Cross-sectional epidemiological study on neurotoxicity of solvents in paints and lacquers

Risk assessments for chronic exposure of children and prospective parents to ethylbenzene (CAS No. 100-41-4)

Potential chronic health risks for children and prospective parents exposed to ethylbenzene were evaluated in response to the Voluntary Children's Chemical Evaluation Program. Ethylbenzene exposure was found to be predominately via inhalation with recent data demonstrating continuing decreases in releases and both outdoor and indoor concentrations over the past several decades. The proportion of ethylbenzene in ambient air that is attributable to the ethylbenzene/styrene chain of commerce appears to be relatively very small, less than 0.1% based on recent relative emission estimates. Toxicity reference values were derived from the available data, with physiologically based pharmacokinetic models and benchmark dose methods used to assess dose-response relationships. An inhalation non-cancer reference concentration or RfC of 0.3 parts per million (ppm) was derived based on ototoxicity. Similarly, an oral non-cancer reference dose or RfD of 0.5 mg/kg body weight/day was derived based on liver effects. For the cancer assessment, emphasis was placed upon mode of action information. Three of four rodent tumor types were determined not to be relevant to human health. A cancer reference value of 0.48 ppm was derived based on mouse lung tumors. The risk characterization for ethylbenzene indicated that even the most highly exposed children and prospective parents are not at risk for non-cancer or cancer effects of ethylbenzene.

The impact of solvent mixtures on neurobehavioral performance: conclusions from epidemiological data

The review of epidemiological studies investigating the neurobehavioral effects of occupational exposure to solvent mixtures sought to contribute to the following issues: (1) Identification of affected cognitive and motor functions. (2) Identification of sensitive neuropsychological tests. (3) Analysis of exposure-effect relationships. The approach was based on the meta-analytical method of effect size estimates. Fifty-three groups from occupational studies were included in the meta-analysis. Forty-eight neuropsychological performance variables could be analyzed as they were included in at least three studies. Seventeen articles provided detailed information on the constituents of mixtures, thereby enabling the computation of an exposure index that allowed the comparison of different mixtures. Significant negative effect sizes were obtained for 12 test variables measuring attention, memory, motor performance and constructional abilities. The greatest proportion of lower performance scores in the exposed groups was shown by different tests of attention: significant effect sizes between d=-0.16 and -0.46 were calculated. Tests of cognitive processing speed, response alternation and inhibition seemed to be sensitive tools for the detection of poorer performance. Exposure-effect relationships were mainly characterized by inconsistent patterns. Crude and inappropriately calculated exposure measures were blamed for this outcome. A healthy worker effect was suggested more consistently: studies examining groups with longer exposure duration obtained smaller effect sizes. Indications of confounding were observed; however, they did not seem sufficient to question consistent effect size patterns. Paying greater attention to the measurement of exposure and including measures of confounding is advisable for future studies and would enhance the explanatory power of cross-sectional studies and meta-analyses.

A cross-sectional study of triallate exposure and neurological health among workers at a pesticide manufacturing and formulating facility

AIMS

To evaluate the relation between an indicator of cumulative exposure to triallate and selected measures of neurological function, including nerve conduction, the prevalence of certain neurological deficits as determined by a medical examination, and vibration perception threshold testing in workers at a pesticide manufacturing plant.

METHODS

Subjects were 50 workers with high estimated triallate exposure ("high triallate" group) and 50 workers with no or low triallate exposure ("no/low triallate" group). Industrial hygienists used existing work histories and personal knowledge of plant operations to develop a triallate score. In-person interviews elicited information on past medical history and on occupational and non-occupational exposures. A neurologist carried out nerve conduction tests of the sural and the peroneal nerves, a standardised neurological examination, and vibration sensation testing.

RESULTS

Differences between the high and the no/low triallate groups were minimal for all but one of the six nerve conduction tests, for the prevalence of neurological abnormalities, and for vibration sensation perception. The high triallate group had lower mean sural nerve peak amplitude than the no/low triallate group (11.7 v 15.2 microV, p = 0.03). This difference was reduced when adjusted for other potential risk factors (12.5 v 14.5 microV, p = 0.25) and was not associated with cumulative triallate score. We also noted several associations between factors other than triallate and nerve conduction measures.

