Eating tropical fruit reduces mercury exposure from fish consumption in the Brazilian Amazon

This study aimed to examine the influence of the consumption of traditional foods on the relationship between fish consumption and mercury (Hg) exposure. A 12-month prospective dietary survey was carried out with 26 adult women from a fish-eating community in the Brazilian Amazon. Food ingestion was determined using a daily food diary, and total hair Hg levels were assessed for each month through sequential analyses using cold vapor atomic absorption spectrometry. Simple and multiple regression analyses showed that the strong relationship between fish consumption and Hg exposure was significantly modified by fruit consumption: for the same number of fish meals, those who ate more tropical fruits had lower hair mercury levels. The findings of this study indicate different ways of maintaining fish consumption while reducing Hg exposure in the Amazon. A number of phytochemicals and nutritional fibers present in fruits might be interacting with Hg in several ways: absorption and excretion, transport, binding to target proteins, metabolism, and sequestration. More studies are required on larger populations to further elucidate the extent and public health implications of the use of fruits to counteract the toxic action of methylmercury.

Blood manganese and alcohol consumption interact on mood states among manganese alloy production workers

Long-term exposure to manganese (Mn) can induce neurotoxic effects including neuromotor, neurocognitive and neuropsychiatric effects, but there is a great interpersonal variability in the occurrence of these effects. It has recently been suggested that blood Mn (MnB) may interact with alcohol use disorders, accentuating neuropsychiatric symptoms. The objective of the present study was to explore a possible interaction between alcohol consumption and MnB on mood states, using an existing data set on Mn exposed workers. Respirable Mn exposure in the plant averaged 0.23mg/m(3) and was correlated with MnB. All participants for whom all data on MnB concentration and mood (assessed with the Profile of Mood States (POMS)) were available and who reported currently drinking alcohol were included in the analyses (n=74). Workers were grouped according to their MnB concentration (<10 and > or =10 microg/l) and alcohol consumption (<400 and > or =400g per week). Two-way ANOVAs were performed on each POMS scale and Mann-Whitney tests were used to assess group differences. Workers in the higher alcohol consumption group had higher scores on three POMS scales: tension, anger and fatigue. There was no difference for POMS scale scores between MnB subgroups. Dividing the group with respect to alcohol consumption and MnB showed that the group with high alcohol consumption and high MnB displayed the highest scores. In the lower MnB category, those in the higher alcohol consumption group did not have higher scores than the others. The interaction term for alcohol consumption and MnB concentration was statistically significant (P<0.05) for the depression, anger, fatigue and confusion POMS scales. There was a tendency for tension (P<0.06), and it was not significant for vigor. This study shows the first evidence of an interaction between MnB and alcohol consumption on mood states among Mn exposed workers and supports the results from a previous population-based study.

Manganese, monoamine metabolite levels at birth, and child psychomotor development

Several studies have demonstrated neurobehavioral impairment related to manganese (Mn) exposure in the workplace. Exposure to high doses of manganese is associated with irreversible neurodegenerative disorders resembling idiopathic Parkinson disease. Although there is a risk of Mn accumulation in the foetus during pregnancy, little information exists about developmental effects of environmental low-level exposure in human. For this reason, we conducted a prospective epidemiological study in 247 healthy pregnant women and their babies to determine the long-term effect of in utero Mn levels on child's psychomotor development. Concurrently, we examined the relationship between Mn tissue levels at delivery and foetal plasma monoamine metabolites. Of the newborns, 195 were examined at 9 months, 126 at 3 years and 100 at 6 years. At 9 months, the Brunet-Lézine scales were administered. The McCarthy scales of children's abilities were used at 3 and 6 years. After adjustment for potential confounding co-factors (child's gender, mother's educational level), negative relationships were observed between cord blood Mn levels and several psychomotor sub-scales at age of 3 years: "attention" (partial r=-0.33, P<0.001), "non-verbal memory" (partial r=-0.28, P<0.01), and "hand skills" (partial r=-0.22, P<0.05). No significant relationships were observed between Mn measures at birth and the general psychomotor indices, Brunet-Lézine developmental quotient (DQ) at 9 months or McCarthy general cognitive index (GCI) at 3 and 6 years. Maternal blood Mn levels were negatively associated with foetal plasma HVA and 5-HIAA concentrations (adjusted for labour duration, child's gender, and smoking during pregnancy), but the adjustment for monoamine levels at birth did not change the association between the Mn levels and the psychomotor scores. These results suggest that environmental Mn exposure in utero could affect early psychomotor development.

Assessment of bioaccumulation, neuropathology, and neurobehavior following subchronic (90 days) inhalation in Sprague-Dawley rats exposed to manganese phosphate

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic manganese (Mn) compound added to unleaded gasoline. It has been suggested that the combustion products of MMT containing Mn, such as manganese phosphate, could cause neurological symptoms similar to Parkinson's disease in humans. The aim of this work was to investigate the exposure-response relationship of bioaccumulation, neuropathology, and neurobehavior following a subchronic inhalation exposure to manganese phosphate in Sprague-Dawley male rats. Rats were exposed 6 h/day, 5 days/week for 13 consecutive weeks at 30, 300, or 3000 microg/m(3) Mn phosphate and compared to controls. Some rats were implanted with chronic EMG electrodes in the gastrocnemius muscle of the hind limb to assess tremor at the end of Mn exposure. Spontaneous motor activity was measured for 36 h using a computerized autotrack system. Rats were then sacrificed by exsanguination and Mn level in different brain tissues and other organs was determined by instrumental neutron activation analysis. Neuronal cell counts were obtained by assessing the sum of five grid areas for the caudate/putamen and the sum of two adjacent areas for the globus pallidus. Increased manganese concentrations were observed in all tissues of the brain and was dose-dependent in olfactory bulb and caudate/putamen. In fact, beginning with the highest level of exposure (3000 microg/m(3)) and ending with the control group, Mn concentrations in the olfactory bulb were 2.47 vs 1.28 vs 0.77 vs 0.64 ppm (P < 0.05) while for the caudate/putamen, Mn concentrations were 1.06 vs 0.73 vs 0.62 vs 0.47 ppm (P < 0.05). The Mn concentrations in lung were also dose-dependent (10.30 vs 1.40 vs 0.42 vs 0.17 ppm; P < 0.05). No statistical difference was observed for loss of neurons in caudate/putamen and globus pallidus. Locomotor activity assessment and tremor assessment did not reveal in neurobehavioral changes between the groups. Our results reinforce the hypothesis that the olfactory bulb and caudate/putamen are the main brain tissues for Mn accumulation after subchronic inhalation exposure.

