Polychlorinated biphenyl poisoning: correlation of sensory and motor nerve conduction, neurologic symptoms, and blood levels of polychlorinated biphenyls, quaterphenyls, and dibenzofurans

In 1979 in Taiwan, more than 2000 people were poisoned with rice cooking oil contaminated with polychlorinated biphenyls (PCB). One hundred ten patients were studied within one year of the exposure. The blood PCB levels were 39.3 +/- 16.6 ppb. The blood levels of the PCB derivatives, polychlorinated quaterphenyls (PCQ) and polychlorinated dibenzofurans (PCDF), were 8.6 +/- 4.8 and 0.076 +/- 0.038 ppb, respectively. Both the sensory and motor nerve conduction velocities (NCV) of the patients were significantly lower than the control. Abnormal slowing of sensory NCV was found in 43.6% and abnormal slowing of motor NCV was seen in 21.8%. Patients who had higher PCQ blood levels had significantly slower median nerve sensory NCV than those with lower PCQ levels. Patients with higher PCB blood levels had significantly slower peroneal nerve motor NCV than those with lower PCB levels.     

20名手传振动作业工人的神经肌电图分析

目的探讨手传振动对作业工人周围神经的损害情况。方法对20名从事手传振动作业工人和30名无接触职业危害的健康成人进行神经肌电图检查分析。结果①MCV检测结果显示正中神经运动传导远端潜伏期延长（占85．0％）、MCV减慢（占35．0％）（P〈0．01）;②SCV捡测结果显示正中神经SCV减慢（占40．0％）、尺神经SCV减慢（占30．0％）（P〈0．01）;③肌电图检查结果表现为小力收缩时多相电位增多（占42．5％）及安静时出现纤颤电位（占15．0％）（P〈0．05或P〈0．01）。结论振动对作业工人周围神经损伤明显,神经肌电图检查最早表现为正中神经运动传导远端潜伏期延长,随着损伤加重,进一步出现神经传导速度减慢,运动和感觉同时受累。     

Effects on the peripheral nervous system of tunnel workers exposed to acrylamide and N-methylolacrylamide

OBJECTIVES: This study evaluates the possible toxic effects on the peripheral nervous system of tunnel workers exposed to acrylamide and N-methylolacrylamide during grouting work. METHODS: Symptoms and nerve conduction velocities (NCV) were recorded for 24 tunnel workers 4 and 16 months after the cessation of exposure during grouting operations. Fifty tunnel workers not involved in grouting operations served as referents. Exposure was assessed by questionnaires, qualitative exposure indices, and measurements of hemoglobin adducts after the cessation of exposure. RESULTS:The exposed workers reported a higher prevalence of symptoms during grouting work than they did in an examination 16 months later. A statistically significant reduction in the mean sensory NCV of the ulnar nerve was observed 4 months postexposure when compared with the values of the reference group (52.3 versus 58.9 m/s, P = 0.001), and the mean ulnar distal delay was prolonged (3.1 versus 2.5 ms, P = 0.001). Both measures were significantly improved when measured 1 year later. Exposure-related improvements were observed from 4 to 16 months postexposure for both the median (motor and sensory NCV and F-response) and ulnar (sensory NCV, F-response) nerves. A significant reversible reduction in the mean sensory amplitude of the median nerve was also observed, while the mean sensory amplitude of the sural nerve was significantly reduced after 16 months. CONCLUSIONS: The results indicate demyelinating and axonal changes in peripheral nerves of tunnel workers in relation to exposure to N-methylolacrylamide and acrylamide during grouting operations. The changes were slight, mostly subclinical, and most of the effects were reversible, with normalization after 1 year.     

