Neurotoxic effect of exposure to low doses of mercury

OBJECTIVES: To assess early effects on the Central Nervous System due to occupational exposure to low levels of inorganic mercury (Hg) in a multicenter nationwide cross-sectional study, including workers from chloro-alkali plants, chemical industry, thermometer and fluorescent lamp manufacturing. The contribution of non-occupational exposure to inorganic Hg from dental amalgams and to organic Hg from fish consumption was also considered. METHODS: Neuropsychological and neuroendocrine functions were examined in a population of 122 workers occupationally exposed to Hg, and 196 control subjects, not occupationally exposed to Hg. Neuropsychological functions were assessed with neurobehavioral testing including vigilance, motor and cognitive function, tremor measurements, and with symptoms concerning neuropsychological and mood assessment. Neuroendocrine functions were examined with the measurement of prolactin secretion. The target population was also characterized by the surface of dental amalgams and sea fish consumption. RESULTS: In the exposed workers the mean urinary Hg (HgU) was 10.4 +/- 6.9 (median 8.3, geometric mean 8.3, range 0.2-35.2) micrograms/g creatinine, whereas in the control group the mean HgU was 1.9 +/- 2.8 (median 1.2, geometric mean 1.2, range 0.1-33.2) micrograms/g creatinine. The results indicated homogeneous distribution of most neurobehavioral parameters among exposed and controls. On the contrary, finger tapping (p < 0.01) and the BAMT (Branches Alternate Movement Task) coordination test (p = 0.05) were associated with occupational exposure, indicating an impairment in the exposed subjects. Prolactin levels resulted significantly decreased among the exposed workers, and inversely related to HgU on an individual basis (p < 0.05). An inverse association was also observed between most neuropsychological symptoms and sea fish consumption, indicating a "beneficial effect" from eating sea fish. On the contrary, no effects were observed as a function of dental amalgams. CONCLUSIONS: In conclusion, this study supports the finding of early alterations of motor function and neuroendocrine secretion at very low exposure levels of inorganic Hg, below the current ACGIH BEI and below the most recent exposure levels reported in the literature.     

Evaluation of the neurotoxic and nephrotoxic effects following long-term exposure to metallic mercury in employed at a chlorine/sodium-hydroxide plant

OBJECTIVES: Within the frame work of a wide multicentre study, a sub-study was developed in order to explore the occurrence of early effects on the central nervous system, on the kidney and on the neuro-immune system in the workers of a chloro-alkali production plant exposed to metallic mercury at airborne concentration levels lower than 0.025 mg/m3 (TLV-TWA). They were compared to a control population of employees of the same huge petrochemical plant with different job that did not implicate exposure to mercury vapors. Specifically, the study aimed at revealing the occurrence of early effects on the central nervous system related with mercury exposure, as can be assessed through neurophysiological and neurobehavioral tests. METHODS: The excretion of urinary mercury was measured by atomic absorption spectrometry. The study of renal function was assessed by measurement of the urinary excretion of some high and low molecular weight protein markers (albumin, beta 2-microglobulin, retinol-binding protein, fibronectin, specific proximal tubule brush border antigens, N-acetyl-beta-D-glucosaminidase). The neurobehavioral status of the study subjects was assessed by means of several test parameters (Simple Reaction Time, Color Word Vigilance Test, Symbol Digit, Finger Tapping, Mood Scale of Kjellberg and Iwanowski, Subjective symptoms questionnaire (QSS), Luria Nebraska Motor Scale, Branches Alternate Movement Task and Tremometry). RESULTS: The values of urinary excretion averaged 12 +/- 8 micrograms Hg/g of creatinine for the exposed workers group (n = 38), while for the reference group (n = 34 cases) urinary excretion was statistically lower, averaging 4 +/- 6 micrograms Hg/g of creatinine. Neither the parameters selected for the assessment of renal functions, nor those chosen to probe the neurobehavioral status of the probands revealed statistically reliable differences between the group of exposed workers (length of exposure: range 1-34 years) and the control group. Nevertheless, some minor but still statistically reliable correlations were found between some neurobehavioral parameters and some demographic variables describing the whole group of tested workers, but not to the level of occupational exposure to mercury. CONCLUSIONS: The results of the study confirm the lack of toxic effects of clinical importance on the central nervous system and on the kidney for values of mercury urinary excretion lower than the suggested index of biological exposure (IBE) of 35 micrograms Hg/gram of creatinine.     

