Visual dysfunction in workers exposed to a mixture of organic solvents

Low-level occupational exposure to BTEX and dyschromatopsia: a systematic review and meta-analysis

Objectives. The present study aimed to assess whether occupational exposure to low concentrations of benzene, toluene, ethylbenzene and xylene (BTEX) is associated with color vision impairment. Methods. We queried PubMed, Scopus, Embase, Web of Science and ProQuest as the main databases, as well as gray literature such as Google Scholar. A random-effects model was used to assess relative risk. A funnel plot was created to assess publication bias. Meta-regression analysis was applied to identify variables that explain the between-study variation in the reported risk estimate. Results. An overall standardized mean difference of 0.529 (95% confidence interval [0.269, 0.788]; p < 0.0001) was obtained in the random-effects model, which corresponded to a medium-size effect. Duration and the levels of exposure to benzene, toluene and xylene were the significant predictors of the magnitude of the combined risk estimate. Chronic exposure to low levels of BTEX was associated with dyschromatopsia determined by the color confusion index. Conclusions. The impairments can occur even at exposures lower than the occupational exposure limits of BTEX. However, there are several flaws in the determination of workers' exposure, which did not allow to establish how low a level of these chemicals can cause color vision impairment.

One-Dimensional Defect Layer Photonic Crystal Sensor for Purity Assessment of Organic Solvents

This paper presents the design and analysis of a one-dimensional defect layer photonic crystal (1D-DLPC) sensor for the assessment of the purity of chemical solvents with enhanced accuracy. Chemical solvents are frequently used in chemical processes as reaction mediums. It is essential to ascertain its purity since impurities can significantly affect the outcome of the reaction. The structure of the proposed one-dimensional defect layer photonic crystal sensor consists of a defect layer sandwiched between alternate layers of ZnO and SiO2 organized with a certain periodicity. It has been shown that the localized defect modes inside the structure can detect minute refractive index changes based on the degree of impurity of chemical solvents. Simulation studies have been performed through the transfer matrix method (TMM) and the performance of the design is evaluated using several metrics such as sensitivity, full width at half-maximum, figure of merit, quality factor, and dynamic range. Results indicate that the designed one-dimensional defect layer photonic crystal sensor has a significantly high efficiency and is suitable for detecting impure solvents.

Exposure to volatile hydrocarbons and neurologic function among oil spill workers up to 6 years after the Deepwater Horizon disaster

BACKGROUND

During the 2010 Deepwater Horizon (DWH) disaster, oil spill response and cleanup (OSRC) workers were exposed to toxic volatile components of crude oil. Few studies have examined exposure to individual volatile hydrocarbon chemicals below occupational exposure limits in relation to neurologic function among OSRC workers.

OBJECTIVES

To investigate the association of several spill-related chemicals (benzene, toluene, ethylbenzene, xylene, n-hexane, i.e., BTEX-H) and total petroleum hydrocarbons (THC) with neurologic function among DWH spill workers enrolled in the Gulf Long-term Follow-up Study.

METHODS

Cumulative exposure to THC and BTEX-H across the oil spill cleanup period were estimated using a job-exposure matrix that linked air measurement data to detailed self-reported DWH OSRC work histories. We ascertained quantitative neurologic function data via a comprehensive test battery at a clinical examination that occurred 4-6 years after the DWH disaster. We used multivariable linear regression and modified Poisson regression to evaluate relationships of exposures (quartiles (Q)) with 4 neurologic function measures. We examined modification of the associations by age at enrollment (<50 vs. ≥50 years).

RESULTS

We did not find evidence of adverse neurologic effects from crude oil exposures among the overall study population. However, among workers ≥50 years of age, several individual chemical exposures were associated with poorer vibrotactile acuity of the great toe, with statistically significant effects observed in Q3 or Q4 of exposures (range of log mean difference in Q4 across exposures: 0.13-0.26 μm). We also observed suggestive adverse associations among those ≥ age 50 years for tests of postural stability and single-leg stance, although most effect estimates did not reach thresholds of statistical significance (p < 0.05).

CONCLUSIONS

Higher exposures to volatile components of crude oil were associated with modest deficits in neurologic function among OSRC workers who were age 50 years or older at study enrollment.

A tool for identifying green solvents for printed electronics

The emerging field of printed electronics uses large amounts of printing and coating solvents during fabrication, which commonly are deposited and evaporated within spaces available to workers. It is in this context unfortunate that many of the currently employed solvents are non-desirable from health, safety, or environmental perspectives. Here, we address this issue through the development of a tool for the straightforward identification of functional and "green" replacement solvents. In short, the tool organizes a large set of solvents according to their Hansen solubility parameters, ink properties, and sustainability descriptors, and through systematic iteration delivers suggestions for green alternative solvents with similar dissolution capacity as the current non-sustainable solvent. We exemplify the merit of the tool in a case study on a multi-solute ink for high-performance light-emitting electrochemical cells, where a non-desired solvent was successfully replaced by two benign alternatives. The green-solvent selection tool is freely available at: www.opeg-umu.se/green-solvent-tool .

