Effects of occupational exposure to mercury vapour on the central nervous system.

Possible effects of mercury on the central nervous system (CNS) were examined in a group of chloralkali workers exposed to mercury (n = 89) and compared with a control group (n = 75), by registration of subjective symptoms, personality changes, forearm tremor, and performance on six computerised psychometric tests in the two groups. The groups were similar in age, education, verbal comprehension, and work tasks. In the chloralkali group, median blood mercury concentration (B-Hg) was 55 nmol/l, serum mercury concentration (S-Hg) 45 nmol/l, and urine mercury concentration (U-Hg) 14.3 nmol/mmol creatinine (25.4 micrograms/g creatinine). Corresponding concentrations in the control group were 15 nmol/l, 4 nmol/l, and 1.1 nmol/mmol creatinine (1.9 micrograms/g creatinine) respectively. The number of self reported symptoms, the scores for tiredness and confusion in the profile of mood states (POMS), and the degree of neuroticism in the Eysenck personality inventory (EPI), were significantly higher in the mercury exposed group compared with the controls. Performance on the psychometric tests and tremor frequency spectra did not differ significantly between the two groups. Dose-response calculations showed weak but statistically significant relations between symptom prevalence and current mercury concentrations in both blood and urine. The performance on three of the psychometric tests was negatively correlated with earlier peak exposures. The findings indicate a slight mercury induced effect on the CNS among the chloralkali workers.     

Renal and immunological effects of occupational exposure to inorganic mercury.

Seven parameters of renal dysfunction (urinary excretion of albumin, orosomucoid, beta 2-microglobulin, N-acetyl-beta-glucosaminidase (NAG), and copper; serum creatinine concentration, and relative clearance of beta 2-microglobulin) were examined in a group of chloralkali workers exposed to mercury vapour (n = 89) and in an unexposed control group (n = 75). Serum concentrations of immunoglobulins (IgA, IgG, IgM) and auto-antibodies towards glomeruli and other tissues were also determined. The parameters examined were compared between the two groups and related to different exposure parameters. In the chloralkali group median blood mercury concentration (B-Hg) was 55 nmol/l, serum mercury (S-Hg) 45 nmol/l, and urine mercury concentration (U-Hg) 14.3 nmol/mmol creatinine (25.4 micrograms/g creatinine). Corresponding concentrations for the control group were 15 nmol/l, 4 nmol/l, and 1.1 nmol/mmol creatinine (1.9 micrograms/g creatinine) respectively. None of the parameters of renal dysfunction differed significantly between the two groups, but there was a tendency to increased excretion of NAG in the exposed group compared with the controls. Also, a statistically significant relation existed between U-Hg and U-NAG (p less than 0.001). Serum immunoglobulin concentrations did not differ between the groups, and serum titres of autoantibodies (including antiglomerular basement membrane and antilaminin antibodies) were low in both groups. Thus the results gave no evidence of glomerular damage or of a tubular reabsorption defect at the current relatively low exposures. The findings still indicate slight, dose related tubular cell damage in the mercury exposed group. There were no signs of a mercury induced effect on the immune system.     

Renal and immunological effects of occupational exposure to inorganic mercury.

Seven parameters of renal dysfunction (urinary excretion of albumin, orosomucoid, beta 2-microglobulin, N-acetyl-beta-glucosaminidase (NAG), and copper; serum creatinine concentration, and relative clearance of beta 2-microglobulin) were examined in a group of chloralkali workers exposed to mercury vapour (n = 89) and in an unexposed control group (n = 75). Serum concentrations of immunoglobulins (IgA, IgG, IgM) and auto-antibodies towards glomeruli and other tissues were also determined. The parameters examined were compared between the two groups and related to different exposure parameters. In the chloralkali group median blood mercury concentration (B-Hg) was 55 nmol/l, serum mercury (S-Hg) 45 nmol/l, and urine mercury concentration (U-Hg) 14.3 nmol/mmol creatinine (25.4 micrograms/g creatinine). Corresponding concentrations for the control group were 15 nmol/l, 4 nmol/l, and 1.1 nmol/mmol creatinine (1.9 micrograms/g creatinine) respectively. None of the parameters of renal dysfunction differed significantly between the two groups, but there was a tendency to increased excretion of NAG in the exposed group compared with the controls. Also, a statistically significant relation existed between U-Hg and U-NAG (p less than 0.001). Serum immunoglobulin concentrations did not differ between the groups, and serum titres of autoantibodies (including antiglomerular basement membrane and antilaminin antibodies) were low in both groups. Thus the results gave no evidence of glomerular damage or of a tubular reabsorption defect at the current relatively low exposures. The findings still indicate slight, dose related tubular cell damage in the mercury exposed group. There were no signs of a mercury induced effect on the immune system.     