Investigations on neurotoxicity of chemical substances at the workplace. V. Determination of the motor and sensory nerve conduction velocity in persons occupationally exposed to lead

A cross-sectional study was performed in order to investigate the influence of chronic lead-exposure on the peripheral nervous system. We examined 148 male workers of a storage battery manufacturing plant, who had been exposed to lead metal and inorganic lead compounds for 1 to 28 years (mean 11 years). Fifteen workers with non-occupational risks of peripheral neuropathy (former diseases, alcohol abuse, medication) were excluded from the study. The investigation program comprised: case history, physical examination, analyses of blood- and urine-samples and determination of maximal motor, mixed and sensory conduction velocity (NCV) of the ulnar and median nerve of the right forearm. Objectively no worker showed any signs of health effects related to lead exposure. The "Biological Monitoring" included the determination of (1) Blood-lead level (Pb-B), (2) Free erythrocyte porphyrins (FEP), (3) delta-Aminolevulinic acid dehydratase (ALA-D) and (4) delta-Aminolevulinic acid in urine (ALA-U). Further "time-weighted-average (TWA)"-values of Pb-B were calculated on the basis of several determinations over the period 1975-1981. The following "actual" ("TWA") median values resulted: Pb-B 53 micrograms/dl (54 micrograms/dl), ALA-U 5.6 mg/l (8.4 mg/l), FEP 2.0 mg/l (2.0 mg/l). The "Biologischer Arbeitsstoff Toleranz Wert (BAT)" of 70 micrograms/dl for Pb-B was exceeded in 15 workers (11%), and of 15 mg/l for ALA-U in 30 cases (23%). In comparison with age-matched controls, the lead workers showed a mild slowing of NCV with mean values between 0.8 and 2.0 m/s. Multiple stepwise regression analyses revealed statistically significant correlations between the four NCV and age as well as Pb-B. There were better correlations by using "TWA" than "actual" data of Pb-B. Consideration of the results of the regression analyses, together with an evaluation of the individual neurophysiological status as a function of internal lead exposure, a "dose-effect-relationship" was found only in the case of Pb-B exceeding 70 micrograms/dl. From our study it is concluded that chronic lead exposure resulting in blood-lead levels of below 70 micrograms/dl is no occupational risk causing a functionally significant slowing of nerve conduction velocities.     

Investigation on neurotoxicity of occupational exposure to cyclohexane: a neurophysiological study.

OBJECTIVES: To examine the effect of occupational exposure to cyclohexane on the peripheral nervous system. METHODS: A nerve conduction study was performed on 18 workers exposed to cyclohexane in a luggage factory and on age and sex matched occupationally unexposed controls. 12 workers had been exposed to n-hexane (median 2.8 years) before the start of exposure to cyclohexane. To confirm the effect of exposure, a follow up study was performed on nine workers one year after the first study. The mean exposure to cyclohexane was 1.2 years in the first study. A symptom survey was performed. The exposure was measured by air sampling of the breathing zone of each worker. The urinary metabolite cyclohexanol was also monitored. RESULTS: The concentration of airborne cyclohexane ranged from 5 to 211 ppm. The urinary concentration of cyclohexanol ranged from 0.12 to 1.51 mg/l. There was a strong correlation between the cyclohexane exposure in personal air and urinary cyclohexanol. No differences were found in nerve conduction velocities (NCV) between workers exposed to cyclohexane and age and sex matched controls. The results of the follow up study showed significant improvements in peroneal motor NCV (P < 0.01) and sural sensory NCV (P < 0.05) and in ulnar motor distal latency (MDL, P < 0.05) and peroneal MDL (P < 0.05) compared with the first study. Although the past n-hexane exposure affected the first neurophysiological study, the effect had disappeared in the second study, one year later. CONCLUSION: Occupational exposure to the concentrations of cyclohexane experienced in this study had no adverse effects on the peripheral nervous system.     

