The Atmospheric Pollution Characteristics And Health Risks Of Polycyclic Aromatic Hydrocarbons In Lanzhou Valley,Western China

For decades,the environmental pollution of polycyclic aromatic hydrocarbons(PAHs)has been a major concern of the researchers,a large number of epidemiological studies supported that the human health effects which are believed to be associated with PAHs pollution exposure directly or indirectly.Probable routes of human exposure to PAHs are inhalation,ingestion and dermal contact.It is significant to assess risks and health effects of human exposure to PAHs,which can provide the theoretical basis for controlling and mitigation of PAHs pollution.Lanzhou,as a typical industrialized city located in the semi-arid region of northwest China,in which industrial activities and vehicle exhaust as well as other dietary habits such as barbecue have caused a large amount of PAH emissions in Lanzhou valley,in addition,the characteristics of semiclosed dumbbell-shaped basins also caused the airflow block which would promote the accumulation of pollutants in valley.Therefore,this thesis would like to investigate atmospheric pollution characteristics and exposure risks of PAHs as well as its health effects in Lanzhou valley by combining external exposure method and internal exposure method.Firstly,the passive air samplers have been employed to collect atmospheric samples in order to investigate the PAH pollution levels and spatial distribution characteristics as well as its seasonal variation in Lanzhou valley.Then the carcinogenic risk of atmospheric PAHs in Lanzhou valley was assessed by the benzo [a] pyrene(BaP)toxicity equivalent method and the lifetime excess carcinogenic risk(ECR)based on the observed PAH concentrations.Finally,we used the in vitro bioassay SOS/umu to evaluate the genotoxic and its variations of temporal and spatial distribution of air passive samples in Lanzhou valley,moreover,the PAH contributions to the genotoxic of atmospheric samples were also evaluated based on the SOS/umu bioassay of PAH standards.In addition,we chose two kinds of special populations which are lactating women and infants(susceptible population)and petrochemical workers(occupational population)as the research object to study the health risks and effect of human exposure to PAHs in Lanzhou valley by internal exposure method.That the health risks of lactating women and infants exposure to PAHs(susceptible population)were assessed based on PAH concentrations in breast milk,comparing ingestion dose of infant from human milk PAHs and inhalation dose of infant from exposure to air PAHs to analysis the main route of infant exposure to PAHs.For petrochemical workers of another special population,we firstly used PAHs metabolite urinary 1-Hydroxypyrene(1-OHP)as a biomarker to assess the internal exposure dose of occupational workers exposure to PAHs,and then employed PBTK model and ILCR model to evaluate the health effects of occupational workers exposure to PAHs.The conclusions of this thesis are as follows:(1)The atmospheric pollution characteristics and sources of EPA priority controlled 16 PAHs in the study area showed that the annual average concentration of ?16PAHs(particlulate phase + gaseous phase)was 132-462 ng/m3.The atmospheric PAH levels were higher in winter than that in summer,and particulate phase ?16PAHs were higher than that in gaseous phase.Low molecular weight PAHs(2-3 rings)are mainly distributed in gaseous phase,while the middle(4 rings)and high molecular weight(5-6 rings)PAHs are mainly distributed in particulate phase.The sampling site close to the point source where PAHs concentration exhibited the highest level(The sum of atmospheric ?16PAHs concentration in particulate and gaseous phase was 680 ng/m3).The major sources of PAHs pollution in Lanzhou valley were mainly related to the combustion of fossil fuels and coal as well as traffic emission.The study results also indicated that the transportation emission and combustion of fossil fuels contribute 65.5% of all sources in winter,while 59.6% in summer,which showed that more PAHs emission would be released in winter due to the increasing consumption of fossil fuels and coal in winter.(2)That the potential cancer risk assessment of EPA priority controlled atmospheric 16 PAHs in the study area showed that the average ?PAHs16-BaPeq concentration(particlulate phase + gaseous phase)was 40.7 ng/m3 in winter,and the average ?PAHs16-BaPeq concentration(particlulate phase + gaseous phase)was 28.2 ng/m3 in summer.?PAHs16-BaPeq concentrations at all sampling sites in present study were higher than BaPeq standard of China's Ministry of Environmental Protection,which suggested that local residents were under a potential cancer risk due to PAHs exposure need to be pay attention.The ECR(excess cancer risk)of human exposure to PAHs during winter and summer sampling periods were 45-3540 cancer cases and 31-2451 cases per million people,respectively.