Biological monitoring of environmental and occupational exposure to mercury

Summary Biological monitoring was used to assess mercury exposure from occupational and environmental sources in a group of chloralkali workers (n = 89) and in a control group (n = 75). In the control group, the median value for blood mercury (B-Hg) was 15 nmol/l, that for serum mercury (S-Hg) was 4 nmol/l and that for urinary mercury (U-Hg) was 1.1 nmol/mmol creatinine. Corresponding levels in the chloralkali group were 55 nmol/l, 45 nmol/l and 14.3 nmol/mmol creatinine, respectively. In the control group, there were statistically significant relationships between fish consumption and both B-Hg and S-Hg values (P < 0.001), whereas U-Hg correlated best with the individual amalgam burden (P < 0.01). In the chloralkali group, the mercury levels in blood and urine were significantly related to the type of work (P < 0.001) but not to the length of employment, to fish consumption or to the quantity of dental amalgam fillings. In both groups there were poor correlations between smoking or alcohol intake and the mercury levels in blood and urine. The results strongly suggest that fish is an important source of methylmercury exposure and that amalgam fillings are probably the most important source of inorganic mercury exposure among occupationally unexposed individuals. In the chloralkali group, mercury exposure from fish and amalgam was overshadowed by occupational exposure to inorganic mercury.     

Endocrine function in mercury exposed chloralkali workers.

OBJECTIVE--The aim was to study whether functional impairment of the pituitary, thyroid, testes, and adrenal glands of humans occupationally exposed to mercury (Hg) vapour can be shown as a result of accumulation of Hg in these glands. METHODS--Basal concentrations of thyrotrophin (TSH), prolactin, free thyroxine (free T4), free 3,5,3'-triiodothyronine (free T3), antibodies against thyroperoxidase, and testosterone in serum, as well as cortisol in morning urine were measured in 41 chloralkali workers exposed (10 years on average) to Hg vapour, and in 41 age matched occupationally unexposed referents. The chloralkali workers had a mean urinary Hg concentration (U-Hg) of 15 nmol/mmol (27 micrograms/g) creatinine, and a mean blood Hg concentration (B-Hg) of 46 nmol/l. For the reference group U-Hg and B-Hg were 1.9 nmol/mmol (3.3 micrograms/g) creatinine and 17 nmol/l respectively. RESULTS--The serum free T4 concentration and the ratio free T4/free T3 were slightly, but significantly, higher in the subgroups with the highest exposure, and the serum free T3 was inversely associated with cumulative Hg exposure. This indicates a possible inhibitory effect of mercury on 5'-deiodinases, which are responsible for the conversion of T4 to the active hormone T3. Serum total testosterone, but not free testosterone, was positively correlated with cumulative Hg exposure. Prolactin, TSH and urinary cortisol concentrations were not significantly associated to exposure. CONCLUSION--Apart from inhibition of the deiodination of T4 to T3, the endocrine functions studied seem not to be affected by exposure to Hg vapour at the exposure levels of the present study. Growth hormone secretion was not studied.     

Effects of occupational exposure to mercury vapor on lymphocyte micronuclei

For 26 chloralkali workers exposed to inorganic mercury and 26 age-matched, occupationally unexposed referents, the frequency and size distribution of micronuclei were determined in peripheral lymphocytes stimulated with either phytohemagglutinin or pokeweed mitogen. For the exposed workers the mean concentrations of mercury in urine, plasma, and erythrocytes were 16 nmol/mmol of creatinine, 48 nmol/l, and 78 nmol/l, respectively, and their mean exposure time was 10 years. Neither the frequency nor the size of micronuclei was significantly different in the two groups; nor were there any correlations to current mercury levels. However, in the exposed group, and with phytohemagglutinin as the mitogen, a statistically significant correlation between previous exposure to mercury (cumulative exposure or number of blood mercury peaks) and the frequency of micronuclei was found. This association was also present when the effects of age and smoking were allowed for, and it may indicate an accumulation of cytogenetic effects in T-lymphocytes.     