Urinary and blood markers of internal mercury dose in workers from a chlorakali plant and in subjects not occupationally exposed: relation to dental amalgam and fish consumption

OBJECTIVES: The aim of this paper was both to evaluate the internal dose of Hg in occupationally exposed workers (35 Chloralkali workers) compared to that of non occupationally exposed controls (40 workers of the same plant of Portotorres and 22 residents on the island of Carloforte, usual consumers of local fish, mostly tuna fish with relatively high Hg levels) and to assess the relevance of environmental and individual exposure factors linked to lifestyle, sea fish consumption and amalgam fillings. METHODS: All subjects filled out a questionnaire concerning the working history and lifestyle. The amalgam fillings area was measured by medical inspection using a standardised schedule attached to the questionnaire. Mercury in urine (HgU) was measured in all cases, while in a subgroup of our study total blood mercury (HgB) and its organic and inorganic component were also assessed. Furthermore, for 8 of the Carloforte group mercury in hair was also available. RESULTS: Values of urinary mercury excretion of the Chloralkali workers were significantly higher (median value of 15.4, range 4.8-35.0 micrograms/g creatinine, 94.3% of the cases having values > 5 micrograms/g creatinine) than those observed both among the reference group (median value of 1.9, range 0.4-5.6 micrograms/g creatinine, 12.5% of the cases having values a little greater than 5 micrograms/g creatinine) and among the residents in Carloforte (median value of 6.5, range 1.8-21.5 micrograms/g creatinine, 59.1% of the cases having values > 5 mcg/g creatinine). The HgU values observed in this group were in turn significantly higher than those of the non occupationally exposed workers living near Sassari (p = 0.03). Only in this last group were the HgU concentrations statistically significantly related to the extension of the amalgam fillings area (Pearson r = 0.53, p < 0.01). In the Carloforte group HgU was significantly related to the number of fish meal consumed per week (Pearson r = 0.48, p < 0.02). HgB (median value of 5.9, range 3.4-21.6 micrograms/l) as well as its inorganic component (median value of 2.4, range 1.8-4.6 micrograms/l) were significantly higher in the Chloralkali group compared to the other two groups. In all cases of the Carloforte group the ratio between the organic component and the total HgB was higher than 85%, while this ratio was significantly lower in the other two groups. The relationship between HgU and HgB was statistically significant, considering both total blood mercury and the inorganic and the organic components separately. A statistically significant relationship between the sea fish consumption per week and both total HgB (Pearson r = 0.82) and the organic component in this matrix (Pearson r = 0.84, p < 0.001) was observed among 16 non-occupationally exposed subjects. However, the significant relationship between organic blood mercury and sea fish consumption was almost entirely supported by the data observed in the Carloforte group. Total hair mercury levels analysed in 8 subjects of the Carloforte group were high (median value of 9.6, range 1.4-34.5 micrograms/g) and significantly related to sea fish consumption, and to both the individual Hg urinary excretion (Pearson r = 0.83) and to the organic component of blood mercury (Pearson r = 0.87). CONCLUSIONS: According to several experimental human and animal trials and to some recent studies on methylmercury toxicokinetic models, our results suggest that the organic compounds absorbed by usual sea fish consumption may be partially demethylated, increasing the inorganic Hg concentration in the kidney and consequently its urinary excretion, as was observed in the Carloforte group.     

Neurobehavioral changes of shipyard painters exposed to mixed organic solvents

This study was conducted to evaluate neurobehavioral changes arising from occupational exposure to organic solvents among shipyard painters and to establish whether a dose-effect relation existed where there was any observed impairment of neurobehavioral performance by running the test of Simple Reaction Time (SRT), Symbol Digit Substitution (SD), and Finger Tapping Speed (FT) with a computer-assisted neurobehavioral test battery. The study group consisted of 180 shipyard painters and 60 reference workers. The workers answered a self-administered questionnaire on occupational, medical history, and demographic characteristics including age, work duration, education level, and quantity and frequency of alcohol and smoking, and performed three psychometric tests on the Korean Computerized Neurobehavioral tests. To estimate cumulative exposure level, samples of ambient air on 61 painters were analyzed using a gas chromatograph. Shipyard painters and the reference group showed significant differences in the results of test of SD, FT of dominant hand, and FT of non-dominant hand. The test results of SD of shipyard painters also showed significant difference by duration of work. This suggests that occupational exposure of organic solvent could induce neurobehavioral changes in the shipyard painters. Therefore an objective neurobehavioral tests recommended on evaluating neurobehavioral performance of long-term solvent-exposed shipyard workers.     