(3)The results involving in in vitro genetic toxicity tests of passive samples from the study area showed that the genotoxicity of passive air samples in winter was greater than that in summer,and the induction rate(IR)of all winter's samples exceeded standard 1.5 which indicated that there were direct mutagens in the tested air sample extracts,especially in the wintertime.The genotoxicity of the gaseous samples in winter was higher than that of the particulate samples,possibly due to the increasing in the use of fossil fuels in winter improved the level of nitro radicals,this reaction increased the rate of PAHs transformed to PAHs derivatives that more toxic than parent PAHs;second reason might be the weaker photosynthesis in winter increased the lifespan of genetic toxic substances exsited.The significant statistical correlation was found for low TEF PAH compounds such as ACY,FLO,PHE(TEF=0.001),and ANT,BghiP(TEF=0.01).Therefore,further SOS/umu genetic toxicity test of PAH standards showed that the PAHs had a certain contribution to the direct genetic toxicity of the air samples.So it is obvious that the genetic toxicity of the total extract was higher than that of the single PAHs,indicating that the genetic toxicity of air pollution in the environment was not a simple additive action of pollutants' genotoxicity because the total extracts of air samples integrated multiple air pollutants.(4)That the study results for the health risk of lactating women and infant(susceptible population)exposure to PAHs based on internal exposure method in study area showed that the concentration range of EPA priority controlled atmospheric 15 PAH in human breast milk samples in Lanzhou valley were 7.26-44.92 ng/g lipid(NAP has a high background and fast metabolism rate in human body,so EPA priority controlled 15 PAHs except for NAP in breast milk were analyzed),in which low and middle molecular weight PAHs contributed 70.1% to total 15 PAHs in breast milk.Statistical analysis method was performed to determine the relationship between subject characteristics and PAHs concentration of human milk,from the results we could found that the dietary habits such as barbecue could elevate the human milk PAH levels,moreover,the second-hand smoke exposure also could affect the PAH levels of human milk.Furthermore,the risks of daily intake PAHs from human milk and inhalation for infant showed that ingestion doses from human milk PAHs in Lanzhou valley were much higher than inhalation doses from exposure to air PAHs.Ingestion doses of infants accounted for 64.52%-94.79% of the total intake doses of individual PAHs from both inhalation and ingestion,while inhalation doses of infants from exposure to air PAHs were only contributed 5.21%-28.38% of the total dose.The average ingestion dose of BaP for infants in this study was lower than upper bound of BaP dietary exposure doses.However,the estimated margin of exposure(MOE)values were higher than that proposed by the European Food Safety Authority(EFSA)which indicated that there was potential hazard for the consumption of these human milk samples by infants in Lanzhou valley.(5)That the results of health risk of petrochemical workers(occupational population)exposure to PAHs using internal exposure dose method in study area showed that the average urinary 1-OHP concentration after creatinine adjustment(adjust the varying degree of dilution in urine samples)was 1.96 ?mol/mol creatinine,and petrochemical workers group was significantly higher with an average concentration of 2.34 ?mol/mol creatinine than that in the office group(T-test,P=0.023).The urinary 1-OHP concentrations in petrochemical workers group who have the smoking habits were significantly higher than biological exposure limits which indicated that PAHs exposure could cause genetic damage to petrochemical workers.In addition,the impact of smoking habit on petrochemical workers group were higher than that on the office group,indicating that two major exposure sources(occupational exposure and smoking)of petrochemical workers may have an interaction that would lead to an increase in the PAHs internal dose.The correlation between 1-OHP concentration and red cell index showed that red blood cell abnormality risk increased with increasing PAHs exposure level.PBTK model results also improved this conclusion.Occupational exposure concentration which was the most influential variable on the workers' inhalation exposure to PAHs.Inhalation PAHs risk by ILCR model indicated that there is a potential cancer risk for petrochemical workers,this need to attract some attention.