Renal and immunologic markers for chloralkali workers with low exposure to mercury vapor

OBJECTIVES: The aim of this study was to investigate renal function and immunologic markers among chloralkali workers with long-term low exposure to mercury vapor. METHODS: Forty-seven currently exposed workers were compared with reference workers matched for age in a cross-sectional design. RESULTS: The mean urinary mercury concentration was 5.9 (range 1.1-16.8) nmol/mmol creatinine (Cr) for the exposed workers and 1.3 (range 0.2-5.0) nmol/mmol Cr for the referents. The chloralkali workers had been exposed for an average of 13.3 (range 2.8-34.5) years. The activity of N-acetyl-beta-D-glucosaminidase in urine (U-NAG) was higher in the exposed workers (mean 0.18 U/mmol Cr versus 0.14 U/mmol Cr, P=0.02). Associations between current urinary mercury, cumulative urinary mercury, and cumulative urinary mercury per year (intensity) and U-NAG, autoantibodies to myeloperoxidase (anti-MPO) and proteinase 3 in serum, respectively, were observed. The activity of U-NAG and anti-MPO was increased in the workers with the highest exposure, as assessed by their mean intensity of exposure. The highest activity of U-NAG was observed in the exposed workers with the lower concentrations of selenium in whole blood. CONCLUSIONS: The study indicates an effect of exposure on the kidney proximale tubule cells, possibly modified by individual selenium status, and an effect mediated by neutrophil granulocytes.     

Chronic mercury exposure examined with a computer-based tremor system

Tremor is being increasingly evaluated by quantitative computer-based systems to differentiate its causes. In this study, a group of mercury-exposed workers were assessed to determine whether tremor characteristics differed by exposure level. Workers were classified into two groups: those with an average urine mercury concentration below the American Conference of Government Industrial Hygienist Biological Exposure Index of 35 micrograms/g creatinine, and those with an average urine mercury concentration above the Biological Exposure Index. Tremor characteristics (including intensity, harmonic index, center frequency, standard deviation of the center frequency, and tremor index) were measured and recorded with a computer-based tremor system. Sixteen of 17 workers who were potentially exposed to mercury participated in the study. Three workers had a mean urine mercury concentration of 27.0 micrograms/g-creatinine and were assigned to the low-exposure group, and 13 workers had a mean urine mercury concentration of 200.2 micrograms/g-creatinine and were assigned to the high-exposure group. There was a statistically significant difference in the tremor index (which compiles five individual tremor parameters into a single value) between the two groups (P = 0.04; Wilcoxon's rank sum test). Other tremor characteristics did not differ significantly between the groups. Tremor index may be more useful than measures of individual tremor parameters in differentiating normal from subclinical pathological tremors among groups of workers with chronic mercury exposure.     

Effects of elemental mercury exposure at a thermometer plant

This study compares 84 mercury-exposed workers at a thermometer manufacturing facility with 79 unexposed workers for evidence of chronic mercury toxicity. Personal breathing-zone air concentrations of mercury ranged from 25.6 to 270.6 micrograms/m3 for thermometer workers. Urinary mercury levels in the study population ranged from 1.3 to 344.5 micrograms/g creatinine, with eight (10%) participants exceeding 150 micrograms/g creatinine and three workers exceeding 300 micrograms/g creatinine, which indicates increased absorption of mercury among the thermometer workers. All urine mercury levels in the comparison group were compatible with normal background levels in unexposed adults (less than 10 micrograms/g creatinine). Thermometer plant workers reported more symptoms than did controls; in general, these differences were not statistically significant and could not be specifically associated with mercury exposure. Static tremor, abnormal Romberg test, dysdiadochokinesia, and difficulty with heel-to-toe gait were more prevalent among thermometer workers than control workers, which could not be associated with recent mercury exposure; there was some suggestion of an association with chronic exposure. There were no intergroup differences for the standard clinical tests of renal function except for a significantly higher mean specific gravity among the thermometer workers. A positive correlation was found, however, between urinary N-acetyl-b-D-glucosaminidase (NAG) and urinary mercury. There was no consistent evidence for intergroup differences in proximal renal tubule function, as measured by urinary beta 2-microglobulin (B2M) or retinol binding protein (RBP).     

