Development of a model (SWNano) to assess the fate and transport of TiO2 engineered nanoparticles in sewer networks.

A new model, SWNano (Sewer-Water Nano), has been developed in the present study that quantitatively simulates the spatio-temporal changes in the concentrations of TiO2 ENPs of dispersed and aggregated forms in the sewage water and sediment of a sewer network. As a brief example of SWNano applications, a small section of the entire sewer network of Seoul, Korea, was chosen to study where the sewage water was experimentally characterized. The predictions of SWNano present important findings that i) heteroaggregation is the most significant process following the advective transport among the fate and transport processes in the sewer pipes, ii) the heteroaggregation of TiO2 ENPs with SPMs in the sewage water can substantially (a few % to more than 50%) reduce the freely dispersed TiO2 ENPs depending on the magnitude of attachment efficiency, and iii) accurate determination of attachment efficiency is of critical importance in predicting the quantity of individual forms of ENPs exiting the sewer system. The predictions strongly suggest that the fate and transport of TiO2 ENPs in the sewer networks be taken into account to improve the assessment of exposure to TiO2 ENPs in the aquatic ecosystems, which warrants further development and use of models like SWNano.

Disparities in the utilisation of preventive health services by the employment status: An analysis of 2007-2012 South Korean national survey.

OBJECTIVES: This study aims to investigate the differences in the utilisation of preventive health services among standard, nonstandard workers, the self-employed, and unpaid family workers. METHODS: We used the 4th and 5th Korea National Health and Nutrition Examination Survey, a nationwide survey conducted from the year 2007 to 2012. Economically active workers between the ages of 25 and 64 were grouped into standard, nonstandard, the self-employed, and the unpaid family workers (N = 16,964). Outcome variables are the uptake of preventive health services including influenza vaccination, regular medical check-up, and four types of cancer screenings. We used multivariate logistic models. RESULTS: Overall, non-standard workers, the self-employed, and unpaid family workers were less likely to use the preventive health care compared to the standard workers. In particular, the self-employed were less likely to use all the six services compared to the standard workers and showed the lowest level of uptakes among the four working groups. Moreover, the service uptake of the non-standard workers was lower than that of standard workers in all services; except the colon cancer screening. On the other hand, unpaid family workers showed mixed results. While the uptake of influenza vaccination and regular health screening were lower, participation to the cancer screening was not lower compared to that of standard workers. CONCLUSION: There were gaps in the utilisation of preventive services among workers depending on their employment types. Access to preventive health care services of nonstandard workers, the self-employed, and unpaid family workers should be prioritised.

Development of a multimedia model (POPsLTEA) to assess the influence of climate change on the fate and transport of polycyclic aromatic hydrocarbons in East Asia.

A dynamic multimedia model (POPsLTEA) for an East Asia region was developed and evaluated to quantitatively assess how climate change (CC) alters the environmental fate and transport dynamics of 16 polycyclic aromatic hydrocarbons (PAHs) in air, water, soil, and sediment. To cover the entire model domain (25°N-50°N and 98°E-148°E) where China, Japan, and South and North Koreas are of primary concern, a total of 5000 main cells of 50km×50km size were used while 1008 cells of a finer spatial resolution (12.5km×12.5km) was nested for South Korea (33°N-38°N and 126°E-132°E). Most of the predicted concentrations agreed with the observed values within one order of magnitude with a tendency of overestimation for air and sediment. Prediction of the atmospheric concentration was statistically significant in both coincidence and association, suggesting the model's potential to successfully predict the fate and transport of the PAHs as influenced by CC. An example study of benzo(a)pyrene demonstrates that direction and strength of the CC influence on the pollution levels vary with the location and environmental media. As compared to the five year period of 2011 to 2015, the changes across the model domain in the annual geometric mean concentration over the years of 2021 through 2100 were predicted to range from 88% to 304%, from 84% to 109%, from 32% to 362%, and from 49% to 303%, in air, soil, surface water, and sea water, respectively, under the scenario of RCP8.5.