Smoking, urinary cotinine levels and incidence of visual impairment

The longitudinal relationship between smoking status and risk of developing visual impairment (VI) remains unclear. We examined the relationship of smoking status and urinary cotinine level, an objective measure of smoking, with incidence of VI. This cohort study included 279,069 individuals free of VI who were followed for up to 8.8 years (median 4.8 years). VI was defined as when bilateral visual acuity was worse than 0.5 (cutoffs of 0.3 Logarithm of the Minimum Angle of Resolution). During 1,324,429.8 person-years of follow-up, 7852 participants developed new-onset bilateral VI. Self-reported current smoking status was associated with increased risk of developing VI in both men and women, with a stronger association in women (P for interaction = 0.01). Multivariable adjusted hazard ratios (95% confidence intervals) for incident VI comparing current smokers to never-smokers were 1.14 (1.04–1.25) in men and 1.52 (1.28–1.80) in women. Urinary cotinine levels of ≥ 100 ng/ml were significantly associated with increased risk of incident VI, and these associations remained when introducing changes in urinary cotinine and other confounders during follow-up as time-varying covariates. Cigarette smoking assessed based on self-report and urinary cotinine level was associated with increased incidence of VI. Our findings identify smoking as an independent risk factor for VI.

Chronic Exposure to Solvents Among Construction Painters: Reductions in Exposure and Neurobehavioral Health Effects

OBJECTIVE

The aim of this study was to assess the neurobehavioral effects of lifetime solvent exposure by comparing the performance of painters and demographically comparable controls.

METHODS

Performance of exposed painters (N = 133) was compared with unexposed tapers, glaziers, or carpenters (N = 78) on the following domains: motor/perceptual speed, visual contrast, attention, working memory/planning, and visual and verbal memory. Lifetime exposure was estimated with questionnaires, field measurements, and paint composition.

RESULTS

After controlling for confounders, lifetime solvent exposure did not predict reduction in performance for overall domains of function. Lifetime solvent exposures predicted subtle alterations for individual tests of verbal learning, motor coordination, and visuospatial accuracy.

CONCLUSION

Concentrations of solvents in paints have steadily declined during the working lifetime of subjects in this study. Although reduced performance was observed on individual tests, these alterations were not consistent across tests and unlikely to be of clinical significance.

The neuro-ophthalmological effects related to long-term occupational exposure to organic solvents in painters

PURPOSE

Organic solvents are widely used in many industries, and usually, exposure occurs with mixtures of solvents. Organic solvent mixtures are known for their ability to affect tissues of high lipid content including the myelin sheath in the nervous system. The purpose of this work was to study the evidence that long-term (more than 10 years) exposure to organic solvent mixtures among painters can induce neuro-ophthalmological effects on the function of retinal ganglion cells and the optic tract.

METHODS

Twenty workers with long-term occupational exposure to mixed organic solvents were compared to 40 control subjects. The controls were matched for age, gender, and demographic characteristics but were not occupationally exposed to any known organic solvents, using the following comparators: visual evoked potential (VEP), electroretinogram (ERG), color vision (CV), and contrast sensitivity (CS) testing. Environmental monitoring was done in the work environment with consideration to the American Conference of Governmental Industrial Hygienists Threshold Limit Values (ACGIH-TLVs).

RESULTS

The exposed group had significantly longer latency and higher amplitude of VEP waves especially P100, higher Color Confusion Index (CCI), especially affecting the blue-yellow spectrum, and lower Log CS. There was no significant difference between exposed and nonexposed groups in full-field flash ERG response; however, in the pattern ERG, the exposed group had significantly longer latency of P50, which reflects changes in the retinal ganglion cell.

CONCLUSION

Long-term occupational exposure to mixed organic solvents appeared to affect the optic tract functions in the form of increasing latency of VEP response, affecting the quality of CV and decreasing CS. It also affects the retinal ganglion cell layer with increased latency of P50 of the pattern ERG response.

