Asbestos exposure among Seoul metropolitan subway workers during renovation of subway air-conditioning systems

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.     

Potential source of asbestos in non-asbestos textile manufacturing company

Recently, a worker with lung carcinoma and a metastatic brain tumor was diagnosed as having a work-related disease. He had been employed in a non-asbestos textile company for 25 years. Consequently, to identify and explore possible causative agents for lung cancer in a non-asbestos textile manufacturing company and establish a causal relationship between exposure and lung cancer, an epidemiological investigative study was conducted and the work processes the worker was engaged in were examined. Air samples were taken from the workplace and during the drilling processes, and a suspected causative material was analyzed. The study revealed that the subject had been employed in the non-asbestos textile manufacturing company for 25 years from 1973 and his responsibilities included repairing spinning machines. In particular, the subject was involved in drilling B-bushings that were used to protect against gear abrasion in the spinning machines. An analysis of the B-bushings using a transmission electron microscope equipped with an energy dispersive X-ray analyzer indicated that they contained crocidolite asbestos fibers. Air samples obtained when drilling the B-bushings clearly indicated that the subject had most likely been exposed to crocidolite fibers when installing the B-bushings in the spinning machines. The frequency and duration of the work suggested that there would be a sufficient degree of exposure to crocidolite fibers to cause lung cancer. Except for smoking and asbestos exposure, no other chemical exposure was suspected for developing lung cancer in the workplace. Smoking appeared to be more of a potentiating risk factor in conjunction with the asbestos exposure. Accordingly, this case may provide significant evidence in identifying the cause of the mesothelioma or lung carcinoma found among workers in non-asbestos textile manufacturing companies elsewhere.     

Contamination by Cd, Cu, Pb, and Zn in mine wastes from abandoned metal mines classified as mineralization types in Korea

The objective of this study was to investigate heavy metal contamination and geochemical characteristics of mine wastes, including tailings, from 38 abandoned mines classified as five mineralization types. Mine waste materials including tailings and soils were sampled from the mines and the physical and chemical characteristics of the samples were analyzed. The particle size of tailings was in the range of 10–100 μm. The pH of the waste covered a wide range, from 1.73 to 8.11, and was influenced by associated minerals and elevated levels of Cd, Cu, Pb, and Zn, extracted by a Korean Standard Method (digestion with 0.1 mol L⁻¹ HCl), which were found in the wastes. Half of the samples contained heavy metals at levels above those stipulated by the Soil Environmental Conservation Act (SECA) in Korea. In addition, extremely high concentrations of the metals were also found in mine wastes extracted by aqua regia, especially those from mines associated with sulfide minerals. Thus, it can be expected that trace elements in mine wastes may be dispersed both downstream and downslope through water and wind. Eventually they may pose a potential health risk to residents in the vicinity of the mine. It is necessary to control mine wastes by using a proper method for their reclamation, such as neutralization of the mine wastes using a fine-grained limestone.     

Human health risk assessment of explosives and heavy metals at a military gunnery range

In this research, a risk assessment was undertaken in order to develop the remediation and management strategy of a contaminated gunnery site, where a nearby flood controlling reservoir is under construction. Six chemicals, including explosives and heavy metals, posing potential risk to environmental and human health, were targeted in this study. A site-specific conceptual site model was constructed, based on effective, reasonable exposure pathways, to avoid any overestimation of the risk. Also, conservative default values were adapted to prevent underestimation of the risk when site-specific values were not available. The risks posed by the six contaminants were calculated using the API’s Decision Support System for Exposure and Risk Assessment, with several assumptions. In the crater-formed-area (Ac), the non-carcinogenic risks (i.e., HI values) of tri-nitro-toluene (TNT) and Cd were slightly larger than 1, but for RDX (Royal Demolition Explosives) was over 50. The total non-carcinogenic risk of the whole gunnery range was calculated to be 62.5, which was a significantly high value. The carcinogenicity of Cd was estimated to be about 10⁻³, while that for Pb was about 5 × 10⁻⁴, which greatly exceeded the generally acceptable carcinogenic risk level of 10⁻⁴–10⁻⁶. It was concluded from the risk assessment that there is an immediate need for remediation of both carcinogens and non-carcinogens before construction of the reservoir. However, for a more accurate risk assessment, further specific estimations of the changes in environmental conditions due to the construction of the reservoir will be required; and more over, the effects of the pollutants to the ecosystem will also need to be evaluated.     

