Cross sectional observation of the effects of carbon disulphide on arteriosclerosis in rayon manufacturing workers

OBJECTIVE

A prospective cohort study was designed to clarify the relations between occupational exposure to carbon disulphide (CS2) and its effects on arteriosclerosis in workers in 11 Japanese rayon manufacturing factories. This report is a cross sectional baseline observation in the first study year.

METHODS

Study subjects were 432 male rayon workers (mean (range) age 35.5 (19.1-47.8); duration of exposure 13.4 (0.3-29.0)) and 402 male referent workers (age 35.8 (18.9-49.8)). Exposure to CS2 was assessed by determining the concentration of 2-thiothiazolidine-4-carboxylic acid (TTCA) in urine. Mean (SD) TTCA was 3.42 (2.73) mg/g creatinine (Cr) (n = 422). About a quarter of the urine samples were > 5 mg/g Cr, a biological exposure index recommended by the American Conference of Governmental Industrial Hygienists. Health effects on arteriosclerosis were evaluated by measuring blood pressure, serum lipids, pulse wave velocity of the aorta, stiffness and blood flow of the carotid artery, and blood coagulation and fibrinolysis indices, and by use of brain magnetic resonance imaging, electrocardiogram (at rest and after exercise), ophthalmograph, and Rose's questionnaire. Information on potential confounding factors was collected by self administered questionnaire.

RESULTS

Prevalence of microaneurysm of the retinal artery was significantly higher in workers exposed to CS2 (8.1%) than in referent workers (3.4%), and increased with age. Other examinations did not show any differences between the two groups even after allowance for confounding factors.

CONCLUSIONS

Significant effects of CS2 on arteriosclerosis were not found in current rayon manufacturing workers, with the exception of induction of microaneurysm of the retinal artery.

Cross sectional observation of the effects of carbon disulphide on the nervous system, endocrine system, and subjective symptoms in rayon manufacturing workers

OBJECTIVES

A prospective cohort study was initiated to clarify whether the current level of exposure to carbon disulphide (CS2) is low enough to prevent occurrence of subclinical health impairments or to ameliorate health effects due to past high exposure. This paper describes the effects of exposure to CS2 on the nervous and endocrine systems, and the subjective symptoms in a baseline observation.

METHODS

The effects were evaluated of CS2 on the median nerve conduction velocity, neurobehavioural and psychological tests, and subjective symptoms related to solvents in 432 male workers exposed to CS2 and 402 reference workers from 11 rayon factories in Japan. Adjustment was made for potential confounding factors such as age or alcohol drinking. Exposure to CS2 was either dichotomised or categorised into three groups by job type.

RESULTS

Reductions were observed in motor (-1.9 m/s) and sensory (-0.91 m/s for orthodromic and -1.1 m/s for antidromic) nerve conduction velocities in the workers exposed to CS2 at the spinning and refining processes. Small but significant increases were found in self rated depression scale score and decrease in digit span (backward) in the workers exposed to CS2. Of 54 subjective symptoms many were increased--namely, heavy feeling in the head, light headedness, fainting after suddenly standing up, tremor, dullness, and increased sensitivity of skin in the extremities, reduced grasping power, reduced sexual desire, and increased rough skin. The endocrinological indicator--the concentration of glycosylated haemoglobin--was also increased in the workers exposed to CS2.

CONCLUSIONS

Subclinical effects on the nervous system and on glucose metabolism were found in the workers exposed to CS2. One interpretation is that relatively higher exposure to CS2 in the past may induce these, but the effects are still not entirely ameliorated under the current exposure to CS2. Another possibility is that the current exposure to CS2 may cause these positive findings. A follow up observation is necessary to clarify these questions.

[Coefficient of linear correlation between levels of fibrinogen, antithrombin III, thrombin-antithrombin complex and lipid fractions in women exposed chronically to carbon disulfide]

The authors examined 65 women, aged 22-58 years. They were derived from two industrial populations of different production profiles, and divided into three groups. Group I--the control group--was composed of 20 women, mean age 44.5 +/- 12.02 years, employed in the DANA Enterprise, Szczecin, not exposed to carbon disulfide; Group II--the group studied--comprised 22 women, mean age 42.5 +/- 4.95 years, employed in the WISKORD Enterprise, Szczecin, chronically exposed to carbon disulfide at the concentration of 9.36-23.4 mg/m2; and Group III--included 23 women, mean age 46.7 +/- 8.81 years, suffering from diabetes mellitus II. The study reveals that carbon disulfide exerts significant adverse effect on plasma lipid fractions, and induces changes in the coagulation system, creating the risk of ischaemic diseases.

