Clinical and neurobehavioural study of the acute and chronic neurotoxicity of styrene

A cross sectional field study of workers exposed to styrene was performed to evaluate possible acute and chronic neurotoxic effects. A total of 36 workers of four companies handling polyester resin materials for one to 16 years (median: 7 years) and two control groups were each examined on a Monday. The control group 1 (formed to compare acute effects) consisted of 20 men from two companies with no exposure to neurotoxic chemicals. To compare chronic effects, a second control group was formed by "one to one matching" with respect to age, socioeconomic status, and pre-exposure intelligence level. Ambient air monitoring using active sampling (short time) and passive samplers (long time) showed styrene in air concentrations as follows: range 3-251 ppm (median: 18 ppm) and concentrations 140-600 ppm during lamination of the inside of boats. For biological monitoring the results were as follows (postshift samples: range/median): styrene in blood: 5-482 micrograms/dl (39 micrograms/dl), mandelic acid urine: 0.01-3.64 g/l (0.21 g/l), and phenylglyoxylic acid urine: 0.01-0.87 g/l (0.19 g/l). The clinical examination found no signs or symptoms of peripheral neuropathy or encephalopathy. The principal work related health complaints were acute, reversible irritation of the eyes that occurred after exposure to styrene concentrations of 200 ppm or more. The neurobehavioural tests showed no significant differences in acute effects (p greater than 0.05) between the two groups or between preshift and postshift testing. Nor were there any significant differences in the relevant neurobehavioural variables between the styrene workers and the controls. It is concluded that occupational exposure to styrene concentrations in air up to 100 ppm causes no adverse acute or chronic effects on the central nervous system.     

Chronic neurobehavioural effects of toluene

Neurobehavioural tests were undertaken by 30 female workers exposed to toluene and matched controls with low occupational exposure to toluene. The environmental air levels (TWA) of toluene was 88 ppm for the exposed workers and 13 ppm for the controls. The toluene in blood concentrations for the exposed workers was 1.25 mg/l and for the controls 0.16 mg/l. Statistically significant differences between workers exposed to toluene and controls in neurobehavioural tests measuring manual dexterity (grooved peg board), visual scanning (trail making, visual reproduction, Benton visual retention, and digit symbol), and verbal memory (digit span) were observed. Further, the performance at each of these tests was related to time weighted average exposure concentrations of air toluene. The workers exposed to toluene had no clinical symptoms or signs. The question arises as to whether these impairments in neurobehavioural tests are reversible or whether they could be a forerunner of more severe damage.     

Chronic neurobehavioural effects of toluene.

Neurobehavioural tests were undertaken by 30 female workers exposed to toluene and matched controls with low occupational exposure to toluene. The environmental air levels (TWA) of toluene was 88 ppm for the exposed workers and 13 ppm for the controls. The toluene in blood concentrations for the exposed workers was 1.25 mg/l and for the controls 0.16 mg/l. Statistically significant differences between workers exposed to toluene and controls in neurobehavioural tests measuring manual dexterity (grooved peg board), visual scanning (trail making, visual reproduction, Benton visual retention, and digit symbol), and verbal memory (digit span) were observed. Further, the performance at each of these tests was related to time weighted average exposure concentrations of air toluene. The workers exposed to toluene had no clinical symptoms or signs. The question arises as to whether these impairments in neurobehavioural tests are reversible or whether they could be a forerunner of more severe damage.     

Blood benzene concentrations in workers exposed to oxygenated fuel in Fairbanks,Alaska

