【作者】 蔡婧；

【导师】 张大年； 修光利；

【作者基本信息】 华东理工大学 ， 环境工程， 2013， 博士

【摘要】 由燃料不完全燃烧产生的黑碳颗粒物(Black Carbon, BC),在大气传输过程中会引发一系列气候、环境和健康风险。黑碳颗粒物粒径范围为0.1～1μm,因此能够进入人体的呼吸系统,甚至深达肺部,并可能通过引发呼吸道的炎性反应而诱发哮喘等疾病。近年来,黑碳颗粒物的暴露风险研究已成为是国内外学者重要的研究领域。尽管大量的流行病学和毒理学研究将黑碳暴露与呼吸系统和心血管疾病关联,但这些研究的结论大多建立在室外定点观测结果的基础上。由于个体行为以及污染物时空分布差异,定点观测对人群暴露风险的表征有一定的局限性,研究结果具有较大的不确定性。建立更为准确的个体暴露表征方法得到国内外学者的重视。因此,解析黑碳污染的时空分布、探索定点黑碳观测水平对个体暴露水平的代表度及有效性,既可以对现有的流行病学结果进行补充,提高暴露风险评价的可靠性；又可以更准确地比较不同环境黑碳水平与暴露风险的关系。论文围绕城市地区个体黑碳暴露特征开展研究,首次对新近设计的MicroAeth黑碳采样仪应用于个体黑碳暴露特征研究的可行性进行了全面的评估,并将该采样体系应用于纽约地区个体黑碳暴露与儿童呼吸道急性效应关系的研究,以及上海地区地铁站工作人员黑碳个体暴露特征的研究中。基于上海和纽约两大城市进行的室内外和个体黑碳的观测,论文尝试比较了两大城市黑碳污染分布特征和个体暴露特征。在纽约地区的研究,对9-10岁儿童(包括哮喘儿童)进行了室内黑碳观测以及多次重复24小时个体黑碳和呼吸道指标(肺功能测试和呼出气一氧化氮)采集,采用多元线性方程表征了室内外黑碳水平对个体黑碳暴露水平的表征度；建立线性混合效应模型,估算了个体黑碳暴露与9～10岁纽约儿童呼吸道急性效应的关系；在上海地区开展的研究,则初步对比分析了上海地区室内外黑碳观测水平与个体暴露水平的关系,并通过对某地铁站工作人员的个体黑碳暴露采样,评估了封闭空间个体污染物暴露特征,估算了不同环境中个体黑碳暴露长期、短期的相对风险度。通过论文的研究,取得了如下主要研究成果：(1)纽约城市地区,中心点位黑碳浓度呈冬夏高,春秋低的季节分布特征及工作日高于周末的周分布特征；而同时期测得的不同家庭室内黑碳浓度具有显著差异。该污染特征表明纽约地区黑碳主要受人为活动(局部源贡献)和气象因素主导而与纽约地区略有不同,上海地区碳污染时空分布特征还可能受到周边外地源短程或长距离输入的作用。(2)对纽约地区中心点位、家庭室内黑碳和个体黑碳浓度水平的对比发现,中心点位和家庭室内黑碳不能完全表征对个体黑碳暴露特征。中心点位黑碳仅能表征个体黑碳37%的变异性；而家庭室内黑碳浓度水平在非供暖季对个体黑碳的表征度为59%,供暖季为45%。这一结果主要与黑碳在城市地区显著的时空分布和研究对象的个体行为差异有关。因此个体采样对于研究黑碳暴露风险更为有效。(3)线性混合效应模型结果显示,个体黑碳日均浓度每增加1μg/m3,非哮喘儿童的肺功能指标FEV1/FVC和FEF2575/FVC分别下降0.008个单位和0.03个单位(p<0.05),表明黑碳对非哮喘儿童的肺功能有抑制作用；但对哮喘儿童却没有观察到类似的结论。个体黑碳日均浓度与研究人群炎症指标的关系不明显。模型结果还发现,室内环境中NO的浓度与呼吸道炎性指标具有显著相关性。室内环境空气质量值得关注。(4)通过对上海某地铁站工作人员个体采样与定点监测结果比较,在上海地区无论室内还是室外固定点观测,对个体黑碳浓度进行表征的结果都存在较大的误差。地铁站定点观测值对个体黑碳暴露真实水平的估计偏低近2倍。地铁室内研究结果还表明,尽管车控室环境中黑碳水平相对较低,但是由于地铁站采样对象在车控室滞留时间占到72%,导致人体在车控室的黑碳暴露剂量高于非车控室。因此,地铁工作人员职业黑碳暴露健康风险研究应以车控室环境为主；而公众短期暴露急性健康效应研究应以非车控室环境为主。论文的主要特色和创新点在于：(1)对MicroAeth黑碳采样仪个体采样中湿度和振动的影响进行了系统的分析和研究,提出了异常数据自动诊断和处理的方法,为该仪器在暴露研究中的应用奠定了基础。(2)采用多次重复测定个体黑碳水平和多次重复采集生物指标来研究黑碳呼吸道健康效应,降低了由随机抽样导致的个体效应带来的不确定性。在混合效应模型中,将随机效应列入调整项,提高了模型表征总体样本特征的精度。(3)以上海地区地铁站个体黑碳暴露特征为研究对象,比较了封闭空间黑碳水平与个体暴露水平,评估了不同环境中长期、短期黑碳暴露的风险度。相似的研究尚未见报道,可为探讨黑碳职业暴露和公众暴露水平,以及制定污染物控制对策提供依据。(4)论文基于个体暴露风险特征研究,建立了完整的,包括室外固定点采样、室内采样以及个体采样的暴露特征表征体系关系,具有特色,可为更为准确的评价个体黑碳暴露提供依据。更多还原