Rhythm patterns of basic brain bioelectric activity in workers chronically exposed to carbon disulfide

The work aimed at defining the pattern and frequency of rhythm disturbances in basic brain bioelectric activity in EEG recordings, routinely regarded as normal, in workers exposed to chronic carbon disulfide (CS2) poisoning, without detected symptoms of organic lesions in the nervous system. The study covered 188 viscose spinners occupationally exposed to changing concentrations of CS2 vapours whose mean annual results of measurements ranged between 10 and 35 mg/m3, and the mean individual exposure fell within the range of 9.9-41.6 mg/m3 (mean--25.8 mg/m3). The frequency of alpha rhythm was analysed in EEG recordings with exclusive or nearly exclusive alpha rhythm in two groups studied. The presence or absence of subjective symptoms was taken as a criterion for the selection of subjects. Group I was composed of 116 subjects with subjective symptoms. Group II consisted of 72 workers with neither subjective nor objective symptoms. The age in group I ranged from 26 to 65 years (mean, 48.7 years), and the duration of employed from 5 to 39 years (mean, 23.3 years). The complaints reported were of neurasthenic and polyneuropathic type. The age in group II ranged from 28 to 63 years (mean, 49.4 years), the duration of occupational exposure accounted for 8-43 years (mean, 25.6 years). The control group included 194 persons with EEG routinely regarded as normal, matched by gender, age and work shift distribution. The subjects in Group I reported most frequently the following complaints: headache (72.4%), vertigo (48.3%), increased emotional irritability (42.2%), dysmnesia (36.2%), sleep disorders (27.6%), concentration difficulties (25.9%), limb pains (36.2%) and paraesthesia (27.6%). In the groups of subjects chronically exposed to CS2, both with subjective neurological symptoms, and without subjective or objective neurological symptoms, EEG recordings, routinely regarded as normal, did not reveal constant and symmetrical frequency of alpha rhythm waves. EEC recordings in the CS2 exposed workers with subjective neurological symptoms revealed almost constant frequency (12.9%) or slightly fluctuating frequency (41.4%) in 54.3% of subjects. In 45.7% of subjects considerable fluctuation of alpha rhythm frequency at the range of 3-4 Hz was found. Frequency disturbances applied to both sides, however, they were more pronounced in the leftside leads. Statistical analysis showed, neither in Group I nor in Group II, significant relationship between the pattern of alpha rhythm frequency fluctuations, the duration of CS2 exposure and the cumulative exposure index. Substantial and asymmetric fluctuations of alpha rhythm frequency found in the exposed group of subjects with subjective symptoms were considered as subclinical disturbances in the function of the central nervous system.

[Studies on biological monitoring of adrenocortical function in workers exposed to carbon disulfide]

OBJECTIVE

To study the effects of carbon disulfide on adrenocortical function and analyze and compare the various biological materials used in biological monitoring by observing the changes of adrenocortical hormones and their metabolites in blood, saliva and urine of a viscose rayon mill exposed to carbon disulfide for long-term.

METHODS

Cortisol in blood and saliva was determined by 125I-radioimmunoassay (RIA), cortisol and cortisone in urine by high performance liquid chromatogaphy (HPLC), and their metabolite 17-ketosteroid by chemical method. Data collected were analyzed by SPSS software in microcomputer to compare their difference between two groups, relationship between them and concentrations of carbon disulfide, and consistence between nontraumatic indices in saliva and urine and blood hormone.

RESULTS

Levels of adrenocortical hormones and their metabolites in blood, urine and saliva decreased in the workers exposed to concentrations of carbon disulfide exceeding the national allowable standard, and correlated closely with them. There was a good correlationship between indices in blood and in urine.

CONCLUSION

Blood cortisol, urine free cortisol, cortisone and its metabolite 17-ketosteroid all are good indices for biological effects reflecting adrenocortical function, and detection for urine cortisol and its metabolite is more practicable because of its non-traumatic features.

