Background: Phthalate esters (PAEs) are ubiquitously used in indoor consumer products as plasticizers.Due to their low vapor pressure, PAEs exist indoors mainly in three phases: gas phase, particle phase and dust phase.As known from the literature, some adverse health effects are correlated with exposure to indoor PAEs.Therefore, it is important to investigate indoor concentrations of PAEs in different phases to assess the health effects.Objective: The objective of this study was to measure the concentration of indoor PAEs in Xi'an city, to identify the associations between the contaminant level and several potential influence factors and to estimate the daily intake of phthalates in Xi'ancity.Methods 28 rooms in the residences and offices were selected to collect samples of indoor air and dust.Particle phase and gas phase in air were sampled by SVOCs sampler independently and the dust was collected for dust phase PAEs.Phthalates were extracted through Soxhlet extractor and analyzed by gas chromatography-mass spectrometry.Several parameters of each room were recorded, including the volume of the room, the area of the potential contamination sources, ventilation habits and decoration history for evaluating the impact factors of indoor PAEs presence.Based on the measured concentration of indoor PAEs in different phases, the exposure to indoor phthalates for different aged people was estimated.Results The results showed that DMP, DIBP, DBP, DEHP were found in most samples.According to the medians of concentration, DIBP (0.64/0.46-particle/gas, μg/m3; 206.7-dust, μg/g), DBP (0.34/0.26-particle/gas, μg/m3; 122.1-dust, μg/g) and DEHP (0.37/0.30-particle/gas, μg/m3; 532.9-dust, μg/g) were the main phthalates both in indoor air and dusts in Xi'an..And the concentration of the phthalates is correlated positively with the potential area of the source but is no significantly correlated with the ventilation habits and decoration time.Conclusions The pollution level of phthalates in Xi'an indoor environment is moderate compared with the data in the literature.And Inhalation and oral uptake are estimated as the important routes of phthalates exposure compared with dermal adsorption, In addition,toddlers were estimated at top risk of phthalates exposure..