Review of neurobehavioral deficits and river fish consumption from the Tapajós (Brazil) and St. Lawrence (Canada)

Our research group is carrying out studies on neurobehavioral changes associated with eating fish from the Upper St. Lawrence River (Québec, Canada) and the Lower Tapajós River (Brazilian Amazon). Here, these studies are reviewed with respect to exposure, effects and intervention. Although mercury (Hg) levels in piscivorous fish are similar in both regions, in the Amazon, fish constitutes the dietary mainstay, while in Quebec, fish consumption is primarily occasional. Mercury exposure of Amazonian fish-eaters was considerably higher than Québec (median blood total Hg: 28 and 1 μg/l, respectively), but fish from the St. Lawrence contain multiple contaminants. For the Tapajós River, increasing hair Hg was associated with reduced motor and visual functions. Comparison of neurobehavioral performance of Québec fish-eaters and non fish-eaters showed a consistent pattern of information processing slowing among the former; these deficits were not related to blood methyl Hg levels. Early changes associated with exposure can be used to trigger intervention. Since fish provide important essential nutrients, mitigation must balance the beneficial and harmful effects. In Canada, advisories from environmental and health agencies consider both these aspects. In the Amazon, we are currently involved in a participatory research whose goal is to reduce Hg absorption, while maintaining fish consumption.

Manganese accentuates adverse mental health effects associated with alcohol use disorders

BACKGROUND

A population-based study on early neurotoxic effects of environmental exposure to manganese (Mn) enabled us to investigate the relation between blood Mn levels (MnB), alcohol consumption, and risk for alcohol use disorders (AUD) on mental health.

METHODS

Participants were selected using a random stratified sampling procedure. Self-administered questionnaires provided data on alcohol consumption, sociodemographics, medical history, and lifestyle. Mood states were assessed with the Brief Symptom Inventory (BSI), and risk for AUD was surveyed using a behavioral screening questionnaire and categorized into no, low, and high risk. Of 297 participants, 253 current drinkers who had responded to all questions on alcohol use were retained.

RESULTS

Psychologic distress increased with risk for AUD and alcohol consumption > or = 420 g/week. Higher MnB levels (> or =7.5 microg/L) intensified the relation between risk for AUD and BSI scale scores. The Prevalence odd ratios for positive cases of psychologic distress with risk for AUD, 1.98 [1.13-3.46], differed when divided by MnB strata: lower MnB: 1.34 [0.64-2.85]; higher MnB: 4.22 [1.65-10.77].

CONCLUSIONS

These findings suggest that higher levels of blood manganese significantly increase neuropsychiatric symptoms associated with risk for alcohol use disorders.

A comparative study of manganese and lead levels in human umbilical cords and maternal blood from two urban centers exposed to different gasoline additives

Manganese (Mn) and lead (Pb) are two neurotoxic chemicals and experimental evidence suggests that they can cross the placental barrier. Tetraethyl lead was still in use as an antiknock agent in Paris during the sampling period of the study, while it has been replaced by methylcyclopentadienyl manganese tricarbonyl (MMT) in Canada since 1977. By 1990, MMT was in 100% of gasoline in Canada. In a study of 160 pairs of mothers-neonates in Montreal and 206 pairs in Paris, we compared levels of Mn and Pb in the umbilical cord and in maternal blood. Neonates and mothers had significantly higher Pb levels in Paris where lead additives were still used in gasoline. Geometric mean maternal blood Pb levels were 5.4 microg/dl compared to 2.1 microg/dl in Montreal and cord blood Pb levels were 3.2 microg/dl in Parisian mothers compared to 1.7 microg/dl in Montreal. The prevalence of Paris Pb values superior to the 95th percentile of the Montreal distribution was highly elevated in all media studied. The prevalence of high Mn levels in umbilical cord blood was also significantly higher in Montreal. Surveillance programs are important to limit Pb overexposure and associated neurological effects in neonates where tetraethyl Pb is still in use as a gasoline additive. Since Mn is an essential element and dietary Mn intake may differ between Montreal and Paris, the difference observed with regard to high Mn values between Montreal and Paris cannot, at this time, be attributed to MMT in Montreal's gasoline. Further studies are needed to infer an association between Mn emissions from MMT and prenatal exposure to Mn.

