• Journal of Environmental Health Sciences
• /
• v.48 no.4
• /
• pp.227-235
• /
• 2022

Background: Abandoned metal mines are classified as vulnerable areas with the highest level of soil contamination among risk regions. People living near abandoned metal mines are at increased risk of exposure to toxic metals. Objectives: This study aimed to evaluate the correlation between soil contamination levels in areas around abandoned metal mine and the blood lead levels of local residents. Moreover, we assess the possibility of using soil contamination levels as a predictive indicator for human exposure level. Methods: Data from the Survey of Residents around Abandoned Metal Mines (2013~2017, n=4,421) and Investigation of Soil Pollution in Abandoned Metal Mines (2000~2011) were used. A random coefficient model was conducted for estimation of the lower level (micro data) of the local resident unit and the upper level (macro data) of the abandoned metal mine unit. Through a fitted model, the variation of blood lead levels among abandoned metal mines was confirmed and the effect of the operationally defined soil contamination level was estimated. Results: Among the total variation in blood lead levels, the variation between abandoned mines was 18.6%, and the variation determined by the upper-level factors such as soil contamination and water contamination was 8.1%, which was statistically significant respectively. There was also a statistically significant difference in the least square mean of blood lead concentration according to the level of soil contamination (p=0.047, low: 2.32 ㎍/dL, middle: 2.38 ㎍/dL, high: 2.59 ㎍/dL). Conclusions: The blood lead concentration of residents living near abandoned metal mines was significantly correlated with the level of soil contamination. Therefore, in biomonitoring for vulnerable areas, operationally defined soil contamination can be used as a predictor for human exposure level to hazardous substances and discrimination of high-risk abandoned metal mines.

• Journal of Preventive Medicine and Public Health
• /
• v.31 no.3 s.62
• /
• pp.449-459
• /
• 1998

This study was started to find out if plasma malondialdehyde(MDA), $\alpha-tocopherol$ and erythrocyte superoxide dismutase(SOD) activity could be markers of biological activity resulting from exposed to lead in workers. Blood samples were randomly obtained from lead-exposed workers(n=29), $CO_2$, welders(n=60) and office workers(n=60). We used whole blood to analyse blood lead with atomic absorption spectrophotometer. Superoxide dismutase activity in erythrocyte was measured with spetrophotometer. MDA and $\alpha-tocopherol$ in plasma were measured with high performance liquid chromatography. Lead-exposed workers was significantly high in blood lead concentration$(29.37{\mu}g/d\ell)$ compared with welders$(6.42{\mu}g/d\ell)$ and office workers$(5.01{\mu}g/d\ell)$. The level of plasma MDA was significantly higher in the lead-exposed workers($1.87{\mu}mol/g$ cholesterol) than the welders($1.41{\mu}mol/g$ cholesterol) and office workers($1.41{\mu}mol/g$ cholesterol). Erythrocyte SOD activity in lead-exposed workers(56.80 U/g Hb) was significantly increased than those of welders(37.63 U/g Hb) and office workers(20.47 U/g Hb). The plasma $\alpha-tocopherol$ level of lead-exposed workers($4.93{\mu}g/g$ cholesterol) was statistically different from welders($4.25{\mu}g/g$ cholesterol) and office workers$4.28{\mu}g/g$ cholesterol). Neither age nor smoking was related to SOD or MDA level. Blood lead was significantly correlated with erythrocyte SOD activity(r=0.405), plasma MDA(r=0.296) and $\alpha-tocopherol$ (r=0.207). Plasma MDA was also significantly correlated with SOD (r=0.217). In multiple regression analysis, the change of MDA and SOD activity level related to the blood lead concentration. These results suggested that the increase of plasma MDA and erythrocyte SOD activity in lead-exposed workers had a close relationship with the oxidative stress induced by lead.