Results of magnetic resonance imaging in long-term manganese dioxide-exposed workers

Within a cross-sectional study, the neurotoxic effects of occupational exposure to manganese were examined. From a group of 90 (58 male and 32 female) workers, 11 men with long-term and high exposure to manganese dioxide (MnO2) dust were defined as exposed workers. Eleven age-matched workers of similar socioeconomic status were used as a reference group. Ambient air and biological monitoring (blood, urine, hair), clinical (Webster Rating Scale, WRS), neurophysiological (visual evoked potentials (VEP), nerve conduction velocity (NCV), electroencephalography (EEG)), and motor performance (Wiener Testsystem) examinations were performed. The pallidal index (PI), the ratio of globus pallidus to subcortical frontal white-matter signal intensity in T1-weighted magnetic resonance imaging (MRI) planes multiplied by 100, was used. For the individual body burden, manganese in blood was the most reliable biomarker. A "job-exposure matrix" for the cumulative Mn-exposure index (CEI) was calculated for each worker. The results of WRS, VEP, NCV, EEG, and motor performance tests showed no significant group differences. However, the pallidal index was increased in Mn-exposed persons. Furthermore, a statistically significant positive correlation was found between CEI and pallidal index. The results of other studies are discussed. The meaning of MRI findings for health status as well as gender-specific differences should be examined in further follow-up studies.     

Different behaviour of inorganic and organic mercury in renal excretion with reference to effects of D-penicillamine.

Inorganic and organic mercury was measured in the red cells, plasma, and urine of five laboratory workers to examine the effect of D-penicillamine. The workers had had no particular exposure to mercurials. Before and during administration of D-penicillamine, inorganic mercury levels in plasma were significantly correlated with those in urine or 24-hour urinary outputs, but no significant correlation was found for organic mercury. Administration of D-penicillamine enhanced 24-hour urinary output to a much greater extent in organic than inorganic mercury. All the organic mercury levels in blood, red cells, and plasma were increased by D-penicillamine. This contrasted with the decrease of inorganic mercury levels in plasma.     

Different behaviour of inorganic and organic mercury in renal excretion with reference to effects of D-penicillamine.

Inorganic and organic mercury was measured in the red cells, plasma, and urine of five laboratory workers to examine the effect of D-penicillamine. The workers had had no particular exposure to mercurials. Before and during administration of D-penicillamine, inorganic mercury levels in plasma were significantly correlated with those in urine or 24-hour urinary outputs, but no significant correlation was found for organic mercury. Administration of D-penicillamine enhanced 24-hour urinary output to a much greater extent in organic than inorganic mercury. All the organic mercury levels in blood, red cells, and plasma were increased by D-penicillamine. This contrasted with the decrease of inorganic mercury levels in plasma.     

Subclinical neurotoxicity of mercury vapor revealed by a multimodality evoked potential study of chloralkali workers

Pattern visual, brainstem auditory, and somatosensory evoked potential (EP) studies were performed on 26 chloralkali workers. The intensity of mercury vapor exposure in these workers was estimated from the individual working history. Mercury levels in blood, urine, and hair were determined with atomic absorption spectrometry. The EP findings were compared with those from individually matched normal subjects. In brainstem auditory and somatosensory EP studies, prolonged neural conduction times in the central nervous system (CNS) were found in workers exposed to mercury vapor. In the pattern visual EP study, mercury workers had higher interpeak amplitudes. Findings of this study suggested that chronic exposure to mercury vapor would affect the CNS functions. A multimodality EP study is a useful adjunct in evaluation of chronic mercury neurotoxicity, especially in an epidemiological study.     

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).     

Electroneurographic findings in workers exposed to mercury]

25 mercury-exposed workers as well as 27 age-matched controls were investigated in an electroneurographic study. The population of mercury-exposed workers was found to have --an increased latency of distal motor action potential at both median and peroneal nerves --an increased latency of distal sensory action potential at median nerve --a decrease of amplitudes of evoked muscle potentials at both median and peroneal nerves --a reduced motor nerve conduction velocity at both examined nerves --a reduced antidromic sensory nerve conduction velocity at median nerve. To detect early changes in nerval function we recommend regularly electroneurographic examinations of mercury-exposed people.     

