Effect of benzene, toluene, xylene on the semen quality and the function of accessory gonad of exposed workers

The effects on semen and the function of accessory gonad of workers after short and long term exposure to benzene, toluene, and xylene were examined. The semen and blood of 24 married workers exposed to benzene, toluene, and xylene were collected. Routine sperm characteristic, acrosin activity, and Lactate dehydrogenase C4 (LDH-C4) relative activity were detected. The results showed that benzene, toluene, and xylene were found in the blood and semen of some ex-workers at workplaces where the air concentration of benzene, toluene, and xylene exceeded the maximum allowable concentration (MAC). No such solvents were detected in the blood and semen of workers of the control group. The sperm vitality and sperm motility decreased in the exposed workers. The mean acrosin activity, gamma-GT activity and LDH-C4 relative activity in the exposed workers were lower, and fructose concentration was higher than those in the control. There were negative correlations between sperm vitality, sperm activity, acrosin activity, or LDH-C4 relative activity and working history. These results suggest that the mixture of these solvents could affect the sperm and the function of accessory gonad. This might be one reason of the abnormal pregnancy outcome among the wives of workers exposed to benzene, toluene, and xylene.

Effect of thinner inhalation on lipid peroxidation and some antioxidant enzymes of people working with paint thinner

Paint thinner is a commonly used industrial solvent with considerable potential for abuse by inhalation. Paint thinner is taken into the body by inhalation or by contact with the skin. Paint thinner is oxidized gradually by cytochrome P450-dependent monooxygenase and consequently free radicals are produced. In the present study we measured plasma malondialdehyde (MDA, a product of lipid peroxidation) levels as an indicator of oxidative damage and activity levels of antioxidant enzymes gluthatione peroxidase (GSH-Px) and superoxide dismutase (SOD) in erythrocytes of a group of people (n = 18) working with paint thinner. The control group was composed of 18 healthy adults. There was a statistically significant (p < 0.001) increase in MDA (2.0+/-0.7 nmol ml(-1)) and GSH-Px (86.5+/-16.6 U g(-1) Hb) activity levels in people working with paint thinner compared with control subjects (MDA: 1.0+/-0.3 nmol ml(-1); GSH-Px: 53.9+/-14.5 U g(-1) Hb). Similarly, there was also an increase (p < 0.05) in the SOD levels (1079+/-214.6 U g(-1) Hb) of people working with paint thinner compared with controls (953.3+/-46.7 U g(-1) Hb). Based on our results, it can be concluded that paint thinner inhalation may increase lipid peroxidation and consequently induce antioxidant enzymes.

Dose-related color vision impairment in toluene-exposed workers

Occupational exposure to various neurotoxic chemicals can impair color vision. We evaluated this possibility in toluene-exposed workers. Thirty-three rubber workers and 16 referents were studied. We estimated toluene exposure by measuring urinary excretion of the unmodified form of the solvent (i.e., TolU). Color vision was tested with the Lanthony D-15 desaturated panel, and the outcomes were expressed quantitatively with the Color Confusion Index and the Total Confusion Index. Toluene-exposed workers had a subclinical reduction in color vision, compared with referents. We related this effect to solvent cumulative exposure--estimated as the product of urinary excretion of unmodified toluene by previous toluene exposure duration. This approach supports the hypothesis that impairment progresses as exposure continues. In the examined group of workers, toluene exposure was within the occupational limit proposed by the American Conference of Governmental Industrial Hygienists. The observed loss in color vision raises doubts on the real protection afforded by this limit--at least for effects of the solvent on the eyes. Finally, the Total Confusion Index was a more sensitive index than the Color Confusion Index in the evaluation of toluene-related color-vision impairment, suggesting that this index should be adopted in future studies of the effects of chemicals on color perception.

Effect of repeated exposure to methanol and toluene vapor on the metabolism of rats

Wistar male rats were repeatedly exposed to methanol and toluene vapors individually and simultaneously by inhalation 6 hours a day, five days a week for 4 weeks. Blood was obtained from the tail of the rats up to 23 hours after the end of 4-week exposure and the methanol and toluene concentrations were measured. Major metabolites of methanol and toluene, that is, formic acid and hippuric acid in urine were measured up to 6 days after the end of 4-week exposure. The biological half time of toluene in blood in the simultaneous exposure group was shorter than that in the toluene exposure group. This tendency was almost the same as that for one-day exposure, although the biological half time of solvents in the rat blood was prolonged. The half times of methanol were also longer than those for one-day exposure.