• Journal of Environmental Science International
• /
• v.19 no.4
• /
• pp.527-532
• /
• 2010

Exposure to lead, particularly at chronic low-dose levels, is still a major public health concern. The present study is aimed to evaluate the blood lead levels in populations resident in some abandoned mine areas of Chungbuk, Korea. Eight hundreds and sixty-six subjects who reside in abandoned mine area located in Chungbuk, Korea, were enrolled this study. We evaluated the blood lead level according to the age, gender, and working history in mines. For statistical analysis, SPSS ver 12.0 was used. The geometric mean blood lead levels was $2.93\;{\mu}g/{\ell}$ and nobody showed levels over the guidelines of WHO. Ex-smokers and current-smokers showed significantly higher blood lead levels compared to that of non-smokers. The blood lead levels in individuals with a history of working in a mine was higher than those in individuals without such histories. The populations resident in some Chungbuk abadoned mine area showed low levels of lead in blood. This suggest that lead poisoning might not be induced by abandoned mine in Chungbuk, Korea.

• Journal of Preventive Medicine and Public Health
• /
• v.24 no.4 s.36
• /
• pp.516-530
• /
• 1991

A case-control study was conducted to investigate the effect of low-level blood lead on the blood pressure. The plasma renin activity(PRA) was measured also to investigate one of the possible mechanisms by which lead nay play a role to influence on the blood pressure. Seventy-two hypertensive and sixty -nine control study subjects were selected from the workers who had no history of b-related lead exposure, in Ulsan city and it's vicinity, Korea. In addition to measuring blood lead levels and PRA, body mass index(BMI), hematocrit, serum sodium, potassium, creatinine, ionized calcium, and cholesterol were measured. Also, the habits of smoking, alcohol drinking and family history of hypertension were checked. The blood lead level of the hypertensive group was $19.8{\pm}5.5{\mu}g/dl$, which was significantly higher than that of the control group, $12.5{\pm}4.7{\mu}g/dl$(p<0.01). On multiple logistic regression analysis, the odds ratio of blood lead level on the occurence of high blood pressure was 1.38, also statistically significant (p<0.01). There was no significant differences between the hypertensive and the control group in the PRA or In (PRA), but there was a marginally significant linear relationship between blood lead and PRA in the hypertensive group(p<0.1). In conclusion, blood lead level which has been known to be within normal limits may be one of the possible risk factors of hypertension and PRA alteration by lead may act as one of the mechanisms.

• Journal of Preventive Medicine and Public Health
• /
• v.28 no.2 s.50
• /
• pp.398-405
• /
• 1995

We experienced a case of occupational lead poisoning employed in a secondary lead smelting plant for 12 years. The patient was 39-year-old male and had been felt dizziness, recent memory impairment and intermittent severe abdominal pain for 2 years. On admission, blood lead level was $92.9{\mu}g/dl$, urinary lead level was $19.9{\mu}g/l$ and zinc protoporphyrin level was $226.0{\mu}g/dl$. On the blood test, hemoglobin was 10.6g/dl and showed normocytic normochromic anemia. There were no abnormal findings in the biochemical and hormonal tests. Decrease of I.Q. and use of words in speaking were found in the psychiatric and psychologic examinations. We observed the finding of motor polyneuropathy in the nerve conduction velocity test. Computed tomographic finding showed calcification lesions in the basal ganglia, dentate nuclei, caudate nuclei, and especially characteristic multiple calcifications were located in the subcortical white matter.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1996.04a
• /
• pp.477-480
• /
• 1996

The main objective of this research is to develop the optimal control method for a Distribution Center - multi Branch inventory distribution system. With the continuous review policy, the distribution center places an order for specific order quantity to an outside supplier, and the order quantity is replenished after a certain lead time. Also, each branch places an order for particular order quantity to the distribution center to satisfy the customer demands, and receives the replenishment after a lead time. When an out of stock condition occurs during an order cycle, a backorder is placed to the upper level to fill the unfilled demands. With these situation, variable demand and variable lead time are used for better industrial practice. Futher, actual lead times with a generic lead time distribution are used in developing the control model. Under the actual lead time model, the customer service measures actually attained for the distribution center and each branch are explained as the effective customer service measures. Thus, throughout the optimal control (using computer search procedures), we can set the desired service levels for the distribution center and each branch to produce the effective service level for each branch which is consistent with the goal level of service for each branch. At the same time, the entire distribution system keeps minimum inventories.