Neuropsychological dysfunction, mood disturbance, and emotional status of munitions workers

The objective of this study was to compare the neuropsychological function, emotional status, visual function, and illness prevalence of 265 former munitions plant workers (M age = 56.7 years, M years of education = 12.07; 201 African American, 64 White) exposed to organic solvents for an average of 17.03 years with that of a group of 77 unexposed controls (M age = 51.3 years, M years of education = 13.07; 30 African American, 47 White). Neuropsychological tests were selected from the World Health Organization Neurobehavioral Core Test Battery, Wechsler Adult Intelligence Scale-III (WAIS-III), and Wechsler Memory Scale-III (WMS-III) and also included the Brief Symptom Inventory, Profile of Mood States, Beck Anxiety Inventory, and Beck Depression Inventory. Vision tests included the Lanthony d-15 color vision, the Vistech Contrast Sensitivity, and the Snellen. The exposed group showed greater deficits than the controls in verbal learning (WMS-III Logical Memory I Learning Slope and Word Lists I Recall), visuomotor tracking speed (Cancellation H, WAIS-III Digit Symbol-Coding) and psychomotor function (Dynamometer and Grooved Pegboard), and dysfunction in emotional status, illness prevalence, and visual function. African American workers reported higher levels of exposure than Whites. Exposure relations demonstrated increased neuropsychological dysfunction with increased exposure.

Pesticide usage and health consequences for women in developing countries: out of sight, out of mind?

Pesticide exposures of women in developing countries are aggravated by economic policy changes associated with structural adjustment programs and globalization. Women in these countries, particularly in the agricultural sector, are increasingly exposed. Since they are concentrated in the most marginal positions in the formal and informal workforces, and production is organized in a gender-specific way, opportunities for women to control their exposures are limited. Data from developing countries show that: 1) women's exposures to pesticides are significantly higher than is recognized; 2) poisonings and other pesticide-related injuries are greatly underestimated for women; 3) for a given adverse outcome from exposure, the experience of that outcome is gender-discriminatory; 4) erroneous risk perception increases women's exposures. The hiatus in knowledge of gender-specific exposures and effects is related to gender biases in the nature of epidemiologic inquiry and in the literature, and the gendered nature of health workers' practices and surveillance. Recommendations are made for strong, independent organizations that provide opportunities for women to control their environments, and the factors affecting their health, as well as gender-sensitive research to address the particularities of women's pesticide exposures.

Assessment of bioaccumulation and neurotoxicity in rats with portacaval anastomosis and exposed to manganese phosphate: a pilot study

The use of the additive methylcyclopentadienyl manganese tricarbonyl in unleaded gasoline has resulted in increased attention to the potential toxic effects of manganese (Mn). Hypothetically, people with chronic liver disease may be more sensitive to the adverse neurotoxic effects of Mn. In this work, bioaccumulation of Mn, as well as histopathology and neurobehavioral damage, in end-to-side portacaval anastomosis (PCA) rats exposed to Mn phosphate via inhalation was investigated. During the week before the PCA operation, 4 wk after the PCA operation, and at the end of exposure, the rats were subjected to a locomotor evaluation (day-night activities) using a computerized autotrack system. Then a group of 6 PCA rats (EXP) was exposed to 3050 microg m(-3) (Mn phosphate) for 8 h/day, 5 days/wk for 4 consecutive weeks and compared to a control group (CON), 7 PCA rats exposed to 0.03 microg m(-3). After exposure, the rats were euthanized and Mn content in tissues and organs was determined by neutron activation analysis. The manganese concentrations in blood (0.05 microg/g vs. 0.02 microg/g), lung (1.32 microg/g vs. 0.24 microg/g), cerebellum (0.85 microg/g vs. 0.64 microg/g), frontal cortex (0.87 microg/g vs. 0.61 microg/g), and globus pallidus (3.56 microg/g vs. 1.33 microg/g) were significantly higher in the exposed group compared to the control group (p <.05). No difference was observed in liver, kidney, testes, and caudate putamen between the two groups. Neuronal cell loss was assessed by neuronal cell counts. The loss of cells in globus pallidus and caudate putamen as well as in frontal cortex was significantly higher (p <.05) for the EXP group. Assessment of the locomotor activities did not reveal any significant difference. This study constitutes a first step toward our understanding of the potential adverse effects of Mn in sensitive populations.

[Association between work exposure to neurotoxic substances with workers' relationships with their social network]

BACKGROUND

This study explored the impact on family life and social relations that may result from symptoms associated with exposure to neurotoxic substances in the workplace. We assessed the associations between exposure to neurotoxic substances in the workplace, workers'mental health, and workers'relationships with their social network.

METHODS

A sample of 53 workers and their spouse completed a series of questionnaires, an interview on work history, and a structured interview assessing their personal relationships. Exposure to neurotoxic substances in the workplace were assessed by an interview, using a semiquantitative classification system. Mental health was measured with the Profile of Mood States (POMS), and marital satisfaction with the Marital Adjustment Test (MAT). The social network's characteristics were assessed with the Northern California Community Study Interview Schedule (NCCS). The associations between exposure and social networks were assessed with regression analyses.

RESULTS

There were no associations between exposure and marital satisfaction. However, we found a negative association between workers'exposure and degrees of overlap between husbands' and wives' social networks (Pearson's correlation r=-0.27; p<0.05) and a positive association between exposure and workers' dependency on their support network (r=0.46; p<0.01).

CONCLUSION

The results are discussed in terms of variables potentially linking exposure to social relationships as well as in terms of couples' vulnerability to marital distress among exposed workers.

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.