电焊作业对工人神经行为功能的影响

目的探讨电焊作业对作业工人神经行为功能的影响。方法采用世界卫生组织（WHO）推荐的神经行为核心测试组合（Neurobehavioural Core Test Batteries简称NCTB）,对45名无急、慢性锰中毒作业工人和对照组45名工人的情感状态（Profiles of Mood States Test简称POMS）、简单视觉运动反应时、数字跨度、手提转捷度、数字译码、Benton视觉保留、目标测试Ⅱ等进行测试,并对测试结果进行比较分析。结果发现电焊作业组工人在抑郁、疲劳、精力充沛三项情感状态指标与对照组比较有明显差异（P〈0．01,P〈0．05）;发现电焊作业组工人在简单视觉运动反应时、数字跨度、手提转捷度、数字译码、Benton视觉保留与对照组比较差异有非常显著性（P〈0．01）。结论电焊作业对神经行为功能有一定影响,工龄与神经行为负效应关系不明显。     

职业性接汞对神经行为功能的影响

对５６名无症状的接触汞工人进行了神经行为功能测试。结果表明：接触组的数字跨度、提转捷度、数字译码、视觉保留以及情感状态的有力－好动项得分明显低于对照组；简单反应时的各项指标匀较对照组慢；而情感状态的疲惫惰性项、因惑－迷茫项得分高于对照组。提示汞对接触者的损伤主要表现为运动直辖市能力、记忆力、反应能力及情感状态的改变。     

Mercury levels in urine and hair of children in an Andean gold-mining settlement

This field study investigated mercury (Hg) levels in urine and hair of Andean children of indigenous Saraguro and Metizo gold miners in the Nambija, Ecuador gold mining settlement. Spot samples of urine and hair samples were collected concurrently from 80 children each. Urine samples were used to determine the inorganic Hg burden, while hair samples were used as an index of methylmercury (MeHg) exposure from consumption of Hg contaminated fish. The mean level of Hg in urine (HgU) was 10.9 microg/L, and the mean level in hair (HgH) was 6.0 microg/g. Regression analysis showed a significant association (r = 0.404, p = 0.0007) between matched HgU and HgH samples. Mean HgU and HgU levels tended to be higher for children aged 6-14 years than for a younger group. The wide range of Hg levels in the urine and hair of Andean children of gold miners may place them at risk for neurodevelopmental and learning disorders.     

汞接触者行为毒理学评价方法的探讨

本文综合有关文献后提出包含八项神经行为测试组合,对35名金属汞接触者及其对照组进行了神经行为和若干实验室指标测试及多类判别分析等统计处理。结果发现,汞接触者在临床、实验室指标未发现异常下,神经行为已出现改变:认识功能尤其是记忆力、注意力方面,还有手工操作敏捷度、手运动速度方面均明显下降。在情感方面表现为厌烦、易疲劳。我们认为汞接触者行为功能测试可以作为汞中毒早期评价指标,其指标组合以本顿视觉保留测试、简单反应时及数字广度为佳。     