• Journal of the Semiconductor & Display Technology
• /
• v.22 no.2
• /
• pp.104-111
• /
• 2023

The semiconductor industry, which relies on global supply chains, has recently been facing longer lead time for material procurement due to supply chain uncertainties. Moreover, since increasing customer satisfaction and reducing inventory costs are in a trade-off relationship, it is challenging to determine the appropriate safety stock level under demand and lead time uncertainties. In this paper, we propose a framework for determining safety stock levels by utilizing the optimization method to determine the optimal safety stock level. Additionally, we employ a linear regression method to analyze customer satisfaction scores and inventory costs based on variations in lead time and demand. To verify the effectiveness of the proposed framework, we compared safety stock levels obtained by the regression equations with those of the conventional method. The numerical experiments demonstrated that the proposed method successfully reduces inventory costs while maintaining the same level of customer satisfaction when lead time increases.

• Journal of Korea Water Resources Association
• /
• v.51 no.12
• /
• pp.1207-1216
• /
• 2018

Discharge or water level predictions at tidally affected river reaches are currently still a great challenge in hydrological practices. This research aims to predict water level of the tide dominated site, Jamsu bridge in the Han River downstream. Physics-based hydrodynamic approaches are sometimes not applicable for water level prediction in such a tidal river due to uncertainty sources like rainfall forecasting data. In this study, TensorFlow deep learning framework was used to build a deep neural network based LSTM model and its applications. The LSTM model was trained based on 3 data sets having 10-min temporal resolution: Paldang dam release, Jamsu bridge water level, predicted tidal level for 6 years (2011~2016) and then predict the water level time series given the six lead times: 1, 3, 6, 9, 12, 24 hours. The optimal hyper-parameters of LSTM model were set up as follows: 6 hidden layers number, 0.01 learning rate, 3000 iterations. In addition, we changed the key parameter of LSTM model, sequence length, ranging from 1 to 6 hours to test its affect to prediction results. The LSTM model with the 1 hr sequence length led to the best performing prediction results for the all cases. In particular, it resulted in very accurate prediction: RMSE (0.065 cm) and NSE (0.99) for the 1 hr lead time prediction case. However, as the lead time became longer, the RMSE increased from 0.08 m (1 hr lead time) to 0.28 m (24 hrs lead time) and the NSE decreased from 0.99 (1 hr lead time) to 0.74 (24 hrs lead time), respectively.

• Korean Management Science Review
• /
• v.13 no.1
• /
• pp.47-55
• /
• 1996

Rapid globalization of production and marketing functions makes choice of international transportation mode of great importance. In this paper, transportation mode is characterized by two factors, mean and variability of transportation lead time. We developed a simple mathematical model to estimate the relative impact of mean lead time, lead time variance and demand variance on the required average inventory level under specified service rates.

• Korean Journal of Community Nutrition
• /
• v.3 no.2
• /
• pp.167-173
• /
• 1998

This study was performed to assess the lead and cadmium status of children residing in urban factory area and to see if there is a difference of lead and cadmium status between the group with normal iron status. The mean lead concentration of male hair was 9.55ppm which is significantly higher than 6.61 ppm that of female. The mean lead concentration of male urine sample was 0.04ppm, 10.3ppm and $48.14\mu{g/L}$, which is higher than 0.08ppm, 6.08ppm and $20.69\mu{g/L}$ of normal group, respectively. In a suboptimal group the proportion of children whose urinary lead is higher than normal$(35\mu{g/L)$was 87.3%, whereas 2.5% for a normal group. The mean cadmium concentration of male hair was 2.58ppm, which is higher than 2.48ppm that of a female. The mean cadmium concentration of erythrocyte, hair and urine was 0.25ppm, 2.65ppm and $38.83\mu{g/L}$, which is higher than 0.20ppm, 2.40ppm and $19.78\mu{g/L}$ of the normal group, respectively. The proportion of children whose urinary cadmium level is higher than the low limit of risk of cadmium intoxication$(40\mu{g/L)}$ was 21.4%, whereas 0% for a mormal group. Urinary lead and cadmium level showed significantly negative correlation with the RBC count, hematocrit, hemoglobin and serum ferritin, whereas they had significantly positive correlation with FEP/Hb(p<0.01). There was no correlation between the IQ and the level of lead and cadmium.