Organic solvent exposure and contrast sensitivity: comparing men and women

The goal of this study was to compare the visual contrast sensitivity (CS) of men and women exposed and not exposed to organic solvents. Forty-six volunteers of both genders aged between 18 and 41 years (mean±SD=27.72±6.28) participated. Gas station attendants were exposed to gas containing 46.30 ppm of solvents at a temperature of 304±274.39 K, humidity of 62.25±7.59% and ventilation of 0.69±0.46 m/s (a passive gas chromatography-based sampling method was used considering the microclimate variables). Visual CS was measured via the psychophysical method of two-alternative forced choice using vertical sinusoidal gratings with spatial frequencies of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, and 16.0 cpd (cycles per degree) and an average luminance of 34.4 cd/m2. The results showed that visual CS was significantly lower (P<0.05) in the following groups: i) exposed men compared to unexposed men at frequencies of 0.2, 0.5, 1.0, and 2.0 cpd; ii) exposed women compared to unexposed women at a frequency of 5.0 cpd; and iii) exposed women compared to exposed men at a frequency of 0.5 cpd, even at exposures below the tolerance limit (300 ppm). These results suggest that the visual CS of exposed men was impaired over a wider range of spatial frequencies than that of exposed women. This difference may have been due to the higher body fat content of women compared to that of men, suggesting that body fat in women can serve as a protective factor against neurotoxic effects.

Chronic Organic Solvent Exposure Changes Visual Tracking in Men and Women

Organic solvents can change CNS sensory and motor function. Eye-movement analyses can be important tools when investigating the neurotoxic changes that result from chronic organic solvent exposure. The current research measured the eye-movement patterns of men and women with and without histories of chronic organic solvent exposure. A total of 44 volunteers between 18 and 41 years old participated in this study; 22 were men (11 exposed and 11 controls), and 22 were women (11 exposed and 11 controls). Eye movement was evaluated using a 250-Hz High-Speed Video Eye Tracker Toolbox (Cambridge Research Systems) via an image of a maze. Specific body indices of exposed and non-exposed men and women were measured with an Inbody 720 to determine whether the differences in eye-movement patterns were associated with body composition. The data were analyzed using IBM SPSS Statistics version 20.0.0. The results indicated that exposed adults showed significantly more fixations (t = 3.82; p = 0.001; r = 0.51) and longer fixations (t = 4.27; p = 0.001, r = 0.54) than their non-exposed counterparts. Comparisons within men (e.g., exposed and non-exposed) showed significant differences in the number of fixations (t = 2.21; p = 0.04; r = 0.20) and duration of fixations (t = 3.29; p = 0.001; r = 0.35). The same was true for exposed vs. non-exposed women, who showed significant differences in the number of fixations (t = 3.10; p = 0.001; r = 0.32) and fixation durations (t = 2.76; p = 0.01; r = 0.28). However, the results did not show significant differences between exposed women and men in the number and duration of fixations. No correlations were found between eye-movement pattern and body composition measures (p > 0.05). These results suggest that chronic organic solvent exposure affects eye movements, regardless of sex and body composition, and that eye tracking contributes to the investigation of the visual information processing disorders acquired by workers exposed to organic solvents.

Visual functions of workers exposed to organic solvents in petrochemical industries

AIM

The purpose of this study was to evaluate the visual functions of workers exposed to organic solvents in petrochemical industries.

MATERIALS AND METHODS

Thirty workers from the petroleum refinery and 30 age-matched controls (mean age) were recruited. Visual functions and occupational exposure levels were assessed among both the groups. Visual acuity, contrast sensitivity, color vision, and visual fields were evaluated at the workplace. The biological samples, namely blood and urine, were collected at the workplace and transported to the laboratory for analysis. The urinary excretion of hippuric and methylhippuric acid as well as creatinine was measured by high performance liquid chromatography.

RESULTS

The mean age of the workers and controls were 39.7 ± 7.6 years and 38.6 ± 8.1, years respectively. The mean years of experience of the workers were 15.6 ± 6.8 years. Visual acuity was >0.01 LogMAR among both the control and case groups. The contrast sensitivity was reduced at 12cpd among workers. Comparison between groups was done using independent sample t-test. The mean difference in color confusion index was 0.11 ± 0.05 (P = 0.037*). The mean difference in visual fields was -0.31 ± 0.36 dB (P = 0.933). The mean difference in urinary hippuric acid level (urinary metabolite of toluene) between the groups was 0.19 ± 0.96 g/g creatinine (P = 0.049FNx01). The mean difference in the excretion of methylhippuric acid (urinary metabolite of xylene) was 0.06 ± 0.04g/g creatinine (P = 0.154). We also found that exposure was a significant risk factor for color vision defect with an odds ratio of 4.43 (95% CI: 1.36-14.4); P = 0.013.

CONCLUSION

The study results showed that contrast sensitivity and color vision were affected among workers in petrochemical industry.

Impaired colour vision in workers exposed to organic solvents: A systematic review

OBJECTIVE

To evaluate recent evidence concerning the relationship between the exposure to organic solvents and the impairment of colour vision.

METHODS

A bibliographic search was conducted for scientific papers published in the last 15 years, in the LILACS, PubMed, Science Direct, EBSCO, and Cochrane databases that included observational studies assessing the relationship between impairment in colour vision and exposure to organic solvents.