 Objective: In November 1992 residents of Fairbanks, Alaska became concerned about the potential health effects of an oxygenated fuel program during which 15% (by volume) methyl tertiary butyl ether (MTBE) was added to gasoline. To address those concerns, we earlier completed a survey of occupational exposure to MTBE. We conducted a follow-up survey of workers’ exposure to benzene from gasoline in Fairbanks. Design: Cross-sectional exposure survey. Methods: We examined blood concentrations of benzene from a convenience sample of workers taken in December 1992 during the oxygenated fuel program and from another convenience sample of workers taken in February 1993 after the program was suspended. Results: In December, the median blood benzene concentration of samples taken from four mechanics after their workshift (postshift) was 1.32  μg/l (range, 0.84–2.61 μg/l), and seven nonmechanics (drivers and other garage workers) had a median postshift blood benzene concentration of 0.27 μg/l (range, 0.09– 0.45 μg/l). In February, nine mechanics had a median postshift blood benzene concentration of 1.99 μg/l (range, 0.92–3.23 μg/l), and nine nonmechanics had a median postshift blood benzene concentration of 0.26 μg/l (range, 0.2–0.46 μg/l). Conclusion: Mechanics had higher blood benzene concentrations than did nonmechanics, but further study is needed to determine the impact of the oxygenated fuel program on exposure to benzene. Received: 6 November 1995/Accepted: 2 April 1996     

Urinary 1-hydroxypyrene concentrations in coke oven workers

OBJECTIVES: To investigate the relation of individual occupational exposure to total particulates benzene soluble fraction (BSF) of ambient air with urinary 1-hydroxypyrene (1-OHP) concentrations among coke oven workers in Taiwan. METHODS: 80 coke oven workers and 50 referents were monitored individually for the BSF of breathing zone air over three consecutive days. Exposures were categorised as high, medium, or low among coke oven workers based on exposure situations. The high exposure group (n = 18) worked over the oven. The medium and low exposure groups (n = 41 and n = 21) worked at the side of the oven for > 4 hours and < 4 hours a day, respectively. Urine was collected before the shift on the morning of day 1 and after the shift on the afternoon of day 3 to find the change of 1-OHP concentrations across the shift. RESULTS: The median (range) changes of urinary 1-OHP concentrations across the shift for various exposure situations (microgram/g creatinine) were as follows: high 182 (7 to 3168); medium 9 (-8 to 511); low 7 (-6 to 28); and referents 0.2 (-2 to 72). This change of urinary 1-OHP was highly associated with individual occupational exposure to the BSF in air (r = 0.74 and 0.64, p < 0.001). The regression model showed significant effects of individual exposures to the BSF and alcohol consumption on urinary postshift 1-OHP after adjusting for preshift 1-OHP in the total population (n = 130). More exposure to the BSF led to higher postshift 1-OHP (p < 0.001); current drinkers of > 120 g/week had lower urinary postshift 1-OHP than never and former drinkers (p = 0.01). A 10-fold increase in the average BSF in air resulted in about a 2.5-fold increase in postshift 1-OHP among the 80 coke oven workers. CONCLUSION: Urinary 1-OHP concentrations can be used as a good biomarker to assess individual exposure to the BSF in air. Alcohol drinking may modify the toxicokinetic pathway of the BSF; the effects of alcohol should be investigated further in occupational studies.

 

     

N,N- Dimethylformamide – influence of working conditions and skin penetration on the internal exposure of workers in synthetic textile production

Objectives: This study examined the external and internal exposure to the solvent N,N-dimethylformamide (DMF) of 126 workers from a factory producing synthetic fibers. Methods: Air measurements were carried out using personal air samplers with diffusion tubes (Dräger, ORSA 5). For the purpose of biological monitoring the levels of N-methylformamide (NMF) in urine were measured in preshift and postshift samples. Determinations were carried out using gas chromatography. Anamnestic data were collected with standardized questionnaires, including personal data, working history and current working conditions, and former and current illness with regard to the effects of DMF. Skin diseases were documented by a dermatologist. Results: DMF concentrations measured in the air ranged between <0.1 and 37.9?ppm (median 1.2?ppm). Concentrations of NMF varied from 0.05 to 22.0?mg/l (preshift values) and from 0.9 to 100.0?mg/l (postshift values). The creatinine-related values (0.02–44.6?mg/g preshift; 0.4–62.3 postshift) were subject to less variation and therefore represented the level of exposure better than the values related to volume. Additional investigation of a subcollective (n?=?31) over a period of 4 days showed that NMF did not accumulate in the organism. The positive but relatively weak association observed between the DMF concentrations measured in the workplace air and the values recorded for internal exposure in this study can be explained by influencing factors such as dermal absorption or protective clothing. Interindividual differences in internal exposure were found for the specific work areas. The German BAT value (15?mg NMF/l urine) was exceeded in 36 persons (29%) despite the use of breathing protection and protective gloves, without increased values being measured in the air. Increased absorption without higher-level exposure could particularly also be observed in employees with eczema. Conclusions: From the point of view of the prevention of disease, biological monitoring is the best instrument for exposure assessment of workers exposed to DMF.     