Sequential analysis of hair mercury levels in relation to fish diet of an Amazonian population, Brazil

Several studies in the Amazonian Basin have shown that riverine populations are exposed to methylmercury through fish consumption. It has been suggested that seasonal variations in hair mercury observed through sequential analyses may be related to the changes in fish species ingested by the local communities. The aim of the present study was to investigate the relationship between fish-eating practices and seasonal variation in mercury exposure. A group of 36 women from a village located on the banks of the Tapajós River, a major tributary of the Amazon, comprised the present study population. An interview-administered questionnaire was used to gather information on socio-demographic characteristics, fish-eating practices and other relevant information. The women also provided hair samples of at least 24 cm in length for mercury analysis. Hair total and inorganic mercury concentration was measured using a cold vapor atomic absorption analytical method. Trigonometric regression analysis was done to assess the seasonal variation of total mercury levels. Variations in inorganic mercury were examined by repeated measures analysis of variance, and analysis of contrast variable with a polynomial transformation. The results showed that hair mercury levels varied with the season. Higher levels were observed in months corresponding to the dry season, with lower levels in the rainy season. Herbivorous fish predominated the diet for 47.2% of the women during the dry season, but this rose to 72.2% during the rainy season. Those who reported eating fish daily had higher mercury levels in hair compared to those who only ate fish a few times per week. Retrospective mercury analyses, evaluated by the quantity of mercury present in each centimeter of hair, indicate that mean mercury level of the population decreased over the 2 years prior to the study. The percentage of inorganic mercury over the total mercury in hair increased towards the extremities of the hair strand. Higher percentages of inorganic mercury were found for the group who ate more fish (on a daily consumption basis). These results support the assumption that there are seasonal variations in methylmercury exposure and also a relationship between type of fish species consumed and the resulting hair mercury levels.

Cumulative exposure to styrene and visual functions

BACKGROUND

Results from a 1990-1992 longitudinal study of several reinforced plastics plants showed that for those workers whose styrene exposure had decreased, color vision (CV) improved; while near visual contrast sensitivity (CS) was poorer.

METHODS

In 1999, we retested these visual functions in 18 workers with good visual acuity. A cumulative exposure index (CEI), corrected for respirator use, was calculated for each worker.

RESULTS

Intra-individual comparison of mandelic acid (MA) showed a significant decrease over time (Friedman; P = 0.015), but current values were not related to CEI. For CV, no significant difference was observed between 1992 and 1999; present results were not related to MA or CEI. The CS profile decreased over time, with significant differences at 3 cpd (Friedman; P < 0.05). CS did not vary with MA levels, but was significantly depressed at the intermediate frequencies among those in the upper CEIH category (Kruskal-Wallis; P < 0.05).

CONCLUSIONS

These findings suggest that CS loss increases with long-term cumulative exposure, reflecting chronic damage to the neuro-optic pathways.

Chronic nervous-system effects of long-term occupational exposure to DDT

Dichlorodiphenyltrichloroethane (DDT) is a compound with moderate toxicity that is judged to be safe for occupational use, although little is known about its long-term effects on the human nervous system. We investigated chronic nervous-system effects of long-term occupational exposure to DDT by comparing the neurobehavioural performance of retired malaria-control workers with a reference group of retired guards and drivers. DDT-exposed workers did worse on tests assessing various neurobehavioural functions than controls; performance significantly deteriorated with increasing years of DDT application. Our results could not be explained by exposure to cholinesterase-inhibiting pesticides or other potential confounding factors.

Cytogenetic damage related to low levels of methyl mercury contamination in the Brazilian Amazon

The mercury rejected in the water system, from mining operations and lixiviation of soils after deforestation, is considered to be the main contributors to the contamination of the ecosystem in the Amazon Basin. The objectives of the present study were to examine cytogenetic functions in peripheral lymphocytes within a population living on the banks of the Tapajós River with respect to methylmercury (MeHg) contamination, using hair mercury as a biological indicator of exposure. Our investigation shows a clear relation between methylmercury contamination and cytogenetic damage in lymphocytes at levels well below 50 micrograms/gram, the level at which initial clinical signs and symptoms of mercury poisoning occur. The first apparent biological effect with increasing MeHg hair level was the impairment of lymphocyte proliferation measured as mitotic index (MI). The relation between mercury concentration in hair and MI suggests that this parameter, an indicator of changes in lymphocytes and their ability to respond to culture conditions, may be an early marker of cytotoxicity and genotoxicity in humans and should be taken into account in the preliminary evaluation of the risks to populations exposed in vivo. This is the first report showing clear cytotoxic effects of long-term exposure to MeHg. Although the results strongly suggest that, under the conditions examined here, MeHg is both a spindle poison and a clastogen, the biological significance of these observations are as yet unknown. A long-term follow-up of these subjects should be undertaken.

Mercury methylation along a lake-forest transect in the Tapajós river floodplain, Brazilian Amazon: seasonal and vertical variations

The seasonal and spatial variations of net methylmercury production in sediments, soils and other sites were evaluated by assays with 203Hg at different depths and locations along a lake-forest transect at lake Enseada Grande, Tapajós river. Soil and sediment samples were taken at the surface and at different depths up to 9 cm. Fresh samples and acidified controls (1-3 g dry wt.) were slurried with local water and incubated in the dark at 25-28 degrees C for 3 days with 0.5-1.6 microg Hg g(-1) (dry wt.) added as 203HgCl2. CH3 203Hg was extracted and measured in scintillation cocktail after acid leaching. Methylmercury production varied by orders of magnitude among sites and among sediment or soil layers. Seasonal variations were smaller than those with sample depth and location. In both seasons, MeHg formation in sediment and soil or flooded soil decreased with depth and was, in the top layers, one order of magnitude higher in the C-rich littoral macrophyte zone (2.3-8.9%) and flooded forest (3.2-4.5%) than in the center of the lake (0.2-0.56%). Similar MeHg production was found in slurried dry soils (dry season) and in soils already flooded for months. In the macrophyte zone soil (dry season), methylation was mainly associated with the thin Paspalum sp. rootlet layer. In the forest site, vertical variation in methylation was less pronounced in flooded than in dry soils and during the inundation the higher methylation rate was found in the flocculent sediment settled over the litter layer. The roots of floating Paspalum sp. were an important Hg methylation site, particularly those heavily colonized with periphyton (3.4-5.4%). Methylation in surface or near-bottom water was undetectable (< 3 x 10(-2)%) at all sites. Flooded forests and macrophyte mats are specific features of the Amazon and are important links between Hg inputs from natural and manmade sources and MeHg exposure of local populations through fish intake.

