Environmental Behavior And Human Inhalation Exposure Of Particles And Typical Organic Contaminants In Indoor And Outdoor Air

The environmental behaviors and health effects of airborne pollutants depend on their physical and chemical properties,such as number concentrations,mass concentrations,size distributions and chemical components.The general population spends approximately 90% of their time indoors and therefore is more exposed to pollution indoors than outdoors.Therefore,assessment of air pollution effects on the general population should include both indoor and outdoor measurements.The present study selected schools,offices and residences located in three districts(Tianhe,Luogang,and Zengcheng)of Guangzhou with different urbanization levels as field sampling sites.Atmospheric submicron particles(size range of 14-660 nm)number concentrations were measured by Scanning Mobility Particle Sizer(SMPS).Size-fractionated particle(size range of 0.056-18 μm)and gaseous samples were collected using a 10-stage Micro-Orifice Uniform Deposition Impactor(MOUDI)with a PUF chamber and analyzed for typical semi-volatile organic pollutants,polycyclic aromatic hydrocarbons and flame retardants.Both instruments were simultaneously operated in and outside of sampling sites during October-November 2014(dry weather season)and June-August 2015(wet weather season).The objectives of the present study were to(1)evaluate the seasonal variation of particle number and mass concentrations indoors and outdoors;(2)examine the infiltration of outdoor particles into indoor environment among all sampling sites;(3)explore the characteristics and distribution patterns of particle-bound and gaseous PAHs and FRs indoors and outdoors;(4)compare the daily intakes of particle-bound and gaseous FRs,and(5)assess the inhalation exposure risk to size-dependent particle-bound and gaseous PAHs and FRs for different age groups from children,adolescents,adults to seniors under real life scenarios.Only particle mass concentrations in dry weather season were significantly higher than those in wet weather season.Furthermore,size distribution of particle mass and number concentrations were influenced by human activities,especially with indoor source emission such as cooking and smoking.The indoor and outdoor particle number concentrations were positively correlated with each other at all three sampling settings for both dry and wet weather seasons(r2 = 0.13-0.65,p < 0.001).The infiltration factors and indoor/outdoor ratios of particles(14-660 nm)were estimated at 0.30-0.75 and 0.85-1.5,respectively,which were comparable to or higher than those(0.12-0.76 and 0.03?1.1)found in cites of other countries under infiltration conditions.Furthermore,the average infiltration factor of fine particle numbers(50?660 nm)in an office was 0.61 during a severe haze episode,indicating that approximately 60% of outdoor particles penetrated indoors.All findings suggested an efficient transport of outdoor particle sources into indoor environment,confirming that exposure of the general public to indoor particles in China should not be overlooked due to effective infiltration of outdoor particles and frequent heavy haze episodes.Spatial distributions of PAHs and FRs showed that the higher total concentrations occurred in residential areas than in other settings,and indoors than in outdoor environments.Compositional profiles and size distributions of PAHs and FRs were similar indoors and outdoors,especially for PAHs,which showed the high correlations and indicated that outdoor source may have contributed to 38-99% and 62-100% of variations for indoor concentrations.In addition,OPFRs was the dominant component of FRs,followed by PBDEs.Atmospheric particle size distributions of PAHs and OPFRs at indoor and outdoor environments in urban Guangzhou,suggesting the different emission sources and mechanisms.Gas-particle partition of semivolatile organic contaminants was comprehensively affected by the sub-cooled liquid vapor pressures at 298 K,octanol-air partition coefficients,and particle size distribution.The deposition fractions and concentrations of size-dependent PAHs and FRs in the human respiratory tract were calculated by the International Commission on Radiological Protection deposition model.Both deposition concentrations of particle-bound PAHs and FRs followed the sequence of head airway tracheobronchial region > alveolar region.Coarse particle-bound PAHs and FRs were the major contributors to the deposition concentrations in the head airway,whereas fine particles contained the majority in tracheobronchial region and alveolar region.The daily inhalation intake values of airborne PAHs and FRs four age groups followed the sequence of children(< 6 years,PAHs:1.1 ng kg-1 bw d-1;FRs:208 ng kg-1 bw d-1)> adolescents(6?17 years,PAHs:0.51 ng kg-1 bw d-1;FRs:103 ng kg-1 bw d-1)> adults(18?60 years,PAHs:0.33 ng kg-1 bw d-1;FRs:81 ng kg-1 bw d-1)> seniors(> 60 years,PAHs:0.19 ng kg-1 bw d-1;FRs:69 ng kg-1 bw d-1).In addition,the estimated health risk from human inhalation exposure to airborne PAHs and FRs were lower than the Safe Acceptable Range,which indicate the low risk for residents in Guangzhou.