Chang Ho Yu

Bio: Chang Ho Yu is an academic researcher from New Jersey Department of Health and Senior Services. The author has contributed to research in topics: Hexavalent chromium & Population. The author has an hindex of 11, co-authored 27 publications receiving 404 citations. Previous affiliations of Chang Ho Yu include Kyungpook National University & University of Medicine and Dentistry of New Jersey.

Passive dosimeters for nitrogen dioxide in personal/indoor air sampling: A review

Abstract: Accurate measurement of nitrogen dioxide concentrations in both outdoor and indoor environments, including personal exposures, is a fundamental step for linking atmospheric nitrogen dioxide levels to potential health and ecological effects. The measurement has been conducted generally in two ways: active (pumped) sampling and passive (diffusive) sampling. Diffusion samplers, initially developed and used for workplace air monitoring, have been found to be useful and cost-effective alternatives to conventional pumped samplers for monitoring ambient, indoor and personal exposures at the lower concentrations found in environmental settings. Since the 1970s, passive samplers have been deployed for ambient air monitoring in urban and rural sites, and to determine personal and indoor exposure to NO2. This article reviews the development of NO2 passive samplers, the sampling characteristics of passive samplers currently available, and their application in ambient and indoor air monitoring and personal exposure studies. The limitations and advantages of the various passive sampler geometries (i.e., tube, badge, and radial type) are also discussed. This review provides researchers and risk assessors with practical information about NO2 passive samplers, especially useful when designing field sampling strategies for exposure and indoor/outdoor air sampling.

The Bioaccessibility of Lead (Pb) from Vacuumed House Dust on Carpets in Urban Residences

Abstract: Risk assessments for toxicants in environmental media via oral exposure often rely on measurements of total concentration in a collected sample. However, the human digestive system cannot dissolute all of a toxicant present in the binding matrix, and cannot absorb it with nearly 100% efficiency. In vitro bioaccessibility has been developed as a method to estimate oral bioavailability of a toxicant using a physiologically-based extraction procedure. Bioaccessibility measurements are more physiologically relevant than strong acid leaching measurements of concentration. A method for measuring bioaccessible lead in house dust was derived from the bioaccessibility method currently used for heavy metals in contaminated soils. House dust was collected from carpets in typical urban residences. Bioaccessible lead was measured in house dust (<75 microm) from the homes of 15 participants. The bioaccessibility ranged from 52.4% to 77.2% in gastric fluid, and 4.9% to 32.1% in intestinal fluid. House dust samples from five homes were analyzed to assess the relationship among lead bioaccessibility of three particle size fractions (<75, 75-150, and 150-250 microm). Changes in lead bioaccessibility as a function of particle size fraction were not significant for gastric fluid (p= 0.7019); however they were significant for intestinal fluid (p= 0.0067). This decrease of bioaccessibility may result from the readsorption of dissolved lead onto the dust particles or precipitation of lead with phosphates in a high-pH environment. The bioaccessibility data obtained for two biofluids were applied to the IEUBK model, and results for intestinal bioaccessibility of lead provide support for the model default value of 30% lead bioavailability of dust as a reasonable population indicator for dose, but the higher values for gastric bioaccessibility of lead appeared to provide an upper bound that approached actual blood lead levels in the children living in the studied homes. This upper bound seemed to overcome some of the limitations of the model when it lacks child-specific activity data and characterization of all exposure routes.

The Environmental Protection Agency

Abstract: The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

Applied Linear Regression Models

Abstract: (1991). Applied Linear Regression Models. Journal of Quality Technology: Vol. 23, No. 1, pp. 76-77.

Bus driver well-being review: 50 years of research

Abstract: This review paper consolidates the key research on the occupational health of urban bus drivers since the 1950s. Several electronic databases were searched and 27 key studies were identified, which form the basis of this paper. Early findings that bus drivers are liable to suffer ill health as a result of the job remain true today. The research has, however, demonstrated a greater understanding that specific stressors result in certain physical (cardiovascular disease, gastrointestinal disorders, musculoskeletal problems, fatigue), psychological (depression, anxiety, post-traumatic stress disorder) and behavioural outcomes (substance abuse). Bus driver ill health will have consequences for organisational performance in terms of employee absence, labour turnover and accidents. Stressors for bus drivers include poor cabin ergonomics, rotating shift patterns and inflexible running times. Over the last few decades, the heightening of other work stressors such as traffic, and violence from passengers have compounded the situation for bus drivers. Greater attention to salient moderating and mediating variables in the stressor–strain relationship is featuring in more recent research. Despite such theoretical advances, the research needs to also concentrate on practical interventions that are systematically implemented and evaluated, to improve the well-being of bus drivers. By improving this human side of the role, it is expected that the efficiency of this transport will be enhanced for bus drivers, operators and passengers alike. 2005 Elsevier Ltd. All rights reserved.

The enhanced photoreduction of Cr(VI) to Cr(III) using carbon dots coupled TiO2 mesocrystals

Abstract: The photocatalytic reduction efficiency of hexavalent chromium (Cr2O72− (Cr(VI)) is suffering from high recombination of photoinduced charges, poor adsorption capacity of Cr(VI), and slow desorption of product trivalent chromium (Cr3+ (Cr(III))) from photocatalyst surface. In this work, carbon dots (CDs) was coupled with TiO2 mesocrystals (MT), where CDs displayed both the electron collectors and the active sites. During photoreduction of Cr(VI), the as-prepared CD/MT exhibited activity about 5.4 times higher than the pure TiO2 mesocrystals. The positive charges on the CD/MT surface favored the selective adsorption of Cr(VI) and rapid desorption of Cr(III), which has an obvious promotion on the photocatalytic reduction of Cr(VI) and retention of photoreduction activity. Meanwhile, the CDs coupled on TiO2 mesocrystals facilitated the separation of photogenerated charges. This work provides a simple and effective adsorption-photoreduction-desorption mechanism for the photocatalytic reduction of Cr(VI).