| Numerous epidemiological studies in recent years have documented a positive association between ambient particulate concentration level and adverse health outcomes including cardiovascular and respiratory morbidity, mortality and hospital admissions. However, much less is known about indoor particulate matter exposure level and associated health risks. In particular, study on particulate matter in the indoor air of classroom is needed, since children are more susceptible to environmentally hazardous factors and are more vulnerable to health hazards than adults and spend a large part of their time in classrooms.On this background, five classrooms in No.1 Elementary School Affiliated to Xuanwu Normal School were chosen for investigation of indoor air quality. In the autumn measurement period (23rd Oct. 2006 to 8th Nov. 2006) and in the winter measurement period (25th Dec. 2006 to 29th Dec. 2006), various dust particle fractions (PM10 and PM2.5) were monitored indoors and outdoors continuously by portable monitors and samplers. Additionally, data on indoor environmental parameters (temperature, relative humidity and carbon dioxide) and classroom characteristic parameters (room area, area of opened windows or louver windows, number of occupants, room area/occupant, room volume/occupant, floor and class level) were collected simultaneously.In this research, exposure to particulate matter in the indoor air of classrooms in autumn and in winter was firstly analyzed in entirety. Applying statistics softwares, the impact of different parameters on particulate matter (PM10 and PM2.5) mass concentration was then quantitatively analyzed. And the models of indoor particulate matter in two measuring periods were established using the multiple linear regression model. The main conclusions were included as follows:(1) Exposure to PM10 and PM2.5 in the indoor air of classrooms in autumn and in winter was high, especially that of PM2.5 in autumn (median: 0.204mg/m3). And the range of particulate matter mass concentrations was very wide. The median in autumn was higher than that in winter while the means were close in two seasons.(2) The PM10 and PM2.5 mass concentrations obtained with light scattering method were in general higher than those obtained with the filter-based gravimetric technique. Compared to the filter-based gravimetric method, the light scattering method resulted in an increase in the daily values by 56.3% (PM10, indoor), 182.2% (PM2.5, indoor), 33.5% (PM10, outdoor) and 237.8% (PM2.5, outdoor) respectively.(3) When ventilation in classrooms was adequate, compared to indoor sources, ambient particulate concentrations had a significant impact on indoor ones. While inadequate, due to the absence of typical indoor sources of particulate matter, such as cooking, heating and cigarette smoke, the increased concentrations associated with increased physical activity of the pupils and peak values were observed at end of ten-minute breaks.(4) The indoor PM10 and PM2.5 mass concentrations were related to different parameters including relative humidity, temperature, carbon dioxide, area of opened windows or louver windows, number of occupants and room volume/occupant and so on. For example, a significant positive correlation between relative humidity and PM10 and PM2.5 mass concentrations was observed in two seasons (p<0.001); a significant negative correlation between carbon dioxide and PM2.5 mass concentrations was observed in autumn (p<0.01) while a significant positive correlation between the two parameters was observed in winter (p<0.05).(5) No marked differences in indoor PM10 and PM2.5 mass concentrations were observed between autumn and winter (p>0.05). However, a statistically significant influence of class level on the indoor PM10 and PM2.5 mass concentrations was apparent in both measuring periods (p<0.05). The differences in indoor PM10 and PM2.5 mass concentrations in autumn between Floor 1 and Floor 4 was no statistical significant while there was a statistical significant difference in winter.
|
PDF Full Text Request