Renal effects of low doses of mercury

OBJECTIVES: The present study was aimed at investigating early markers of renal damage and dysfunction in subjects exposed to low doses of mercury from different sources. Different groups of subjects were examined with urinary Hg excretion (HgU) ranging from 0.1 to 35.0 micrograms/g creatinine: 122 occupationally exposed workers, 22 subjects living in a non-polluted area, but consuming large amounts of tuna and sword fish, and 197 controls. METHODS: Several markers of renal changes were measured in urine (albumin, fibronectin, beta 2-microglobulin, retinol-binding protein, tubular antigens, N-acetyl-beta-D-glucosaminidase activity) and serum (beta 2-microglobulin and cystatin C). Serum autoantibodies towards collagen, laminin and tubular antigens were assessed in subjects with abnormal renal markers. The role of glutathione-S-tranferases GSTT1 and GSTM1 polymorphisms in the inter-individual variability of biological response to Hg was also investigated. RESULTS: Renal markers were not correlated with HgU. None of such markers differed significantly between exposed workers and controls, except for urinary beta 2-microglobulin, which was decreased in Hg-exposed workers (GM = 55.8 vs 86.6 micrograms/g creatinine), in the absence of any changes in serum concentration. Subjects usually eating tuna and sword fish showed an increased urinary excretion of beta 2-microglobulin, albumin and fibronectin. Serum titres of auto-antibodies did not differ between the groups. Neither in controls nor in exposed workers were the observed differences modified by the GSTM1 and GSTT1 genotypes. CONCLUSION: The present study did not provide evidence of any changes in kidney integrity and function in subjects exposed to very low levels of inorganic Hg resulting in urinary Hg lower than 35 micrograms/g creatinine. Nor did we obtain evidence of Hg-induced autoimmunity towards kidney components. The potential modifying role of GST polymorphisms could not be clarified in the absence of effects associated with exposure to the risk factor, i.e., to inorganic Hg. Preliminary data suggesting nephrotoxic effects of organic Hg from a diet rich in large fish resulting in increased levels of both blood and urinary Hg--which however did not exceed 20 micrograms/g creatinine--deserves further investigation.     

Surveillance of workers exposed to mercury vapour:validation of a previously proposed biological threshold limit value for mercury concentration in urine

A cross-sectional epidemiological study was carried out among subjects exposed to mercury (Hg) vapour, ie, a group of 131 male workers (mean age: 30.9 yr; average duration of exposure, 4.8 yr) and a group of 54 female workers (mean age, 29.9 yr; average duration of exposure 7 yr). The results were compared with those obtained in well-matched control groups comprising 114 and 48 male and female workers, respectively. The intensity of current Hg vapour exposure was rather moderate as reflected by the levels of mercury in urine (HgU) (mean and 95th percentile: males 52 and 147 micrograms/g creatinine; females 37 and 63 micrograms/g creatinine) and of mercury in blood (mean and 95th percentile: males 1.4 and 3.7 micrograms/dl; females 0.9 and 1.4 microgram/dl). Several symptoms mainly related to the central nervous system (memory disturbances, depressive feelings, fatigue, irritability) were more prevalent in the Hg-exposed subjects. They were, however, not related to exposure parameters. In both male and female Hg-exposed workers no significant disturbances were found in short-term memory (audioverbal), simple reaction time (visual), critical flicker fusion, and colour discrimination ability. Only slight renal tubular effects were detected in Hg-exposed males and females, ie, an increased urinary beta-galactosidase activity and an increased urinary excretion of retinol-binding protein. The prevalence of these preclinical renal effects was more related to the current exposure intensity (HgU) than to the duration of exposure and was detected mainly when HgU exceeds 50 micrograms/g creatinine. Changes in hand tremor spectrum recorded with an accelerometer were found in the Hg-exposed males only. The prevalence of abnormal values for some hand tremor parameters (total velocity and total displacement in the 2-50-Hz band) was mainly increased in male workers exposed for more than 10 yr. Unlike the renal tubular effects, the preclinical signs of tremor were more related to the integrated exposure than to the current exposure. Since the female workers, who have been exposed to Hg vapour levels usually insufficient to increase their HgU levels above 50 micrograms/g creatinine, did not exhibit any change in hand tremor pattern, the results of the present study tend to validate our previously proposed biological threshold limit value of a HgU of 50 micrograms/g creatinine for workers chronically exposed to mercury vapour.     

应用手工化测试研究机动车尾气污染对儿童神经行为功能的

目的采用手工化神经行为功能测试初步探讨低水平机动车尾气暴露对儿童神经行为功能的影响。方法根据环境监测数据和道路机动车流量，在福建省泉州市某区选择机动车尾气污染程度不同的2所小学作为研究现场。以调查学校二、三年级所有学生为研究对象，进行问卷调查和神经行为功能测试，最后选择在当地居住时间≥3年、测试时健康状况良好的861名儿童进行分析。结果2所学校瑞文测试得分基本相同；学校B划消测试得分低于学校A，但是差异无统计学意义（P=0．071）；ANOVA显示学校B儿童的数字符号、目标瞄准追踪、符号记入、连接数字测试的得分显著低于学校A（P〈0．001）。在控制其他因素后，位于机动车尾气污染严重地区的学校B儿童的数字符号、目标瞄准追踪、符号记入、连接数字测试的得分比低暴露的学校A的儿童分别低2．9、11．5、5．6和1．6分，差异有统计学意义（P〈0．001）。结论长期低水平机动车尾气暴露对儿童的神经行为功能有不良影响。     

