Characterization, Source Apportionment and Health Risk Assessment of PM2.5 for a Rural Classroom in the Amazon: A Case Study

Classrooms are microenvironments in which children and teenagers may be exposed to fine particulate matter (PM2.5). Iranduba is a rural city in the Amazon region close to many brick kilns and road with high traffic levels. In this study, indoor and outdoor PM2.5 levels were measured in a classroom in Iranduba, and the PM2.5 exposure effects on student’s health were calculated. High indoor PM2.5 concentrations and high indoor-to-outdoor ratio values indicated particle accumulation within the classroom. The high percentage of black carbon (10%) in the dry season revealed the influence of burning processes on PM2.5 composition. Se, S, and Pb had an enrichment factor > 5, indicating that there is an important source for these elements in the city. The positive matrix factorization (PMF) model indicated soil resuspension, burning processes and vehicular emissions as the main PM2.5 sources. The excess risk shows that our classroom occupants are expected to be 30% more likely to develop lung-cancer than a group exposed to a background level of PM2.5. Therefore, it is important to have an effective ventilation system in order to reduce the accumulation of pollutants within the classroom and also to control/decrease the emission of pollutants in the city.

教室是儿童与青少年可能暴露于细颗粒物（PM2.5）的微环境。伊兰杜巴（Iranduba）是亚马逊地区的乡村城市，周边分布大量砖窑，且紧邻交通流量极高的道路。本研究对伊兰杜巴某教室的室内外PM2.5浓度进行了实测，并计算了PM2.5暴露对学生健康的影响效应。较高的室内PM2.5浓度与室内外浓度比值，表明教室内存在颗粒物积聚现象。旱季黑碳占比高达10%，这一结果揭示了燃烧过程对PM2.5组分的影响。硒（Se）、硫（S）与铅（Pb）的富集因子大于5，说明该城市存在这些元素的重要排放源。正定矩阵因子分解（Positive Matrix Factorization, PMF）模型结果显示，土壤扬尘、燃烧过程及机动车排放是该区域PM2.5的主要来源。超额风险分析结果表明，该教室的暴露人群罹患肺癌的风险较暴露于PM2.5背景浓度水平的人群高出30%。因此，搭建高效通风系统以降低教室内污染物积聚，并管控、削减城市污染物排放，具备重要的现实意义。