Mercury and selenium in workers previously exposed to mercury vapour at a chloralkali plant.

The concentrations of total mercury (B-Hg), inorganic mercury (B-IHg), and methyl mercury (B-MeHg) in whole blood, urinary mercury (U-Hg), and selenium in urine (U-Se) and whole blood (B-Se) were determined in 74 chloralkali workers previously exposed to Hg vapour, and compared with 51 age matched referents. Dental amalgam state, fish consumption, and exposure related indices were studied with regard to the determined elements. A significant relation between the surface of dental amalgam and U-Hg (Pearson's r = 0.63, p < 0.001) was found among the referents. Mean U-Se was significantly lower (p < 0.001) among the subjects previously exposed to Hg (34.1 nmol/mmol creatinine) compared with that for the referents (42.6 nmol/mmol creatinine). A significant negative relation between the cumulative Hg dose and U-Se was also found. The mechanisms and the clinical significance of these findings are not clear. No relation between current U-Hg and previous occupational exposure to Hg was found among subjects in whom exposure had ceased more than one year before the study.     

Relation between exposure related indices and neurological and neurophysiological effects in workers previously exposed to mercury vapour.

A cross sectional study of aspects of their neurology was carried out on 77 chloralkali workers previously exposed to mercury (Hg) vapour and compared with 53 age matched referents. The chloralkali workers had been exposed for an average of 7.9 years at a concentration of 59 micrograms Hg/m3 in the working atmosphere. The individual mean urinary concentration of Hg for each year of exposure was 531 nmol Hg/1. On average the exposure had ceased 12.3 years before the examinations. Both the median sensory nerve conduction velocity and the amplitude of the sural nerve were associated with measures of cumulative exposure to Hg. An association was also found between years since first exposure to Hg and aspects of the visual evoked response. Previously exposed subjects with postural tremor or impaired coordination also had alterations in visual evoked response. These results may indicate an effect of previous exposure to mercury vapour on the nervous system, possibly in the visual pathway, cerebellum, and the peripheral sensory nerves.     

Neuropsychological function in manganese alloy plant workers

Objectives The objective was to investigate potential nervous system effects of manganese (Mn) exposure in workers employed in manganese-alloy-producing plants.Methods One hundred male Mn alloy plant workers were compared with 100 age-matched referents. The subjects were examined with a comprehensive neuropsychological test battery. Exposure was assessed by measurement of Mn concentrations in the workroom air, blood and urine.Results The geometric mean (GM) concentration of inhalable Mn in workroom air was 301 g/m³. The GM concentration of Mn in whole blood (181 nmol/l vs 160 nmol/l) (P=0.002) and urine (0.9 nmol/mmol creatinine vs 0.4 nmol/mmol creatinine) (P<0.001) was higher among the exposed subjects than among the referents. The Mn-exposed subjects had increased postural tremor while conducting a visually guided tremor test (static steadiness test) compared with the referents (mean number of contacts 94 vs 59 (P= 0.001); duration of contacts (in seconds) 5.1 vs 3.5 (P=0.003)). The tremor had larger frequency dispersion, indicating that the tremor included a wider variety of frequencies, among the exposed subjects than among the referents, assessed by the TREMOR test system. Smoking habits (self-reported) influenced the tremor parameters significantly, the Mn-exposed smokers having more tremor than the non-smoking Mn-exposed subjects. No differences between the groups were found in tests for cognitive functions, reaction time or in symptom reporting.Conclusion The Mn-exposed subjects had increased hand tremor compared with their referents. The tremor was related to exposure parameters. Smoking habits (self-reported) influenced the tremor parameters.     

