Over the last several decades a wide variety of studies have linked mercury exposure to various visual impairments, most notably color vision loss. Unfortunately the majority of these studies have been done overseas and mercury toxicity is not tested for when being evaluated for color vision loss.
Toxicol Ind Health. 2015 Aug;31(8):691-5.
Ophthalmic findings in acute mercury poisoning in adults: A case series study.
Aslan L1, Aslankurt M2, Bozkurt S3, Aksoy A2, Ozdemir M2, Gizir H2, Yasar I2.
The aim of this study is to report ophthalmic findings of acute mercury poisoning in 48 adults referred to emergency department. Full ophthalmologic examination including the best corrected visual acuity, external eye examination, reaction to light, a slit-lamp examination, funduscopy, intraocular pressure measurements, and visual field (VF) and color vision (CV) tests were performed at the presentation and repeated after 6 months. The parametric values of VF test, the mean deviation (MD), and pattern standard deviation (PSD) were recorded in order to compare patients and the 30 healthy controls. The mean parameter of color confusion index in patients was found to be statistically different than controls (p < 0.01). The MD and PSD in patients were different from controls statistically significant (p < 0.01 and p < 0.01, respectively). There was no correlation between the ocular findings and the urine and blood mercury levels. Methyl mercury, held in the school laboratory for experimental purpose, may be a source of poisoning. In this case series, we showed that acute exposure to mercury had hazardous effect on the visual system, especially CV and VF. We propose that emphasizing the public education on the potential hazards of mercury is crucial for preventive community health.
Handb Clin Neurol. 2015;131:325-40. doi: 10.1016/B978-0-444-62627-1.00017-2.
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.
Color vision impairment in workers exposed to mercury vapor.
[Article in Polish] Med Pr. 2011;62(3):227-35. Jedrejko M, Skoczyńska A.
Source: Akademia Medyczna we Wrocławiu, Katedra i Klinika Chorób Wewnetrznych, Zawodowych i Nadciśnienia Tetniczego.
Acquired reversible dyschromatopsia has been associated with occupational exposure to mercury vapor. Early-detected impairments in color discrimination precede adverse permanent effects of mercury, so they may help to monitor the health of the exposed workers. The aim of this study was to evaluate the color discrimination ability in this group of workers, using Lanthony D-15d test.
MATERIAL AND METHODS:
Employed in a chloralkali plant, 27 male workers exposed to mercury vapor and 27 healthy white-collar workers (control group) were qualified for the study. To assess color discrimination, the Lanthony 15-Hue desaturated test (Lanthony D-15) was used. In order to investigate quantitative and qualitative results, the Lanthony D-15d scoring software was performed. Urinary mercury was determined using flameless atomic absorption spectrometry.
In the workers exposed to mercury vapor, urine mercury concentration was 117.4 +/- 62.6 microg/g creatinine on average compared with 0.279 +/- 0.224 mg/g creatinine in the control group (p < 0.0001). In 18 exposed persons (66.7%), the results of the Lanthony D-15d test showed qualitative changes, which are borderline corresponding to the early stage of developing dyschromatopsia type III. The quantitative analysis of the test findings indicated a significantly higher value of the Color Confusion Index (CCI) in the right eye in the exposed group compared to the control group (p = 0.01), with no significant difference in the CCI in the left eye. In the exposed group, the CCI in the right eye was significantly higher than the CCI in the left eye (p = 0.0005). There was neither correlation between CCI and the level of urinary mercury, nor between CCI and duration of exposure.
The results showed that the Lanthony D-15d test is useful in the detection of early toxic effects in the eyesight of the workers exposed to mercury vapor. The observed color vision impairments are borderline corresponding to the early stage of developing dyschromatopsia type III.
Ophthalmic Physiol Opt. 2010 Sep;30(5):724-30. doi: 10.1111/j.1475-1313.2010.00764.x.