【Abstract】 Black carbon (BC), which mainly results from incomplete combustion of biomass and fossil fuels, is responsible for significant climate, environmental and health effects in the atmosphere. BC with particle size ranging from0.1to1μm, can enter the respiratory system, possibly penetrating deep into the lungs; this might trigger asthma attacks or other diseases by causing airway inflammation. In recent years, scientific attention has shifted to the role of BC as a risk factor of human health.A mountain of epidemiological and toxicological studies implicate that exposure to BC is associated significantly with respiratory and cardiovascular diseases. In those studies, the assessment of exposure to air pollutants has been primarily based on ambient measurements. However, stationary data may not properly reflect personal exposure due to the differences in personal activities among different subjects and the spatial heterogeneity of the air pollutants measured (e.g. BC). Interpretation of findings from epidemiologic and toxicological studies has been hampered by uncertainties in exposures. Accordingly, much attention has been directed toward the need for more appropriate exposure assessment methodology. A detailed study on the characteristics of temporal and spatial distribution of BC in urban settings and the contribution of outdoor/indoor BC levels to personal BC exposure will help in gaining a better understanding of the extent to which fixed-site BC measurements are representative of personal exposure, which is essential to the validation of epidemiological studies that are based on stationary measurements as well as to the determining of the true association between BC exposure and human health.This study focuses on the characteristics of personal exposure to BC in urban settings. It validated a newly developed BC monitor-MicroAeth for personal BC exposure measurements and investigated for its application in personal exposure study. MicroAeth was used as a personal BC sampler in the study on relationship of personal BC exposure and airway response in Children in New York City (NYC) and in the study on characteristics of personal exposure to BC in a Shanghai (SH) subway station. Based on the outdoor/indoor BC monitoring and personal BC sampling in both NYC and SH, this study preliminarily compared characteristics of ambient BC distributions and personal BC exposures among two cities. Home indoor BC,6repetitions of personal BC measurements as well as lung function and exhaled NO data were collected from9-10years old children in NYC:multivariable linear regression was conducted to model the relationship between ambient, home indoor and personal BC; linear mixed effected models were conducted to estimate the relationship between personal BC exposure and airway acute response in9-10years old children in NYC. A preliminary comparison of outdoor/indoor BC and personal BC was conducted in the SH study. And it characterized the personal exposure to air pollutants in an enclosed space and assessed the long-term and short-term risks of BC exposure in different environments via conducting personal sampling on staff from a subway station in SH.The main results from this study are described below:(1) It is very apparent from central site BC and home indoor BC measurements that BC is temporally and spatially heterogeneous in NYC. Strong seasonal (higher BC levels in winter and summer than ones in spring and autumn) and weekly patterns (higher BC in weekdays than one in weekend) suggest that BC distribution in NYC is mainly affected by meteorological conditions and local sources; in contrast with BC distribution characteristics in NYC, the SH area seems to be significantly affected by contributions from regional and long distance transportation in addition to local BC sources(2) Comparison among ambient, home indoor and personal measurements show that ambient BC at central site can explain37%of variability of personal BC; while home indoor BC in non-heating season and heating season can explain59%and45%of variability of personal BC, respectively, suggesting that ambient BC and home indoor BC do not adequately reflect personal BC exposure of a cohort of NYC children; while home indoor BC performs better than ambient BC due to the fact that most of the subjects’ time is spent at home and BC concentrations are heterogeneously distributed in NYC. Hence, to accurately capture BC exposures of a cohort of NYC children, personal monitoring is essential.(3) Linear mixed effect model analysis shows that the lung function of FEVi/FVC and FEF2575/FVC will decrease0.8%and0.03with1μg/m3of personal BC increases among non asthmatic children, suggesting exposure to BC may have adverse effects on lung development in children without asthma; however, similar results were not observed in children with asthma. The levels of inflammation biomarkers were significantly associated with home indoor NO, but not with personal BC, suggesting that more attention needs to be paid on indoor air quality.(4) Similarly, it was concluded that outdoor/indoor BC do not adequately reflect personal BC exposure based on the comparison of stationary measurements and personal sampling conducted by staff working in a subway station in Shanghai. It suggested that the strength of exposure risk to BC in the Shanghai area varies greatly among different environments. Although BC levels in the dispatcher’s office in a subway station were relatively lower than in non-office environments, the exposure dose of personal BC was higher in the office probably due to the fact that subjects spent approximately72%of their workday in the office environment. Therefore, it indicated that the office should be considered as the priority environment for professional exposure risk study, while the non-office environment should be considered as the priority one for the study of public exposure risk.Overall, the following points stand out in this study:(1) As far as we are aware, the usage of the microAeth as a personal BC real-time monitor has not been validated in peer-reviewed literature. This study presented on the detailed analysis of the performance of the microAeth as a personal sampler under varying conditions of humidity and vibration. A post hoc procedure was developed to identify causes of and to remediate problematic BC readings for personal data quality assurance and control.(2) The repeated personal BC, lung function and inflammation biomarkers measurements obtained for each subject enables the use of the linear mixed effect model with random intercepts for random effect adjustment to investigate the relationship between BC exposure and airway response with much less uncertainty.(3) As far as we aware, a study on characteristics of personal exposure to BC in Shanghai subway stations has not been published in the scientific literature. This study characterized personal BC exposure in professional environments, i.e. a subway station, and assessed long-term and short-term exposure risks in different subway micro-environments by comparing personal BC levels and BC concentrations in an enclosed space. Furthermore, it provides information for the investigation of both professional and public exposure risk and provides a scientific basis for enacting measures for air pollution control.(4) This study stands out in its establishment of a complete exposure characterization, including ambient, indoor and personal measurements and provides a better understanding of proper BC exposure assessment.更多还原