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

Drug use disorder following early life exposure to tetrachloroethylene (PCE)-contaminated drinking water: a retrospective cohort study

BACKGROUND

Many studies of adults with occupational exposure to solvents such as tetrachloroethylene (PCE) have shown adverse effects on cognition, mood and behavioral problems. Much less is known about neurotoxic effects in early life at lower exposure levels seen in community settings. We recently reported that illicit drug use was more frequent among adults from Cape Cod, Massachusetts who were exposed to PCE-contaminated drinking water during gestation and early childhood than their unexposed counterparts. Using newly collected data from this population-based retrospective cohort study, the current analysis examines whether early life PCE exposure is also associated with drug use disorder over the life course.

METHODS

Three-hundred and sixty-three subjects with prenatal and early childhood PCE exposure and 255 unexposed subjects were studied. These individuals (median age: 40-41 years) completed self-administered questionnaires on the eleven established diagnostic criteria for drug use disorder and confounding variables. A validated leaching and transport model was used to estimate exposure to PCE-contaminated water.

RESULTS

Overall, 23.3% of subjects reported having at least one criterion for drug use disorder over their lifetime. Early life PCE exposure was associated with a modest increase in the lifetime presence of one or more diagnostic criteria for drug use disorder (adjusted RR: 1.4, 95% CI: 1.0-1.8). Compared to unexposed subjects, PCE-exposed subjects were more likely to report having most diagnostic criteria of drug use disorder, including neglecting major roles due to drug use, physical and psychological problems related to drug use, and giving up activities due to drug use. No dose-response relationships were observed with increasing levels of PCE exposure.

CONCLUSIONS

These results suggest that exposure to PCE-contaminated drinking water during early life modestly increases the risk of developing diagnostic criteria for drug use disorder later in life. Because this study has several limitations, these findings should be confirmed in follow-up investigations of other exposed populations with more diverse racial and socioeconomic characteristics.

Reversibility of neuroimaging markers influenced by lifetime occupational manganese exposure

Manganese (Mn) is a neurotoxicant that many workers are exposed to daily. There is limited knowledge about how changes in exposure levels impact measures in magnetic resonance imaging (MRI). We hypothesized that changes in Mn exposure would be reflected by changes in the MRI relaxation rate R1 and thalamic γ-aminobutyric acid (GABAThal). As part of a prospective cohort study, 17 welders were recruited and imaged on two separate occasions approximately two years apart. MRI relaxometry was used to assess changes of Mn accumulation in the brain. Additionally, GABA was measured using magnetic resonance spectroscopy (MRS) in the thalamic and striatal regions of the brain. Air Mn exposure ([Mn]Air) and cumulative exposure indexes of Mn (Mn-CEI) for the past three months (Mn-CEI3M), past year (Mn-CEI12M), and lifetime (Mn-CEILife) were calculated using personal air sampling and a comprehensive work history, while toenails were collected for analysis of internal Mn body burden. Finally, welders' motor function was examined using the Unified Parkinson's Disease Rating Scale (UPDRS). Median exposure decreased for all exposure measures between the first and second scan. ΔGABAThal was significantly correlated with ΔMn-CEI3M (ρ = 0.66, adjusted p = 0.02), ΔMn-CEI12M (ρ = 0.70, adjusted p = 0.006) , and Δ[Mn]Air (ρ = 0.77, adjusted p = 0.002). ΔGABAThal significantly decreased linearly with ΔMn-CEI3M (quantile regression, β = 15.22, p = 0.02) as well as Δ[Mn]Air (β = 1.27, p = 0.04). Finally, Mn-CEILife interacted with Δ[Mn]Air in the substantia nigra where higher Mn-CEILife lessened the ΔR1 per Δ[Mn]Air (F-test, p = 0.005). While R1 and GABA changed with Mn exposure, UPDRS was unaffected. In conclusion, our study shows that effects from changes in Mn exposure are reflected in thalamic GABA levels and brain Mn levels, as measured by R1, in most brain regions.

Long-term Neurotoxic Effects of Early-life Exposure to Tetrachloroethylene-contaminated Drinking Water

BACKGROUND

Tetrachloroethene (PCE) is a common environmental and occupational contaminant and an acknowledged neurotoxicant. From 1968 through 1983, widespread contamination of public drinking water supplies with PCE occurred in the Cape Cod region of Massachusetts. The source of the contamination was a vinyl liner applied to the inner surface of water distribution pipes.

OBJECTIVES

A retrospective cohort study (the Cape Cod Health Study) was undertaken to examine possible health consequences of early-life exposure to PCE-contaminated drinking water. This review describes the study methods and findings regarding the effects of prenatal and childhood exposure on neurologic outcomes during early adulthood, including vision, neuropsychological functioning, brain structure, risky behaviors, and mental illness. The review also describes the strengths and challenges of conducting population-based epidemiologic research in this unique setting.