Immunological and in-vivo neurological studies on a benzoic acid-specific T cell-derived antigen-binding molecule from the serum of a toluene-sensitive patient

T-cell-derived antigen-binding molecules (TABMs) specific for benzoic acid were isolated from the serum of a toluene-sensitive patient. The resulting purified TABMs (BA-TABMs) did not contain immunoglobulin G and were associated with the cytokine transforming growth factor-beta (TGF-beta). BA-TABMs bound to benzoic acid conjugated to human serum albumin (BA-HSA), as well as to other chemicals conjugated to human serum albumin-including dinitrophenol and oxazolone. The binding of BA-TABMs to the conjugated chemicals increased the level of detectable TGF-beta, and a similar effect was observed with the unconjugated chemicals, benzoic acid and 2,4-dinitrophenol glycine. The increase in TGF-beta was critically dependent on the ratio between BA-TABMs and the conjugated or unconjugated chemicals; the increase was optimum at intermediate concentrations and absent at low and high concentrations. The authors used an established animal model in vivo and demonstrated that TGF-beta enhanced the inflammatory response induced by the release of neuropeptides from sensory nerves; this enhancement occurred in a dose-dependent manner. The BA-TABMs also enhanced this neurogenic inflammatory response in a dose-dependent manner, and this effect was blocked by anti-TGF-beta antibody. When the authors added either BA-HSA or benzoic acid, the effect of BA-TABMs on neurogenic inflammation was further enhanced at intermediate concentrations of antigen and was unaltered or reduced at higher concentrations. TABMs specific to particular chemicals, as a result of their association with cytokines (e.g., TGF-beta), may be implicated in symptom production in chemically sensitive patients.

Experimental irritant contact dermatitis due to cumulative epicutaneous exposure to sodium lauryl sulphate and toluene: single and concurrent application

In clinical practice, cutaneous exposure to a variety of irritants such as surfactants and solvents is frequent. Although the induction of irritant dermatitis by single irritants has been extensively studied in recent years, our knowledge of the effects of simultaneous application of different irritants is limited. Using non-invasive techniques for measurements of transepidermal water loss (TEWL) and skin colour reflectance, we quantified the irritant effects of single and concurrent application of 0.5% sodium lauryl sulphate (SLS) and undiluted toluene (TOL) in vivo. The irritants were applied twice daily for 30 min to the volar forearms of 20 volunteers. Repeated application of SLS and TOL induced an irritant reaction, as indicated by an increase in TEWL and skin redness. In contrast to SLS alone, the application of TOL alone induced only a moderate increase in TEWL, confirming previous results. Concurrent application of SLS/TOL and TOL/SLS induced significantly stronger reactions than those caused by twice daily application of each irritant on its own. Our results demonstrate that a mixed application of an anionic detergent and an organic solvent has an additive effect on skin irritation. It is suggested that pretreatment with SLS causes an increased susceptibility to TOL irritation and vice versa. Thus, the necessity for special precautions against skin absorption of TOL when handling detergents such as SLS is emphasized.

Perfluoropolyethers in the prevention of irritant contact dermatitis

BACKGROUND

Perfluoropolyethers (PFPEs) are non-reactive perfluorinated (no hydrogen atoms) liquid polymers that showed promise as ingredients of protective preparations in occupational dermatology.

OBJECTIVE

The aim of this study was to investigate if oil-in-water (o/w) emulsions containing 0.5, 1.0, 2.0 and 4.0% PFPEs (molecular weight 6,250 D) prevent epidermal barrier disruption induced by a repetitive irritation test (RIT).

METHODS

PFPE-containing o/w emulsions and the emulsion base alone were evaluated against a set of 4 irritants [10% sodium lauryl sulphate (SLS), 0.5% sodium hydroxide (NaOH), 15% lactic acid (LA), and undiluted toluene (TOL)] in the RIT. Ten subjects were tested on the paravertebral skin of the mid-back. Irritation was assessed by visual scoring, transepidermal water loss (TEWL) and colorimetry.

RESULTS

Both the emulsion base and all PFPE-containing preparations significantly suppressed irritation by SLS and NaOH. Against LA and TOL, only the 4% PFPE-containing preparation was significant as assessed by TEWL.

CONCLUSION

A 4% PFPE-containing o/w emulsion significantly inhibits irritation due to a wide spectrum of hydrophilic and lipophilic irritants. o/w emulsions with lower concentrations of PFPE are also effective against SLS and NaOH, but this is also true for the cream base alone. Therefore, further studies are necessary to evaluate if a minimum of 4% PFPE in the base provides additional benefit.