Renal function of chloralkali workers after the cessation of exposure to mercury vapor

OBJECTIVES: The aims of the study were to assess renal function in chloralkali workers previously exposed to mercury vapor and to assess the impact of selenium status on the biomarkers of kidney function. METHODS: Forty-nine chloralkali workers previously exposed to mercury vapor were compared with 49 age-matched referents in a cross-sectional study. Selected biomarkers of kidney function and biomarkers of selenium status were measured. The index group had been exposed for 13.1 (range 2.8-34.5) years on the average at a mean urinary mercury excretion of 9.3 (range 4.0-25.4) nmol/mmol creatinine a year. The exposure had ceased on an average of 4.8 (range 4.2-10.0) years prior to the examinations. RESULTS: No statistically significant differences were found between the groups for the measured biomarkers of kidney function. The serum selenium concentration and serum glutathione peroxidase activity were associated with the activity of N-acetyl-beta-D-glucosaminidase in urine (U-NAG). The results indicate that having higher glutathione peroxidase activity or a higher serum selenium concentration results in a lower excretion of U-NAG. This effect was the most pronounced in the oldest third of the participants. Apparently the well-known association between U-NAG and age could only be found for the participants with a lower selenium status. CONCLUSIONS: Increased activities of U-NAG during ongoing exposure to mercury vapor appear to be reversible upon cessation of exposure. Selenium status has a substantial impact on U-NAG activity and should be considered in studies of U-NAG excretion.     

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.     

Subjective symptoms and psychological performance of chlorine-alkali workers

Subjective symptoms and psychological performances on a computer-administered test battery were studied among a group of 60 chlorine-alkali workers and their matched referents. The exposure time of the group exposed to inorganic mercury vapor had been about 14 years, and the estimated long-term average exposure had been about 25 micrograms/m3 of air. The exposed workers had an actual mercury concentration of 51.9 (SD 25.0, range 15-150) nmol/l in blood and 84.1 (SD 56.6, range 15-260) nmol/l in urine. Neither perceptual motor nor memory nor learning abilities of the mercury-exposed workers showed any disturbances in a comparison with the referents. However, the exposed group reported statistically significantly more memory disturbances than the referents. Strain caused by three-shift work was a possible cofactor for other increased subjective symptoms, namely, for sleep disorders, fatigue, and confusion.     

Biological aspects of occupational exposure to cadmium and several other metals

We have performed several cross-sectional epidemiological surveys among workers exposed to cadmium, mercury vapour or manganese in order to assess : their early biological or functional effects; the biological tests allowing an assessment of the amount of metal absorbed or stored in the body; the acceptable exposure levels. Studies have also been carried out among persons exposed to inorganic arsenic in order to define its inactivation mechanism and to develop a biological test of exposure. The kidney is the main critical organ following long-term exposure to cadmium. To prevent the occurrence of renal changes in the majority of male workers exposed to cadmium, its concentration in renal cortex should not exceed 215 micrograms/g (wet weight), and that in urine : 10 micrograms/g creatinine. A blood cadmium level of 1 microgram/100 ml has been suggested as maximum tolerable level for long-term exposure. Prolonged exposure to mercury vapour may lead to renal and neurological disturbances. The preclinical signs of nephrotoxicity are correlated with the amount of mercury absorbed which may be assessed by monitoring the mercury level in urine. The neurotoxic effects (particularly tremor) are mainly related to the integrated exposure (duration and intensity). A maximal permissible level of 50 micrograms Hg/g urinary creatinine is proposed to prevent the occurrence of these toxic effects. An exposure to manganese dust for 7 years on the average at a level below the maximum allowable airborne concentration (5 mg/m3) recommended by the ACGIH in the USA may still lead to a slight reduction in psychomotor and spirometric performances and interfere with calcium metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)     

A study of autoantibodies and circulating immune complexes in mercury-exposed chloralkali workers