Subclinical impairment of colour vision among workers exposed to styrene.

The effects of exposure to styrene were studied among 60 men aged 20 to 56 (mean 29.5) employed in shipbuilding. Exposure was due to the handling of glass reinforced polyester materials. The study was cross sectional and the workers were compared with a control group matched for age, social and occupational state, and ethnic origin. During the study, the mean atmospheric exposure to styrene was 24.3 ppm. Mean urinary elimination was 230 mg/g creatinine for mandelic acid and 57.4 mg/g creatinine for phenylglyoxylic acid. The Farnsworth 100 hue test showed no significant differences between the exposed and control groups for error scores. A significant difference was found, however, for the number of subjects with errors axis in the red-green, or blue-yellow ranges, or both, which was larger among the exposed workers (32/60 v 20/60 for the controls (p < 0.05)). Psychometric tests were also conducted, using the World Health Organisation (WHO) neurobehavioural core test battery. Of the seven tests it included, anomalies were only found for the aiming test. These results suggest that exposure to moderate styrene concentrations of the order of 25 ppm can lead to impairment of colour vision.     

Subclinical impairment of colour vision among workers exposed to styrene.

The effects of exposure to styrene were studied among 60 men aged 20 to 56 (mean 29.5) employed in shipbuilding. Exposure was due to the handling of glass reinforced polyester materials. The study was cross sectional and the workers were compared with a control group matched for age, social and occupational state, and ethnic origin. During the study, the mean atmospheric exposure to styrene was 24.3 ppm. Mean urinary elimination was 230 mg/g creatinine for mandelic acid and 57.4 mg/g creatinine for phenylglyoxylic acid. The Farnsworth 100 hue test showed no significant differences between the exposed and control groups for error scores. A significant difference was found, however, for the number of subjects with errors axis in the red-green, or blue-yellow ranges, or both, which was larger among the exposed workers (32/60 v 20/60 for the controls (p < 0.05)). Psychometric tests were also conducted, using the World Health Organisation (WHO) neurobehavioural core test battery. Of the seven tests it included, anomalies were only found for the aiming test. These results suggest that exposure to moderate styrene concentrations of the order of 25 ppm can lead to impairment of colour vision.     

Longitudinal study to explore chronic neuropsychologic effects on solvent exposed workers

AIM: The aim of the study was to examine possible neurotoxic effects on the central nervous system (CNS) in relation to a chronic solvent exposure at the workplace. METHOD: The collective included 127 workers exposed to solvent mixtures, such as spray painters and printers. They were examined twice by means of a physical examination, neuropsychological testbattery, biological and air monitoring. RESULTS: Major component of the solvents were white spirits in concentrations up to 127 ppm in air and 2,666 microg/l in blood. Single substances were mainly toluene and xylenes in concentrations below current threshold values at the workplace. During the 2 yr interval, the concentrations of solvents decreased, and no significant associations between the neuropsychological tests and the solvent exposure were found. Regarding the whole working history of each participant, we found a significant reduction on information processing velocity and performance in the trailmaking test, as well as more complaints of workers with higher solvent exposure in the past. CONCLUSIONS: A slight increase of subjective complaints and a deteriorated power of concentration seems to be associated with chronic solvent exposure.     