Study of the genotoxicity of toluene

Chromosome analysis was conducted for peripheral lymphocytes of 23 printers exposed to toluene concentrations of 590 mg/m3 in a rotary machine workshop and to rotogravure printing inks. The percentages of aberrant cells were 2.30 in the printers and 1.46 in the control group (n = 22) (p < .05). The concentration of hippuric acid in printers was significantly higher than in the control group (p < .01), and the level of blood toluene at the end of the workshift was 0.500 mg/l. The authors also examined rotogravure printing inks-considered a potential source of genotoxic polycyclic aromatic hydrocarbons because they contained carbon black-their use in printing plants, and previous documentation of increased chromosomal aberrations in rotogravure printers. Only milligrams of fluorene and phenanthrene per gram of the printing inks were found; no polycyclic aromatic hydrocarbons with carcinogenic properties were discovered in the inks. The authors used Salmonella typhimurium indicator strains TA 98, TA 100, TA 1537, and YG 1041 in spot tests and indicator strains TA 98 and TA 100 in plate-incorporation assays to determine that there was no bacterial mutagenicity of all four colors of rotogravure inks. Urinary mutagenicity, which was evaluated with a microsuspension assay containing YG 1041 indicator strain both in the presence and absence of metabolic activation, was also studied. No significant difference in bacterial mutagenicity was found between the exposed and control groups. The increased percentage of aberrant cells in printers can be explained by exposure to genotoxicants that are not excreted in urine. Toluene was the most likely cause of the aberration.

Multicentre study for the development of an in vivo model to evaluate the influence of topical formulations on irritation

Although skin protective products to prevent irritant skin reactions are in wide use, neither standardized test models to prove differences in efficacy exist, nor has the quality or the reproducibility of results been evaluated in a multicentre approach. This should be mandatory when developing or testing skin care products. Therefore, we have designed a multicentre study in an approach to find a standardized test procedure for the evaluation of skin protective products. In this irritation study, a repeated short-time occlusive irritation test (ROIT) with a standardized protocol has been evaluated in 2 phases (12 days and 5 days protocol) in 4 (n=20) respectively 6 (n=33) skilled centres. The skin reaction was induced by 2 irritants (0.5% aq. SLS and toluene, 2x a day for 30 min). Its modification by 3 different cream bases with different hydrophilicity was analyzed. The irritation was monitored by bioengineering methods (TEWL measurement, colorimetry) and by clinical scoring. The evaluation showed that significant results could already be achieved with the 5-day protocol. Furthermore, in spite of the expected inter-centre variations due to heterogeneity of the individual threshold of irritation, interpretation of clinical score, and inter-instrumental variability, the ranking of the vehicles regarding reduction of the irritant reaction was consistent in all centres.

Psychological test performance during experimental challenge to toluene and n-butyl acetate in cases of solvent-induced toxic encephalopathy

OBJECTIVES

This study determined whether performance in neurobehavioral tests deteriorates during subjectively annoying chemical challenge below known neurotoxic thresholds among persons with toxic encephalopathy with subjective hypersensitivity to chemicals.

METHODS

Subjects with symptoms and previous neuropsychological test results compatible with toxic encephalopathy (TE) of either type 2A (N=12) or 2B (N=12) and unexposed referents (N=12) were challenged in an exposure chamber. In a counterbalanced design, the subjects were exposed on 2 occasions to increasing air concentrations of n-butyl acetate and toluene at levels well below the thresholds for neurotoxic effects. Attention and motor speed tests were given (i) in room air outside the chamber before the challenge, (ii) in room air inside the chamber before the exposure, (iii) at 12 ppm (44 or 56 mg/m3), and (iv) at 48 ppm (at 180 or 228 mg/m3).

RESULTS

For both substances the TE groups showed a slight increase (deterioration) in the simple reaction-time task during chemical exposure, but not in the complex reaction-time task or in the digit symbol test of the Wechsler Adult Intelligence Scale. Contrary to reference subjects, the TE subjects did not show any improvement or learning effect in the digit symbol test over the chamber phases. n-Butyl acetate tended to affect cognitive functioning more obviously than toluene did. Suggestion or expectancy effects were not observed in any group in the clean-air baseline conditions.

CONCLUSIONS

The results do not support the notion that men with subjective hypersensitivity to chemicals would be more affected than healthy men regarding cognitive functioning during annoying solvent exposure below thresholds for acute neurotoxic effects.