METHODS

Participants were identified by cross-matching birth certificates and water system data. Information on health outcomes and confounding variables was collected from self-administered surveys (n = 1689), neuropsychological tests (n = 63), vision examinations (n = 63), and magnetic resonance imaging (n = 42). Early-life exposure to PCE was estimated using a leaching and transport model. The data analysis compared the occurrence of each health outcome among individuals with prenatal and early childhood PCE exposure to unexposed individuals while considering the effect of confounding variables.

FINDINGS

The study found evidence that early-life exposure to PCE-contaminated drinking water has long-term neurotoxic effects. The strongest associations were seen with illicit drug use, bipolar disorder, and post-traumatic stress disorder. Key strengths of the study were availability of historical data on affected water systems, a relatively high exposure prevalence and wide range of exposure levels, and little confounding. Challenges arose mainly from the historical nature of the exposure assessments.

CONCLUSIONS

The Cape Cod Health Study demonstrates how scientists can take advantage of unique "natural experiments" to learn about the health effects of environmental pollution. This body of work has improved our understanding of the long-term health effects of early-life exposure to this common environmental contaminant and will help risk assessors and policymakers ensure that drinking water supplies in the United States are safe for vulnerable populations.

Searching for a neurologic injury's Wechsler Adult Intelligence Scale-Third Edition profile

This study aimed to investigate the presence of a Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) cognitive profile in a Portuguese neurologic injured sample. The Portuguese WAIS-III was administered to 81 mixed neurologic patients and 81 healthy matched controls selected from the Portuguese standardization sample. Although the mixed neurologic injury group performed significantly lower than the healthy controls for the majority of the WAIS-III scores (i.e., composite measures, discrepancies, and subtests), the mean scores were within the normal range and, therefore, at risk of being unobserved in a clinical evaluation. ROC curves analysis showed poor to acceptable diagnostic accuracy for the WAIS-III composite measures and subtests (Working Memory Index and Digit Span revealed the highest accuracy for discriminating between participants, respectively). Multiple regression analysis showed that both literacy and the presence of brain injury were significant predictors for all of the composite measures. In addition, multiple regression analysis also showed that literacy, age of injury onset, and years of survival predicted all seven composite measures for the mixed neurologic injured group. Despite the failure to find a WAIS-III cognitive profile for mixed neurologic patients, the results showed a significant influence of brain lesion and literacy in the performance of the WAIS-III.

Organic solvent exposure and depressive symptoms among licensed pesticide applicators in the Agricultural Health Study

PURPOSE

Although organic solvents are often used in agricultural operations, neurotoxic effects of solvent exposure have not been extensively studied among farmers. The current analysis examined associations between questionnaire-based metrics of organic solvent exposure and depressive symptoms among farmers.

METHODS

Results from 692 male Agricultural Health Study participants were analyzed. Solvent type and exposure duration were assessed by questionnaire. An "ever-use" variable and years of use categories were constructed for exposure to gasoline, paint/lacquer thinner, petroleum distillates, and any solvent. Depressive symptoms were ascertained with the Center for Epidemiologic Studies Depression Scale (CES-D); scores were analyzed separately as continuous (0-60) and dichotomous (<16 versus ≥16) variables. Multivariate linear and logistic regression models were used to estimate crude and adjusted associations between measures of solvent exposure and CES-D score.

RESULTS

Forty-one percent of the sample reported some solvent exposure. The mean CES-D score was 6.5 (SD 6.4; median 5; range 0-44); 92% of the sample had a score below 16. After adjusting for covariates, statistically significant associations were observed between ever-use of any solvent, long duration of any solvent exposure, ever-use of gasoline, ever-use of petroleum distillates, and short duration of petroleum distillate exposure and continuous CES-D score (p < 0.05). Although nearly all associations were positive, fewer statistically significant associations were observed between metrics of solvent exposure and the dichotomized CES-D variable.

CONCLUSIONS

Solvent exposures were associated with depressive symptoms among farmers. Efforts to limit exposure to organic solvents may reduce the risk of depressive symptoms among farmers.

Exploring associations between prenatal solvent exposures and teenage drug and alcohol use: a retrospective cohort study

BACKGROUND

Investigating the effects of prenatal and childhood exposures on behavioral health outcomes in adolescence is challenging given the lengthy period between the exposure and outcomes. We conducted a retrospective cohort study in Cape Cod, Massachusetts to evaluate the impact of prenatal and early childhood exposure to tetrachloroethylene (PCE)-contaminated drinking water on the occurrence of risk-taking behaviors as a teenager. An increased occurrence of risk-taking behaviors, particularly illicit drug use, was observed in those highly exposed to PCE. We hypothesized that there may be other sources of prenatal solvent exposure such as maternal consumption of alcoholic beverages during pregnancy which might modify the previously observed associations between PCE and risk-taking behaviors and so we conducted an exploratory analysis using available cohort data. The current report presents the results of these analyses and describes the difficulties in conducting research on long-term behavioral effects of early life exposures.