Neurobehavioural changes and persistence of complaints in workers exposed to styrene in a polyester boat building plant: influence of exposure characteristics and microsomal epoxide hydrolase phenotype

OBJECTIVES—To investigate neurobehavioural effects and the persistence of complaints in workers exposed to styrene relative to exposure characteristics and the enzyme microsomal epoxide hydrolase (mEH) activity.
METHODS—A cross sectional study was performed in a retrospective cohort of workers of a polyester boat building plant 3 years after the main activity shut down in 1989. Workers still currently exposed to a much lower concentration of styrene in air than before (n=27) and formerly exposed workers (n=90) were compared with matched control workers (n=64). Currently and formerly exposed workers laminated 4700 and 3610 hours on average at mean exposure to styrene concentrations of 148 and 157 mg/m³ respectively. A structured neurological anamnesis into former and present complaints, the NSC-60 questionnaire, and computer assisted neurobehavioural tests (NES) were administered. The mEH phenotype activity was measured in lymphocytes with a novel gas chromatography-mass spectroscopy (GC-MS) method.
RESULTS—For the period before 1989, currently and formerly exposed workers reported more complaints than control workers which related well with the mean exposure to airborn styrene concentration (p=0.03). Most complaints disappeared after the end of exposure, although the chest, equilibrium, and somatic category scores of NSC-60 and the number of workers reporting diminished sense of smell remained increased in formerly exposed workers (p0.05). Symbol-digit substitution and digit span forwards test results were worse in currently and formerly exposed workers (p0.01). In the combined group of currently and formerly exposed workers, the symbol-digit substitution and colour-word vigilance results related well to duration of exposure (p<0.01 and p=0.03) and mEH phenotype activity (p=0.01 and p=0.05), whereas the digit span forwards results only showed associations of borderline significance (duration of exposure (p=0.08) and mEH phenotype activity (p=0.08)).
CONCLUSION—Most subjective symptoms were reversible but some persisted after the end of exposure to styrene, whereas dysfunction of visuomotor performance and perceptual speed seemed to persist. Duration of exposure at lamination tasks and the interaction, duration of exposure×concentration of exposure, were found to be the best predictors of worsening visuomotor and perceptual speed performances. Activity of the mEH phenotype may play a modulating part in styrene neurotoxicity. The results suggested that less than 10 years of exposure to atmospheric styrene at an average concentration of 155 mg/m³ may result in persistent neurotoxic effects.


Keywords: styrene; neurobehavioural performance; neurotoxicity; microsomal epoxide hydrolase     

Isopropanol and methylformate exposure in a foundry: exposure data and neurobehavioural measurements

Objectives: The aim of this study was to determine the dose-effect relationship between solvent exposure and acute neurobehavioural effects at the worksite. Methods: In a balanced design, ten workers in a Swiss foundry were monitored for 15 days at ten different times during work. Urine samples were taken in the morning and at the time of examination, and personal exposure to isopropanol and methylformate was measured with active samplers. Neurobehavioural tests such as postural balance (bipedal, bipedal blind, monopedal), simple reaction time and digit span of the Neurobehavioural Evaluation System (NES2) and a combined memory and reaction-time test, the combi-test, were performed. A rating of well-being, and the last consumption of alcohol, caffeine, nicotine and medication were reported. Results: Average environmental concentrations of isopropanol were at 44 ppm (±16 ppm), and at 36 ppm (±21 ppm) for methylformate. Maximum values of personal exposure to isopropanol reached barely the maximal allowable concentration (MAC) value (400 ppm); the methylformate personal exposure of three workers exceeded the MAC value (100 ppm). Urine concentrations of methanol were high (3.1 ± 2.3 mg/l in the morning, 7.8 ± 4.9 mg/l after exposure) compared with the results of other studies; concentrations of isopropanol were rather low (0.88 ± 0.73 mg/l after exposure). Conclusions: Nevertheless, between personal exposure and biomonitoring, linear correlation was found. Methylformate exposure correlated with methanol and formic acid concentration in the urine, and isopropanol exposure with its concentration in the urine. With the neurobehavioural tests used, no solvent effect in relation to the dose could be determined. Received: 21 January 2000 / Accepted: 20 May 2000     

Neuropsychological effects of exposure to naphtha among automotive workers.