Cerebellar dysfunction in chronic toluene abuse: beneficial response to amantadine hydrochloride

CASE REPORT

A 21-year-old man who had sniffed toluene since the age of 13 presented with a 4-year history of progressive cerebellar dysfunction and visual deterioration. The patient's condition did not improve despite 5 months of abstinence. Magnetic resonance imaging revealed cerebral atrophy and hypointensity signals in the white matter and bilaterally in the globus pallidus, thalamus, red nucleus, and substantia nigra. Amantadine hydrochloride therapy (100 mg/d, then 200 mg/d) resulted in dramatic improvement of his cerebellar and visual symptoms.

Methodology in epidemiological studies of human neurobehavioral toxicity: a case study with critical review

Health care professionals and government decision makers concerned with neurotoxicity increasingly rely on neuropsychological research studies. An example is an article relied upon by the U.S. Environmental Protection Agency that reported effects on neurobehavioral performance in a group of factory workers exposed to toluene by Foo, Jeyaratnam, and Koh in 1990, which is described as lacking reliability and as having implausible contents. A critical review can serve as an educational tool for neuropsychologists, to emphasize the need to design and document their research and interpret findings without speculation. For example, in the Foo, et al. study the implications of the findings for the general population cannot be interpreted. To conclude that this study has identified toluene as the cause of neurobehavioral deficits is a leap of inference far exceeding the power in their study. The review underscores the need for more critical reviews of research relied upon by decision makers and researchers.

Mortality in a cohort of toluene exposed employees (rotogravure printing plant workers)

Since the beginning of the 1960s, toluene has been used as a solvent in all German rotogravure printing plants in a high degree of purity. These particular exposure conditions allow the investigation of the potential carcinogenicity of long-term toluene exposure. A historical cohort study was performed that included 6830 German men from 11 plants who were exposed to toluene from 1960 to 1992 in three work areas with different exposure levels. Overall, 466 deaths were observed, which provided a standardized mortality ratio (SMR) of 91.3 for overall mortality. A significantly decreased SMR for total mortality was seen in one of the three work areas (SMR = 67). Mortality from cancer did not differ substantially from the expected level, but in one of the work areas, mortality from cancers of the bone (Ninth Revision of the International Classification of Disease [ICD]-9 170; SMR = 813) and connective tissue (ICD-9 171; SMR = 631) was significantly elevated. In the entire cohort, mortality from lung cancer was increased by about 35% above total mortality, and by about 95% in one work area with low toluene exposure (not statistically confirmed). The SMR for death from alcohol dependence was statistically significantly increased (ICD-9 303; SMR = 314).

Individual prior information in a physiological model of 2H8-toluene kinetics: an empirical Bayes estimation strategy

Physiologically-based toxicokinetic (PBTK) models are widely used to quantify whole-body kinetics of various substances. However, since they attempt to reproduce anatomical structures and physiological events, they have a high number of parameters. Their identification from kinetic data alone is often impossible, and other information about the parameters is needed to render the model identifiable. The most commonly used approach consists of independently measuring, or taking fom literature sources, some of the parameters, fixing them in the kinetic model, and then performing model identification on a reduced number of less certain parameters. This results in a substantial reduction of the degrees of freedom of the model. In this study, we show that this method results in final estimates of the free parameters whose precision is overestimated. We then compared this approach with an empirical Bayes approach, which takes into account not only the mean value, but also the error associated with the independently determined parameters. Blood and breath 2H8-toluene washout curves, obtained in 17 subjects, were analyzed with a previously presented PBTK model suitable for person-specific dosimetry. Model parameters with the greatest effect on predicted levels were alveolar ventilation rate QPC, fat tissue fraction VFC, blood-air partition coefficient Kb, fraction of cardiac output to fat Qa/co and rate of extrahepatic metabolism Vmax-p. Differences in the measured and Bayesian-fitted values of QPC, VFC and Kb were significant (p < 0.05), and the precision of the fitted values Vmax-p and Qa/co went from 11 +/- 5% to 75 +/- 170% (NS) and from 8 +/- 2% to 9 +/- 2% (p < 0.05) respectively. The empirical Bayes approach did not result in less reliable parameter estimates: rather, it pointed out that the precision of parameter estimates can be overly optimistic when other parameters in the model, either directly measured or taken from literature sources, are treated as known without error. In conclusion, an empirical Bayes approach to parameter estimation resulted in a better model fit, different final parameter estimates, and more realistic parameter precisions.