Color-space distortions following long-term occupational exposure to mercury vapor.
Feitosa-Santana C, Bimler DL, Paramei GV, Oiwa NN, Barboni MT, Costa MF, Silveira LC, Ventura DF.
Source: Department of Psychology, University of Chicago, Chicago, IL 60637, USA. firstname.lastname@example.org
Color vision was examined in subjects with long-term occupational exposure to mercury (Hg) vapor. The color vision impairment was assessed by employing a quantitative measure of distortion of individual and group perceptual color spaces. Hg subjects (n = 18; 42.1 ± 6.5 years old; exposure time = 10.4 ± 5.0 years; time away from the exposure source = 6.8 ± 4.6 years) and controls (n = 18; 46.1 ± 8.4 years old) were examined using two arrangement tests, D-15 and D-15d, in the traditional way, and also in a triadic procedure. From each subject’s ‘odd-one-out’ choices, matrices of inter-cap subjective dissimilarities were derived and processed by non-metric multidimensional scaling (MDS). D-15d results differed significantly between the Hg-group and the control group (p < 0.05), with the impairment predominantly along the tritan axis. 2D perceptual color spaces, individual and group, were reconstructed, with the dimensions interpreted as the red-green (RG) and the blue-yellow (BY) systems. When color configurations from the Hg-group were compared to those of the controls, they presented more fluctuations along both chromatic dimensions, indicating a statistically significant difference along the BY axis.
In conclusion, the present findings confirm that color vision impairments persist in subjects that have received long-term occupational exposure to Hg-vapor although, at the time of testing, they were presenting mean urinary concentration within the normal range for non-exposed individuals. Considering the advantages of the triadic procedure in clinical evaluation of acquired color vision deficiencies, further studies should attempt to verify and/or improve its efficacy.
J Occup Environ Med. 2009 Dec;51(12):1403-12.
Preliminary findings on the effects of occupational exposure to mercury vapor below safety levels on visual and neuropsychological functions.
Barboni MT, Feitosa-Santana C, Zachi EC, Lago M, Teixeira RA, Taub A, da Costa MF, Silveira LC, Ventura DF.
Source: Neuroscience and Behavior, University of Sao Paulo, Sao Paulo, Brazil. email@example.com
To evaluate whether there are visual and neuropsychological decrements in workers with low exposure to Hg vapor.
Visual fields, contrast sensitivity, color vision, and neuropsychological functions were measured in 10 workers (32.5 +/- 8.5 years) chronically exposed to Hg vapor (4.3 +/- 2.8 years; urinary Hg concentration 22.3 +/- 9.3 microg/g creatinine).
For the worst eyes, we found altered visual field thresholds, lower contrast sensitivity, and color discrimination compared with controls (P <0.05). There were no significant differences between Hg-exposed subjects and controls on neuropsychological tests. Nevertheless, duration of exposure was statistically correlated to verbal memory and depression scores.
Chronic exposure to Hg vapor at currently accepted safety levels was found to be associated with visual losses but not with neuropsychological dysfunctions in the sample of workers studied.
Vis Neurosci. 2008 May-Jun;25(3):487-91.
Irreversible color vision losses in patients with chronic mercury vapor intoxication.
Feitosa-Santana C, Barboni MT, Oiwa NN, Paramei GV, Simões AL, Da Costa MF, Silveira LC, Ventura DF.