The association between exposure to naphtha and neurobehavioural measures was examined prospectively over one year among workers employed at an automotive plant that used naphtha to calibrate fuel injectors. The neurobehavioural tests included those that assess mood, basic intelligence, and functioning of the cerebral frontal lobes and limbic system and were designed so that acute, reversible, and chronic effects of solvent exposure could be assessed. Participants were 248 workers in June 1988, and the testing was repeated on 185 of these workers in 1989. Concentrations of naphtha at the plant ranged from six to 709 mg/m3, although exposure was greater in 1988 than in 1989. Duration of exposure for individual subjects ranged from 0.8 to 7.3 years. Cross sectional data analyses showed significant associations between level of exposure to naphtha and slower timed scores on trails A, and greater reports of negative affective symptoms on profile of mood states scales in 1988 but not 1989. Threshold model analyses of the 1989 data showed an association between score on visual reproductions immediate recall and daily exposure to naphtha at or above 1050 h x mg/m3. Models of chronic exposure showed no associations between chronic exposure and negative neurobehavioural outcome. Results suggest that naphtha produces mild acute reversible effects on function of the central nervous system at or above daily exposures of 540 h x mg/m3 (approximately 90 ppm/h).     

Neurobehavioural evaluation of Venezuelan workers exposed to inorganic lead.

OBJECTIVES--To assess neurobehavioural effects of low exposure to lead, 43 workers from a lead smelter and 45 workers from a glass factory were evaluated with the World Health Organisation neurobehavioural core test battery (NCTB) in a cross sectional study. METHODS--The NCTB comprises a questionnaire and seven tests that measure simple reaction time, short-term memory (digit span, Benton), mood (profile of mood states), eye-hand coordination (Santa Ana pegboard, pursuit aiming II), and perceptual speed (digit-symbol). RESULTS--Smelter workers were employed on average for four years, and had a mean blood lead concentration of 2.0 mumol/l (42 micrograms/dl). Glass factory workers had a mean of 0.72 mumol/l (15 micrograms/dl). Historical blood lead concentrations were used to classify exposure based on current, peak, and time weighted average. Although the exposed workers performed less well than the non-exposed in 10 of 14 response variables, only profile of mood states tension-anxiety, hostility, and depression mood scales showed a significantly poorer dose-response relation with blood lead concentration in multiple linear regression models that included age, education, and alcohol intake as covariates. The frequency of symptoms of anger, depression, fatigue, and joint pain were also significantly increased in the exposed group. CONCLUSION--This study is consistent with the larger body of neurobehavioural research of low occupational exposure to lead. The small effects found in this study occurred at blood lead concentrations slightly lower than those reported in several previous studies.     

Serum fluoride as an indicator of occupational hydrofluoric acid exposure

Summary To define the relationship between ionic fluoride concentration in the serum of workers and the amount of hydrofluoric acid (HF) in the work environment, pre-and postshift serum and urine samples of 142 HF workers and 270 unexposed workers were examined. The maximum and minimum concentrations of HF in the air in each workshop varied from the mean by less than 30%. The pre-exposure levels of serum and urinary fluoride in HF workers were higher (P < 0.001) than the control values. This suggests that fluoride excretion from the body continues for at least 12 h. The postshift serum and urinary fluoride concentrations of these workers were significantly higher (P < 0.001) than the preshift concentrations. A good correlation (r = 0.64) was obtained between postshift serum fluoride and postshift urine fluoride. There was a linear relationship between mean serum fluoride concentration and HF concentration in the workshop. A mean fluoride concentration of 82.3 g/l with a lower fiducial limit (95%, P = 0.05) of 57.9 g/l was estimated to correspond to an atmospheric HF concentration of 3 ppm. This is the maximum allowable environmental concentration recommended by the Japanese Association of Industrial Health, and it is also the threshold limit value suggested by the American Conference of Governmental Industrial Hygienists. The results demonstrate that exposure to HF can be monitored by determining the serum fluoride concentration.     