Liver damage among shoe repairers

BACKGROUND

The risk of hepatotoxicity in the shoe industry has already been suggested, however, there has been no investigation among the craftsmen who repair shoes.

METHODS

A group of 33 shoe repairers who work in supermarkets, and who use the same glues which contain mixtures of potentially hepatotoxic solvents were identified. A control group of 61 workers not exposed to hepatotoxic substances was also examined. All participants completed a questionnaire designed to identify potential risk factors and the main non-occupational confounding factors for hepatotoxicity. Laboratory tests, commonly used in clinical practice, were done to check whether they were useful markers of hepatotoxicity due to exposure to solvent mixtures, and to investigate which tests should be used in the screening campaigns.

RESULTS

The exposed workers had a higher prevalence of elevated mean alanine aminotransferase (ALT), aspartate aminotransferase (AST), conjugated bilirubin (P=0.0001), and alkaline phosphatase (AP) (P=0.004) than controls did. The number of workers who had values outside the upper limit of normal for our laboratory was significantly higher (ALT P=0.034, AST P=0. 037, conjugated bilirubin P=0.014). Exposed workers all had a ratio of ALT to AST greater than 1, with a mean of 1.5; it was > 1.6 in more than half the exposed workers.

CONCLUSIONS

The findings suggest that there is the possibility of liver involvement among even asymptomatic shoe repairers, and that periodic liver screening may be useful; furthermore, use of these tests (especially the ratio of ALT to AST) for craftsmen who repair shoes, and are exposed to solvent mixtures, is advisable even when environmental monitoring indicates levels below the threshold limit values (TLVs).

[Significance of urinary concentrations of S-benzyl-N-acetylcysteine (S-BMA) in subjects exposed to toluene]

Toluene is a widely diffuse solvent for oils, resins, rubber and paints, either alone or as a major component in a mixture; in the industrial environment it is currently present at concentrations of ppm. Toluene can be absorbed via the lungs or via the skin. The absorption of toluene via inhalation is related to the exposure level as well as the activities level of workers. Once absorbed into the body, toluene is metabolized in man to benzoic acid, followed by hepatic cytochrome P450 catalyzed glycine conjugation to form hippuric acid. Relatively small amounts appear in urine as o-cresol and p-cresol where they occur as glucoronide and sulfate derivate. Only a minor fraction of inhaled solvent is conjugated with glutathione with the production of S-benzyl-N-acetylcysteine (S-BMA). Several biological indicators have been proposed for evaluating toluene exposure in the workplace. These include urinary hippuric acid, toluene in blood, toluene in breath, o-cresol in urine and toluene in urine. We examined a group of 18 workers occupationally exposed to toluene, determining the concentrations of toluene in ambient air and S-BMA in urine. All urine samples were collected at the end of work shift. The renal excretion of S-BMA showed highly significant correlations with environmental data and with the other established parameters of biological monitoring of toluene. The median ambient air concentration was 15.7 ppm ranging from 2.9 to 70.3 ppm, the median concentration of S-BMA was 16.0 micrograms/g creatinine. S-BMA was detectable in urine samples of a control group of 87 subjects non occupationally exposed to toluene. Most of unexposed subjects showed S-BMA values lower than 10 micrograms/g creatinine both in smokers and in nonsmokers and no significant difference was found in samples (20) collected at three intervals during one day. Our finding further indicates that the metabolite S-BMA could be a marker of occupational toluene exposure.

Reproductive endocrine effects of acute exposure to toluene in men and women

OBJECTIVES

Despite observation of adverse reproductive effects of toluene, including alterations of serum gonadotropins (luteinising hormone (LH) and follicle stimulating hormone (FSH)) in humans, little is known of the mechanism of toxicity. The hypothesis was tested that toluene acutely suppresses pulsatile gonadotropin secretion by measuring LH and FSH at frequent intervals during controlled exposure to toluene.

METHODS

Women in the follicular and luteal phases of the menstrual cycle and men were randomised to inhale filtered air with or without 50 ppm toluene through a mouthpiece for 3 hours (19% of the OSHA permissible exposure limit). Blood was sampled by intravenous catheter at 20 minute intervals for 3 hours before, 3 hours during, and 3 hours after exposure. Plasma LH, FSH, and testosterone were measured. Pulse amplitude, pulse frequency, and mean concentrations of LH and FSH for each of the 3 hour periods before, during and after exposure to toluene versus sham exposure were calculated with the ULTRA pulse detection program and compared by analysis of variance (ANOVA) with repeated measures.

