant-related activities. They also suggest that window films can serve as a useful medium for time-resolved assessment of indoor phthalate accumulation and its potential exposure relevance.