Association between Low-level Mercury Exposure and Neurobehavioral Functions in Korean Adults Living in a Coastal City

OBJECTIVES: The aim of this study was to determine the association between low-level mercury exposure and neurobehavioral functions in adults living in coastal regions of Korea. METHODS: We selected 172 adults aged 20-65 years living in a city in the coastal region of Korea. A sociodemographic survey was conducted, mercury levels in the blood, urine, and hair were measured, and the associations according to computerized neurobehavioral tests were determined using univariate analysis. After adjustment for associated variables, a multivariate linear regression analysis was performed. RESULTS: The geometric mean mercury levels in the blood, urine, and hair were 5.41 microg/L (range, 0.00-15.84 microg/L), 1.17 microg/g-creatinine (range, 0.00-32.86 microg/g-creatinine), and 1.37 mg/kg (range, 0.42-6.56 mg/kg), respectively. Variables that were associated with simple reaction time according to the neurobehavioral test results were age and urine mercury level. Variables associated with choice reaction time were the recent use of Korean traditional medicine and urine mercury level. Variables associated with the right-hand finger tapping speed test were age, gender, smoking behavior, education level, monthly household income, and urine mercury level. Variables associated with the left-hand finger tapping speed test were age, gender, education level, and urine mercury level. After adjustment for associated variables, there was no significant association between urine mercury level and simple reaction time (beta=25.96; p=0.47), choice reaction time (beta=50.37; p=0.32), or the number of left-hand finger taps (beta=-1.54; p=0.21). However, urine mercury level was significantly associated with the number of right-hand finger taps (beta=-3.86; p=0.01). CONCLUSIONS: We found no evidence that low-level mercury exposure in adults is associated with deficits in neurobehavioral functions. A longer follow-up study is required to confirm this conclusion.

Effect of Partial Sleep Deprivation on Auditory Event Related Potential and Reaction Time in Medical Students.

The aim of the present study was to evaluate the effects of partial sleep deprivation on the cognitive status and alertness of medical students using auditory event related potential (ERP) and auditory reaction time (RT) using sleep questionnaire, Stanford Sleepiness Scale (SSS), auditory ERP (P300) and RT. Sleep time was significantly shorter in the test condition as compared to the baseline values (p<0.001). Significantly higher values on the SSS (p<0.05) were found after sleep restriction. The P300 latency and amplitude significantly decreased (p<0.01 and p<0.001 respectively) when the test values were compared to the baseline. RT also showed a significant decrease (p<0.001) in the test condition as compared to the baseline values. However, no significant correlation could be ascertained between SSS and P300 amplitude and latency as well as RT. This study demonstrates that partial sleep deprivation produces variable effects on the cognitive status of medical students as reflected by the decrease in P300 amplitude and latency. Alertness of medical students seemed to show an improvement as reflected by the decrease in RT.

Relationship between Blood Lead Concentration and Neurobehavioral Function of Children / 대한산업의학회지

OBJECTIVES: To evaluate effects of lead on the central nervous system of children by measuring blood lead concentration, computerized neurobehavioral function and intelligence of elementary school students. METHODS: The study was conducted with 208 elementary school students living in the vicinity of Pohang Industrial Complex in October and November, 2005. Data on demographic characteristics, living environments and lifestyle habits were collected from subjects. RESULTS: Blood lead levels of elementary school students ranged from 0.76-4.97 microg/dl, which is below the 10 microg/dl recommended level of CDC. The blood lead levels were similar with those reported in other domestic and international studies. Neurobehavioral tests revealed that most third grade students reacted slowly and their speed declined in simple reaction time (p or =3.00 microg/ dl was 3.21 in third grade students and 4.28 in sixth grade students. Low academic achievement was observed among third grade students (p<0.05) and six grade students (p<0.05) as the average blood lead level increased. Correlation analysis on the association of blood lead concentration with neurobehavioral tests revealed a positive correlation between blood lead levels and reaction time of choice reaction time and symbol digit substitution in third grade students. A positive correlation was observed between blood lead levels and reaction time of symbol digit substitution and finger tapping speed in sixth grade students. There was a negative correlation between blood lead levels and reasoning ability of third grade students (r=-0.247) and vocabulary ability of six grade students (r=-0.255). CONCLUSION: There have been few studies on the effects of blood lead on the central nervous systems of children in Korea. The study supports the findings of earlier studies that blood lead has an impact on children. However, the study did not confirm significant association of blood lead concentration with each neurological and motor test conducted for this study due to a small sample size and relatively low blood lead levels of elementary school students. Further studies using a similar assessment methods would be helpful to evaluate the effects of low blood lead levels on the central nervous systems of children.

Relationship between Blood Lead Concentration and Neurobehavioral Function of Children / 대한산업의학회지

OBJECTIVES: To evaluate effects of lead on the central nervous system of children by measuring blood lead concentration, computerized neurobehavioral function and intelligence of elementary school students. METHODS: The study was conducted with 208 elementary school students living in the vicinity of Pohang Industrial Complex in October and November, 2005. Data on demographic characteristics, living environments and lifestyle habits were collected from subjects. RESULTS: Blood lead levels of elementary school students ranged from 0.76-4.97 microg/dl, which is below the 10 microg/dl recommended level of CDC. The blood lead levels were similar with those reported in other domestic and international studies. Neurobehavioral tests revealed that most third grade students reacted slowly and their speed declined in simple reaction time (p or =3.00 microg/ dl was 3.21 in third grade students and 4.28 in sixth grade students. Low academic achievement was observed among third grade students (p<0.05) and six grade students (p<0.05) as the average blood lead level increased. Correlation analysis on the association of blood lead concentration with neurobehavioral tests revealed a positive correlation between blood lead levels and reaction time of choice reaction time and symbol digit substitution in third grade students. A positive correlation was observed between blood lead levels and reaction time of symbol digit substitution and finger tapping speed in sixth grade students. There was a negative correlation between blood lead levels and reasoning ability of third grade students (r=-0.247) and vocabulary ability of six grade students (r=-0.255). CONCLUSION: There have been few studies on the effects of blood lead on the central nervous systems of children in Korea. The study supports the findings of earlier studies that blood lead has an impact on children. However, the study did not confirm significant association of blood lead concentration with each neurological and motor test conducted for this study due to a small sample size and relatively low blood lead levels of elementary school students. Further studies using a similar assessment methods would be helpful to evaluate the effects of low blood lead levels on the central nervous systems of children.