Assessment of exposure to manganese in welding operations during the assembly of heavy excavation machinery accessories

Welder exposure to metals in various industrial sectors is poorly characterized. We had the opportunity to carry out an exploratory study to characterize manganese exposure in welding operations in a recently established Quebec factory that assembled accessories for heavy excavation machinery. Ten workers were sampled for total manganese for at least two consecutive days out of three followed by two consecutive days for respirable manganese (with a size selective sampler with a median cut-off of 4 microns), during a typical week in the summer of 1998. Parts being welded were characterized as large or small. Small parts were those being welded on tables during subassembly. Workers were divided into two groups according to the parts they were welding. Seventy-eight percent of the total manganese exposure levels of welding operations during the assembly of large accessories of heavy excavation machinery exceeded the manganese American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) of 0.20 mg/m3 (GM 0.24 mg/m3, n = 14) while none exceeded the TLV during the assembly of small pieces (GM 0.06 mg/m3, n = 8). Welding operations during the assembly of large heavy excavation machinery accessories may pose a significant health hazard. Considering the importance of task-related variables affecting exposure among workers, further studies are needed to better characterize exposure determinants of welding operations during the assembly of heavy excavation machinery accessories.

Methylmercury exposure affects motor performance of a riverine population of the Tapajós river, Brazilian Amazon

Gold mining and deforestation in the Brazilian Amazon are increasing mercury pollution of the extensive water system, exposing riverine populations to organic mercury through fish-eating. The aim of the present study was to evaluate the effect of such exposure on motor performance. This cross-sectional study was carried out in May 1996, in a village located on the banks of the Tapajós river in the Amazonian Basin, Brazil. Information concerning sociodemographics, health, smoking habits, alcohol drinking, dietary habits and work history were collected using an interview-administered questionnaire. Mercury concentrations were measured by cold vapor atomic absorption in blood and hair of each participant, of whom those aged between 15 and 79 years were assessed for motor performance (n = 84). Psychomotor performance was evaluated using the Santa Ana manual dexterity test, the Grooved Pegboard Fine motor test and the fingertapping motor speed test. Motor strength was measured by dynamometry for grip and pinch strength. Following the exclusion of 16 persons for previous head injury, working with mercury in the goldmining sites, or for diabetes, the relationship between performance and bioindicators of mercury was examined using multivariate statistical analyses, taking into account covariables. All participants in the study reported eating fish, which comprised 61.8% of the total meals eaten during the preceding week. The median hair total mercury concentration was 9 microg/g. Organic mercury accounted for 94.4 = 1.9% of the total mercury levels. Multivariate analysis of variance indicated that hair mercury was inversely associated with overall performance on the psychomotor tests, while a tendency was observed with blood mercury. Semipartial regression analyses showed that hair total mercury accounted for 8% to 16% of the variance of psychomotor performance. Neither hair nor blood total mercury was associated with the results of the strength tests in women and men. Although dose-effect relationships were observed in this cross-sectional study, they may reflect higher exposure levels in the past. The findings of this study demonstrated neurobehavioral manifestations of subtle neurotoxic effects on motor functions, associated with low-level methylmercury exposure.

Beyond the workplace: an exploratory study of the impact of neurotoxic workplace exposure on marital relations

BACKGROUND

The impact on family life and social relations that may result from symptoms associated with exposure to neurotoxic substances has never been addressed. This exploratory study assessed the associations between exposure to neurotoxic agents in the workplace, mental health, and marital difficulties.

METHODS

Fifty-five (55) male workers and their spouses completed standardized measures of mental health and marital difficulties. Workers' exposure to neurotoxic substances was evaluated by questionnaire and interview, using a semiquantitative classification system.

RESULTS

A positive relation was observed between exposure level and measures of workers' psychological symptoms and marital stress; no relation was observed between workers' exposure level and wives' psychological symptoms. More severe exposure to neurotoxic substances was associated with wives' reports of more severe marital conflicts, and this association was mediated by husbands' psychological symptoms. As compared to low exposure husbands, high exposure husbands reported higher degrees of stress surrounding marital discussions, more consistent incidence of minor physical assaults by wives, and stronger associations between their levels of stress, the verbal aggressions of wives, and the number of marital conflicts.

CONCLUSIONS

The results of this study confirm that neurotoxic exposure is a risk factor for mental health and suggest how this may influence marital relations. Because of the importance of these findings for the well-being of workers and their families, these associations should be further studied.

Combining quantitative and qualitative approaches in occupational health for a better understanding of the impact of work-related disorders

Over the past years, the work situation has experienced important transformations, notably, the technological revolution and globalization, the influx of women into the labor market, an increased dependence on chemical substances, and a transfer of production and many hazardous procedures from North to South. These changes have important repercussions on the nature and type of occupational exposures, as well as on the labor force, affecting the relation between work and health. While quantitative studies have dominated occupational health research over the past half century, qualitative methods can serve to ground quantitative data with regard to defining the research questions, providing further information on the impact of work conditions on health and well-being, and reducing errors in exposure and health outcomes. Combining qualitative and quantitative methods in a complementary fashion can lead to a better understanding of the rapidly changing work environment and labor situation and a means for developing appropriate strategies for preventive intervention.

