Biomedical subjects

D Mergler

Publications and source records attributed to D Mergler.

69 records · Page 4Linked to original sources

PubMedDate not supplied

Colour vision impairment and alcohol consumption.

The relationship between alcohol intake and colour discrimination capacity was examined among 136 persons of whom 16 were undergoing treatment in a detoxification centre. Current weekly alcohol consumption (or prior to treatment for those in the centre) was obtained with a detailed questionnaire, which divided week and weekend drinking into types of alcohol (beer, wine, spirits). Alcohol consumption varied from 0-5824 g/week; median: 266 g/week. Qualitative and quantitative assessment of acquired dyschromatopsia was obtained with a colour arrangement test, the Lanthony D-15 desaturated panel. In all age categories, the prevalence of dyschromatopsia increased with alcohol intake. Moreover, all the heavy drinkers (greater than 751 g/week) presented a certain degree of dyschromatopsia, whether or not they were undergoing treatment for alcoholism in a detoxification centre. Colour loss was primarily in the blue-yellow range; however, 4 of the 16 persons from the detoxification centre presented complex dyschromatopsia patterns including red-green loss. This raises the question of possible progressive deterioration. Multiple regression analysis showed that colour vision loss was significantly related to both age (p less than 0.001) and alcohol intake (p less than 0.01). These results underline the importance of taking into account the contribution of alcohol consumption in studies on acquired dyschromatopsia.

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PubMedDate not supplied

Colour vision loss among disabled workers with neuropsychological impairment.

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.

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PubMedDate not supplied

Blood manganese content at birth and cord serum prolactin levels.

Manganese (Mn) is both an essential element and, at a high dose, a potent neurotoxin that can interact with dopaminergic neurotransmission. Plasma prolactin (PRL), an indirect indicator of dopaminergic functioning, has been shown to vary with Mn exposure in adults, but little is known about this relation in the developing brain. The objective of this study was to examine the relations between maternal and cord Mn blood concentrations at birth and PRL cord blood levels. Blood Mn levels were determined in 87 pregnant women at delivery, and PRL was measured in the cord blood plasma. Mn cord blood concentration (mean 34.4 microg/l, range 16.7-89.4) was significantly and positively related to cord PRL levels. These findings suggest that Mn accumulation in utero could contribute to PRL level variation in neonates, which, in turn, may influence important developmental parameters.

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Very low level environmental exposure to lead and prolactin levels during pregnancy.

Lead (Pb) is a well-known poison interfering with calcium homeostasis and dopaminergic pathway. We hypothesized that environmental Pb exposure can interact with prolactin (PRL) secretion, regulated by calcium and dopamine, during pregnancy and in fetus. The objective of this longitudinal study was to determine the relationships between blood Pb concentration and serum PRL levels in 101 pregnant women recruited during pregnancy and their fetuses exposed to low environmental levels of Pb. We observed a significant negative relationship between maternal blood Pb concentrations and maternal serum PRL levels. Cord blood PRL was weakly correlated with blood Pb levels. Our results suggest that maternal physiological parameters in pregnancy can be modulated by low level of Pb exposure and indicate a particular susceptibility of pregnant women to its toxic effects.

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Color vision and occupational toluene exposure.

We examined the relationship between acquired color vision loss and exposure to toluene and total hydrocarbons among 125 male workers. Seventy-two toluene-exposed printers were compared with 34 workers from the same photogravure plant with ambient background exposure, and with 19 workers from a bookbinding plant located in the same town (nonexposed). Environmental mean toluene exposure level at workstation was estimated from individual 8-h sampling. Historic exposure data from the last 30 years were used to construct two cumulative exposure indices, one for toluene and one for total hydrocarbons. Airborne toluene levels were overall lower than the current Threshold Limit Value (TLV) of 50 ppm. Color vision was assessed by the Lanthony D-15 desaturated panel. Color vision loss was quantitatively established by the Color Confusion Index (CCI) and classified by type of acquired dyschromatopsia according to Verriest's classification. CCI was positively related to current airborne toluene levels, and cumulative exposure indices for toluene and total hydrocarbons (.18< or =r< or =.35). Odds ratios of acquired dyschromatopsia were significant for current airborne toluene, toluene, and total hydrocarbon past exposure (1.27 [1.02-1.58], 1.21 [1.04-1.39], 1.15 [1.02-1.31], respectively). In conclusion, this study suggests that the Lanthony D-15 desaturated panel detects early neurotoxic effects among workers exposed to toluene.