[Methodologic guidelines related to neurologic and neurophysiologic examinations in a population occupationally exposed to carbon disulfide (CS2)]

A range of neurological and neurophysiological examinations of persons chronically exposed to carbon disulfide (CS2), together with appropriate methods were presented. The principles of the subjective and objective examinations of persons suspected to be chronically exposed to CS2 were discussed. A characteristic syndrome of subjective symptoms with their neurasthennic and polyneuropathic nature was highlighted. The usefulness of neurophysiological examinations in the diagnosis of chronic CS2 poisoning, and particularly the value of the brain evoked potentials, were evaluated.

[Study on electroneuromyography of 175 workers exposed to carbon disulfide]

A study on electroneuromyography of 175 workers exposed to carbon disulfide demonstrated that electroneuromyographic abnormalities of these workers were in accordance with characteristic alteration of axonal polyneuropathy. Electroneuromyography was an objective and sensitive method to detect the early damage of peripheral nerve caused by low-level exposure to carbon disulfide. The dose-response relationship between the exposure to carbon disulfide and the damage of peripheral nerve was demonstrated.

[The effect of carbon disulphide on menopause, concentration of monoamines, gonadotropins, estrogens and androgens in women]

The clinical examinations covered 1710 women. The investigations were performed on 199 women with symptoms of menopause, who were selected and divided into two groups. The first control group (I) included 80 women employed in the Industrial Clothing Factory "Dana" in Szczecin, without contact with carbon disulphide. The second study group (II) comprised 119 women employed in the Synthetic Fibres Factory "Chemitex-Wiskord" and exposed chronically to carbon disulphide in concentration of 9.36-23.4 mg/m3. The microclimate conditions of the production halls in both groups were similar (Tab. 1). Menopause was present in 16.59% of women in the population chronically exposed to carbon disulphide, as compared with 8.05% in the normal population. Mean age at menopause in women of the first group was 48.1 years and 43.9 years in the second group. In the studied group of menopausal women retrospective estimation of menopausal and gestational cycles shows statistically significant increase in abortion and disorders of menstrual cycles (p < 0.001) (Tab. 2). The women chronically exposed to CS2 had significantly more frequently headaches, weight gain and loss of libido (p < 0.001). In the normal group fatigue, palpitations and hot flushes were found significantly more often (p < 0.001) (Tab. 4). The serum concentrations of estrone (p < 0.01), estradiol, progesterone, 17-hydroxyprogesterone were significantly decreased in women chronically exposed to CS2 (p < 0.001). No significant differences in the level of FSH or LH were noted between both groups (Tab. 3). The daily excretion of adrenaline and noradrenaline in urine concentrations of dopamine in plasma of women chronically exposed to CS2, was significantly lower (p < 0.001), but the serum concentrations of serotonin (Tab. 5), testosterone, dehydroepiandrosterone sulphate (DHAS) and prolactin in plasma were significantly higher (p < 0.001). No difference concerning the level in serum of dehydroepiandrosterone and beta-endorfine was found (Tab. 6). Significant negative linear correlations between serotonin and FSH (r = -0.45; p < 0.001), serotonin and daily excretion of adrenaline (r = -0.43; p < 0.01) or noradrenaline (r = -0.58; p < 0.001) were disclosed in the exposed group. In this group a positive correlation was noted between the concentration of serotonin and prolactin (r = 0.45; p < 0.001).

Electrophysiological investigation of central, peripheral and autonomic nerve function in workers with long-term low-level exposure to carbon disulphide in the viscose industry

OBJECTIVE

Neurotoxicity of carbon disulphide (CS2) is well known. The air concentration at the workplace at which such adverse effects can first be observed is the subject of controversial discussion.

METHODS

In a cross-sectional study on CS2-exposed workers peripheral motor and sensory nerve conduction studies, somatosensory evoked potentials, thermotesting and investigation of forced respiration sinus arrythmia have been carried out. The data from 222 workers exposed to CS2 in the viscose industry were evaluated and compared with data from 191 employees from the same factory with similar physical and psychological stress factors but without detectable occupational contact to neurotoxic substances. Median exposure to CS2 was below the currently valid occupational-medical threshold limit value (MAK-value) of 10 ppm. Multiple linear or multiple logistic regression analysis was used to check for statistical differences.

RESULTS

Binary evaluation (comparison of exposed persons versus controls after multiple linear regression) revealed a slightly lower value in the exposed group for the motor nerve conduction velocity (MNCV, -0.76 m/s, median 48 m/s), but a long way from pathological thresholds. No dose-response relationship could be found within the exposed group for any evaluation criteria of CS2-exposure. Somatosensory evoked potentials, thermotesting and analysis of heart rate variability yielded no indication of a neurotoxic effect of CS2.