Physical Examinations and Industrial Productivity

Forty-two workers from a chemical plant producing inorganic mercury compounds were evaluated for neurologic, nephrotic, and ophthalomogic toxicity. Despite elevated blood and urinary mercury levels, routine clinical testing such as physical examination, blood chemistries, and urinalysis were generally normal. These findings from the routine examination are in contrast to the complaints of neuropsychological symptoms, elevated urinary n-acetyl B-D-glucosaminidase (NAG) levels, decreased motor nerve conduction velocities, and the presence of lenticular opacities on slit-lamp examination that were found, when organ systems known to be affected by mercury were targeted. More sensitive but objective indicators of toxicity need to be included in routine medical screening so as to help diagnose the etiology of neuropsychological symptoms and prevent long-term sequelae in workers exposed to mercury.     

Sensitive indicators of inorganic mercury toxicity

Forty-two workers from a chemical plant producing inorganic mercury compounds were evaluated for neurologic, nephrotic, and ophthalmologic toxicity. Despite elevated blood and urinary mercury levels, routine clinical testing such as physical examination, blood chemistries, and urinalysis were generally normal. These findings from the routine examination are in contrast to the complaints of neuropsychological symptoms, elevated urinary n-acetyl B-D-glucosaminidase (NAG) levels, decreased motor nerve conduction velocities, and the presence of lenticular opacities on slit-lamp examination that were found, when organ systems known to be affected by mercury were targeted. More sensitive but objective indicators of toxicity need to be included in routine medical screening so as to help diagnose the etiology of neuropsychological symptoms and prevent long-term sequelae in workers exposed to mercury.     

振动性神经病的实验和临床研究

探讨振动性神经病的神经功能改变及其评价指标。以家兔为实验对象,测定振动负荷前 坐骨神经传导速度的变化与非接振家兔相对照,以砂轮磨光工为对象,进行现场调查,健康检查,测定其短潜伏时体感诱发电位,正中神经的感觉和运动神经传导速度,并与对照工人比较。     

Urinary mercury excretion and body weight on workers exposed to mercury vapour

Summary From the 5-year record of health checks including urinary mercury levels and body weights on 33 workers exposed to mercury vapour in a tungsten rod manufacturing factory, the relationships between the level of urinary mercury and the body weight, and between the change of urinary mercury levels and that of body weights, were analysed. Except for the workers with the short period of exposure, on whom no significant correlation was found, correlations between the changes; urinary mercury and body weight, were much stronger than those between the levels. In contrast to the significant negative correlations in the mentioned relationships on the workers with the long period of continuous exposure at atmospheric concentrations below 0.2 mg/m³, there was significant positive correlations on the workers with occasional, short-period exposures at much lower concentrations of mercury. The importance of analysis on the change of exposure and its relation to the effect was emphasized, and possible effects of mercury to the regulation of body weight was discussed.     

接汞男工血清及精浆乳酸脱氢酶C4同工酶活性测定

本研究应用乳酸脱氢酶Ｃ４同工酶活性加热－乳酸基质比色法对２５名汞蒸气接触男工和１５名正常对照男工的血清及精浆ＬＤＨ－Ｘ活性进行测定，发现长期接触低浓度的汞蒸气可致接触者的精浆ＬＤＨ－Ｘ相对升高并与血汞浓度有关，结果提示汞蒸气接触可能对接触男工射出精液中精子的结构完整性有不良影响。     

Effects of low exposure to inorganic mercury on psychological performance

The effects of low exposure to inorganic mercury on psychological performance was investigated: the study groups included eight chronically exposed workers and 20 who were only occasionally exposed. These were compared with a control group of 22 subjects from the same plant who were not exposed to mercury. All subjects were administered the WHO test battery to detect preclinical signs of central nervous system impairment: the battery includes the Santa Ana (Helsinki version) test, simple reaction time, the Benton test, and the Wechsler digit span and digit symbol. In addition, the Gordon test was used to study personality profiles and the clinical depression questionnaire. Urinary mercury was used as indicator for internal dose. To this effect, urinary mercury observed in workers examined from 1979 to 1987 was evaluated. Of the pyschic functions explored by behavioural tests, only short term auditory memory was found to be impaired in the chronically exposed workers (p less than 0.05 compared with the controls). The chronically exposed workers were also found to be more depressed than those in the two other groups. No changes of visual motor functions were observed. The personality of the occupationally exposed workers was found to be considerably changed compared with that of the control group. On the basis of the results obtained and in view of urinary mercury mean concentrations in the exposed group which were 30-40 micrograms/l over the years, it is suggested that the TLV-TWA for mercury should be lowered to 0.025 mg/m3 and that the biological urinary exposure indicator for biological monitoring should be 25 micrograms/l.     