Source: Núcleo de Neurociências e Comportamento, Universidade de São Paulo, São Paulo, Brazil. firstname.lastname@example.org
This longitudinal study addresses the reversibility of color vision losses in subjects who had been occupationally exposed to mercury vapor. Color discrimination was assessed in 20 Hg-exposed patients (mean age = 42.4 +/- 6.5 years; 6 females and 14 males) with exposure to Hg vapor during 10.5 +/- 5.3 years and away from the work place (relative to 2002) for 6.8 +/- 4.2 years. During the Hg exposure or up to one year after ceasing it, mean urinary Hg concentration was 47 +/- 35.4 mug/g creatinine. There was no information on Hg urinary concentration at the time of the first tests, in 2002 (Ventura et al., 2005), but at the time of the follow-up tests, in 2005, this value was 1.4 +/- 1.4 microg/g creatinine for patients compared with 0.5 +/- 0.5 microg/g creatinine for controls (different group from the one in Ventura et al. (2005)). Color vision was monocularly assessed using the Cambridge Colour Test (CCT). Hg-exposed patients had significantly worse color discrimination (p < 0.02) than controls, as evaluated by the size of MacAdam’s color discrimination ellipses and color discrimination thresholds along protan, deutan, and tritan confusion axes. There were no significant differences between the results of the study in Ventura et al. (2005) and in the present follow-up measurements, in 2005, except for worsening of the tritan thresholds in the best eye in 2005. Both chromatic systems, blue-yellow and red-green, were affected in the first evaluation (Ventura et al., 2005) and remained impaired in the follow-up testing, in 2005. These findings indicate that following a long-term occupational exposure to Hg vapor, even several years away from the source of intoxication, color vision impairment remains irreversible.
Can J Ophthalmol. 2007 Oct;42(5):660-2.
Mercury exposure and its implications for visual health.
Collins C, Saldana M.
In adult monkeys and humans, methylmercury exposure has been linked to constriction of the visual field and abnormal colour vision. Korogi et al.5 performed magnetic resonance (MR) imaging of the brains of patients with known Minamata disease. The visual cortex, the cerebellar vermis and hemispheres, and the postcentral cortex were significantly atrophic. MR also demonstrated lesions in the calcarine area, cerebellum, and postcentral gyri. When Korogi et al. later looked at the striate cortex in patients with known Minamata disease and visual field constriction they found a correlation between the visual field defect and the extent of dilatation of the calcarine fissure.6 From electrophysiological testing of workers exposed to mercury vapors a significant reduction was found of the visual evoked potential (VEP) latency, especially for the N75.7 Further work completed in 2003 identified greater colour confusion, more errors on colour testing, and an increased frequency of type III dyschromatopsias (blue–yellow confusion axis) in comparison with the control group.
Cavalleri et al.8 studied a group of workers with high levels of urinary mercury and found a dose-related impairment of colour discrimination. Following changes to the workers’ work practices, mercury levels 12 months later had fallen to one-tenth of the previous levels and their colour vision had returned almost to normal. Children with raised blood mercury concentrations have been studied for changes in visual function testing. Saint- Amour et al.,9 examining preschool Inuit children living in Nunavik, northern Quebec, reported reduced VEP latency similar to the values found in mercury-exposed workers.
Cian Collins, MRCOphth, Manual Saldana, MRCOphth
Princess Alexandra Eye Pavilion
Braz J Med Biol Res. 2007 Mar;40(3):409-14.
Long-term loss of color vision after exposure to mercury vapor.
Feitosa-Santana C, Costa MF, Lago M, Ventura DF.
Source: Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Prof. Mello Moraes 1721, 05508-900 São Paulo, SP, Brazil. email@example.com
We evaluated the color vision of 24 subjects (41.6 +/- 6.5 years; 6 females) who worked in fluorescent lamp industries. They had been occupationally exposed to mercury vapor (10.6 +/- 5.2 years) and had been
away from the source of exposure for 6.4 +/- 4.04 years. Mean urinary concentration of mercury was 40.6 +/- 36.4 microg/g creatinine during or up to 1 year after exposure and 2.71 +/- 1.19 microg/g
creatinine at the time of color vision testing or up to 1 year thereafter. All patients were diagnosed with chronic mercury intoxication, characterized by clinical symptoms and neuropsychological
alterations. A control group (N = 36, 48.6 +/- 11.9 years, 10 females, 1.5 +/- 0.47 microg mercury/g creatinine) was subjected to the same tests. Inclusion criteria for both groups were Snellen VA 20/30 or
better and absence of known ophthalmologic pathologies. Color discrimination was assessed with the Farnsworth D-15 test (D-15) and with the Lanthony D-15d test (D-15d). Significant differences were found
between the two eyes of the patients (P < 0.001) in both tests. Results for the worst eye were also different from controls for both tests: P = 0.014 for D-15 and P < 0.001 for D-15d. As shown in previous
studies, the D-15d proved to be more sensitive than the D-15 for the screening and diagnosis of the color discrimination losses. Since color discrimination losses were still present many years after the end
of exposure, they may be considered to be irreversible, at least under the conditions of the present study.