汞作业工人神经行为功能的研究

对某金矿工人１９９人（对照组１０８人）进行的神经行为功能研究表明：接触组情绪状况得分（除有力－好动一项）和其余各项行为学指标得分均低于对照组。且随接触汞浓度增加，大多数行为功能得分呈递减趋势。在较低汞浓度接触组（平均为０．０１１４ｍｇ／ｍ＾３）神经行为功能得分明显低于对照组。尿汞含量〈４９．８５ｎｍｏｌ／Ｌ的汞作业工人神经行为异常人数明显高于对照组。提示：长期职业接触汞蒸气在未引起明显的临床损害之     

The inhibition of mercury absorption by dietary ethanol in humans: cross-sectional and case-control studies

Aims: To investigate this phenomenon in a large scale human study with low level Hg exposed dentists.

Methods: Data were collected for a sample of 1171dentists, and both cross sectional and case-control methods were utilised to examine the data.

Results: Abstainers (n = 345) had significantly higher urinary mercury concentrations (HgU) than drinkers (n = 826): 5.4 µg/l v 4.8 µg/l. Multiple linear regression showed a significant effect of ethanol dose on HgU after adjusting for potential confounders. A case-control analysis in which cases were defined as those individuals with urinary Hg concentrations of 15 µg/l (≈ top 5%), and controls as those with concentrations of <1.0 µg/l (≈ bottom 5%), showed a clear protective dose-response relation; there was a decreasing risk of being a "case" (having an HgU 15 µg/l) with increasing ethanol consumption. The significance of the adjusted model is p<0.001, and the χ² test for trend across ethanol consumption categories in the adjusted model is p<0.05, confirming the dose-response relation.

Conclusion: We believe that this straightforward investigation provides the first specific confirmation in a large scale human study of the inhibitory effect of ethanol on urinary mercury concentration, and by inference, on mercury absorption.

     

Comparison of renal function and psychomotor performance in workers exposed to elemental mercury

Summary Renal function and psychomotor performance (eye-hand coordination, arm-hand steadiness) of a group of 43 workers exposed to mercury vapor were examined. Their mean age and average duration of exposure to mercury were 38 and 5 years, respectively. The results were compared with those obtained in a matched group of 47 control workers. Increased proteinuria and albuminuria were found slightly more prevalent in the Hg-exposed group than in the control workers. These results are in agreement with those found during a previous study carried out in another group of workers also exposed to elemental mercury (Bucket et al. 1980). The scores of the psychomotor tests were less satisfactory in the Hg workers than in the control workers, the arm-hand steadiness test being more discriminative than the eye-hand coordination test. Preclinical changes in psychomotor function can be detected independently of the presence of signs of renal dysfunction. No clear-cut relationships were found between the prevalence of abnormal psychomotor scores and the level of mercury in blood (HgB) or in urine (HgU). Increased prevalences of abnormal psychomotor scores seem however to occur for HgB between 1 and 2 g/100 ml and for HgU between 50 and 100 g/g creatinine. Therefore, a biologic threshold limit value of 50 g/g creatinine is proposed for urinary mercury to prevent the development of preclinical effects on the central nervous system. A similar critical HgU level based on renal dysfunction prevalences has been suggested in a previous study.This study was supported by a grant from the Commission of the European Communities     

Urinary excretion of mercury after occupational exposure to mercury vapour and influence of the chelating agent meso-2,3-dimercaptosuccinic acid (DMSA).