Assessment of climate change impact on the fates of polycyclic aromatic hydrocarbons in the multimedia environment based on model prediction.

The objective was to quantitatively understand the impacts of climate change (CC) under the A1B scenario on the contamination levels of 11 polycyclic aromatic hydrocarbons (PAHs) from pyrogenic sources in the environmental media based on model prediction. To predict the impacts of CC in South Korea, a revised version of KoEFT-PBTs, a dynamic multimedia model for persistent organic pollutants in South Korea, was used. Simulations were conducted for the period from 2000 to 2049 under the A1B scenario with the emission data for 2009 and the results for Seoul and Kangwon were compared to those under no climate change (NCC) scenario. Due to CC, the average of annual or monthly average concentration changes within a factor of two for the PAHs in air, soil and water. Time dependent comparison indicates that the maximum increase induced by CC in the monthly average concentration ranges from 10 to 10(2) in air and water. Change in advective flux due to wind speed difference between A1B and NCC dictates the change of the atmospheric PAHs levels while wet particle deposition due to rain rate difference contributes to some extent to the change of 5 and 6 ring PAHs. Whether the concentration change is positive or not depends primarily on the emission strength of internal sources relative to those in surrounding areas. The CC induced changes in atmospheric depositions and degradation rate in soil play a leading role in the change of soil concentration. In water, runoff and degradation are the key processes to the CC induced concentration change. Both in soil and water, the relative importance of individual key processes varies with PAHs. The difference between the two scenarios in wind speed and in rain rate shows stronger correlations with the concentration change than the temperature change.

Need of accurate model prediction of variability of the concentration ratio for testing coherence among environmental quality objectives: a case study of polycyclic aromatic hydrocarbons.

Maintaining coherence among environmental quality objectives (EQOs) should be an important consideration for the EQOs to be met simultaneously. The objectives of the present work were to demonstrate the need of accurate variability prediction by models and to present considerations in selecting models for testing coherence of the EQOs. SimpleBox and POPsME were chosen as the two different types of models to compare the prediction variability and its influence on the results of coherence test among the maximum permissible concentrations (MPCs) of polycyclic aromatic hydrocarbons (PAHs) in South Korea. False calls by these models on coherence were found to occur often due to inaccurate prediction of variability in the concentration ratio at steady state, strongly suggesting that models for coherence test should be accurate in predicting not only the point value representing the concentration ratio but the variability of the value. It was demonstrated that spatially resolved dynamic models would have an intrinsic advantage over one box steady state models in reducing the rate of false negative call.

Development and evaluation of a dynamic multimedia model (ECORAME) for local scale assessment of aquatic ecological exposure to chemicals originating from sources in environmental media.

Use of multimedia models (MMMs) has been limited in exposure assessment for aquatic ecosystems at local scale typically due to their coarse spatial resolution and inability to predict the individual concentrations of multiple streams within a watershed cell. An MMM named ECORAME is presented which overcomes the limitations by treating each water segment as an independent cell rather than a compartment within a watershed cell. This offers two advantages for exposure assessment, i.e., i) the spatial resolution for water is readily adjustable and ii) multiple water streams within one watershed cell could be handled individually. Model evaluation with respect to polycyclic aromatic hydrocarbons (PAHs) demonstrated that ECORAME's prediction of relative concentration agreed with measured values within a factor of five or less. A case study of PAHs using ECORAME shows that the concentration can change by more than 10 fold over the 40km main stream stretch of the Han River in Seoul, Korea. The concentration difference among multiple streams in the same watershed cell could be substantial (greater than 100 fold). Besides a need of finer spatial resolutons than those typically used in MMMs, the results strongly suggest that exposure prediction capability for individual streams in the same watershed is necessary for local scale assessment. As demostrated with ECORAME, the need can be effectively met by handling the water segments as individual cells in future MMMs.