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.

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.

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.

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.

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.

The geochemistry of mercury in central Amazonian soils developed on the Alter-do-Chão formation of the lower Tapajós River Valley, Pará state, Brazil

In an oxisol-spodosol system developed on the terrestrial surface of the lower Tapajós Valley, the determination of total mercury (Hg), organic carbon (C), iron and aluminum oxy-hydroxide (Fe(cdb) and Al(cdb)) concentrations in the surface soil horizons are used to characterise the geochemical processes controlling the accumulation of Hg in soils under natural vegetation cover and in deforested and cultivated sites. Oxisols from the plateau have homogeneous and relatively high background Hg contents and burdens constituting an important natural reservoir of Hg for the region (90-210 ng/g dry wt. and 19-33 mg/m2 for the first 20 cm). The Fe(cdb) and Al(cdb) contents associated with the fine fraction (< 63 microns) of the soil suggest that oxy-hydroxides and, particularly Al-substituted Fe oxy-hydroxides, control the Hg concentrations observed in all of the soils of the study region. Consequently, the geochemistry of these minerals along the slopes governs the accumulation or the release of the Hg according to the natural evolution of the soil cover and/or following the degradation of soils by erosion after deforestation and cultivation. These observations have important implications for the interpretation of Hg contamination patterns observed in Amazonian aquatic systems that could be linked to different drainage sources of Hg from the terrestrial surface. The sandification and podzolisation that is characteristic of the evolution of numerous pedological systems in the equatorial Amazon could be responsible for exportation of the naturally accumulated Hg, as for other metals, by acidic complexation and migration to the black waters of the Amazon. In the central Amazon region, as a result of the fragility of the soil cover, deforestation and cultivation, affecting principally the superficial soil, promote the selective erosion of fine particles enriched in oxides and Hg. The erosion of soil could be responsible for an important release of Hg, transported in particulate form by drainage waters.

Neurotoxic effects of low-level methylmercury contamination in the Amazonian Basin

Many studies have demonstrated mercury contamination in the Amazonian ecosystem, particularly in fish, a dietary mainstay of populations in this region. The present study focused on potential health effects of this low-level methylmercury exposure. The study was carried out in a village on the Tapajós River, a tributary of the Amazon, on 91 adults inhabitants (15-81 years), whose hair mercury levels were inferior to 50 mu/g. Performance on a neurofunctional test battery and clinical manifestations of nervous system dysfunction were examined in relation to hair mercury concentrations. Near visual contrast sensitivity and manual dexterity, adjusted for age, decreased significantly with hair mercury levels (P < 0.05), while there was a tendency for muscular fatigue to increase and muscular strength to decrease in women. For the most part, clinical examinations were normal, however, hair mercury levels were significantly higher (P < 0.05) for persons who presented disorganized movements on an alternating movement task and for persons with restricted visual fields. These results suggest dose-dependent nervous system alterations at hair mercury levels below 50 micrograms/g, previously considered a threshold for clinical effects. The profile of dysfunction in this adult population is consistent with the current knowledge on methyl-mercury poisoning. The long-term implications of these findings are unknown and need to be addressed.

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.

Blood levels of total and organic mercury in residents of the upper St. Lawrence River basin, Québec: association with age, gender, and fish consumption

Increased consumption of lake fish was associated with higher blood mercury concentrations among 289 residents of Southwest Quebec living on the southern bank of the Upper St. Lawrence River System. This increase in blood mercury was reflected in the organic fraction and to a lesser extent with total blood mercury. Repeat analyses on a small subpopulation showed a correlation coefficient between time 1 and time 2 of approximately 0.7 for total mercury and for organic mercury. With one exception, blood total mercury concentrations were less than 5 ppb. Blood mercury concentrations were higher among men than women. One individual had much higher total mercury concentrations in blood (i.e., 70 ppb) which were attributed to fish consumption based on medical and dietary history. The values for these subjects are compared with other North American data on blood mercury levels.

Early manifestations of manganese neurotoxicity in humans: an update

It is possible to detect early signs of neurotoxic dysfunction associated with occupational and environmental exposure to manganese; neurophysiologic and neurobehavioral tests can be used in the absence of clinical manifestations. Although outcomes from individual studies vary, they collectively show a pattern of slowing motor functions, increased tremor, reduced response speed, enhanced olfactory sense, possible memory and intellectual deficits, and mood changes. This overall portrait is consistent with the action of manganese on the central nervous system. In reports to date, there is little consistency in dose-effect relationships between internal parameters of manganese exposure (blood manganese, urinary manganese, hair manganese) and external measures and neurologic outcomes. Several studies suggest the existence of dose-effect relationships, but additional clarification is needed.

Peripheral markers of catecholaminergic dysfunction and symptoms of neurotoxicity among styrene-exposed workers

AIM

A cross-sectional investigation was carried out to assess possible relations between styrene-induced changes in three peripheral markers of catecholaminergic dysfunction and self-reported symptoms of neurotoxicity.

SUBJECTS

Male workers (n = 46) aged 14-60 (mean 29.5) years who had been exposed to styrene for an average of 6 (0.2-29) years were recruited in glassfiber reinforced plastics plants. A control group of 30 blue-collar workers aged 22-52 (mean 35) years and with no history of exposure to chemicals was recruited from local industries. Styrene exposure ranged from 5 to 120 ppm (8 h-TWA), the median level being relatively low (25 ppm, 8 h-TWA). Styrene metabolites, mandelic and phenylglycoxylic acids (MAPGA) in the "next morning" urine spot samples ranged from 32.0 to 931.1 mg/g creatinine (median 186.5).