RESULTS

Eleven studies were selected that were performed on an economically active population and used the Lanthony D-15 desaturated test (D-15d), measured the exposure to organic solvents, and included unexposed controls. It was found that there is a statistically significant relationship between the exposure to organic solvents and the presence of an impairment in colour vision.

CONCLUSIONS

The results support the hypothesis that exposure to organic solvents could induce acquired dyschromatopsia. The evaluation of colour vision with the D-15d test is simple and sensitive for diagnosis. More studies need to be conducted on this subject in order to better understand the relationship between impaired colour vision and more severe side effects caused by this exposure.

Toluene inhalation exposure for 13 weeks causes persistent changes in electroretinograms of Long-Evans rats

Studies of humans chronically exposed to volatile organic solvents have reported impaired visual functions, including low contrast sensitivity and reduced color discrimination. These reports, however, lacked confirmation from controlled laboratory experiments. To address this question experimentally, we examined visual function by recording visual evoked potentials (VEP) and/or electroretinograms (ERG) from four sets of rats exposed repeatedly to toluene. In addition, eyes of the rats were examined with an ophthalmoscope and some of the retinal tissues were evaluated for rod and M-cone photoreceptor immunohistochemistry. The first study examined rats following exposure to 0, 10, 100 or 1000ppm toluene by inhalation (6hr/d, 5d/wk) for 13 weeks. One week after the termination of exposure, the rats were implanted with chronically indwelling electrodes and the following week pattern-elicited VEPs were recorded. VEP amplitudes were not significantly changed by toluene exposure. Four to five weeks after completion of exposure, rats were dark-adapted overnight, anesthetized, and several sets of electroretinograms (ERG) were recorded. In dark-adapted ERGs recorded over a 5-log (cd-s/m(2)) range of flash luminance, b-wave amplitudes were significantly reduced at high stimulus luminance values in rats previously exposed to 1000ppm toluene. A second set of rats, exposed concurrently with the first set, was tested approximately one year after the termination of 13 weeks of exposure to toluene. Again, dark-adapted ERG b-wave amplitudes were reduced at high stimulus luminance values in rats previously exposed to 1000ppm toluene. A third set of rats was exposed to the same concentrations of toluene for only 4 weeks, and a fourth set of rats exposed to 0 or 1000ppm toluene for 4 weeks were tested approximately 1year after the completion of exposure. No statistically significant reductions of ERG b-wave amplitude were observed in either set of rats exposed for 4 weeks. No significant changes were observed in ERG a-wave amplitude or latency, b-wave latency, UV- or green-flicker ERGs, or in photopic flash ERGs. There were no changes in the density of rod or M-cone photoreceptors. The ERG b-wave reflects the firing patterns of on-bipolar cells. The reductions of b-wave amplitude after 13 weeks of exposure and persisting for 1year suggest that alterations may have occurred in the inner nuclear layer of the retina, where the bipolar cells reside, or the outer or inner plexiform layers where the bipolar cells make synaptic connections. These data provide experimental evidence that repeated exposure to toluene may lead to subtle persistent changes in visual function. The fact that toluene affected ERGs, but not VEPs, suggests that elements in the rat retina may be more sensitive to organic solvent exposure than the rat visual cortex.

Retinal and visual system: occupational and environmental toxicology

Occupational chemical exposure often results in sensory systems alterations that occur without other clinical signs or symptoms. Approximately 3000 chemicals are toxic to the retina and central visual system. Their dysfunction can have immediate, long-term, and delayed effects on mental health, physical health, and performance and lead to increased occupational injuries. The aims of this chapter are fourfold. First, provide references on retinal/visual system structure, function, and assessment techniques. Second, discuss the retinal features that make it especially vulnerable to toxic chemicals. Third, review the clinical and corresponding experimental data regarding retinal/visual system deficits produced by occupational toxicants: organic solvents (carbon disulfide, trichloroethylene, tetrachloroethylene, styrene, toluene, and mixtures) and metals (inorganic lead, methyl mercury, and mercury vapor). Fourth, discuss occupational and environmental toxicants as risk factors for late-onset retinal diseases and degeneration. Overall, the toxicants altered color vision, rod- and/or cone-mediated electroretinograms, visual fields, spatial contrast sensitivity, and/or retinal thickness. The findings elucidate the importance of conducting multimodal noninvasive clinical, electrophysiologic, imaging and vision testing to monitor toxicant-exposed workers for possible retinal/visual system alterations. Finally, since the retina is a window into the brain, an increased awareness and understanding of retinal/visual system dysfunction should provide additional insight into acquired neurodegenerative disorders.