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PubMedDate not supplied

Visual dysfunction among former microelectronics assembly workers.

Although known neurotoxins with potential ophthalmotoxic properties are commonly used in microelectronics assembly, there has been no systematic study of visual disturbances among past or present workers in this industry. The objective of the present study was to compare visual functions, using a matched-pair design, between former workers from a microelectronics plant and a local reference population. From an initial population of 180 former workers and 157 potential referents, 54 pairs were matched for age (+/- 3 y), education (+/- 2 y), sex, ethnic origin, and number of children. Near and far visual acuity, chromatic discrimination, and near contrast sensitivity were assessed monocularly. Paired comparisons (Signed-rank Wilcoxon test) revealed that the former microelectronics workers had significantly lower contrast sensitivity, particularly in the intermediate frequencies, independently of near visual acuity loss. There were no differences for far visual acuity in both eyes. Even though near visual acuity and color vision were compromised among the former workers, the differences were only significant for one eye, as was the prevalence of acquired dyschromatopsia (chi-square for matched pairs, p less than .001). These findings suggest a pattern of contrast sensitivity deficits consistent with impairment to foveal and/or neuro-optic pathways among these former microelectronics workers. Exposure to ophthalmotoxic chemicals is proposed as the most probable risk factor.

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Long-term exposure to "low levels" of manganese oxides and neurofunctional changes in ferroalloy workers.

Occupational exposure to manganese can cause early neurobehavioral effects in low- or a-symptomatic workers. A battery of neuropsychological tests was administered to a group of 61 ferroalloy male workers and 87 controls. The average (geometric mean) manganese concentrations in total dust at the plant have changed from 1981 to 1997 respectively from 1597.03 micrograms/m3 to 239 micrograms/m3 at the furnace area; from 151.53 to 255.76 micrograms/m3 at the casting area; from 167 to 54.7 micrograms/m3 at the maintenance (welding operations), yielding a current overall value of 54.25 micrograms/m3. A cumulative exposure index was calculated for each alloy worker and the average value (geometric mean) resulted to be 1204.87 micrograms/m3 x years, which divided by the average length of exposure (15.17 years), showed the concentration of 70.83 micrograms/m3 of manganese in total dust. Blood and urinary manganese geometric means resulted significantly higher in the exposed workers (9.18 micrograms/l and 1.53 micrograms/g creatinine, respectively) than in controls (5.74 micrograms/l and 0.40 microgram/g creatinine, respectively). A positive correlation was observed between the airborne manganese concentrations in total dust and blood manganese (n = 55; R = 0.36; R2 = 0.13; p = 0.0068), whereas no association resulted between cumulative exposure index and both blood manganese and urinary manganese. Higher prevalence of symptoms reporting was observed in the alloy workers concerning irritability, loss of equilibrium and rigidity. Tremor parameters including the central frequency and its dispersion, resulted to be statistically different in the exposed workers compared to the controls. Motor functions exploring the coordination of rapid and alternating movements and memory functions resulted to be impaired in the manganese workers. Dose-effect relationships were observed between the cumulative exposure index and some of the test results, whereas no relationship was found with the airborne manganese concentrations and the biological indicators of exposure. These findings are consistent with the existing knowledge of a cumulative mechanism of action of manganese, which must be carefully considered when setting safe exposure levels. In order to be protective for the entire working life, the average annual exposure level should be lower than 100 micrograms/m3.

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PubMedDate not supplied

Manganese neurotoxicity, a continuum of dysfunction: results from a community based study.