CONCLUSION

Isolated decrease of MNCV in binary evaluation is, with regard to the known mechanism of CS2-neurotoxicity and the lack of a dose-response relationship, obviously not due to toxic effects. We interpret our results as showing that an adverse effect of carbon disulphide at the exposure ranges found was not detectable in the exposed group.

Heart rate variability in workers exposed to carbon disulfide

It is assumed that the cardiovascular impairments resulting from CS2 exposure may be associated with some functional disturbances within the autonomic nervous system. We adopted the heart rate variability (HRV) analysis to investigate the sympathetic and parasympathetic functions of the autonomic nervous system in workers exposed to carbon disulfide. The studies were performed on 152 workers, aged 24-66, with the period of exposure ranging from 5-38 years and 93 age-matched, non-exposed, healthy individuals as the control group. The HRV analysis concerned time-domain (AVG R-R, SD R-R, modal, median, minimum and maximum values) and frequency-domain indices (power spectrum in the very low-VLF, low-LF and high-HF frequency bands) calculated using the fast Fourier transformation. In the exposed group, neurovegetative regulation impairments could be observed. They were expressed as increased heart rate at rest, reduced power spectrum: total (TPS) and within HF, LF and VLF frequency bands as well as the absence of the physiological dependence of HRV parameters on age. These abnormalities could be found even in the group of workers exposed to the lowest CS2 levels (0-10 mg/m3) and they concerned the VLF band. In workers under conditions of exposure to 10-18 mg/m3 the dysfunction of the autonomic control referred both to its sympathetic and parasympathetic part and was found to be more intense in workers exposed to the highest CS2 concentrations (over 18 mg/m3). In view of our findings we concluded that occupational exposure to carbon disulfide may bring about an impaired neurovegetative regulation of the cardiovascular function.

A review of carbon disulfide exposure data and the association between carbon disulfide exposure and ischemic heart disease mortality

Recent regulatory efforts have devoted attention to carbon disulfide (CS2) exposure and its potential effects on the cardiovascular system. To investigate the association between CS2 exposure and ischemic heart disease (IHD) mortality, the analysis presented here had the following objectives: (i) to review historical CS2 exposure data in the viscose rayon industry and identify trends and (ii) to use these historical data to suggest a standard mortality ratio (SMR)-exposure relationship and a threshold level for occupational exposure to CS2, CS2 exposure data were extracted from published studies and used with the SMR versus exposure score relationship developed by Sweetnam et al. (Br. J. Ind. Med. 44, 220-227, 1987) to relate SMRs directly to exposure. Upper and lower bound exposure profiles were derived and used to identify exposure thresholds. For an IHD SMR equal to 100, the upper and lower bound exposures were 60 and 20 ppm, respectively. The analysis indicates that the risk of IHD mortality and its relationship to CS2 exposure is meaningful only for workers exposed to high level for many years. These high levels, which existed many years ago, are no longer found in the workplace. The results of this analysis suggest a safe regulatory exposure level for CS2 between 15 and 20 ppm.

Effects of exposure to carbon disulfide (CS2) on electrocardiographic features of ischemic heart disease among viscose rayon factory workers

The objective of the study was to evaluate viscose plant workers for electrocardiographic manifestations resulting from exposure to carbon disulfide (CS2). A total of 162 workers (118 in an exposure group and 44 in a reference group) were evaluated using a health questionnaire, physical check-up, biochemical analysis of blood samples and electrocardiograms (ECG). The exposure group consisted of workers in the following areas: viscose manufacturing, cellophane processing, ripening, and filament spinning. Reference group workers were from the administrative office, rolling area, pulp processing, and testing office. Only slight differences were found in the biochemical analyses of the two groups, with the exception of sodium (Na) levels. Personal and area sampling results were found to have a high variation due to different locations within the plant and a wide range of manufacturing processes. Highest CS2 concentrations were found in the ripening area (54.60 ppm) and the filament spinning area (19.60 ppm). Using a multiple logistic regression model to control variables (age, gender, body mass index, duration of employment, cholesterol, smoking, and alcohol), we found a relative risk for ECG abnormalities 4.18 times significantly higher for the exposure group. The authors feel that the installation of an adequate ventilation system could greatly reduce the risk of workers developing CS2-induced cardiovascular abnormalities.