Braz J Med Biol Res. 2007 Mar;40(3):415-24.
Mercury toxicity in the Amazon: contrast sensitivity and color discrimination of subjects exposed to mercury.
Rodrigues AR, Souza CR, Braga AM, Rodrigues PS, Silveira AT, Damin ET, Côrtes MI, Castro AJ, Mello GA, Vieira JL, Pinheiro MC, Ventura DF, Silveira LC.
Source: Departamento de Fisiologia, Universidade Federal do Pará, 66055 Belém, Pará (PA), Brazil.
We measured visual performance in achromatic and chromatic spatial tasks of mercury-exposed subjects and compared the results with norms obtained from healthy individuals of similar age. Data were obtained
for a group of 28 mercury-exposed subjects, comprising 20 Amazonian gold miners, 2 inhabitants of Amazonian riverside communities, and 6 laboratory technicians, who asked for medical care. Statistical norms
were generated by testing healthy control subjects divided into three age groups. The performance of a substantial proportion of the mercury-exposed subjects was below the norms in all of these tasks. Eleven
of 20 subjects (55%) performed below the norms in the achromatic contrast sensitivity task. The mercury-exposed subjects also had lower red-green contrast sensitivity deficits at all tested spatial
frequencies (9/11 subjects; 81%). Three gold miners and 1 riverine (4/19 subjects, 21%) performed worse than normal subjects making more mistakes in the color arrangement test. Five of 10 subjects tested
(50%), comprising 2 gold miners, 2 technicians, and 1 riverine, performed worse than normal in the color discrimination test, having areas of one or more MacAdam ellipse larger than normal subjects and high
color discrimination thresholds at least in one color locus. These data indicate that psychophysical assessment can be used to quantify the degree of visual impairment of mercury-exposed subjects. They also
suggest that some spatial tests such as the measurement of red-green chromatic contrast are sufficiently sensitive to detect visual dysfunction caused by mercury toxicity.
Environ Toxicol Pharmacol. 2005 May;19(3):517-22. Epub 2005 Jan 23.
Visual impairment on dentists related to occupational mercury exposure.
Canto-Pereira LH, Lago M, Costa MF, Rodrigues AR, Saito CA, Silveira LC, Ventura DF.
Source: Departamento de Psicologia Experimental, Instituto de Psicologia, e Núcleo de Pesquisa em Neurociências e Comportamento, Universidade de São Paulo, 05508-900 São Paulo, SP, Brazil.
A detailed assessment of visual function was obtained in subjects with low-level occupational mercury exposure by measuring hue saturation thresholds and contrast sensitivity functions for luminance and
chromatic modulation. General practice dentists (n=15) were compared to age-matched healthy controls (n=13). Color discrimination estimated by the area of Mac Adam ellipses was impaired, showing diffuse
discrimination loss. There was also reduction of contrast sensitivity for luminance and chromatic (red-green and blue-yellow) modulation, in all tested spatial frequencies. Low concentrations of urinary
mercury (1.97±1.61μg/g creatinine) were found in the dentists group. Color discrimination as well as contrast sensitivity function, assessed psychophysically, constitutes a sensitive indicator of subtle
neurotoxic effect of elemental mercury exposure.