Survey‐Based Approach for Hydrological Vulnerability Indicators Due to Climate Change: Case Study of Small‐Scale Rivers1

Jung, Yong and Minha Choi, 2012. Survey‐Based Approach for Hydrological Vulnerability Indicators Due to Climate Change: Case Study of Small‐Scale Rivers. Journal of the American Water Resources Association (JAWRA) 48(2): 256‐265. DOI: 10.1111/j.1752‐1688.2011.00608.x Abstract: The vulnerability indicators can be used to develop water resource policy in the context of climate change. The Delphi method, an interactive prediction technique, is an efficient way to apply weighting functionality to vulnerability indicators consisting of three parts: Exposure, Sensitivity, and Adaptive Capacity on climate change. The Delphi method is an anonymous iterative survey of expert opinion, which is then shared with other participants. A total of three different rounds were carried out. The first round was a problem selection set, and the second and third were the standard Delphi survey. Fifty‐eight experts (66% academic and 34% practitioner) were invited. The rates of reply were 59, 50, and 38% for the first, second, and third Delphi processes, respectively. The degree of consensus of the Delphi survey was validated via variance changes and Kendall’s W test. Exposure and Adaptive Capacity presented increased levels of agreement among respondents in their given priorities. Particularly strong convergence (0.20 to 0.71 in Kendall’s W) of the experts’ opinions for Adaptive Capacity was observed. The results of this study indicate that finalized factors with ultimate weights through the Delphi method can be a strong support for governmental policy making with respect to climate change.     

Reduction of Norovirus Surrogates Alone and in Association with Bacteria on Leaf Lettuce and Tomatoes During Application of Aqueous Ozone

Food and Environmental Virology - Retail foodservice establishments (FSE) frequently utilize washes with sanitizing agents during fresh produce preparation. This study evaluated the efficacy of...     

Monitoring biofouling based on aerobic respiration in reverse osmosis system

A monitoring method of biofouling in reverse osmosis (RO) system was proposed based on the fluorescent signal of resorufin, which is reduced by nicotinamide adenine dinucleotide released from viable cells during aerobic respiration. The fluorescent signal of resorufin reduced by planktonic cells and microorganisms of biofilm showed linearity, indicating its feasibility to monitor biofouling in a RO system. For the application of the method to the lab-scale RO system, the injection concentration of resazurin and the injection flow rate were optimized. Biofilm on RO membranes continuously operated in a lab-scale RO system was estimated by resorufin fluorescence under optimized detection condition. As a result, resorufin fluorescence on RO membrane showed a significant increase in which the permeability of RO system decreased by 30.48%. Moreover, it represented the development of biofilm as much as conventional biofilm parameters such as adenosine triphosphate, extracellular polymeric substances, and biofilm thickness. The proposed method could be used as a sensitive and low-cost technology to monitor biofouling without autopsy of membranes.     

Characterization of particulate matter from diesel passenger cars tested on chassis dynamometers

Emission characterization of particle number as well as particle mass from three diesel passenger cars equipped with diesel particulate filter(DPF), diesel oxidation catalyst(DOC)and exhaust gas recirculation(EGR) under the vehicle driving cycles and regulatory cycle.Total particle number emissions(PNEs) decreased gradually during speed-up of vehicle from 17.3 to 97.3 km/hr. As the average vehicle speed increases, the size-segregated peak of particle number concentration shifts to smaller size ranges of particles. The correlation analysis with various particulate components such as particle number concentration(PNC),ultrafine particle number concentration(UFPNC) and particulate matter(PM) mass was conducted to compare gaseous compounds(CO, CO_2, HC and NOx). The UFPNC and PM were not only emitted highly in Seoul during severe traffic jam conditions, but also have good correlation with hydrocarbons and NOxinfluencing high potential on secondary aerosol generation. The effect of the dilution temperature on total PNC under the New European Driving Cycle(NEDC), was slightly higher than the dilution ratio. In addition, the nuclei mode(DP: ≤ 13 nm) was confirmed to be more sensitive to the dilution temperature rather than other particle size ranges. Comparison with particle composition between vehicle speed cycles and regulatory cycle showed that sulfate was slightly increased at regulatory cycle, while other components were relatively similar. During cold start test, semivolatile nucleation particles were increased due to effect of cold environment. Research on particle formation dependent on dilution conditions of diesel passenger cars under the NEDC is important to verify impact on vehicular traffic and secondary aerosol formation in Seoul.     

Extension of TACOM to the complexity of tasks designed for abnormal situations in nuclear power plants

TACOM (TAsk COMplexity) is a measure for evaluating the complexity of tasks prescribed for emergency situations in nuclear power plants. Five sub-measures constituting TACOM represent five different aspects of the task complexity exhibited in operating procedures for emergency situations. The practicality of TACOM has been verified through a series of empirical studies. However, tasks designed for abnormal situations that can significantly affect the safety of nuclear power plants, also need a proper measure for evaluating their complexity. TACOM provides a process, a systematic cognitive task analysis method and a set of guidelines to support its application. Therefore, although the characteristics of abnormal task situations are not the same as those of emergency situations, TACOM seems to be reasonably applied to abnormal situations or at least to offer meaningful insights for developing a measure for evaluating the complexity of tasks in abnormal situations. Thus this study examined the applicability of TACOM to abnormal situations through case studies. Particular attention was paid to the sufficiency and appropriateness of the three methodological tools, which are the process, the cognitive task analysis method and the set of guidelines. Collective consideration of the case studies and the characteristics of tasks prescribed for abnormal situations led us to draw the conclusion that TACOM could be reliably used for abnormal situations as well. This paper reports the process of how to apply TACOM to the tasks of abnormal situations and discusses some lessons learned through this application.