Neurotoxicity of long-term low-level exposure to carbon disulphide: results of questionnaire, clinical neurological examination and neuropsychological testing

OBJECTIVE

Carbon disulphide (CS2) is highly neurotoxic. There is ample evidence of damage to the peripheral and central nervous system. The air concentration at which such adverse effects can first be observed is presently a subject of controversy.

METHODS

In a cross-sectional study of CS2-exposed workers from the viscose industry and healthy controls, data on neurological complaints, basic laboratory diagnosis, clinical neurological examination and neuropsychological testing were evaluated. Data were from 222 workers in the viscose industry exposed to CS2 and 191 employees from the same factory with similar physical and psychological stress factors but without occupational contact with neurotoxic substances. Multiple linear or multiple logistic regression analysis was used to check for statistical differences.

RESULTS

The median of the CS2-measurements using personal air sampling was below the current maximum concentration permissible (MAK value) in Germany (10 ppm) in all departments. The threshold limit value was, however, exceeded in almost 10% of the persons investigated. Exposure fluctuated between < 0.2 and 65.7 ppm (median of all departments was 4.02 ppm). As a parameter of internal exposure, CS2-metabolite 2-thio-1,3-thiazolidine-4-carboxylic acid (TTCA) concentrations in the urine of the exposed persons were between < 0.16 and 10.9 mg/g creatinine (median 1.43 mg/g).

CONCLUSIONS

Neither an increase in subjective complaints nor an increase in pathological findings in clinical-neurological and neuropsychological examination could be found in persons exposed to CS2 at the exposure levels described.

Epidemiology of occupation and coronary heart disease: research agenda

Little is known about occupational risks for coronary heart disease. A few specific toxins encountered occupationally are known to affect the heart, most prominently carbon disulfide, nitroglycerin, and carbon monoxide. Of these, carbon monoxide is the most common occupational exposure; it is also a common environmental exposure due to vehicle exhaust. Environmental tobacco smoke, noise, heat, and cold are suspected occupational risk factors for cardiovascular disease. In addition, stress at work may increase heart disease, although little is known conclusively with this regard. Unemployment may also increase risk of heart disease. Shift work, which disrupts circadian rhythms, has also been linked to heart disease, although there again, the data are far from conclusive. Physical activity at work, either too much or too little, can also be a risk factor for heart disease. While in general, more physical activity results in less heart disease, heavy lifting (in occupational and nonoccupational settings) has been associated with increased risk of heart attack. Further epidemiologic research into all these areas is warranted.

Epidemiology of occupation and coronary heart disease: research agenda

Little is known about occupational risks for coronary heart disease. A few specific toxins encountered occupationally are known to affect the heart, most prominently carbon disulfide, nitroglycerin, and carbon monoxide. Of these, carbon monoxide is the most common occupational exposure; it is also a common environmental exposure due to vehicle exhaust. Environmental tobacco smoke, noise, heat, and cold are suspected occupational risk factors for cardiovascular disease. In addition, stress at work may increase heart disease, although little is known conclusively with this regard. Unemployment may also increase risk of heart disease. Shift work, which disrupts circadian rhythms, has also been linked to heart disease, although there again, the data are far from conclusive. Physical activity at work, either too much or too little, can also be a risk factor for heart disease. While in general, more physical activity results in less heart disease, heavy lifting (in occupational and nonoccupational settings) has been associated with increased risk of heart attack. Further epidemiologic research into all these areas is warranted.

Carbon disulfide induced polyneuropathy: sural nerve pathology, electrophysiology, and clinical correlation

We report the clinical features, electrophysiological studies, sural nerve pathology and recovery course of carbon disulfide-(CS2) induced polyneuropathy in a 48-year-old man who worked in a viscose rayon plant. Sural nerve biopsy 2 years later still showed degeneration of both axon and myelin with a predominant loss of large myelinated fibers and remyelination. Electrophysiologic studies revealed mixed axonal and demyelinating polyneuropathy. To our knowledge, this is the first human report of sural nerve pathology in the recovery stage due to CS2 intoxication. After diagnosis, the patient was removed from the toxic environment. In the following three years, he showed part recovery predominantly in motor function compatible with the serial nerve conduction studies. We conclude that CS2 polyneuropathy may partly recover years after cessation of exposure.