Neurotoxicity of solvents

Worldwide, several hundred million tons of organic solvents are used annually in household, industry, and other occupational settings. Millions of workers are regularly exposed to organic solvents considered neurotoxic. Acute neurotoxicity due to high exposure of solvent is usually evident, but the nature of long-term effects, such as chronic solvent encephalopathy (CSE), has raised uncertainty even among experts. Earlier studies were criticized for their methodology, mainly epidemiologic studies or investigations of exposed groups with many possible confounders and inadequate exposure assessment. However, an increasing number of studies have been performed since, also on workers with defined CSE based on differential diagnostics. During the last decade, evidence has emerged to enable identification of CSE, a necessity for the early recognition and prevention of progression of dysfunction and disability. Selected chemicals are presented here due to their widespread use, neurotoxic potential, and ability to cause solvent encephalopathy. Constant introduction of new chemicals may introduce new hazardous chemicals or known chemicals may reveal new health effects. It is important to keep an open mind for new findings of solvent-related neurobehavioral effects.

Reconsideration of the WHO NCTB strategy and test selection

The World Health Organization-recommended neurobehavioral core test battery (NCTB) became the international standard for identifying adverse human behavioral effects due to neurotoxic chemical exposure when it was first proposed in 1983. Since then the WHO NCTB has been repeatedly cited as the basis for test selection in human neurotoxicology research. A discussion group was held before the International Symposium on Neurobehavioral Methods and Effects in Occupational and Environmental Health to review the NCTB and reconsider its tests. The workshop made three consensus recommendations to the International Congress on Occupational Health (ICOH) Scientific Committee on Neurotoxicology and Psychophysiology (SCNP):. 1. A 'screening' battery of broadly sensitive tests is needed as guidance to the field of human neurotoxicology 2. The SCNP should convene a panel to reconsider the functions measured and the tests in the WHO NCTB 3. Three disciplines should be represented in the panel recommending a revised NCTB: neuropsychology; experimental psychology; neurology. This recommendation will be pursued at the next meeting of the International Congress on Occupational Health (ICOH) Scientific Committee on Neurotoxicology and Psychophysiology (SCNP).

Color vision impairments among shipyard workers exposed to mixed organic solvents, especially xylene

OBJECTIVES

We evaluated color vision impairment in workers exposed to organic solvents, especially xylene.

METHODS

Three groups of subjects, comprising 63 workers occupationally exposed to organic solvents, 122 non-exposed workers in the same industry, and 185 subjects from the general population as controls, were evaluated for color vision. Exposure to solvents was indirectly evaluated by measuring the concentration of a urinary metabolite. Color vision was assessed using the Lanthony Desaturated 15-hue (Lanthony D-15) panel.

RESULTS

Color confusion index (CCI) values in the exposed group were significantly higher than in the non-exposed workers or the general population, after adjustment for age and education, and significantly correlated with the concentration of methylhippuric acid. Color vision impairments were detected more frequently among the exposed group, and the most common types were type III and complex impairments. The rate of type III impairments was 9.52% in the exposed group, 1.64% in the non-exposed group, and 1.62% in the general population.

CONCLUSION

Our results support the hypothesis that acquired color vision impairments could be induced by exposure to xylene. Testing for color vision impairment is a relatively simple, non-invasive and sensitive diagnostic method for relatively low-level exposures to xylene.

Comparison of work-related symptoms and visual contrast sensitivity between employees at a severely water-damaged school and a school without significant water damage

BACKGROUND

The National Institute for Occupational Safety and Health (NIOSH) conducted a health hazard evaluation (HHE) of a water-damaged school in New Orleans (NO), Louisiana. Our aim in this evaluation was to document employee health effects related to exposure to the water-damaged school, and to determine if VCS testing could serve as a biomarker of effect for occupants who experienced adverse health effects in a water-damaged building.

METHODS

NIOSH physicians and staff administered a work history and medical questionnaire, conducted visual contrast sensitivity (VCS) testing, and collected sticky-tape, air, and dust samples at the school. Counting, culturing, and/or a DNA-based technology, called mold-specific quantitative PCR (MSQPCR), were also used to quantify the molds. A similar health and environmental evaluation was performed at a comparable school in Cincinnati, Ohio which was not water-damaged.

RESULTS

Extensive mold contamination was documented in the water-damaged school and employees (n = 95) had higher prevalences of work-related rashes and nasal, lower respiratory, and constitutional symptoms than those at the comparison school (n = 110). VCS values across all spatial frequencies were lower among employees at the water-damaged school.

CONCLUSIONS

Employees exposed to an extensively water-damaged environment reported adverse health effects, including rashes and nasal, lower respiratory, and constitutional symptoms. VCS values were lower in the employees at the water-damaged school, but we do not recommend using it in evaluation of people exposed to mold. Am. J. Ind. Med. 55:844-854, 2012. This article is a U.S. Government work and is in the public domain in the USA.