CONCLUSION

The results were consistent with the absence of an association between triallate and measures of neurological function.

Neurotoxic effects of organic solvents among workers in paint and lacquer manufacturing industry

Introduction Organic solvents are chemically different compounds with one common feature: they dissolve fats, oils, resins, cellulose acetate and cellulose nitrate, which makes them widely used in industry. Most often organic solvents are used in paint and lacquer industries, in production of pesticides, plastics, explosives, rubber, cellulose, air conditioners, in pharmaceutical industry and in leather industry. The aim of this research was to analyze the working environment and professional hazards in paint and lacquer manufacturing industry and evaluate effects of chronic exposure to mixture of organic solvents on nervous system of exposed workers. Methodology The exposed group consisted of 50 workers professionally exposed to these noxae, while the control group consisted of 30 workers who have never been exposed to these noxae. Results Examination of working environment in departments of paint and lacquer manufacturing revealed presence of white spirit and toluene above allowed levels. Exposed workers more frequently complained of fatigue, hand numbness, enhanced excitation, and concentration difficulties, forgetfulness and headaches, than workers from the control group. Electroneurographic examination of n. medianus showed reduced motor and sensitive conduction velocity among exposed in comparison to workers from the control group. Reduced motor and sensitive conduction velocity was correlated with duration of exposure to these noxae. Terminal latency of n. medianus was statistically, significantly longer in the exposed group than in the control group. Workers in the exposed group have statistically significantly longer reaction time in response to acoustic and visual stimuli. Discussion Segmental demyelination and axonal degeneration, as forms of damage to peripheral nerves, were identified as responsible for peripheral neuropathy associated with occupational exposure to organic solvents. Conclusion Results of this study show possible neurotoxic effects of noxae detected in the phase of analysis of working conditions and working environment of examined workers.

Occupational exposure to organic solvents and long-term nervous system damage detectable by brain imaging, neurophysiology or histopathology

The purpose of the present review is to assess the evidence published in scientific literature that industrial organic solvents as a generic group have the ability to induce long-term nervous system damage in workers that can be detected by techniques other than neuropsychological testing. The main body of evidence considered in this review was 40 studies involving the use of brain imaging, neurophysiological testing, gross autopsy or histopathology in groups of workers with long-term solvent exposure. Case reports involving both solvent abuse and occupational exposure, and experimental animal data have also been reviewed as supporting data. A number of the studies in groups of workers provide evidence of the presence of marginal atrophic abnormalities in the brain or deficits in nerve conduction velocity in solvent-exposed workers. However, there are limitations in the design of many of these studies, the strength of association between exposure and effect is not consistently strong, no dose-response relationship can be detected, the reported changes lack specificity and there is no coherence between the human and experimental animal data. Overall, it is not possible to draw reliable conclusions with respect to the presence or absence of nervous system damage related to the common properties of organic solvents.

Mood and behavioral symptoms in individuals with chronic solvent exposure

Psychiatric symptoms have been reported for individuals who experience chronic exposure to low levels of organic solvents. However, it is not known what proportion of such individuals experience psychiatric disorder; which specific disorders may be characteristic of this population; or whether bioaccumulation of lead contributes to the relationship between solvent exposure and psychiatric symptoms. Twenty-nine male journeymen painters and 32 male non-painter control subjects were administered semi-structured diagnostic interviews for DSM-III-R Axis I and Axis II disorders. Career solvent exposure and blood lead levels were also measured. Painters and control subjects did not differ significantly with respect to age, intelligence, or demographic characteristics. Results showed that the probability of being diagnosed with a mood disorder differed significantly in painters (41%) and control subjects (16%). Painters (66%) and control subjects (50%) did not differ for substance use diagnoses. Groups also did not differ for personality disorders involving an onset before 25 years of age. In contrast, painters exhibited a sub-clinical pattern of personality dysfunction involving symptomatology that was measured allowing for late onset (after age 25). Finally, a significant dose-response relationship was observed between career solvent exposure, blood lead level, and personality symptoms. In summary, these data showed an increased rate of psychological disturbance in a significant and substantial number of painters. However, not all painters were so characterized. This overall pattern raises a question regarding a potential role for differential vulnerability, which requires empirical validation.