Epidemiological study of the systemic ophthalmological effects of carbon disulfide

A total of 123 male viscose rayon workers who were exposed to carbon disulfide, and an additional 67 workers who were not exposed to any toxic agent in the working environment, underwent a thorough ophthalmological examination. The relationship between exposure and ophthalmological results was analyzed with univariate and multivariate methods. The most striking findings were strong associations between exposure and the 100-HUE color vision score and excess of microaneurysms in the exposed group. The current threshold limit value appeared to protect against these effects.

Mortality among workers exposed to carbon disulfide

Mortality experience was investigated at a plant in Ontario that produced viscose rayon, with carbon disulfide as a main raw material. Work-history records for 279 deceased workers at the plant (plant A) were obtained and compared with those for 511 deceased workers at a pulp and paper plant in the same city (plant B). In a proportional mortality analysis, using as a reference the general population of Ontario, at both plants there were fewer deaths from ischemic heart disease than expected (the proportional mortality ratios [PMRs] were 83 at plant A and 95 at plant B) but more deaths than expected from cerebrovascular disease (PMRs were 115 at plant A and 149 at plant B). In a subgroup of plant A workers who had been employed in high-carbon-disulfide exposure areas, deaths from ischemic heart disease were less than expected (PMR = 82), particularly among those who worked in these areas for more than 5 y. Most deaths occurred among those aged 65 y or more. Mortality from strokes, however, was greater than expected (PMR = 207, p < .05); the excess was confined to workers who died at age 65 y or older (PMR = 229, p = .01). Proportional mortality from strokes was also increased in the pulp workers among those who died at age 65 y or older (PMR = 153). In a case-control analysis, the risk of ischemic heart disease at plant A was slightly less than at plant B (odds ratio (OR] = 0.92, 95% confidence interval [CI] = 0.60-1.42), with no association between risk and years worked in high-carbon-disulfide areas (OR/y = 0.99, 95% CI = 0.94-1.03). Among those who died at age 65 y or older, the risk of stroke in the high-exposure subgroup was (a) increased significantly, compared with other plant A workers (OR = 4.92, 95% CI = 1.66-14.65); and (b) increased slightly, compared with plant B workers (OR = 1.37, 95% CI = 0.83-2.26). These results suggested an unusually low risk of strokes among other plant A workers. The risk of stroke was associated with years in high-carbon-disulfide areas (OR/y = 1.03, 95% CI = 0.96-1.1 0). The observed increase in proportional mortality from strokes may represent a chance finding, but a causal role for exposure cannot be excluded.

Urinary homovanillic acid and vanillylmandelic acid in workers exposed to carbon disulfide

Homovanillic acid (HVA) and vanillylmandelic acid (VMA), two end products of dopamine metabolism, were measured in 60 workers exposed to carbon disulfide (CS(2)) in a rayon factory and in 48 unexposed workers. The airborne CS(2) concentrations in eight major exposure zones of the plant were measured monthly over a period of 4 years, from 1990 to 1994. In addition, the exposure concentrations and exposure history of each worker were integrated to estimate the overall lifetime exposure. Industrial hygiene data showed that the geometric mean concentrations of CS(2) in the plant ranged from 2.68 to 20.19 ppm, and more than 15% of the studied population had been repeatedly exposed to CS(2) at concentrations exceeding the ACGIH recommended time-weighted average of 10 ppm. The results showed that there was a significantly lower level and a higher proportion of CS(2) workers with decreased HVA and VMA excretion. However, there were no statistical correlations between the two dopaminergic metabolites and the mean CS(2) concentration, and years of employment. In contrast, significant dose-effect relationships were observed between these two metabolites and the integrated cumulative exposure (ICE) variable. The correlation coefficients for ICE and HVA, and ICE and VMA were -0.35 (p < 0.01) and -0.20 (p <0.05), respectively. These data suggest that chronic exposure to CS(2) was associated with measurable reduction in catecholamine metabolite concentrations. This finding is compatible with the earlier observations in laboratory animals that CS(2) exposures interfere with neurochemical metabolism.