Prenatal and early childhood exposure to tetrachloroethylene and adult vision

BACKGROUND

Tetrachloroethylene (PCE; or perchloroethylene) has been implicated in visual impairments among adults with occupational and environmental exposures as well as children born to women with occupational exposure during pregnancy.

OBJECTIVES

Using a population-based retrospective cohort study, we examined the association between prenatal and early childhood exposure to PCE-contaminated drinking water on Cape Cod, Massachusetts, and deficits in adult color vision and contrast sensitivity.

METHODS

We estimated the amount of PCE that was delivered to the family residence from participants' gestation through 5 years of age. We administered to this now adult study population vision tests to assess acuity, contrast sensitivity, and color discrimination.

RESULTS

Participants exposed to higher PCE levels exhibited lower contrast sensitivity at intermediate and high spatial frequencies compared with unexposed participants, although the differences were generally not statistically significant. Exposed participants also exhibited poorer color discrimination than unexposed participants. The difference in mean color confusion indices (CCI) was statistically significant for the Farnsworth test but not Lanthony's D-15d test [Farnsworth CCI mean difference = 0.05, 95% confidence interval (CI): 0.003, 0.10; Lanthony CCI mean difference = 0.07, 95% CI: -0.02, 0.15].

CONCLUSIONS

Prenatal and early childhood exposure to PCE-contaminated drinking water may be associated with long-term subclinical visual dysfunction in adulthood, particularly with respect to color discrimination. Further investigation of this association in similarly exposed populations is necessary.

Long-term occupational exposure to organic solvents affects color vision, contrast sensitivity and visual fields

The purpose of this study was to evaluate the visual outcome of chronic occupational exposure to a mixture of organic solvents by measuring color discrimination, achromatic contrast sensitivity and visual fields in a group of gas station workers. We tested 25 workers (20 males) and 25 controls with no history of chronic exposure to solvents (10 males). All participants had normal ophthalmologic exams. Subjects had worked in gas stations on an average of 9.6±6.2 years. Color vision was evaluated with the Lanthony D15d and Cambridge Colour Test (CCT). Visual field assessment consisted of white-on-white 24–2 automatic perimetry (Humphrey II-750i). Contrast sensitivity was measured for sinusoidal gratings of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0 and 20.0 cycles per degree (cpd). Results from both groups were compared using the Mann–Whitney U test. The number of errors in the D15d was higher for workers relative to controls (p<0.01). Their CCT color discrimination thresholds were elevated compared to the control group along the protan, deutan and tritan confusion axes (p<0.01), and their ellipse area and ellipticity were higher (p<0.01). Genetic analysis of subjects with very elevated color discrimination thresholds excluded congenital causes for the visual losses. Automated perimetry thresholds showed elevation in the 9°, 15° and 21° of eccentricity (p<0.01) and in MD and PSD indexes (p<0.01). Contrast sensitivity losses were found for all spatial frequencies measured (p<0.01) except for 0.5 cpd. Significant correlation was found between previous working years and deutan axis thresholds (rho = 0.59; p<0.05), indexes of the Lanthony D15d (rho = 0.52; p<0.05), perimetry results in the fovea (rho = −0.51; p<0.05) and at 3, 9 and 15 degrees of eccentricity (rho = −0.46; p<0.05). Extensive and diffuse visual changes were found, suggesting that specific occupational limits should be created.

Chemical exposure in occupational settings and related health risks: a neglected area of research in Pakistan

In Pakistan a huge number of workers is routinely exposed to various types of chemical contaminants but there is a dearth of information as to the impact of these agents, due to a lack of a routine surveillance system and proper reporting. Prolonged and sometimes acute occupational exposures to varied organic chemicals may result in numerous health related problems. Studies from all over the world have shown adverse health outcomes of chemicals that are commonly used in various occupations. Such chemical exposures are not just confined to the workplace, but the residents surrounding industrial sites also face significant health risks due to indirect chemical exposure. Occupational exposure is a multidimensional risk factor that varies from one occupation to another, and is associated with health decline in workers. Common determinants of workplace hazards include improper, or lack of use of self-protective equipment, active and passive exposure to cigarette smoke as well as the socio-demographic and economic background of workers. There may be more than one cause of occupational stress and psychophysical disturbance among workers such as workload, lower salaries, and lack of social and medical facilities; indeed, their general health is poor. Therefore, in Pakistan, it is particularly important to focus on these issues and set rules and regulations to create occupational hazard awareness among workers, which will promote health safety at work places. If priorities are given to the correct use of self-protective equipment, adopting proper hygiene at the workplace and to avoid smoking, occupational exposures and consequent health risks may be minimized significantly.

Oculo-Visual Findings among Industrial Mine Workers at Goldfields Ghana Limited, Tarkwa

Objective:

The focus of this study was to evaluate the visual status of mine workers who were directly involved in mining and/or are exposed to the mining environment.

