PubMed · 14575229
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S V N Rajendra Gopal, C V Rao. 2003. Burn--the hypothesis.. https://pubmed.ncbi.nlm.nih.gov/14575229/
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Denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction-amplified genes coding for 16S rRNA was used to assess differences in bacterial community structure as a function of spatial location along the height of two biofilters used to treat a model waste gas stream containing methyl ethyl ketone (MEK). One of the laboratory-scale biofilters was operated as a conventional continuous-flow biofilter (CFB) and the other was operated as a sequencing batch biofilter (SBB). Both biofilters, inoculated with an identical starting culture and operated over a period lasting more than 300 days, received the same influent MEK concentration and same mass of MEK on a daily basis. The systems differed, however, in terms of the fraction of time during which contaminated air was supplied and the overall operating strategy employed. DGGE analysis indicated that microbial community structures differed as a function of height in each of the biofilters. The DGGE banding patterns also differed between the two biofilters, suggesting that operating strategies imposed on the biofilters imparted a sufficiently large selective pressure to influence microbial community structures. This may explain, in part, the superior performance of the SBB over the CFB during model transient loading conditions, and it may open new possibilities for purposely manipulating the microbial populations in biofilters treating gas-phase contaminants in a manner that leads to more favorable treatment performance.
Air quality in underground spaces has seldom been evaluated in Korea. Accordingly, the current study recently evaluated asbestos exposure among Seoul metropolitan subway workers during the renovation of the subway's air-conditioning system. To identify possible routes of asbestos exposure, suspected sources, including gaskets, ceiling boards, ceiling materials, and dust settled inside ducts, were all sampled. Personal air samples were also taken to evaluate any asbestos exposure during the renovation. The asbestos fibers found in the samples were analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer (EDX). Twelve out of eighteen bulk samples contained asbestos, the majority of which was chrysotile fibers. Asbestos was detected in 9 out of 72 personal air samples and the level ranged from 0.003 to 0.02 fibers/cm(3). While asbestos levels were below Korean occupational limit of 2 fibers/cm(3), they were still detectable and therefore further monitoring would be appropriate.
BACKGROUND: The increase in work-related respiratory complaints in artificially ventilated buildings have multiple causes, and intervention studies are a valuable approach to understanding possible mechanisms. STUDY OBJECTIVES: To analyze the effects of an intervention in a ventilation system with > 20 years of continuous use, and with a high rate of building-related respiratory complains. DESIGN: An epidemiologic study was done among individuals working in places with ventilation machinery and ducts with > 20 years of use, before and after intervention. Analysis of symptoms and logistic regression were performed to check the associations between air-conditioning intervention and reported symptoms. RESULTS: The air-conditioning intervention showed a protective effect on building-related worsening of respiratory symptoms (odds ratio, 0.132; 95% confidence interval, 0.030 to 0.575), naso-ocular symptoms (odds ratio, 0.231; 95% confidence interval, 0.058 to 0.915), and persistent cough (odds ratio, 0.071; 95% confidence interval, 0.014 to 0.356). CONCLUSION: Intervention in high-risk occupational locations can be effective in improving perceived indoor air quality.