Environ Toxicol Pharmacol. 2005 May;19(3):523-9. Epub 2005 Mar 17.
Colour vision and contrast sensitivity losses of mercury intoxicated industry workers in Brazil.
Ventura DF, Simões AL, Tomaz S, Costa MF, Lago M, Costa MT, Canto-Pereira LH, de Souza JM, Faria MA, Silveira LC.
Source: Instituto de Psicologia, Universidade de São Paulo, Av. Prof. Mello Moraes 1721, 05508-900 São Paulo, SP, Brazil; Núcleo de Neurociências e Comportamento, Universidade de São Paulo, São Paulo, Brazil.
We evaluated vision loss in workers from fluorescent lamp industries (n=39) who had retired due to intoxication with mercury vapour and had been away from the work situation for several years (mean=6.32
years). An age-matched control group was submitted to the same tests for comparison. The luminance contrast sensitivity (CSF) was measured psychophysically and with the sweep visual evoked potential (sVEP)
method. Chromatic red-green and blue-yellow CSFs were measured psychophysically. Colour discrimination was assessed with the Farnsworth-Munsell 100-hue test, Lanthony D-15d test and Cambridge Colour Vision
Test. Patient data showed significantly lower scores in all colour tests compared to controls (p<.001). The behavioural luminance CSF of the patients was lower than that of controls (p<.001 at all
frequencies tested). This result was confirmed by the electrophysiologically measured sweep VEP luminance CSF except at the highest frequencies-a difference that might be related to stimulus differences in
the two situations. Chromatic CSFs were also statistically significantly lower for the patients than for the controls, for both chromatic equiluminant stimuli: red-green (p<.005) and blue-yellow (p<.04 for
all frequencies, except 2 cycles per degree (cpd), the highest spatial frequency tested) spatial gratings. We conclude that exposure to elemental mercury vapour is associated with profound and lasting losses
in achromatic and chromatic visual functions, affecting the magno-, parvo- and koniocellular visual pathways.
Vis Neurosci. 2004 May-Jun;21(3):421-9.
Multifocal and full-field electroretinogram changes associated with color-vision loss in mercury vapor exposure.
Ventura DF, Costa MT, Costa MF, Berezovsky A, Salomão SR, Simões AL, Lago M, Pereira LH, Faria MA, De Souza JM, Silveira LC.
Source: Instituto de Psicologia and Núcleo de Neurociências e Comportamento, Universidade de São Paulo, SP, Brazil. firstname.lastname@example.org
We evaluated the color vision of mercury-contaminated patients and investigated possible retinal origins of losses using electroretinography. Participants were retired workers from a fluorescent lamp
industry diagnosed with mercury contamination (n = 43) and age-matched controls (n = 21). Color discrimination was assessed with the Cambridge Colour Test (CCT). Retinal function was evaluated by using the
ISCEV protocol for full-field electroretinography (full-field ERG), as well as by means of multifocal electroretinography (mfERG). Color-vision losses assessed by the CCT consisted of higher color-
discrimination thresholds along the protan, deutan, and tritan axes and significantly larger discrimination ellipses in mercury-exposed patients compared to controls. Full-field ERG amplitudes from patients
were smaller than those of the controls for the scotopic response b-wave, maximum response, sum of oscillatory potentials (OPs), 30-Hz flicker response, and light-adapted cone response. OP amplitudes
measured in patients were smaller than those of controls for O2 and O3. Multifocal ERGs recorded from ten randomly selected patients showed smaller N1-P1 amplitudes and longer latencies throughout the 25-deg
central field. Full-field ERGs showed that scotopic, photopic, peripheral, and midperipheral retinal functions were affected, and the mfERGs indicated that central retinal function was also significantly
depressed. To our knowledge, this is the first demonstration of retinal involvement in visual losses caused by mercury toxicity.
Neurotoxicology. 2003 Aug;24(4-5):693-702.