Methods:

A hospital based cross-sectional study was conducted. Four hundred and six (406) workers were conveniently sampled for the study. Information on their socio-demographic data was also collected. In addition, all participants underwent ophthalmic examination.

Results:

The mean age of the workers was 41.1 years. Visual impairment was found in 114 (28.1%) of the study population of which refractive error (56.8%) was the major cause. Presbyopia was also observed in 45.5% of the workers with only 30.3% of them wearing near correction. The prevalence of eye diseases were pterygium/pingueculae (25.8%), conjunctivitis (26.8%), suspected glaucoma (15.3%), and cataract (7.4%).

Conclusions:

Visual impairment and eye diseases were found among the miners.

Psychophysical evaluation of achromatic and chromatic vision of workers chronically exposed to organic solvents

The purpose of this paper was to evaluate achromatic and chromatic vision of workers chronically exposed to organic solvents through psychophysical methods. Thirty-one gas station workers (31.5 ± 8.4 years old) were evaluated. Psychophysical tests were achromatic tests (Snellen chart, spatial and temporal contrast sensitivity, and visual perimetry) and chromatic tests (Ishihara's test, color discrimination ellipses, and Farnsworth-Munsell 100 hue test—FM100). Spatial contrast sensitivities of exposed workers were lower than the control at spatial frequencies of 20 and 30 cpd whilst the temporal contrast sensitivity was preserved. Visual field losses were found in 10–30 degrees of eccentricity in the solvent exposed workers. The exposed workers group had higher error values of FM100 and wider color discrimination ellipses area compared to the controls. Workers occupationally exposed to organic solvents had abnormal visual functions, mainly color vision losses and visual field constriction.

A case study on co-exposure to a mixture of organic solvents in a Tunisian adhesive-producing company

Objectives

to assess environmental and biological monitoring of exposure to organic solvents in a glue-manufacturing company in Sfax, Tunisia.

Methods

Exposure of volunteer workers, in the solvented glue-work-stations, in the control laboratory and in the storage rooms of the finished products, was assessed through indoor-air and urine measurements. Informed consent of the workers was obtained.

Results and discussion

The exposure indexes were found with high values in the solvented workshop as well as in the control laboratory and were respectively, 8.40 and 3.12. These indexes were also correlated with hexane and toluene indoor air concentrations. As to urine, the obtained results for the 2,5-hexandione and hippuric acid, metabolites of hexane and toluene, respectively, were in accord with the indoor-air measurements, with an average of 0.46 mg/l and 1240 mg/g of creatinine.

Conclusion

This study assessed for the first time biological exposure to organic solvents used in Tunisian adhesive industries. Although values are likely to underestimate true exposure levels, some figures exceed European and American occupational exposure guidelines.

Avaliação visual de sujeitos expostos de forma ocupacional a solventes orgânicos através de métodos psicofísicos

Os solventes orgânicos são substâncias neurotóxicas que podem causar efeitos danosos sobre as funções visuais. É comum a exposição ocupacional a esses tipos de substâncias, pois elas apresentam grande aplicabilidade em inúmeras atividades. Os efeitos podem ser quantificados por testes psicofísicos. Os testes mais usados nesse tipo de avaliação são de ordenamento de matizes, como o Teste D15 Dessaturado de Lanthony e o Teste dos 100 Matizes de Farnsworth-Munsell, e avaliação de sensibilidade ao contraste espacial de luminância, como MCT 8000 Vistech, VCTS 6500 Vistech e FACT 101. Em geral esses testes descrevem perda de discriminação de cores, afetando tanto o eixo azul-amarelo quanto o eixo verde-vermelho, e diminuição da sensibilidade ao contraste de luminância principalmente para as frequências espaciais mais baixas. Existe correlação positiva entre os resultados da avaliação psicofísica e vários marcadores biológicos e ambientais, mas essa correlação depende do marcador e do tipo de solvente ao qual os indivíduos são expostos. Fatores como alcoolismo crônico e tabagismo inveterado podem interferir no processo de correlacionar esses resultados.

Visual contrast sensitivity in children exposed to tetrachloroethylene

This study examined relationships between indoor air, breath, and blood tetrachloroethylene (perc) levels and visual contrast sensitivity (VCS) among adult and child residents of buildings with or without a colocated dry cleaner using perc. Decreasing trends in proportions of adults or children with maximum VCS scores indicated decreased VCS at a single spatial frequency (12 cycles per degree [cpd]) among children residing in buildings with colocated dry cleaners when indoor air perc level averaged 336 μg/m³; breath perc level averaged 159.5 μg/m³; and blood perc level averaged 0.51 μg/L. Adjusted logistic regression indicated that increases in indoor air, breath, and blood perc levels among all child participants significantly increased the odds for decreased VCS at 12 cpd. Adult VCS was not significantly decreased by increasing indoor air, breath, or blood perc level. These results suggest that elevated residential perc exposures may alter children's VCS, a possible subclinical central nervous system effect.