Excessive manganese (Mn) has been associated with neurobehavioral deficits and neurological and/or neuropsychiatric illness, but the level at which this metal can cause adverse neurotoxic effects, particularly with long-term exposure, is still unknown. The objective of the present study was to assess nervous system functions in residents exposed to manganese from a variety of environmental sources. A random stratified sampling procedure was used to select participants; persons with a history of workplace exposure to Mn and other neurotoxic substances were excluded. A self-administered questionnaire provided data on socio-demographic variables. Blood samples were analyzed for total manganese (MnB), lead, mercury and serum iron. Nervous system assessment included computer and hand-administered neurobehavioral tests, computerized neuromotor tests, sensory evaluation and a neurological examination. The present analyses include 273 persons (151 women and 122 men); MnB range: 2.5 micrograms/L-15.9 micrograms/L (median: 7.3 micrograms/L). Multivariate analyses were used and neuro-outcomes were examined with respect to MnB, taking into account potential confounders and covariables. Results were grouped according to neurofunctional areas and MANOVA analyses revealed that higher MnB (7.5 micrograms/L) was significantly associated with changes in coordinated upper limb movements (Wilks' lambda = 0.92; p = 0.04) and poorer learning and recall (men: Wilks' lambda = 0.77; p = 0.002; women: Wilks' lambda = 0.86; p = 0.04). Further analyses revealed that with increasing log MnB (Simple regression: p < 0.05) performance on a pointing task was poorer, frequency dispersion of hand-arm tremor decreased, while harmonic index increased, and the velocity of a pronation/supination arm movement was slower. An Mn-age interaction was observed for certain motor tasks, with the poorest performance observed among those _50 y and in the higher MnB category. Differences between genders suggest that men may be at greater risk than women, although effects were also observed in women. These findings are consistent with the hypothesis that Mn neurotoxicity can be viewed on a continuum of dysfunction, with early, subtle changes at lower exposure levels.

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PubMedDate not supplied

Bioindicator and exposure data for a population based study of manganese.

Exposure data and bioindicators were obtained for a study whose objective was detection of early manifestations of manganese (Mn) neurotoxicity in a population with potential environmental exposure. The study included persons with no history of neurotoxic workplace exposure in Southwest Quebec, drawn from seven postal code regions, defining a set of geographically contiguous zones. Blood samples were analyzed for total Mn (MnB), lead (PbB), total mercury (HgT) and serum iron (FeS). Drinking water samples from participants' residences were analyzed for manganese (MnW). At 4 sites, limited 24-hour high volume air samples for total particulates (TP) and PM10, were analyzed for Mn and Pb. Sociodemographic and dietary information was obtained by self-administered questionnaire. The geometric mean (GM) for MnB values (n = 297) was 7.14 micrograms/L. Levels of MnB in women (n = 156; GM 7.50 micrograms/L) were significantly higher than in men (n = 141; GM 6.75 micrograms/L). No relationship was found between MnB and PbB or HgT. FeS was significantly higher in men (GM 18.38 mumol/L) than women (GM 15.0 mumol/L). For women, MnB was correlated to FeS, with a tendency to decrease with increasing age. For men, no relationship was found between MnB levels and either FeS or age, although FeS showed a strong inverse relationship with age. The 24-hour mean levels of MnTP at the 4 sites varied between 0.009 microgram/m3 and 0.035 microgram/m3; intersite differences were not significant. For Mn in PM10 (MnPM10), mean values ranged from 0.007 microgram/m3 to 0.019 microgram/m3; intersite differences were significant. A total of 278 MnW samples were obtained, 16 from residences served by wells. The GM for MnW was 4.11 micrograms/L (range: 0.50-71.1 micrograms/L, excluding wells; MnW for wells ranged from non-detectable to 158.9 micrograms/L. Individually, there was no relation between MnW and MnB. Geographic analysis of the MnB and MnW data by an algorithm grouping contiguous postal code zones, combined with air data, lead to definition of a geographic parameter, distinguishing two regions relative to a former manganese alloy plant, which contributed significantly to MnB. A multiple regression model was developed, explaining 6.7% of the variability in MnB (F = 5.12; p < 0.001); when controlling for gender, geographic region with higher levels of airborne manganese and the frequency of consumption of cereals and leaf vegetables contributed positively to MnB levels, while serum iron was negatively related.

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Quantification of neuromotor function for detection of the effects of manganese.