Color vision impairment in workers exposed to neurotoxic chemicals.
Gobba F, Cavalleri A.
Source: Cattedra di Medicina del Lavoro, Dipartimento di Scienze Igienistiche, Università di Modena e Reggio Emilia, 41100 (MO) Modena, Italy. email@example.com
Recent research shows that occupational exposure to several solvents, metals and other industrial chemicals can impair color vision in exposed workers. Occupation-related color vision impairment usually results in blue-yellow color discrimination loss or, less frequently, a combination of blue-yellow and red-green loss. The eyes may be unequally involved, and the course is variable depending on exposure and other factors. The pathogenesis of occupational color vision loss has not been elucidated; it may be due to, e.g. a direct action of neurotoxins on receptors, possibly on the cone’s membrane metabolism, and/or to an interference with neurotransmitters within the retina. Other possible pathogenetic mechanisms, such as a direct effect to the optic nerve, have also been suggested. Occupational color vision loss is usually sub-clinical, and workers are unaware of any deficit. It can be assessed using sensitive tests, such as the Farnsworth-Munsell 100 Hue (FM-100) or the Lanthony D-15 desaturated panel (D-15 d). The latter is the most widely used for studies in groups of exposed workers, and offers the possibility of a quantitative evaluation of the results by calculation of the Bowman’s Color Confusion Index (CCI), or of the Vingrys’ and King Smith’s Confusion Index (CI). Other advantages of D-15 d are the possibility to perform the test directly at the workplace, and the reproducibility when performed in standardized conditions. In most cases, occupation-related color vision impairment is correlated to exposure levels, and has often been observed in workers exposed to environmental concentrations below the current occupational limit proposed by the ACGIH. Progression with increasing cumulative exposure has been reported, while reversibility is still discussed. Acquired color vision impairment related to occupational exposure to styrene, perchloroethylene (PCE), toluene, carbon disulfide, n-hexane, solvent mixtures, mercury and some other chemicals are discussed. Results show that color vision testing should be included in the evaluation of early neurotoxicity of chemicals in exposed workers. The D-15 d would be useful in the surveillance of workers exposed to solvents and other chemicals toxic to the visual system.
Neurotoxicology. 2003 Aug;24(4-5):711-6.
Color discrimination impairment in workers exposed to mercury vapor.
Urban P, Gobba F, Nerudová J, Lukás E, Cábelková Z, Cikrt M.
Source: National Institute of Public Health, Srobárova 48, 100 48 10 Prague, Czech Republic. firstname.lastname@example.org
To study color discrimination impairment in workers exposed to elemental mercury (Hg) vapor.
Twenty-four male workers from a chloralkali plant exposed to Hg vapor, aged 42+/-9.8 years, duration of exposure 14.7+/-9.7 years, were examined. The 8h TWA air-borne Hg concentration in workplace was 59 microg/m(3); mean Hg urinary excretion (HgU) was 20.5+/-19.3 microg/g creatinine; mean Hg urinary excretion after the administration of a chelating agent, sodium 2,3-dimercapto-1-propane-sulfonate (DMPS), was 751.9+/-648 microg/48h. Twenty-four age- and gender-matched control subjects were compared. Visual acuity, alcohol intake, smoking habits, and history of diseases or drugs potentially influencing color vision were registered.
The Lanthony 15-Hue desaturated test (L-D15-d) was used to assess color vision. The results were expressed quantitatively as Bowman’s Color Confusion Index (CCI), and qualitatively according to Verriest’s classification of acquired dyschromatopsias.
The CCI was significantly higher in the exposed group than in the control (mean CCI 1.15 versus 1.04; P=0.04). The proportion of subjects with errorless performance on the Lanthony test was significantly lower in the Hg exposed group compared to referents (52% versus 73%; P=0.035). The exposed group showed higher frequency of type III dyschromatopsias (blue-yellow confusion axis) in comparison with the control group (12.5% versus 8.3%), however, the difference did not reach statistical significance. Multiple regression did not show any significant relationship between the CCI, and age, alcohol consumption, or measures of exposure.