The spontaneous and chelator mediated excretion of mercury in urine was investigated in male subjects occupationally exposed to mercury vapour (alkaline battery and chloralkali plants) who did not exhibit any sign of kidney damage. The time course of the spontaneous elimination of mercury in urine was examined in seven workers (age 22-40) who had been removed from exposure to mercury vapour (average duration of exposure 4.4 years) because their urinary mercury concentrations repeatedly exceeded 100 micrograms/g creatinine. The post exposure observation period started 10 to 29 days after the date of removal and lasted about 300 days (slow HgU elimination phase). For each worker, the kinetics of the spontaneous HgU decline followed a first order process; the biological half life ranged from 69 to 109 days (mean 90 days). The increased urinary excretion of mercury after a single oral administration of 2 g meso-2,3-dimercaptosuccinic acid (DMSA) was investigated in 16 control workers (group A; age 23 to 49), in 11 workers removed from exposure for at least two years (group B; age 27 to 41), and in 16 workers currently exposed to mercury vapour (group C; age 21 to 58). In group C, the DMSA experiment was repeated twice (three weeks before and three weeks after a holiday) after measures had been taken to reduce the mercury emission. The urinary mercury excretion was significantly higher during the 24 hours after DMSA administration in all groups compared with that in the 24 hours before. The bulk (50-70%) of the DMSA stimulated mercury excretion appeared within the first eight hours. In each group, the amount of mercury (microgram Hg/24h) excreted after DMSA was significantly correlated with that before administration of DMSA. The groups whose exposure had ceased, however, exhibited much higher correlation for coefficients (r=0.97 for group B and 0.86 for group C after three weeks of holiday) than those currently exposed to mercury vapour (r-0.66 for group C before and 9.58 after reduction of exposure). The data suggest that after a few days of cessation of occupational exposure to mercury vapour the HgU before and after administration of DMSA mainly reflects the amount of mercury stored in the kidney, which represents a mercury pool with a slow turnover.     

Urinary excretion of mercury after occupational exposure to mercury vapour and influence of the chelating agent meso-2,3-dimercaptosuccinic acid (DMSA).

The spontaneous and chelator mediated excretion of mercury in urine was investigated in male subjects occupationally exposed to mercury vapour (alkaline battery and chloralkali plants) who did not exhibit any sign of kidney damage. The time course of the spontaneous elimination of mercury in urine was examined in seven workers (age 22-40) who had been removed from exposure to mercury vapour (average duration of exposure 4.4 years) because their urinary mercury concentrations repeatedly exceeded 100 micrograms/g creatinine. The post exposure observation period started 10 to 29 days after the date of removal and lasted about 300 days (slow HgU elimination phase). For each worker, the kinetics of the spontaneous HgU decline followed a first order process; the biological half life ranged from 69 to 109 days (mean 90 days). The increased urinary excretion of mercury after a single oral administration of 2 g meso-2,3-dimercaptosuccinic acid (DMSA) was investigated in 16 control workers (group A; age 23 to 49), in 11 workers removed from exposure for at least two years (group B; age 27 to 41), and in 16 workers currently exposed to mercury vapour (group C; age 21 to 58). In group C, the DMSA experiment was repeated twice (three weeks before and three weeks after a holiday) after measures had been taken to reduce the mercury emission. The urinary mercury excretion was significantly higher during the 24 hours after DMSA administration in all groups compared with that in the 24 hours before. The bulk (50-70%) of the DMSA stimulated mercury excretion appeared within the first eight hours. In each group, the amount of mercury (microgram Hg/24h) excreted after DMSA was significantly correlated with that before administration of DMSA. The groups whose exposure had ceased, however, exhibited much higher correlation for coefficients (r=0.97 for group B and 0.86 for group C after three weeks of holiday) than those currently exposed to mercury vapour (r-0.66 for group C before and 9.58 after reduction of exposure). The data suggest that after a few days of cessation of occupational exposure to mercury vapour the HgU before and after administration of DMSA mainly reflects the amount of mercury stored in the kidney, which represents a mercury pool with a slow turnover.     