Serum hepatic biochemical activity in two populations of workers exposed to styrene

OBJECTIVE—To determine whether hepatic biochemical changes, as measured by routinely available tests indicative of hepatocellular necrosis, cholestasis, or altered hepatic clearance of bilirubin, occur in association with low to moderate exposure to styrene commonly experienced in industrial production.
METHODS—Two independent cross sectional studies were performed comparing serum hepatic transaminases (alanine aminotransferase (ALT) and aspartate aminotransferase (AST)), cholestatic enzymes (alkaline phosphatase (AP) and γ glutamyl transpeptidase (GGT)), and bilirubin in (a) 47 workers of fibreglass reinforced plastics who were exposed to styrene and (b) 21 boat and tank fabricators, with separate referent groups of unexposed workers. Exposure to styrene was assessed in air by dosimetry, and in venous blood by headspace analysis. Hepatic biochemical variables were assessed across strata of exposure to styrene defined as 25 ppm in air, or 0.275 mg/l in blood, adjusting for age, sex, body mass index, and ethanol consumption.
RESULTS—A consistent and significant linear trend for increasing direct bilirubin and direct/total bilirubin ratio was found in association with increasing exposure to styrene, by both air and blood monitoring, in both studies. Mean direct bilirubin concentrations increased from 0.05-0.08 mg% in referents to 0.12-0.19 in workers exposed above 25 ppm, with a significant exposure-response trend (p<0.005). Significantly increased direct/total bilirubin ratios, ranging from 0.22 to 0.35 were associated with exposure to styrene (p<0.001), indicating diminished hepatic clearance of conjugated bilirubin. Also, a significant linear association between the hepatic transaminases ALT and AST and exposure to styrene was found in pooled regression analyses, with an increase in AP of about 10 IU/ml in workers exposed above 25 ppm air or 0.275 mg/l blood styrene in pooled analyses from both studies.
CONCLUSIONS—The consistent finding of increased direct bilirubin and AP concentrations in these two independent studies provides evidence for diminished hepatic clearance of conjugated bilirubin with associated cholestasis in workers exposed to styrene. The finding of a significant linear association between hepatic transaminase concentrations and exposure to styrene in pooled analyses is consistent with mild hepatic injury and associated metabolic dysfunction.


Keywords: hepatotoxicity; styrene; surveillance; bilirubin; aminotransferases     

Urinary mandelic acid concentration after occupational exposure to styrene and its use as a biological exposure test.

Excretion of mandelic acid from workers in the reinforced polyester plastic industry was studied with the determination of urinary mandelic acid concentrations. The styrene exposure level at the workplaces was evaluated with measurements of the styrene concentration in the ambient air. Three different groups (I, II and III) were studied. In group I [n=9, median of the time-weighted average (TWA) of exposure = 23 ppmof styrene, postexposure observation period = 64 h] two excretion slopes were observed, the first with a median half-time of 9.4 h (postexposure period 0--18 h) and a second with a median half-time of 16.6 h (postexposure period 19--64 h). For group II (n=9, median TWA exposure = 248 ppm, postexposure observation period = 15 h) a half-time of 6.4 h was found. These results suggest that the excretion rate of mandelic acid is dependent on the styrene exposure level. In addition the mandelic acid concentrations of 29 workers (group III) before and after the work shift were analyzed. The urinary mandelic acid concentrations of groups I, II and III, sampled immediately after the 8-h work shift, correlated with the 8-h TWA of styrene exposure (n=47, r=0.93). Accordingly about 2,300 mg of mandelic acid per gram of creatinine corresponded to 100 ppm of styrene.     

Impaired colour discrimination among workers exposed to styrene: relevance of a urinary metabolite.