In agreement with previous studies by Cavalleri et al. [Toxicol. Lett. 77 (1995) 351; Environ. Res. Sec. A 77 (1998) 173], the results of this study support the hypothesis that exposure to mercury vapor can induce sub-clinical color vision impairment. This effect was observed at an exposure level below the current biological limit for occupational exposure to mercury. This raises doubts on the actual protection afforded by this limit concerning the effect of mercury on color vision.
Bioinorg Chem Appl. 2003:199-214.
Sensory perception: an overlooked target of occupational exposure to metals.
Source: Cattedra di Medicina del Lavoro, Dipartimento di Scienze Igienistiche, Università di Modena e Reggio Emilia, Via Campi 287 Modena (MO) 41100, Italy. email@example.com
The effect of exposure to industrial metals on sensory perception of workers has received only modest interest from the medical community to date. Nevertheless, some experimental and epidemiological data exist showing that industrial metals can affect vision, hearing and olfactory function, and a similar effect is also suggested for touch and taste. In this review the main industrial metals involved are discussed. An important limit in available knowledge is that, to date, the number of chemicals studied is relatively small. Another is that the large majority of the studies have evaluated the effect of a single chemical on a single sense. As an example, we know that mercury can impair hearing, smell, taste, touch and also vision, but we have scant idea if, in the same worker, a relation exists between impairments in different senses, or if impairments are independent. Moreover, workers are frequently exposed to different chemicals; a few available results suggest that a co-exposure may have no effect, or result in both an increase and a decrease of the effect, as observed for hearing loss, but this aspect certainly deserves much more study. As a conclusion, exposure to industrial metals can affect sensory perception, but knowledge of this effect is yet incomplete, and is largely inadequate especially for an estimation of “safe” thresholds of exposure. These data support the desirability of further good quality studies in this field.
Neurotoxicology. 2000 Oct;21(5):777-81.
Evolution of color vision loss induced by occupational exposure to chemicals.
Gobba F, Cavalleri A.
Source: Dipartimento di Scienze Igienistiche, Università di Modena e Reggio Emilia, Modena, Italy. firstname.lastname@example.org
The evolution of occupationally induced color vision loss was studied in workers exposed to various chemicals. Exposure was evaluated by biological monitoring or personal air samplers, and color vision using the Lanthony D-15 desaturated panel (D-15 d). The effect of short-term interruption of exposure was studied in 39 Styrene (St) exposed workers: at a first examination a dose-related color vision loss was disclosed; a re-test performed after one month’s interruption of exposure did not show any improvement of the effect. The evolution during longer periods was studied in another group of 30 St workers. Exposure and color vision were evaluated, then a follow-up was done 12 months later: the exposure was unmodified or slightly decreased in 20 subjects, and D-15 d outcomes remained unchanged, while St levels had increased and color vision loss progressed in the other 10. Similar results were obtained in 33 PCE exposed dry-cleaners: no change in color perception was observed in 14 workers whose exposure decreased, while in the other 19 a rise in PCE levels was followed by a significant color vision worsening. In 21 Hg exposed workers whose mean urinary excretion of Hg was threefold the BEI proposed by ACGIH, a dose-related impairment in color perception was observed. 12 months after a marked reduction of exposure, an almost complete recovery of the impairment was observed. Our data show that an increase in exposure can induce a worsening in color vision loss. A short interruption in exposure did not reduce the effect. A more prolonged reduction of dose reversed color vision loss in Hg exposed workers, while in solvent-exposed individuals the progression deserves further evaluation. D-15 d proved a useful test for studies on the evolution of color perception in workers exposed to eye-toxic chemicals.
Environ Res. 1998 May;77(2):173-7.