The effect of low level exposure to manganese (Mn) was examined in 297 subjects from southwest Quebec. Blood manganese (MnB) levels as well as other possibly relevant variables were obtained. We tested equipment and analysis procedures that we have developed to quantify aspects of motor function thought to be affected by exposure to toxins, in particular, rapid alternating movements, rapid and precise pointing movements, and tremor. (1) The eurythmokinesimeter measures timing and precision of contacts between a hand-held stylus and a pair of metal targets (proximal/distal). This roughly approximates the finger-to-nose test of the UPDRS. Characteristics quantifying speed, precision and regularity of the movements were calculated, as well as multiple contacts due to tremor and an index based on Fitts' Law eliminating the effect of the trade-off between speed and precision. (2) The diadochokinesimeter accurately measures rapid rotation of the forearms (pronation/supination). Characteristics quantifying the range, speed, period, shape and regularity of the oscillatory movements were calculated, as well as the smoothness of the movement on a fine scale and the coordination between the two hands. (3) Postural tremor of the arm and hand was measured using the accelerometry-based "TREMOR" system of Danish Product Development. We used the amplitude and frequency characteristics provided by the TREMOR system: intensity, center frequency, dispersion and harmonic index. Previous studies have shown that these tests are sufficiently sensitive to detect small differences in performance of different groups of subjects, with indications that some characteristics are also specific to particular conditions. In this study, significant though small effects related to age and gender were found in many of the characteristics. When effects of other variables are removed, low-level exposure to Mn was found to be associated with a decrease in ability to perform regular, rapid and precise pointing movements, a decrease in ability to attain high maximum rotation speeds in rapid alternating movements, and an increase in regularity of tremor oscillations. Moreover, the effects are age-related for levels of MnB 7.5, micrograms/L.

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PubMedDate not supplied

Neuropsychiatric effects of manganese on mood.

Adverse mood effects of overexposure to Manganese (Mn) have been described in 15 studies which frequently report an association of Mn exposure with adverse effects in six dimensions of mood: 1) anxiety, nervousness, irritability; 2) psychotic experiences; 3) emotional disturbance; 4) fatigue, lack of vigor, sleep disturbance; 5) impulsive/compulsive behavior; 6) aggression hostility. Only 1:15 studies used a standardized psychological measure of mood, while the current study of environmental Mn exposure used two standardized mood scales in evaluating low levels of Mn exposure and mood sequelae. The Profile of Moods State (POMS) and Brief Symptom Inventory (BSI) were used, and results indicate that men who are older and have higher Mn levels show significant disturbances on four of the six mood dimensions. Increased scores were seen in the anxiety, nervousness, irritability; emotional disturbance; and aggression, hostility dimensions relative to those who had lower levels of Mn. The BSI and POMS are useful adjuncts in the assessment of mood/Mn effects.

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Pilot study of peripheral markers of catecholaminergic systems among workers occupationally exposed to toluene.

In a pilot study, serum dopamine beta-hydroxylase (DBH), platelets monoamine oxidase type B (MAO B) activities and basal plasma prolactin (PRL) were measured, among 10 workers occupationally exposed to toluene and 10 control subjects, preceding and immediately following vacation. Six exposed subjects were employed in an adhesive tape making industry and 4 in a paint making industry. Their median basal levels of urinary hippuric acid were 0.44 mmole/mmole creatinine (cr) (range 0.23-1.97) and 0.18 mmole/mmole cr (range 0.15-0.19) respectively, the second to last morning of the work week, preceding vacation. The level of basal urinary hippuric acid among the control group was 0.26 mmole/mmole cr (range 0.03-0.38). The workers from the adhesive tape plant reported a significantly higher number of symptoms experienced frequently (Kruskal, Wallis, p < 0.05). On a group basis, serum DBH was lowest among the workers from the adhesive tape plant, who had the highest levels of basal urinary hippuric acid. In addition, a negative relation was observed between hippuric acid and serum DBH, preceding and following vacation (Rho = -0.46, p = 0.05; Rho = -0.51, p = 0.03). The observed changes in serum DBH activity are consistent with its decrease in human, following long-term exposure to styrene, another aromatic hydrocarbon. The findings of this pilot study, on a limited number of individuals suggest that DBH may be a sensitive peripheral bioindicator. Further studies of larger groups should be done to confirm the decrease in serum DBH activity with toluene exposure and explore whether this alteration is related to the neurotoxic impairments associated with exposure.

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Symptom base rates after chemical exposure for white, Hispanic and African-Americans.