Controversies in neurotoxicology: current status

Several controversial neurotoxic syndromes have received notoriety in the past several decades. For each, the controversy involves the most fundamental question about the existence of the disorder as a clinically diagnosable entity. Interestingly, the most controversial of these syndromes share several features, including argument about the existence of each syndrome in the courtroom. The authors focus their discussion on three problems (painter's encephalopathy, silicone breast implant neurotoxicity, and the Gulf War syndrome) for which no scientific consensus has been reached that would establish them as diagnosable disorders. These syndromes do not meet traditional disease criteria, and until a clear set of symptoms and objective signs can be defined, a definite course and clear cause demonstrated, and specific tests and treatments identified, these syndromes are likely to remain highly controversial.

A Neuropsychological Study of Patients Exposed to Organic Solvents

Sixty-seven male patients exposed to organic solvents were neurospychologically examined. Twenty-five subjects had possible causes of encephalopathy other than solvent exposure, leaving 42 patients for the study of the association between exposure and neuropsychological test results. The patients had been heavily exposed for, on average, 24.6 years (range 2-46). The main clinical findings were impairments of psychomotor function, short-term memory, and attention. The results suggest an association between impaired psychomotor speed and exposure duration (r = 0.41; p = 0.007), with moderate to severe impairment occurring after at least 15 years. Forty percent of the patients exposed for more than 30 years had moderate to severely impaired psychomotor speed. The results suggest declining test performance on Trail Making Test B related to exposure duration (r = -0.34; p = 0.03). Further, the individual age-adjusted score on the Digit Span task (WAIS) was reduced when compared with the individual age-adjusted score on the Picture Completion task (WAIS). This reduction was related to exposure duration (r = -0.48; p = 0.002).

Behavioral effects of exposure to organic solvents in carpet layers

Carpet layers and age-matched controls were investigated both at the beginning of a working day and at the end with four subtests of a neuropsychological test battery (NES2). Exposure to toluene, cyclohexane, ethyl acetate, and heptane was measured with personal air sampling methods. One group of carpet layers used water-based adhesives (WBA) on the day the investigation took place and the other group used contact adhesives (CA) on that day. The WBA group was exposed primarily to toluene, and the CA group was exposed to other solvents as well. Initial (before work) differences in neuropsychological scores between all exposed workers and controls could be attributed to differences in education, the carpet layers being somewhat higher educated. No differences were found between the solvent-exposed and control groups that would suggest persistent effects of chronic solvent exposures. The improvement in test scores over the day was the same in both groups. However, evidence for exposure-related changes in test scores over the day were found within the exposed group.

Trichloroethylene--a review of the literature from a health effects perspective

This report reviews the literature on the impact of exposure to trichloroethylene (TCE) on human health. Special emphasis is given to the health effects reported in excess of national norms by participants in the TCE Subregistry of the Volatile Organic Compounds Registry of the National Exposure Registries--persons with documented exposure to TCE through drinking and use of contaminated water. The health effects reported in excess by some or all of the sex and age groups studied were speech and hearing impairments, effects of stroke, liver problems, anemia and other blood disorders, diabetes, kidney disease, urinary tract disorders, and skin rashes.