Use of regression analysis in the study of the association between different mercury exposure routes and some functional variables

AIMS: The "Mercury Multicentric Project" data-set was analysed with the aim to identify a group of biological variables associated with different types of Hg exposure (occupational exposure, fish dietary intake, exposure due to amalgam restorations). The distribution of socio-demographic, biological and surrogate outcome variables was rather different among the collaborating Units. METHODS: Mixed linear models (MLM) were used to overcome the problems related to the heterogeneity of variances among Units. MLM are a generalization of the standard linear models, the generalization being that the data are permitted to exhibit correlation and non constant variability. MLM therefore provide with the flexibility of modelling not only the means of the dependent variable, but also their variances and co-variances as well. This allows to represent the total variability of the dependent variable as a sum of two components: the first attributable to the Units and the other one to the random error. RESULTS AND CONCLUSIONS: A set of biological variables significantly associated with at least one of the Hg exposure variables or with the HgU/creatinine ratio (as surrogate variable for Hg exposure) was identified by means of MLM. This set includes beta 2-MG, sIL8, CD4+, sPRL, FT dominant, BAMT, and some variables related to neurological behaviour. An extension of this analysis will be performed with a structural equations approach in order to study the dose-response relationships among the various variables according to a hierarchical path defined on biological basis. One of the possible simplified general models including all the selected variables is described.     

Blood concentrations of selected volatile organic compounds and neurobehavioral performance in a population-based sample

The authors analyzed data from a national sample to examine the relationships between blood concentrations of selected volatile organic compounds (VOCs) and the assessment scores of neurobehavioral evaluation tests. They calculated summary statistics to describe blood concentrations of 30 VOCs. For instance, the 95th percentiles were as follows: 1,1,1-trichloroethane, 0.799 microg/l; 1,4-dichlorobenzene, 11.081 microg/l; benzene, 0.476 microg/l; and toluene, 0.281 microg/l. For 1,4-dichlorobenzene, benzene, dibromochloromethane, and trichloroethene, a blood level higher than the 95th percentile was associated with a poorer neurobehavioral assessment score than was a blood level up to the 95th percentile. The authors found a linear relationship between blood toluene concentration and the Serial Digit Learning Test score. The findings suggest that exposure to certain VOCs may result in poor neurobehavioral performance. The study was exploratory and precludes a conclusive statement, so further investigation is warranted.     

Neuropsychological and stress evaluation of a residential mercury exposure

Residents of a former factory building converted to apartments were exposed to mercury over a 2-year period. The neurobehavioral and emotional health effects of this exposure and subsequent evacuation are presented. Urine mercury levels were measured before (urine1) and 3-10 weeks after evacuation (urine2) of the building, when neurobehavioral and psychological measures were also completed. Performance on neurobehavioral and psychologic measures were compared between subjects above and below the median for urine1 (>=19 microg/g creatinine) and were correlated with urine1 mercury levels. The high urine mercury group made more errors on a test of fine motor function and 84% of the residents reported clinically significant elevations in somatic and psychologic symptoms. Although subclinical tremor from mercury exposure may have affected subtle hand-eye coordination, other tests of motor function were not affected. Therefore, the observation of reduced hand-eye coordination may be due to chance. Significant levels of psychosocial stress were more closely associated with the evacuation necessitated by mercury exposure rather than a direct effect of mercury exposure.     

Neurophysiological and psychological picture of solvent poisoning

Neurophysiological and psychological tests were administered to 107 patients - 48 men and 59 women - with a diagnosis of solvent poisoning after longstanding (mean 9.6 years for males and mean 7.6 years for females) occupational exposure. Electroencephalography (EEG) and a wide psychological test battery were applied in all cases, and electroneurographic measurements were performed in 77 subjects. Sixty-five percent of the patients showed an abnormal EEG, and excessive beta activity, not induced by drugs, was found in 54% of patients. At least one abnormally slow nerve conduction velocity (CV) was found in 48 out of 77 patients. The scores of Wechsler Adult Intelligence Scale (WAIS) subtests Digit Span (DSp) and Digit Symbol (DSy) among the men and scores of Similarities (Sim), Digit Symbol (DSy), Picture Completion (PC), and Block Design (BD) among the women were statistically significantly lower than in the Finnish standardization sample. Long duration of exposure was related to poor performance in the Santa Ana Dexterity test in both sexes, to poor visual memory among the men and to poor visuoconstructive intellectual tasks among the women. The background frequency in the EEG showed a correlation to the DSp test of WAIS and some relationship emerged also between the former and the BD, the Symmetry Drawing test, the Santa Ana Dexterity test, and the Mira test. Focal slow wave abnormalities were related to inaccurate hand movements in the psychomotor Mira test. Neurophysiological and psychological tests seem to reflect partly different aspects of neurologic effects and their combined use helps in the evaluation of hazards of solvent exposure.