Biomarker research in neurotoxicology: the role of mechanistic studies to bridge the gap between the laboratory and epidemiological investigations

There is an increasing interest in the development and validation of biomarkers for use in biochemical/molecular epidemiological studies. Though the area of neurotoxicology has received much attention in the past several years, it still lags behind with regard to the development of biomarkers, particularly those of health effects and susceptibility. This review discusses several aspects of biomarker research as it relates to neurotoxic compounds and focuses on selected agents (organophosphorus insecticides, styrene, n-hexane, carbon disulfide, acrylamide), which have been the subject of a number of investigations in animals and humans. While traditional biomonitoring approaches and novel techniques (e.g., hemoglobin adducts) provide several measurements for monitoring exposure to neurotoxic chemicals, potential markers of genetic susceptibility have been seldom investigated in a neurotoxicology context. Furthermore, the complexity of the nervous system, together with the multiplicity of end points and the limited knowledge of the exact mechanism(s) of action of neurotoxicants, has led to only limited advancements in the development of biomarkers for neurotoxic effects. Significant progress in this area will depend upon an increased understanding of the cellular, biochemical, and molecular targets directly involved in neurotoxicity.

Carbon disulphide. IV. Cardiovascular function in workers in the viscose industry

OBJECTIVE

The aim of the study was to examine whether an increase can be detected in the prevalence of coronary heart disease or a higher prevalence of unusual cardiological findings in workers with occupational exposure to carbon disulphide (CS2) at the level of the threshold limit value of 10 ppm currently valid in occupational medicine.

METHODS

In a cross-sectional study we investigated 247 men occupationally exposed to CS2 and a comparable control group (n = 222). The current exposure to CS2 was measured using personal air monitoring and biological monitoring of all test persons. A cumulative exposure index (median of CS2 exposure in the past multiplied by the duration of employment) was calculated. In addition to collecting comprehensive anamnestic data on all persons, we carried out a physical examination, an ultrasound examination of the large arteries, a resting and exercise ECG and an echocardiographic examination.

RESULTS

No increase could be found in the prevalence of coronary heart disease or of arteriosclerotic findings in the exposed subjects. There was no difference in the distribution of the performance of the two groups in the ergometric tests. The echocardiogram showed a median increase in the diameter of the left atrium and left ventricle of 1-2 mm in the exposed subjects. These differences could also be confirmed statistically after multiple linear regression analysis. The left ventricular, telesystolic diameter was positively associated (P < 0.05) with internal exposure (CS2 metabolite in urine), and fractional shortening revealed a plausible negative trend (P = 0.0755). Current external exposure (CS2 in air) and cumulative exposure did not influence any of the parameters investigated.

CONCLUSION

The findings may indicate a negatively inotropic effect of CS2 so far unknown in man. However, no clinical relevance for this effect was apparent.

[The influence of chronic exposure to carbon disulfide on metabolism of catecholamines and serotonin in women]

Due to more frequent occurrence of the idiopathic arterial hypertension of borderline type (18.97% of screened women), with values varying from 18.7/12.0 to 21.3/12.7 kPa (140/90-160/95 mm Hg), in women chronically exposed to carbon disulfide as compared to the control group (8.5% women), we decided to investigate the activity of sympathetic-adrenal nad serotoninergic systems that play an important role in the haemostasis of cardiovascular system. The aim of the presented study is to evaluate the linear correlation between: 1) serum dopamine-beta hydroxylase activity and the dopamine concentration in plasma as well as 24-hours adrenaline and noradrenaline excretion in the urine; and 2) between catechol-0-methyltransferase and monoaminoxidase activity and the 24-hours excretion of catecholamine in the urine; next the serum and platelet concentration of serotonin and the arterial blood pressure in women chronically exposed to carbon disulfide. The investigations were performed on 140 women, aged 22 to 55, who were divided into two groups: group-I the control group, covered 50 women employed in the Industrial Clothing Factory "Dana" in Szczecin. Group II-the study group, consisted of women employed in the Synthetic Fibres Factory "Wiskord" in Szczecin-Zydowce, in the carbon disulfide (CS2) atmosphere in concentration from 9.36 to 23.4 mg/m3. The microclimate conditions of the production halls in both groups were similar (Tab. 1). It has been observed that in women chronically exposed to CS2 plasma dopamine concentration (p < 0.001) and DBH serum activity (p < 0.001) are significantly lower as compared to the control group parameters (Tab. 2). Also dopamine concentration and DBH activity are lower in all subgroups of women exposed to CS2 (Tab. 3). In women working in the CS2 atmosphere, 24-hours excretion of adrenaline is significantly lower (p < 0.001) as compared to the control group. Parameters for 24-hours noradrenaline and VMA excretion in the urine do not show any statistical significance (Tab. 4). Plasma (p < 0.001) and platelet (p < 0.001) concentration of serotonin is significantly higher in women exposed to CS2. However, 24-hours 5-HIAA excretion in the urine in women of group II is higher than in group I, but does not give evidence of any statistical significance (Tab. 6). Both serum (p < 0.001) and platelet (p < 0.001) MAO activity is significantly lower in women chronically exposed to CS2. Also COMT erythrocyte activity is significantly lower (p < 0.001) in the studied group women (Tab. 8). The women working in the CS2 evaporation display significantly higher serum concentration of total (p < 0.001), bound (p < 0.001) and free (p < 0.001) tryptophane (Tab. 9). In women exposed to CS2, serum concentration of zinc (p < 0.001) and copper ions (p < 0.001) is significantly lower (Tab. 10). In comparison to the control group parameters, the women exposed to CS2 claim values of systolic and diastolic arterial blood pressure being insignificantly higher. However, in women working in CS2 atmosphere the coefficients of linear correlation between plasma (r = 0.59; p < 0.001) and platelet (r = 0.73; p < 0.001) serotonin concentration and the systolic arterial blood pressure, as well as plasma (r = 0.065; p < 0.001) and platelet (r = 0.72; p < 0.001) serotonin concentration and the diastolic arterial blood pressure are significantly higher (Tab. 11). Significantly positive linear correlation between serotonin concentration and arterial blood pressure in women chronically exposed to CS2 may suggest the important role of this amine in the pathogenesis of arterial hypertension.

