Geon-Woo Lee

Estimation of health risk and effective dose based on measured radon levels in Korean homes and a qualitative assessment for residents’ radon awareness

More than 50% of the worldwide effective radiation dose from natural sources is known to be due to 222Rn. Indoor radon levels were measured in homes with long-term exposure and in relation to time spent for residents. Measurements were conducted after categorizing homes by type, and the results (mean ± S.D) showed that detached houses, apartments and multifamily houses had radon concentrations of 97 ± 110, 51 ± 24 and 59 ± 34 Bq/m3, respectively. Surveys were conducted with 620 people to analyse resident awareness of radon levels and time that residents spend in homes. Using these results, the annual effective dose and risk level were computed. The survey showed that residents of Korean homes had little awareness regarding the source of radon, exposure routes and contamination levels. The excess risk of lung cancer after exposure for 70 years was determined to be 0.55/100 people, which jumped to 2.7/100 people for residents in detached houses in highly exposed areas. Compared to the effects of radon exposure in workplaces and schools, the health risks from radon in Korean homes are especially high. Therefore, the management policies for susceptible groups are important.

House-plant placement for indoor air purification and health benefits on asthmatics

Objectives Some plants were placed in indoor locations frequented by asthmatics in order to evaluate the quality of indoor air and examine the health benefits to asthmatics. Methods The present study classified the participants into two groups: households of continuation and households of withdrawal by a quasi-experimental design. The households of continuation spent the two observation terms with indoor plants, whereas the households of withdrawal passed the former observation terms with indoor plants and went through the latter observation term without any indoor plants. Results The household of continuation showed a continual decrease in the indoor concentrations of volatile organic compounds (VOCs) during the entire observation period, but the household of withdrawal performed an increase in the indoor concentrations of VOCs, except formaldehyde and toluene during the latter observation term after the decrease during the former observation term. Peak expiratory flow rate (PEFR) increased in the households of continuation with the value of 13.9 L/min in the morning and 20.6 L/ min in the evening, but decreased in the households of withdrawal with the value of -24.7 L/min in the morning and -30.2 L/min in the evening in the first experimental season. All of the households exhibited a decrease in the value of PEFR in the second experimental season. Conclusions Limitations to the generalizability of findings regarding the presence of plants indoors can be seen as a more general expression of such a benefit of human-environment relations.

Rational design of oxide/carbon composites to achieve superior rate-capability via enhanced lithium-ion transport across carbon to oxide

Coating oxides with conductive carbon is a widely used strategy to improve the rate capability of oxides by enhancing their electronic conductivity. However, there is a growing concern that a carbon layer may hinder lithium-ion transport to oxides, thus limiting the rate capability. Nonetheless, this issue has not yet been thoroughly investigated, and whether lithium-ion transport across a carbon layer does indeed limit the rate capability remains unclear. To single out the effect of lithium-ion transport across a carbon layer on the rate capability, we propose the rational design and synthesis of nano-perforated graphene (NPG)-wrapped oxide composites using commercial Li4Ti5O12 (LTO) and LiFePO4 (both with a particle diameter of ∼70 nm), wherein the NPG has nano-perforations on the basal plane of graphene. As the number of nano-perforations in the composites increases, the rate capability significantly increases. For example, NPG-wrapped LTO shows a specific capacity of 117.9 mA h g−1 at 100C and could be stably charged–discharged even at 300C. The excellent rate capability is mainly due to the enhancement of lithium-ion transport through the nano-perforations of NPG. Cyclic voltammetry and impedance analyses reveal that the improved rate capability of NPG-wrapped LTO is closely associated with an increase in the area of electrochemically active sites of LTO in the composite due to the enhanced lithium-ion transport through the nano-perforations of NPG, indicating that lithium-ion transport across a carbon layer could limit the rate capability of oxides coated with highly conductive carbon. These salient results will provide further impetus to the design and synthesis of novel high-rate carbon-coated oxides.

Value of a statistical life estimation of carcinogenic chemicals for socioeconomic analysis in Korea.

Objectives To protect public health from risk, the Minister of Environment in Korea legislated an act concerning the registration and evaluation of chemical substances. In this study, we estimated the value of a statistical life (VSL) of carcinogenic chemicals to evaluate the socioeconomic analysis in Korea. Methods The estimation of the health benefit can be calculated through an individual’s VSL and willingness to pay (WTP). To estimate the VSL and WTP, we used a contingent valuation method through a web-based survey. Results The survey is conducted with 1434 people living in Seoul and six large cities. An analysis of the survey is essential to review the distribution of the characteristics of the target population. The statistically significant variables affecting the WTP are location, age, household income, quality of life. Through the review of data, we secured statistical validity. The WTP was estimated as 41205 Korean won (KRW)/person, and the estimated VSL appeared as 796 million KRW/person. Conclusions There is a case in which the amount of statistical life value is estimated in connection with domestic environmental policy, fine dust, etc. However, there are no cases of evaluation for chemical. The utilization of this result is possible for conducting other study with chemicals.

The evaluation of cost-of-illness due to use of cost-of-illness-based chemicals

Objectives This study is conducted to estimate the cost paid by the public suffering from disease possibly caused by chemical and to examine the effect on public health. Methods Cost-benefit analysis is an important factor in analysis and decision-making and is an important policy decision tool in many countries. Cost-of-illness (COI), a kind of scale-based analysis method, estimates the potential value lost as a result of illness as a monetary unit and calculates the cost in terms of direct, indirect and psychological costs. This study estimates direct medical costs, transportation fees for hospitalization and outpatient treatment, and nursing fees through a number of patients suffering from disease caused by chemicals in order to analyze COI, taking into account the cost of productivity loss as an indirect cost. Results The total yearly cost of the diseases studied in 2012 is calculated as 77 million Korean won (KRW) per person. The direct and indirect costs being 52 million KRW and 23 million KRW, respectively. Within the total cost of illness, mental and behavioral disability costs amounted to 16 million KRW, relevant blood immunological parameters costs were 7.4 million KRW, and disease of the nervous system costs were 6.7 million KRW. Conclusions This study reports on a survey conducted by experts regarding diseases possibly caused by chemicals and estimates the cost for the general public. The results can be used to formulate a basic report for a social-economic evaluation of the permitted use of chemicals and limits of usage.