Multiple choice vocabulary test MWT as a valid and short test to estimate premorbid intelligence

The discrepancy between current and premorbid ability is a relevant indicator of acquired mental impairment, which itself is closely related to general cerebral dysfunction. The use of tests sensitive to cerebral dysfunction, raises relatively few problems compared with tests being resistant that are used to estimate premorbid mental ability. For premorbid ability, verbal tests assessing knowledge, especially vocabulary, have been shown to be valid. A test, possibly more insensitive to brain dysfunction than the ones usually administered, is the multiple choice vocabulary test (MWT = Mehrfachwahl-Wortschatz-Test). At present only German versions are available. They are presented in some detail because of their advantages. Construction of the MWT is simple, and it can be easily administered in about five minutes. The results correlate fairly well with global IQ in healthy adults (median of r = 0.72 in 22 samples) and are more insensitive to current disturbances than such tests as the WAIS vocabulary test. The limitations of premorbid tests with respect to diagnostic validity are discussed. It is concluded, that studies which do not control premorbid intelligence have to be considered as a "malpractice" and should not be accepted by scientists.

Retrospective assessment of solvent exposure in paint manufacturing

This paper describes how exposure to solvents at two large paint making sites was assessed in a study carried out to investigate the possibility of neuropsychological effects resulting from long term exposure to organic solvents. A job exposure matrix was constructed by buildings and year. A detailed plant history was taken and this was used to identify uniform exposure periods during which workers' exposure to solvents was not thought to have changed significantly. Exposure monitoring data, collected by the company before the study, was then used to characterise exposure within each uniform exposure period. Estimates were made for periods during which no air monitoring was available. Individual detailed job histories were collected for subjects and controls. The job histories were used to estimate exposure on an individual basis with the job exposure matrix. Exposure was expressed as duration, cumulative dose, and intensity of exposure. Classification of exposure by duration alone was found to result in misclassification of subjects.

Investigation of dose related neurobehavioural effects in paintmakers exposed to low levels of solvents

A cross sectional study was carried out to compare 110 paintmakers exposed to solvents with 110 age matched controls for outcome measures designed to assess cognitive performance and mental health. Hygiene data available for the paintmakers allowed the development of individual indices of solvent exposure and the analyses of health effects in relation to both duration and intensity of exposure. No effects on cognitive functioning or mental health were found in the paintmakers. For most of their period of employment the exposure of the paintmakers had been below current occupational exposure limits. The results are therefore interpreted as providing support for the view that long term exposure at or below current compliance levels does not result in damage to the central nervous system.

Behavioral effects of exposure to organic solvents in Dutch painters

The report describes the results of a cross-sectional study of solvent-exposed young and older Dutch painters and two age-matched control groups. Both traditional and computerized neurobehavioral tests were applied. The study did not detect any major differences between the two groups of painters and their two age-matched control groups. It is argued that this absence of differences is probably not due to a lack of sensitivity of the tests applied or the size of the groups studied. The level of exposure was estimated to be within a range at which previous authors have reported solvent-induced CNS effects.

Neurotoxicity of solvent mixtures in spray painters. I. Study design, workplace exposure, and questionnaire

A multidisciplinary cross-sectional study was carried out in 105 spray painters with long-term solvent exposure (10-44 years) and in 58 control subjects not exposed to solvents. By means of air monitoring the solvent concentrations in the ambient air during spray painting were determined using charcoal and silicagel tubes with pumps and passive samplers. In general, the air concentrations of the individual compounds did not exceed the current limit values (MAK values). Aromatic hydrocarbons like toluene, xylene, ethylbenzene, trimethylbenzene, aliphatic hydrocarbons (e.g., heptane) and acetates (ethylacetate, butylacetate) were determined to be important components of paint solvents. However, in unfavorable work conditions the "exposure index" could exceed the permissible limits two or three times. To assess the body solvent load at the time of examination, biological monitoring (BM) was performed. The main finding was that there was no evidence of neurotoxicologically relevant solvent exposure. Only in the case of methyl hippuric acid in urine spot samples did the spray painters show a higher mean value (80 mg/l) than control subjects (below 20 mg/l), indicating recent xylene exposure. Elevated urinary chromium concentrations (maximum value 29 micrograms/l) were found in 28 spray painters as a result of using zinc chromate-containing wash primers without taking protective measures. To assess the degree of past solvent exposure a special questionnaire was used. This included variables like duration and amount of solvent exposure, the presence of a technical ventilation system, health complaints during painting, etc. Additionally, three "solvent exposure indices'' (SEI) were calculated and used for evaluation of "dose-effect relationships.''(ABSTRACT TRUNCATED AT 250 WORDS)

