Research On Emission Characteristics Of Phthalate Sources And Associated Human Exposure In Vehicular Environment

Phthalate acid esters（PAEs）are commonly-used plasticizers in building materials and indoor consumer products.A large number of studies have clearly pointed out that human exposure to PAEs were associated with numerous adverse health effects,such as reproductive system dysfunction,endocrine disorders and neurodevelopmental disorders.With the rapid development of automobile industry in China,the pollution of PAEs in the traffic microenvironment has become more and more serious.Therefore,it is worthwhile to conduct in-depth research on the PAEs emission,concentration and human exposure in the vehicular environment.However,the variability of some important factors（such as ventilation mode,temperature,and seasonal variations）during the driving process leads to difficulties of measuring the concentration of PAEs in the vehicular environment;and there is a lack of mass transfer model of PAEs transport in vehicular environment,which makes it difficult to accurately estimate PAE concentrations and exposure levels in vehicular environment.Therefore,related research has been carried out,and the main academic contributions are as follows:Firstly,the contents of PAEs in 9 commonly-used interior materials in the Chinese vehicular environment were measured.The results showed that Dn BP and DEHP were detected in 4 and 7 selected materials,respectively.The mass fraction of DEHP was in the range of 3-23%,while the mass fraction of Dn BP was only 0.1-0.8%.The other four PAEs were all below the lower limit of detection.The average y₀ values of Dn BP and DEHP of the materials at room temperature are in the range of2.4-17.5μg/m³ and 0.6-2.3μg/m³,respectively.As the temperature increases,the y₀values of the source materials increases significantly.The mean values of y₀ at 35°C and 45°C are 3-5 times and 7-17 times than those at 25°C,respectively.These findings provide a data basis for PAEs pollution in the vehicular environment.Secondly,the mass transfer model of PAEs under the typical ventilation modes in vehicular environment was firstly developed.Based on the measured source emission characteristics and the mass transfer model,the PAE concentrations in vehicular environment were estimated.The simulated airborne concentrations of Dn BP inside the cabin（0.03-8.37μg/m³）was in good agreement with the measured concentrations in previous studies（0.56-9.77μg/m³）;while the estimated airborne concentrations of DEHP（0.02-5.66μg/m³）were lower than the measured concentrations（1.03-35.5μg/m³）.The temperature inside the cabin had a great influence on PAE concentrations,which resulted in a seasonal variation of PAE concentrations in vehicular environment,i.e.,summer>transitional season>winter.Different ventilation modes mightalso lead to changes in PAE concentrations.PAE concentrations in vehicular environment significantly decreased when there was fresh air supplied.These results provide a theoretical basis for accurately estimating PAE concentrations in vehicular environment.Finally,according to the estimated PAE concentrations,human exposure levels in the vehicular environment were evaluated.The results showed that the total exposure doses of Dn BP and DEHP via inhalation and dermal absorption from the gas-phase were in the ranges of 0.002-0.78μg/kg/day and 0.002-0.21μg/kg/day,respectively.The ratio of Dn BP and DEHP exposure in vehicular environment to the total exposure in typical indoor environments（such as residences and offices）could reach up to 110%and 20%,respectively.Therefore,the vehicular environment might be an considerable site for indoor PAE exposure.The cancer risks resulting from DEHP exposure in vehicular environment ranged 1.45×10^-8-9.82×10^-7.These results provide a scientific basis for evaluating PAE exposure and developing control strategies in vehicular environment.