Effects of low exposure to inorganic mercury on psychological performance.

The effects of low exposure to inorganic mercury on psychological performance was investigated: the study groups included eight chronically exposed workers and 20 who were only occasionally exposed. These were compared with a control group of 22 subjects from the same plant who were not exposed to mercury. All subjects were administered the WHO test battery to detect preclinical signs of central nervous system impairment: the battery includes the Santa Ana (Helsinki version) test, simple reaction time, the Benton test, and the Wechsler digit span and digit symbol. In addition, the Gordon test was used to study personality profiles and the clinical depression questionnaire. Urinary mercury was used as indicator for internal dose. To this effect, urinary mercury observed in workers examined from 1979 to 1987 was evaluated. Of the pyschic functions explored by behavioural tests, only short term auditory memory was found to be impaired in the chronically exposed workers (p less than 0.05 compared with the controls). The chronically exposed workers were also found to be more depressed than those in the two other groups. No changes of visual motor functions were observed. The personality of the occupationally exposed workers was found to be considerably changed compared with that of the control group. On the basis of the results obtained and in view of urinary mercury mean concentrations in the exposed group which were 30-40 micrograms/l over the years, it is suggested that the TLV-TWA for mercury should be lowered to 0.025 mg/m3 and that the biological urinary exposure indicator for biological monitoring should be 25 micrograms/l.     

某荧光灯制造企业汞接触工人职业健康状况及影响因素

[目的]了解某荧光灯制造企业汞接触工人职业健康状况,分析影响尿汞水平的因素。[方法]根据国家相关职业卫生标准对工作场所进行职业卫生学调查,并按照《工作场所空气中有害物质监测的采样规范》（GBZ159-2004）中规定的采样原则在每个岗位设置了一个采样点。对汞接触人员进行职业健康检查,检查内容包括问诊,内、外科,口腔科,实验室检查,B超,心电图等。共调查汞接触工人1031名,其中男性351名,女性680名,年龄20～57岁。[结果]该企业122个检测点空气中汞浓度范围为0．001～0．013mg／m3,均未超标。1031名工人尿汞浓度范围为0．22～58．71μg／m3,中位数为3．26μg／g肌酐,9人尿汞浓度超标,超标率0．87％。尿蛋白阳性198人,阳性率19．20％;神经系统异常113人,异常率10．96％。女性工人的尿汞水平（中位数为3．38μg／g肌酐）商于男性（中位数为3．07μ∥g肌酐）（P=0．036）;年龄与尿汞浓度呈正相关（r=-0．089,P=0．011）;工龄与尿汞浓度无相关。[结论]该企业各岗位空气中汞浓度均低于O．02mg／m。,O．87％的工人尿汞浓度超标。性别和年龄可能为尿汞浓度的影响因素。     

A study of neurophysiological measurements and various function tests on workers occupationally exposed to vibration

Summary Seventy male air grinder operators and 72 age-matched control workers were examined. Both groups of workers worked in the warm climate (20°–33°C) of southern Taiwan. None of the workers had symptoms of white fingers. The investigation program comprised: (1) case history, (2) physical examination, (3) determination of maximal motor conduction velocity, proximal and distal sensory conduction velocity (NCV) of the median and ulnar nerves of the right upper extremity, (4) measurement of skin temperature, nail press test, pain threshold and vibratory sense threshold of the upper extremities, and (5) testing of the motor function. The dose-effect correlation between the NCV, various function tests and total operating time (TOT) was performed by multiple stepwise regression analyses. The regression analyses revealed a statistically significant correlation (dose/effect) between the six NCV, vibratory sense threshold, pain threshold and age, as well as TOT.