| Summary: | 碩士 === 國立成功大學 === 環境醫學研究所 === 103 === Objectives: To evaluate the impacts of the occurrence and type of long-range transportation (LRT) on the distribution of virus and bacteria in Northern Taiwan by quantifying the levels of enterovirus, influenza A virus and bacteria in ambient air on the days before, during, and after LRT and background days. Also, this study preliminarily investigates the relationships between the ambient bacterial concentrations with air pollutants and meteorological factors.
Methods and Materials: The present study monitors the Asian Dust Storm (ADS) events from September 2013 to April 2014. When ADS occurred in the desert and possibly affect Taiwan, daily air samples were collected on the days before, during and after ADS. Also, during this period, a continuous 3-days sampling were performed in the second week of each month to take daily air samples for background days. Two sampling stations located in Northern Taiwan were adopted: Cape Fukuei (CF, Shimen District, New Taipei City) and National Taiwan University (NTU, Daan District, Taipei City). Cassettes with 37-mm Teflon filters (0.2 µm) were utilized to capture ambient enterovirus, influenza Avirus, and bacteria. Daily filter samples were collected using vacuum air pumps for 24 hr. After sampling, reverse transcription quantitative PCR (RT-qPCR) was applied to quantify enterovirus and influenza A virus, and qPCR and propidium monoazide coupled with qPCR were respectively used to quantify total and viable bacteria. We would confirm whether the LRT belongs to ADS and its effect on Taiwan based on the data of meteorological conditions (temperature and wind speed, from Taiwan Centeral Weather Bureau (Taiwan CWB)) and air pollutions (PM10 and PM2.5, from Taiwan Environmental Protection Administration (Taiwan EPA)), the source of air mass (48-hr backward trajectory produced by HYSPLIT model), and satellite images of MODIS sensor. Spearman Correlation Coefficient was used to analyze the relationships that viable and total bacteria have with air pollutants (PM10, PM2.5, NO2, NO, NOX, CO, O3 and SO2) and meteorological factors (temperature, RH, wind speed and cumulative rainfall).
Results and Discussion: A total of two ADS (11/17/2013-11/18/2013, 11/25/2013-11/29/2013) and three frontal pollution cases (FP) (09/16/2013-09/17/2013, 10/12/2013-10/13/2013, 01/03/2014-01/05/2014) were identified in this study. Influenza A virus only detected in the samples collected on the days before and during the FP (1/3-1/5, 2014), with concentrations of 0.87 and 10.19 (copies/m3), respectively. In term of bacteria on background days, the trend of cell concentrations at CF and NTU stations was similar, showed without geographic difference. However, ADS affects the distribution of bacterial concentrations in the atmosphere at two stations in different levels. The total (1.40 log copies/m3) and viable (0.85 log copies/m3) concentrations of bacteria during ADS days at CF station were higher than those detected after ADS (0.23-0.41 log copies/m3). For NTU station, the total (1.44 log copies/m3) and viable (0.77 log copies/m3) concentrations of bacteria before ADS were the highest, and followed by those found on the days during ADS (1.25 and 0.45 log copies/m3 for total and viable cells, respectively). In term of FP events, the impacts of FP were observed at not only CF station but also NTU station. The days during and/or after FP have higher bacterial concentrations than the days before FP. In FP event occurred in January, the respective concentrations of total and viable bacteria were 0.60-1.62 and 0.34-0.78 log copies/m3 for the days during FP as well as 1.05-1.90 and 1.19-1.23 log copies/m3 for the days after FP, which were more abundant than those quantified from the days before FP (0.57-1.19 and 0.17-0.80 log copies/m3 for total and viable cells, respectively). Surprisingly, this study found the bacterial viability were greater than 34% during the event days regardless LRT types, showing the LRT can carry bacteria that are viable and may have adverse health effects. The results of correlation analyses show that PM10 levels significantly and positively correlated with total (r=0.56, p〈0.01) and viable (r=0.49, p〈0.05) bacterial concentrations both on background days. During ADS days, negative correlations between total bacteria and PM2.5 (r=-0.76, p〈0.05), and between viable bacteria and NO2 (r=-0.68, p〈0.05), NOX (r=-0.61, p〈0.05), CO (r= -0.70, p〈0.05) and wind speed (r=-0.66, p〈0.05). However, there were no environmental factors significantly associated with bacterial levels on the days before and after ADS (p〉0.05).
Conclusions: The temporal distribution of total and viable bacterial concentrations between CF and NTU stations were similar, while LRT affects ambient bacteria and influenza A virus at CF station is higher than those at NTU station. Moreover, the impacts of FP on Northern Taiwan seem higher than ADS. FP increased the concentration of bacteria at CF and NTU stations and may continue to two days after FP. Therefore, during and 2 days after LRT, people should avoid activities outdoors in Northern Taiwan, especially the North Coast of Taiwan such as Shimen area. The associations of ambient bacteria with air pollutants and meteorological factors on background days were different from those during ADS days. The enhancers of ambient bacterial levels were the increase of PM10 on background days, but the decline of PM2.5, NO2, NOX, CO and wind speed during ADS days instead.
|
|---|