Neurotoxicity of solvent mixtures in spray painters. II. Neurologic, psychiatric, psychological, and neuroradiologic findings

A multidisciplinary cross-sectional study was performed to examine the chronic neurotoxicity of organic solvents. Participating in the study were 105 persons employed as spray painters and having long-term solvent exposure (10-44 years) and a control group consisting of 58 construction workers, electricians, and plumbers without occupational contact to solvents. Samples were matched for age, preexposure intelligence level, occupation, and socioeconomic status. After controlling for potentially non occupational confounding factors (neuropsychiatric diseases, metabolic disorders, high blood pressure, alcohol intake) 83 spray painters and 42 controls were entered finally into the study. The evaluation included work history, self-rating questionnaire, neurologic investigation, psychiatric analysis using the Present State Examination (PSE), psychological testing, and computerized axial tomography (CAT) of the brain. Physical and neurologic examinations demonstrated no case of overt disorders of the central or peripheral nervous system. An important result of the psychiatric analysis was that the syndromes "special features of depression" and "loss of interest and concentration" occurred significantly more frequently among spray painters than among controls. Further analyses demonstrated an association with chronic exposure over 30 years and repeated acute neurotoxic effects during solvent exposures. Neither psychological nor performance tests demonstrated any statistically significant differences in the performance sets after adjustment according to premorbid intelligence level; this finding supports the presumption of only a low grade of mental dysfunction. Correlation analyses indicated a relationship between subjective health complaints and long-term solvent exposure; however, the effect of age cannot be completely ruled out.(ABSTRACT TRUNCATED AT 250 WORDS)

Exposure to organic solvents and neuropsychological dysfunction: a study on monozygotic twins

Twenty one monozygotic twins exposed to organic solvents were compared with their non-exposed cotwins by performance in psychological tests. A further 28 monozygotic twin pairs were examined as a reference group. The study used 11 tests, 10 of which had shown an effect in previous studies on the results of exposure to solvents. Paired comparisons of the test scores showed the exposed twins to have lower performance in associative learning, digit span, and block design. These results agree with two previous studies that used a similar set of tests. Contrary to some other studies, psychomotor speed was not affected, but the results indicated a marginal effect on the control of hand movements. Further comparison of subgroups with a low and a high exposure showed the prevalence of subtle neuropsychological dysfunction to be greater among the more exposed twins.

The effect of low-level toluene exposure on the developing hippocampal region of the rat: histological evidence and volumetric findings

With the intention of investigating possible morphological alterations effected by toluene in the developing CNS, rat pups were exposed to 100 ppm and 500 ppm of atmospheric toluene from postnatal day 1 until sacrifice at postnatal day 28, when the hippocampal region (area dentata, Ammon's horn, subiculum) was examined light microscopically and alterations in the volumes of the layers of the subdivisions were determined. The layers of Ammon's horn and the subiculum were not affected qualitatively or quantitatively by the 500 ppm exposure. Within the area dentata, the volume of the granule cell layer was 6% smaller in animals exposed to 100 ppm and 13% smaller in animals exposed to 500 ppm than they were in controls. The volumes of the hilus, which is a terminal field of granule cell axons, and the commissural-associational zone of the dentate molecular layer, which is the terminal field of the hilar projection to the granule cells, were smaller (12% and 19%) in animals exposed to 500 ppm than they were in controls. Argyrophilic cells were found in the granule cell layer of all animals exposed to 500 ppm. Pronounced granule cell degeneration was found in one animal exposed to 500 ppm. The granule cell layer of animals exposed to 100 ppm appeared qualitatively normal. The alterations reported here support the few earlier reports of morphological alterations in the CNS of adult laboratory animals. Effects of toluene similar to those described, that is alterations in specific neuron populations and their afferent and efferent terminal fields may complement changes in neurophysiology and behavior that have been observed in prenatally and perinatally exposed rodent pups. Causal relationships, however, remain to be elucidated.

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.