METHODS

Platelet monoamine oxidases B (MAO B) and dopamine beta-hydroxylase (DBH) activities were assessed using methods based on HPLC and electrochemical detection. Plasma prolactin (PRL) was measured by a commercially available immunoassay. Questionnaire 16 (Q16) was used to survey self-reported symptoms.

RESULTS

Although there was no difference in DBH activity between exposed workers and controls, the most highly exposed workers had significantly lower activity than control subjects. A tendency to lower platelet MAO B activity in exposed than in control subjects was observed. The prevalence of plasma DBH and platelet MAO B values below the lower reference limit was similar in the two groups. PRL values exceeding the upper reference limit were higher (14/46 vs 2/30) among styrene-exposed workers, who also exhibited significantly higher median levels (10.0 vs 5.7 micrograms/l) than control subjects. Although the number of reported symptoms was similar among exposed and control subjects, in the exposed group it was positively associated with urinary MAPGA (Rho = 0.30, P = 0.04). Of the three peripheral markers of catecholaminergic dysfunction, plasma DBH was the only parameter negatively related to both urinary MAPGA (F = 9.56, P = 0.003) and the number of reported symptoms (Rho = 0.23, P = 0.05).

CONCLUSIONS

Plasma PRL appears to be a sensitive marker of styrene-induced tubero-infundibular dopaminergic dysfunction in male subjects. DBH in plasma and MAO B in platelets seem to be less suitable markers for biomonitoring effect at the individual level, although DBH was related to the number of reported symptoms and to internal dose. Further studies on a larger and more exposed population are necessary to clarify the significance of these markers for health and their predictive value with regard to both subjective disturbances and concurrently administered performance tests.

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.

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.

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.

[Mental health deterioration in workers exposed to styrene]

Emotional instability which might be an early symptom of more severe disorders, is one of the first manifestations of chronic exposure to organic solvents. The present study measures the association between exposure to styrene and mood states of active workers. A total of 128 workers (85% of the total population) from 3 factories where styrene is used, participated on a voluntary basis. They filled out the following self-administered questionnaires: Profile of Mood States (POMS), Psychiatric Symptom Index and Well-being Index. The results indicate a significant relationship between post work-shift urinary mandelic acid (biological indicator of styrene exposure) and the scores obtained on the POMS scales of tension-anxiety (Spearman's rank correlation rho = 0.30; p < 0.01), anger-hostility (rho = 0.29; p < 0.01), fatigue-inertie (rho = 0.34; p < 0.01), and confusion-bewilderment (rho = 0.23; p = 0.04), as well as the Psychological Distress Index (rho = 0.30; p < 0.01). All scores were adjusted for the effects of 4 potentially confounding variables: age, schooling, alcohol and cigarette consumption. These indicators of mood states do not constitute a diagnosis of mental disease but reveal progressive deterioration of well being associated with neurotoxic exposure in the workplace.

[Monitoring neurotoxic effects among laboratory personnel working with organic solvents]

The relationship between organic solvent exposure and central nervous disorders make early detection of neurophysiologic et neuropsychologic alterations in organic solvent exposed workers a priority. Moreover, the variability in the frequency of exposure and the numerous organic solvents encountered in scientific laboratories render the environmental and biological measurements used in medical surveys almost impossible. The present study was undertaken to appreciate the potential neurotoxic effects of organic solvents handling in laboratory employees. Neurophysiological and neuropsychological tests batteries were used with each worker and data were adjusted for potential confounding factors (age and education level). A Principal Components Analysis were performed to reduce the information and the first five factors corresponded to: mood states, speed coding, contrast vision in high frequencies, manual dexterity and contrast vision in low frequencies. These five factors were compared between the daily manipulators of at least one solvent (n = 75) and the non or occasional solvent users (n = 35). The results from this study showed that subjects directly in contact with solvents had a poorer mood state than those who were not or rarely exposed (p < 0.01) and that independently of the "work activity". Mood state impairment in chronic solvent exposed workers has been shown by many authors, with or without psychomotor alteration, and may reflect possible over-exposure. Detection of this instability may lead to early neurophysiologic alteration in exposed workers and permit health services to intervene before the development of irreversible effects.

Visual dysfunction among styrene-exposed workers

OBJECTIVES

The present study was undertaken to examine the relation between visual functions and occupational exposure to styrene.

METHODS

A total of 128 workers (85% of the total population), from three glass-reinforced plastics plants in Canada, agreed to participate in the study. Environmental and biological measures were made on the day(s) prior to the assessment of near visual acuity (National Optical Visual Chart), chromatic discrimination (Lanthony D-15 desaturated panel), and near contrast sensitivity (Vistech 6000). The analyses were performed on 81 workers with near visual acuity of at least 1 min of arc at 0.5 m.

RESULTS

The subjects were relatively young [29 (SD 8) years], with little seniority [5 (SD 4) years]. Styrene exposure for 8 h ranged from 6 to 937 (first quartile 21 mg.m-3, third quartile 303 mg.m-3), depending on the job site. The end-shift concentrations of urinary mandelic acid ranged from nondetectable to 1.90 mmol.mmol creatinine-1. Significant positive relations were found between the internal and external styrene exposure measurements and color vision loss adjusted for age, alcohol consumption, and seniority in a multiple regression analysis. The multiple regression analysis is also showed that the end-shift concentration of urinary mandelic acid was inversely related to contrast sensitivity at 6 and 12 cycles.degree-1. Logistic multiple regression models indicated that the end-shift concentration of urinary mandelic acid was related to the prevalences of blurred vision, tearing, and eye irritation.

CONCLUSIONS

These findings suggest that there is a positive relation between styrene exposure and early color and contrast vision dysfunction.