Inorganic mercury may cause immunologically mediated disease: e.g., glomerulonephritis, acrodynia, and contact allergy. Animal models have demonstrated the importance of genetic factors in determining susceptibility and resistance to autoimmunity, as well as the specific manifestation of the autoimmune response. Findings in groups of workers with occupational exposure to inorganic mercury have been inconsistent. Objective: To investigate whether an immune response, caused by exposure to inorganic mercury (Hg), could be shown in occupationally exposed workers. Methods: Immunoglobulin G (IgG), antinuclear autoantibodies, antibodies against thyroid, stomach or kidney antigens using indirect immunofluorescence, antibodies against glomerular basement membrane using ELISA, and circulating immune complexes in serum, and albumin in urine, were examined in Hg-exposed workers and controls. The two groups, 41 male chloralkali workers exposed to Hg vapour (mean exposure time 9 years) and 41 unexposed controls were age-matched and recruited from the same company. Hg concentrations in whole blood (B-Hg), plasma (P-Hg), and urine (U-Hg) were determined using cold vapor atomic spectrometry. Design: Cross-sectional study. Results: The mean B-Hg, P-Hg and U-Hg levels were 46 nmol/l, 37 nmol/l, and 27 μg/g creatinine in the exposed group, and 17 nmol/l, 6.9 nmol/l, and 3.4 μg/g creatinine in the referents. No statistically significant differences were found regarding IgG levels, urinary albumin excretion, prevalence of abnormal titers of autoantibodies or circulating immune complexes. There were no statistically significant associations between autoantibodies or immune complexes on the one hand and mercury exposure indices on the other. Conclusion: The results indicate that, if and when lasting autoimmune response occurs at the mercury exposure levels of the present study, it is uncommon. A small fraction of humans may, however, be susceptible to the development of autoimmunity, and there is also a possible “healthy worker” selection. Thus cross-sectional studies of moderate numbers of active workers will have low power to demonstrate autoimmune effects. Received: 2 September 1996 / Accepted: 3 January 1997     

Serum and urinary vanadium of workers processing vanadium pentoxide

Summary Serum and urinary vanadium concentrations were investigated in eight men exposed to vanadium pentoxide dust. The creatinine-adjusted urinary vanadium concentrations were found to correlate with serum vanadium concentrations (r=0.81), but not with the vanadium contents of factory air. The urinary vanadium excretion decreased significantly with the time the workers spent out of exposure. At the beginning of their summer holidays the serum vanadium concentration of the workers was 393 ± 223 (S.D.) nmol/l and the urinary excretion of vanadium 73 ± 50 nmol/mmol of creatinine. Three days after exposure the urinary excretion of vanadium was 46 ± 24 nmol/mmol of creatinine. On the 16th day of their holidays vanadium could be detected in the serum (225 ± 83 nmol/1) and in the urine (48 ± 26 nmol/mmol of creatinine) of the workers. Eight family members of the exposed had less vanadium in urine (32 ± 17 nmol/mmol of creatinine). These results suggest that most of the absorbed vanadium is excreted in the urine within one day after a long-term moderate exposure to vanadium dust.     

Decrease in mercury concentration in blood after long term exposure: a kinetic study of chloralkali workers.

The elimination of mercury (Hg) in blood was investigated in 14 chloralkali workers exposed to metallic Hg vapour for 1-24 (median 10) years. Blood and urine samples were collected on several (median eight) occasions during a period of 17-26 days. The initial Hg concentrations were about 80 nmol/l in whole blood (B-Hg) and 17 nmol/mmol creatinine in urine (U-Hg). The decrease in Hg in whole blood, plasma (P) and erythrocytes (Ery) was best characterised by a two compartment model. In a model with a common half life for all subjects, the best fit for B-Hg was obtained with half lives of 3.8 days for a fast phase and 45 days for a slow phase. The half life of the fast phase was shorter for P-Hg than for Ery-Hg, whereas the opposite was the case for the slow phase. The half lives of the slow phases in whole blood and plasma were longer, and the relative fractions of the slow phases were higher (about 50%) after long term exposure than those (about 20%) reported after brief exposure. Slower elimination indicates higher accumulation of Hg in organs with long half lives, and possibly the presence of at least one additional, even slower compartment. The U-Hg fluctuated substantially during the sampling period, and average concentrations decreased only slightly.     

Tremor in workers with low exposure to metallic mercury

In a fluorescent lamp production factory, a newly developed lightweight balance-tremormeter was used to measure postural tremor of the finger in 21 workers (ages 28 to 61) exposed for 0.5-19 yr to metallic mercury. In addition, tremor was measured in an indirect way by means of a "hole-tremormeter." The excretion of mercury in urine was 9-53 (average 20) mumol/mol creatinine. With increasing mercury excretion, the following parameters increased: the acceleration of the tremor, the contribution of the neuromuscular component (8-12 Hz) to the power spectrum of the acceleration, the width of the power-spectrum and the score on the hole-tremormeter. The study indicates that exposure to metallic mercury below the current TLV (50 micrograms/m3) may increase the tremor of the finger.