RESULTS

In men mean concentrations of LH showed a significant interaction (p < 0.05) between exposure and sampling period, with a greater LH decline during exposure to toluene than sham exposure. However, there was no concomitant effect on testosterone concentrations. The LH pulse frequency of women in the luteal phase showed a trend towards a significant interaction between exposure and sampling period (p = 0.06), with a greater decline in pulse frequency during exposure to toluene than sham exposure. There were no other significant effects of exposure to toluene.

CONCLUSIONS

Three hour exposure to 50 ppm toluene did not result in abnormal episodic LH or FSH secretion profiles, however, subtle effects on LH secretion in men and women in the luteal phase were found. The clinical relevance of these effects is unclear, indicating the need for further study of reproductive function in exposed workers.

Assessment of workers' exposure to aromatic hydrocarbons in a paint industry

A factory survey was conducted in a paint industry in Tehran-Iran. The time-weighted average of toluene and xylene concentration in breathing zone and environmental air were monitored by charcoal tube samplers and GC-FID. The results showed that the tank cleaners had the highest exposure to toluene and xylene (1.5-5.4 times of TLV), while the workers in packaging workshops had the lowest. However, environmental concentration did not show significant differences in workshops and their levels were all lower than the TLV.

Evaluation of organic solvent ototoxicity by the upper limit of hearing

To clarify the effects of organic solvents on hearing, we measured the upper limit of hearing in 93 male workers exposed to organic solvents in 7 factories that produced plastic buttons or baths. Medical examinations, environmental monitoring (i.e., concentration in breathing-zone air), and biological monitoring (i.e., concentration in urine) of the organic solvents were also done. Although the organic solvent concentrations in the environmental monitoring were lower than the occupational exposure limit, the upper limit of hearing was reduced in workers who were exposed for 5 y or more. This reduction was dose-dependent and was related to styrene concentrations in breathing-zone air and mandelic acid concentrations in urine. Even individuals who had normal medical examinations showed a reduced upper limit of hearing. The upper limit of hearing may serve as an early detection indicator of health effects in workers constantly exposed to styrene.

Effects of occupational chronic co-exposure to n-hexane, toluen, and methyl ethyl ketone on NK cell activity and some immunoregulatory cytokine levels in shoe workers

1. To evaluate the effects of occupational long-term co-exposure to n-hexane, toluen, and methyl ethyl ketone (MEK) on NK cell activity and serum IL-2, gamma-IFN levels, we studied a group of workers employed in a shoe factory where the jobs include use of glues and adhesives containing mainly n-hexane, and at low concentrations, toluen and MEK. 2. No differences were found in these parameters even in those workers with 3.3-fold higher mean levels of urine, 2,5-Hxdn and approximately twofold higher mean levels of urine hippuric acid as compared to controls. 3. We conclude that chronic co-exposure to n-hexane, toluen, and MEK at these levels is not associated with an impairment on either NK cell activity or serum IL-2 and gamma-IFN levels.

Risk of chronic effects on the central nervous system at low toluene exposure

This study evaluates the chronic effects on the central nervous system of exposure to low concentrations of toluene (TWA < 20 ppm) on workers in a rotogravure plant. Ninety-eight male workers from a selection pool of 107 (92%) were examined neuropsychologically using a Cognitive Function Scanner, and neurologically by computerized methods measuring co-ordination ability, tremor and position stability. In addition measures of symptoms and former exposure were obtained by questionnaire. The workers were divided into three groups: Group 0 with no exposure to organic solvents (n = 19); Group 1 with exposure to TWA < 20 ppm of toluene for less than 13 years (n = 30) and Group 2 with exposure for more than 12 years (n = 49). Within Group 2, 37 (75%) had been exposed at levels exceeding 100 ppm for 10+ years before 1983. No significant differences were found between Group 0 and Group 1 regarding symptoms and results of the applied tests. Group 2 differed significantly from the two other groups in scoring higher on a symptom index (p = 0.04), particularly regarding concentration ability, reduced memory and fatigue. Group 2 scored significantly poorer on tests for visuospatial function, number learning and word recognition, while no differences regarding neurological functions were observed. The study showed no differences regarding neuropsychological and neurological functions between a non-exposed group of male workers and workers exposed to toluene less than 13 years at TWA < 20 ppm. However, long-term exposure to TWA (time weighted average) of toluene exceeding 100 ppm was associated with impaired neuropsychological function.