Peripheral markers of catecholamine metabolism among workers occupationally exposed to manganese (Mn)

In a preliminary study of 11 men randomly selected in a ferro-alloy plant and of 15 control subjects, platelet monoamine oxidase (MAO) and serum dopamine beta-hydroxylase (DBH) activities were measured. A tendency towards lower MAO-B activity in the exposed workers as compared to control subjects (t = 1.95; P = 0.06) was found whereas DBH activity was similar. In the exposed group, a dose-effect relationship was noted between a manganese (Mn) cumulative exposure index (CEI) and DBH activity (R2 = 0.40, P < 0.05). Since DBH is an expression of catecholamine release, the relative increase in such activity could be envisaged as a compensatory mechanism to a reduced turnover rate as reflected by MAO-B activity. Owing to the limited sample size, these findings should be confirmed by further epidemiological and experimental studies.

Psychological, psychosocial, and psychophysiological sequelae in a community affected by a railroad chemical disaster

Psychological, psychosocial, and psychophysiological sequelae were studied in a community which had experienced a railroad chemical spill of 19,000 gallons of the toxic pesticide metam sodium. Two hundred twenty exposed residents were compared to 114 controls and paired on age, education, gender, race, and number of children. A clinical interview and physiological measurements (blood pressure, pulse, and cortisol level) were taken, the MMPI-2, IES Scale, Mood Scale, Environmental Worry, Perceived Social Support, and Perceived Control Scale and a questionnaire were administered. Results indicated greater levels of depression, anxiety, and somatic symptoms in the spill residents in addition to greater environmental worry and lower perceived social support. Spill residents had higher blood pressure and less fluctuation of cortisol levels than controls. No difference on litigation status was obtained except on the IES, Intrusion and the POMS scales. Chemical disasters are associated with a wide variety of psychological, psychosocial, and physiological distress.

Nervous system dysfunction among workers with long-term exposure to manganese

Neurological disorders, bearing many similarities to Parkinson's disease, have been associated with environmental and occupational exposure to manganese (Mn). To document early nervous system dysfunction associated with long-term exposure to Mn, a battery of neurofunctional tests was administered to workers employed in Mn alloy production. Study participation was 95% (n = 115). A matched pair design was used; actively working men, with no history of workplace exposure to neurotoxins, were recruited from the region as referents. Matching was done on the variables: age (+/- 3 years), educational level (+/- 2 years), smoking status, and number of children. Stationary environmental sampling indicated that Mn levels varied widely (geometric means: Mn dust, 0.89 mg/m3; respirable Mn, 0.04 mg/m3). The alloy workers had significantly higher levels of whole blood Mn (geometric mean: 1.03 microgram/100 ml vs 0.68 microgram/100 ml); no differences were observed for urinary Mn. Univariate analysis (paired t test, Signed Rank and McNemar) and multivariate analysis of variance (Hotelling-Lawley statistic) revealed that the pairs differed on symptom reporting, emotional state, motor functions, cognitive flexibility, and olfactory perception threshold; verbal fluency, basic mathematics, reading capability, and attentional capacity were similar. These findings are consistent with current knowledge on brain Mn activity and suggest that manifestations of early manganism can be observed in well designed population studies, using sensitive testing methods.

Comparison of performance from three continents on the WHO-Recommended Neurobehavioral Core Test Battery

To address the need for standardized test batteries, an expert group convened by the World Health Organization (WHO) and the U.S. National Institute for Occupational Safety and Health during 1983 proposed the Neurobehavioral Core Test Battery (NCTB) to identify nervous system effects of chemical exposures in human populations worldwide. To determine the feasibility of using the NCTB in varied cultures, a cross-cultural assessment was conducted under WHO auspices. Data were collected in 10 countries of Europe, North and Central America, and Asia from over 2300 males and females who were not exposed to chemicals at work, within five age ranges between 16 and 65. Results suggest that performance on two NCTB tests (Simple Reaction Time, Benton Visual Retention) is very similar in a broad range of countries and that performance on four other NCTB tests (Santa Ana, Digit Symbol, Digit Span, Aiming) is relatively more variable from country to country, in both males and females. However, data collected from very poorly educated males in one country revealed very low performance levels suggesting that the NCTB may not provide an adequate reference group for identifying (behavioral) neurotoxic effects in such populations. More research is thus needed on evaluating neurotoxicity in poorly educated subjects.

Stability of psychological impairment: two year follow-up of former microelectronics workers' affective and personality disturbance

For the past twenty years women's complaints in the microelectronics industry have often been diagnosed as mass psychogenic illness, despite evidence of potential exposure to organic solvents, which have been associated with affect and mood changes. In the present study, the standard version of the Minnesota Multiphasic Personality Inventory (MMPI) was used to evaluate affective and personality disturbance among 63 former microelectronics workers (56 women and 7 men) over a two-year period of time. In both 1986 and 1988, the former workers obtained mean scale score elevations beyond two standard deviations above the normative sample (T = greater than 70) on the MMPI clinical scales of schizophrenia, hypochondriasis, psychasthenia, depression and hysteria. For most scales, 86-88 mean score differences did not attain the 0.05 significance level (two-tailed paired t-test) and no significant differences were observed for 86-88 comparison scale scores = greater than 70 (McNemar paired statistic). Although there were too few men to perform gender comparisons, men scored higher than women on 5 scales and all of the men had scores = greater than 70 on hypochondriasis, depression, hysteria, psychasthenia and schizophrenia. These findings reveal that these former microelectronics workers manifested affective and personality disturbances, consistent with organic solvent toxicity, which persisted over a two year period, indicating that they were not reactive, transient hysterical neurosis.