Reversible color vision loss in occupational exposure to metallic mercury.
Cavalleri A, Gobba F.
Source: Sezione di Medicina Preventiva dei Lavoratori, Università di Pavia, Pavia, Italy.
Color vision was evaluated in twenty-one mercury exposed workers and referents matched for sex, age, tobacco smoking, and alcohol habits. The Lanthony 15 Hue desaturated panel (D-15 d) was applied. In the workers, mean urinary Hg (HgU) was 115+/-61.5 microg/g creatinine; in all but one the values exceeded the biological limit (BEI) proposed by the American Conference of Governmental Industrial Hygienists. A dose-related subclinical color vision impairment was observed in Hg-exposed workers compared to the referents. Just after the survey, working conditions were improved. Twelve months later the workers were reexamined. Mean HgU was 10.0 microg/g creatinine and in no subjects was the BEI exceeded. Color perception was significantly improved compared to the first examination and, furthermore, no differences were observed between exposed workers and referents. The results add evidence that the color vision loss observed during the first part of the study was related to Hg exposure and, moreover, show that this effect is reversible. These data indicate that metallic Hg can induce a reversible impairment in color perception. This suggests that color vision testing should be included in studies on the early effects of Hg. The possibility of applying the D-15 d as an early effect index in the biological monitoring of Hg exposed workers should also be entertained.
Toxicol Lett. 1995 May;77(1-3):351-6.
Colour vision loss in workers exposed to elemental mercury vapour.
Cavalleri A, Belotti L, Gobba F, Luzzana G, Rosa P, Seghizzi P.
Source: Sezione di Medicina Preventiva dei Lavoratori, University of Pavia, Italy.
We evaluated colour vision in 33 workers exposed to elemental mercury (Hg) vapour and in 33 referents matched for sex, age, alcohol consumption and cigarette smoking. The results were expressed as colour confusion index (CCI). In the workers urinary excretion of Hg (HgU) ranged from 28 to 287 micrograms/g creatinine. Subclinical colour vision loss, mainly in the blue-yellow range, was observed in the workers. This effect was related to exposure, as indicated by the correlation between HgU and CCI (r = 0.488, P < 0.01). In the workers whose HgU exceeded 50 micrograms/g creatinine, mean CCI was significantly increased compared to the matched referents. The results suggest that exposure to elemental Hg inducing HgU values exceeding 50 micrograms/g creatinine can induce a dose-related colour vision loss.
Neurotoxicol Teratol. 1990 Nov-Dec;12(6):669-72.
Colour vision loss among disabled workers with neuropsychological impairment.
Mergler D, Bowler R, Cone J.
Source: Groupe de recherche-action en biologie du travail, Université du Québec à Montréal, Canada.
Test performance on a neurobehavioural battery was examined with respect to acquired colour vision loss among patients with a history of neurotoxin exposure. The study group included 14 men and 7 women with clinically diagnosed neuropsychological impairment (mean age: 41.3 +/- 8.1 years; mean educational level: 13.4 +/- 1.4 years). Verbal and visual ability, memory and psychomotor function were assessed with the California Neuropsychological Screening Battery. Colour vision was assessed with the Lanthony D-15 desaturated colour arrangement panel. Acquired dyschromatopsia was present in 17 patients (80.9%), 11 of whom manifested patterns of Type II colour vision loss. Simple regression analysis of neuropsychological test performance with respect to colour vision loss, using age-adjusted Z-scores, revealed significant relationships (p less than or equal to 0.05) solely for tests which rely heavily on the visual system. Significant differences in visual task test scores were also observed with the type of dyschromatopsia (Kruskal-Wallis, p less than or equal to 0.05). These findings suggest that poor performance on visual tasks and colour vision loss may both result from damage to neuro-ophthalmic pathways or that loss of integrity of the peripheral visual pathways may affect visual task performance. The authors propose that visual testing should be incorporated into neurobehavioural test batteries.