Vision abnormalities in young children exposed prenatally to organic solvents

Despite an accumulating body of evidence demonstrating that the visual system is an important target for organic solvent toxicity in adults, little attention has been paid to the visual functioning of children with prenatal exposure to organic solvents. The present study aimed to: (1) determine prospectively whether prenatal solvent exposure increases the risk of visual deficits in infants and (2) assess the relationship between estimates of exposure level and integrity of visual responses. A sample of 21 infants born to women who were occupationally exposed to solvents during pregnancy was compared with 27 non-exposed age-matched control infants. All mothers were recruited from Motherisk, an antenatal counseling service in Toronto, Canada. Contrast sensitivity and grating acuity were assessed using a sweep visual evoked potential (VEP) technique whereas chromatic- and achromatic mechanisms were assessed using a transient VEP technique. Exposure level was estimated from questionnaire data obtained during pregnancy. Testers were masked to exposure status. Results showed a significant reduction in contrast sensitivity in the low and intermediate spatial frequency range in solvent-exposed infants compared to controls (p<0.001). With respect to grating acuity, there was a significant effect of exposure level, with children in the high exposed having reduced grating acuity compared with children in the low exposed group (p<0.025) and controls (p=0.02). Regarding color vision, 26.3% of infants in the exposed group versus 0% of the controls produced abnormal VEP responses to the red-green onset stimulus (p<0.01), but not to either blue-yellow or achromatic stimuli. No differences were found with respect to latency or amplitude of chromatic and achromatic response. These findings suggest that prenatal solvent exposure is associated with selective visual deficits, including reduced contrast sensitivity and abnormal red-green vision. Increasing levels of exposure may lead to further visual deficits affecting grating acuity. These findings support the need for a re-evaluation of current occupational exposure standards for pregnant women.

Neurobehavioral science in hazard identification and risk assessment of neurotoxic agents--what are the requirements for further development?

OBJECTIVES

Modern neurobehavioral methods find useful application in research into the early effects of exposure to neurotoxic agents in the environment. This paper briefly describes the history and evolution of neurobehavioral toxicology, reviews some current trends in research in this specific discipline and identifies the most important needs and challenges to be addressed in future studies.

METHODS

All published literature was considered, including ad hoc meeting reports. Further information was obtained directly from experts in the field.

RESULTS

The number of studies (including those in occupational, environmental and pediatric exposure) using neurobehavioral evaluation is constantly increasing. Regulatory agencies are using scientific data obtained through neurobehavioral assessment, which includes other areas such as neurosensory toxicology. However, further development of this discipline is facing a number of problems and issues. Three major areas that deserve further attention have been identified: (1) specific technical issues regarding testing development, (2) epidemiological issues regarding the study design, including the need for meta-analysis/multi-center studies and for longitudinal observation, and statistical issues regarding the most adequate models for the analysis and treatment of complex neurobehavioral datasets, and (3) the need for scientific consensus on the significance of adverse effects identified with neurobehavioral methods.

CONCLUSIONS

The importance of neurobehavioral toxicology in the evaluation of mechanisms of action and for preventive purposes is progressively growing. Further development is needed for the advancement of this discipline through collaboration between experts from different fields.

Effects of Mixed Organic Solvents on Neuromotor Functions among Workers in Buddhist Altar Manufacturing Factories

To clarify the neuromotor effects of long-term exposure to mixed organic solvents, postural sway and tremor were measured in 62 solvent workers of four Buddhist altar manufacturing factories who had worked for 1-46 (mean 12) yr. By using the passive gas sampler, 8-h time-weighted average concentrations in the workers were estimated to be 0.02-8.7 ppm for toluene, 0.02-7.7 ppm for xylene, 0.02-5.5 ppm for styrene and 0.02-40.5 ppm for n-hexane. Sagittal sway and sway area of the posturography with eyes closed were significantly larger in the solvent workers than in 35 age-matched controls (p<0.05), and there was a significant difference in Romberg quotient of sagittal sway between the two groups (p<0.05). Also, tremor intensities at 1.0-5.9 Hz, 6.0-9.9 Hz and 10.0-13.9 Hz with the right hand, and at 6.0-9.9 Hz with the left hand were significantly stronger in the solvent workers than in the controls. Among the solvent workers, transversal and sagittal sways with eyes open and tremor intensity at 10.0-13.9 Hz were significantly related to toluene exposure (p<0.05), which may have been due to the acute effects of such solvents. These findings suggest that long-term exposure to mixed organic solvents may impair neuromotor functions as measured by postural sway and tremor.