The results of a symptom checklist of three matched-pair studies (N = 460) of the following exposed groups are presented: Study 1, a primarily white community (N = 220) environmentally exposed to the pesticide metam sodium; Study 2, a Hispanic group (N = 180) who worked in a microelectronics plant and had extensive past exposure (M = 6.7 yrs) to multiple organic hydrocarbon solvents; and Study 3, an African-American group (N = 168) environmentally exposed to sulfuric acid. Each exposed group was compared to a matched (race, age +/- 3 years, gender, education +/- 2 years and number of children) unexposed reference group, resulting in 90 pairs for the white metam sodium group, 62 pairs for the Hispanic organic solvent group, and 78 pairs for the African-American sulfuric acid group. Symptom prevalence rates and relative risk ratios show very strong associations: in Study 1, the relative risk for all 33 symptoms ranged from 1.5 to 37; in Study 2, the relative risk for 31 of the symptoms ranged from 1.5 to 11.1; and in Study 3, the relative risk for 16 of the symptoms ranged from 1.5 to 6. Mann Whitney U results of each symptom indicate significantly greater symptomatology in the exposed vs. the reference groups in all three studies: in Study 1, at p < .01 for all 33 symptoms; in Study 2, at p < .01 for 31 symptoms, and p < .05 for one additional symptom; and in Study 3, at p < .01 for 24 symptoms and p < .05 for another three symptoms. These results suggest a robust symptom complex following chemical exposure regardless of specific chemical.

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Surveillance of early neurotoxic dysfunction.

Surveillance of early neurotoxic alterations was undertaken in 3 reinforced plastics plants, with a view to preventive intervention. Using a longitudinal study design, exposure parameters (environmental styrene in the respiratory zone of each worker and end-shift mandelic acid (MA)) and neurobehavioral performance (Neurobehavioral Core Test Battery and Field Assessment: Sensory Tests), were assessed at time zero (T0); recommendations were made to reduce exposure at jobsites with the highest risk. Reassessment was made two years later (T2). Complete exposure data was available for 118 workers at T0; 75 were still employed at T2; of these, 57 (76%) returned for testing. Those who returned had more seniority (p < 0.001) and higher MA (p < 0.01) and styrene (p < 0.05) levels at T0 than the others. Analyses, performed on the T0-T2 differences, showed improvement in exposure parameters in Plant 3, where lower levels were observed at T2 for styrene (p < 0.05) and MA (p < 0.001). workers in Plant 3 (n = 29) performed better (p < 0.05) at T2 for short term memory, perceptuo-motor speed, motor precision and manual dexterity; they reported more vigor (p < 0.05) and less anger (p = 0.07). This was not the case for the workers from the other plants. Generally, the T0-T2 difference in MA was associated (Spearman's Rho) with differences in color vision (p < 0.001), simple reaction time (mean and standard deviation), digit span forward, tension, fatigue and the number of symptoms (p < 0.05); aiming precision showed a similar tendency (p < 0.10). These findings suggest that group surveillance of early nervous system changes for jobs with exposure to neurotoxins, using a sensitive neurofunctional test battery, may be useful for preventive intervention.

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Preliminary evidence of neurotoxicity associated with eating fish from the Upper St. Lawrence River Lakes.

Pollution of hydrographic basins has affected the flora and fauna that thrive in these aquatic ecosystems, and fish, which constitute an important food resource, often contain a plethora of potentially toxic chemicals. In a major research project on early neurotoxic effects of environmental exposure to manganese among residents in Southwest Quebec, fish consumption from 2 lakes of the Upper St. Lawrence River System, was surveyed as a potential confounding factor. Participants were selected using a random, stratified sampling strategy from lists of the Quebec Health Plan. Following exclusions, 273 men and women between 20-69 years were retained for the present analysis. A total of 103 (37.7%) reported eating fish from the Upper St. Lawrence. Although fisheaters and non-fisheaters were similar for most socio-demographic variables, significantly more fisheaters (65.2%) reported consuming alcoholic beverages as compared to non-fisheaters (42.4%) (Chi Sq. <0.01). To eliminate this possible bias, fisheaters were matched to non-fisheaters for the variables sex, alcohol consumption (never or occasionally vs. regularly), age (+/-5y) and education (+/-2y). A total of 63 matched pairs were thus created. Paired analyses (t-test or Signed Rank) showed that fisheaters had higher levels of blood organic mercury and lead. Analysis of nervous system functions revealed that both groups performed similarly on tests of sensory function, visual memory and recognition, fine motor performance and some motor tests, but fisheaters performed significantly more poorly (p<0.05) on tests requiring cognitive flexibility, word naming, auditory recall, and more complex motor tasks. The profile of deficits is consistent with diminished capacity for information processing. These observations were made within a study that was not specifically designed to examine the effects of fish eating from these two lakes, and the characterization of fish dietary habits has many limitations. Nevertheless, the findings are sufficiently compelling to warrant further studies, since fish from the Upper St. Lawrence Lakes are known to contain multiple neurotoxic substances.

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