A cross-sectional study on nerve conduction velocities among workers exposed to carbon disulphide

We examined nerve conduction velocities (NCVs) in the ulnar nerve (motor, slower motor fiber and mixed), the peroneal nerve (motor, MCV) and the sural nerve (sensory, SCV) among 46 Japanese workers exposed to carbon disulphide (CS2, CS2-exposed group) and 28 normal control workers (group C). The subjects had not suffered from diseases or injuries of the peripheral or central nervous system. MCV in the peroneal nerve and SCV in the sural sural nerve in the CS2-exposed group were significantly reduced compared with those of group C (p < 0.05 in both), but no significant difference in NCVs of the ulnar nerve was noted between the two groups. In the two subgroups of the CS2 exposed group (currently exposed: group E n = 24; removed from exposure: group R n = 22), NCVs of group E tended to be lower than those of group R in spite of the younger age of group E. MCV in the peroneal nerve and SCV in the sural nerve in group E were significantly reduced compared with those in group C, but not significantly in group R. These findings indicate the existence of a toxic effect of CS2 exposure on the NCV, predominantly evident in the lower limbs in those workers. On removal from CS2 exposure, NCV recovery seemed to be possible.

Carbon disulphide. III. Risk factors for coronary heart diseases in workers in the viscose industry

To evaluate risk factors for coronary heart disease and factors which can influence the course of acute myocardial infarction in workers exposed to CS2 we performed a cross-sectional study of 247 workers in the viscose industry. The control group of 222 men from the same plant was comparable for age, social status and physical work. The CS2 exposure determined by personal air sampling ranged from < 0.2 ppm to 65.7 ppm (median: 4.0 ppm) and the duration of exposure ranged from 4 to 220 (median: 66) months. Using a multiple linear regression model we found neither higher blood pressure at rest or after exercise, nor hyperlipoproteinaemia in a higher degree, nor lower high-density lipoprotein (HDL) or lower apolipoprotein A-I levels, nor higher blood glucose values, nor indicators of direct cardiotoxic effects or signs of disturbances in blood coagulation in the exposed group in comparison to controls. Regarding the influence of chronic exposure on the investigated parameters, we found an inverse correlation of the cumulative exposure (mean CS2 exposure in the department multiplied by the duration of work in this department) with the HDL concentration. The HDL levels correlated with the duration but not with the intensity of exposure. In the same way the apolipoprotein A-I levels showed a negative association with the duration of exposure in the exposed group as well as in the control group. The HDL concentrations showed the same trend for the controls. It therefore seems that this finding is more likely due to confounding factors than to the CS2 exposure. As all subjects (exposed and controls) have done shift work, in some cases for a long time, this kind of work could be responsible for the negative relationship between the duration of employment as a shift worker and the apolipoprotein A-I and HDL levels. At the current air-borne levels no significant differences were found between the exposed persons and the controls in the distribution frequency for blood pressure values, lipoproteins, blood glucose, blood coagulation and indicators of direct cardiotoxic effects.