OBJECTIVES--To survey the loss of colour vision among Japanese workers who have been exposed to styrene concentrations currently considered low (about 20 ppm). Also to assess the effects of styrene by examination of the nature of the relation between disorder of colour vision and age, alcohol consumption, and other variables. METHODS--Colour discrimination was examined in 64 male workers exposed to styrene (mean age; 38.0, mean exposed years; 7.0) and in 69 controls (mean age; 38.0). A standardised questionnaire was adopted to collect work history, occupational or non-occupational solvent exposure, alcohol consumption, and drug use. Colour vision was evaluated by the Lanthony desaturated panel D-15 test. The results of the test were expressed as the colour confusion index (CCI). RESULTS--The mean atmospheric styrene concentration was about 20 ppm. The mean urinary concentration of mandelic acid was 0.22 g/l. There was a significant difference in CCI between exposed workers and age matched controls. Colour vision of workers whose concentration of urinary mandelic acid was > or = 0.42 g/l was significantly impaired when compared with workers whose concentration was < 0.42 g/l. Multiple linear regression analysis that controlled confounding variables such as age, alcohol consumption, smoking, and educational attainment showed that the CCI was significantly related to the concentration of urinary mandelic acid. In both exposed workers and controls, the types of defects were mostly blue-yellow loss, although a few subjects showed complex loss. No one showed only red-green loss. CONCLUSIONS--These findings suggest that exposure to moderate styrene concentrations can lead to impairment of colour vision, and that there is a significant correlation with the urinary metabolite of styrene.     

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-thio1,3-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. Received: 19 December 1995/Accepted: 18 July 1996     

The effects of exposure to aluminium on neurobehavioural function and dopaminergic metabolism

A study was conducted to evaluate the effects of exposure to aluminium (Al) on neurobehavioural function and dopaminergic metabolism among 33 exposed workers compared to 40 controls. The parameters measured included concentrations of Al in air, serum Al and urine Al. WHO Neurobehavioural Core Test Battery was used to measure the neurobehavioural functions. Homovanillic acid (HVA) and vanillymandellic acid (VMA), two end products of catecholamine metabolism were measured using high-pressure liquid chromatography (HPLC). Determinations of Al in serum and urine were carried out using precolumn lumogallion reaction HPLC technique. The geometric mean of the airborne concentration of inhalable Al dust was 1.90 mg/m3 (range 0.62-8.24 mg/m³). The mean concentration of Al in urine was significantly higher in the exposed workers than the controls (12.25 ± 6.04 vs 5.78 ± 3.10 ug/l), but no statistical difference was observed for serum Al (1.68 ± 0.63 vs 1.31 ± 0.40 mug/l); suggesting that urinary Al is a better biomarker for Al exposure. The neurobehavioural evaluation showed that there were significant differences for Santa Ana tests, digit symbol and Benton test, implying that the manual dexterity, eye-hand coordination and memory were poorer in the Al-exposed workers. The data also showed that both of the catecholamine metabolites were higher in the exposed group, especially urinary VMA (p < 0.01). These data reflect that exposure to Al could interfere with the dopaminergic metabolism and neurocognitive function.     

Assessment of the peripheral, central, and autonomic nervous system function in styrene workers.

To investigate the effects of styrene exposure on peripheral, central, and autonomic nervous system functions in man, we measured the distribution of nerve conduction velocities (DCV), short-latency somatosensory evoked potentials (SSEP), and variability in electrocardiographic R-R interval (CVRR) as well as conventional sensory and motor median nerve conduction velocities (SCV and MCV) in eleven styrene-exposed workers. The styrene workers' urinary phenylglyoxylic acid levels ranged from 31 to 419 (mean 169) mg/g creatinine at the end of the work shift on the examination day (estimated exposure to styrene of 22 ppm in air). Control subjects, matched to each styrene worker by sex and age, were selected from healthy adults without cardiovascular, neurologic and other potentially confounding disorders. In the styrene workers, we found that the V80 velocity of the DCV, below which 80% of active nerve fibers lie, and the SCV were both significantly slowed; the CVRR was also significantly reduced. There were no significant differences in SSEP latencies, MCV, or heart rate between the exposed workers and controls. These data, despite the small sample size, suggest that styrene affects the faster myelinated fibers of the peripheral sensory nerves, and that it also affects autonomic nervous activity.