METHODS

The exploratory analysis compared a referent group of subjects with no early life exposure to PCE or alcohol (n = 242) to subjects with only alcohol exposure (n = 201), subjects with only PCE exposure (n = 361), and subjects with exposure to both PCE and alcohol (n = 302). Surveys completed by the subject's mother included questions on prenatal alcoholic beverage consumption and available confounding variables such as cigarette smoking and marijuana use. Surveys completed by the subjects included questions on risk-taking behaviors such as alcoholic beverage consumption and illicit drug use as a teenager and available confounding variables. PCE exposure was modeled using a leaching and transport algorithm embedded in water distribution system modeling software that estimated the amount of PCE delivered to a subject's residence during gestation and early childhood.

RESULTS

Subjects with early life exposure to both PCE and alcohol had an increased risk of using two or more major drugs as a teen (RR = 1.9 (95% CI 1.2, 3.0)) compared to unexposed subjects. Increased risks for only PCE exposure (RR = 1.6 (95% CI 1.0, 2.4) and only alcohol exposure (RR = 1.3 (95% CI 0.7, 2.1)) were also evident but were smaller than the increased risk associated with both exposures. While available confounding variables were controlled, many relevant social risk factors were not obtained due to limitations in the retrospective study design.

CONCLUSIONS

This exploratory analysis found evidence for an additive effect of early life exposure to PCE and alcohol on the risk of use of multiple illicit drugs as a teenager. Because of numerous limitations in this retrospective study, further research is needed to examine longstanding behavioral effects of early life exposures. To be most informative, this research should involve long-term prospective data collection.

No Association Between Unintentional Head Injuries and Early-Life Exposure to Tetrachloroethylene (PCE)-Contaminated Drinking Water

Objective:

Because of emerging evidence that early-life exposure to the solvent tetrachloroethylene (PCE) has long-lasting neurological consequences, we examined the risk of unintentional head injuries following prenatal and childhood exposure to PCE-contaminated drinking water.

Methods:

Participants provided information on head injuries and other relevant characteristics in a self-administered questionnaire. Exposure to PCE was modeled using a leaching and transport algorithm set in water system modeling software.

Results:

We did not observe any evidence of an increased risk of any type of head injury among exposed participants.

Conclusions:

PCE is a widespread water pollutant. Thus, documenting possible health effects of early-life exposure is vital for ensuring that drinking water regulations adequately protect vulnerable populations.

Neuropsychologic evaluation and exposure to neurotoxicants

The history of neuropsychologic assessment describes the development of a psychometric approach to neuropsychologic measurement, based on the initial clinical/theoretical approach exemplified by pioneers, who also discussed different brain functions and hypotheses for clinical exploration and treatment. Early neuropsychologic assessment practices in the USA arose out of the need to screen, diagnose, and treat World War II veterans who returned with brain injuries. Clinical testing was used to determine treatment and rehabilitation potential. Clinical psychologists had previously developed educational tests to investigate students' abilities and disabilities. Using population studies, primarily in the USA, Canada and Europe, neuropsychologists developed standardized test scores, permitting comparisons of scores based on the normal curve and evolving knowledge of brain/behavior relationships. In clinical interpretations, neuropsychologists use extensive normative data based on cognitive, mood, executive, neurologic, and motor brain functions of groups with different cultural and educational backgrounds and psychiatric illnesses. Large groups of workers can be screened with a brief neuropsychologic screening test battery to assess the psychologic status of personnel. Commonly used tests by domain are described, as well as patterns of acute and chronic neurotoxicant exposures, treatment, and rehabilitation. Future developments will relate imaging studies to neuropsychologic performance.

Advanced analysis of finger-tapping performance: a preliminary study

BACKGROUND

The finger-tapping test is a commonly employed quantitative assessment tool used to measure motor performance in the upper extremities. This task is a complex motion that is affected by external stimuli, mood and health status. The complexity of this task is difficult to explain with a single average intertap-interval value (time difference between successive tappings) which only provides general information and neglects the temporal effects of the aforementioned factors.

AIMS

This study evaluated the time course of average intertap-interval values and the patterns of variation in both the right and left hands of right-handed subjects using a computer-based finger-tapping system.

STUDY DESIGN

Cross sectional study.

METHODS

Thirty eight male individuals aged between 20 and 28 years (Mean±SD = 22.24±1.65) participated in the study. Participants were asked to perform single-finger-tapping test for 10 seconds of test period. Only the results of right-handed (RH) 35 participants were considered in this study. The test records the time of tapping and saves data as the time difference between successive tappings for further analysis. The average number of tappings and the temporal fluctuation patterns of the intertap-intervals were calculated and compared. The variations in the intertap-interval were evaluated with the best curve fit method.

RESULTS

An average tapping speed or tapping rate can reliably be defined for a single-finger tapping test by analysing the graphically presented data of the number of tappings within the test period. However, a different presentation of the same data, namely the intertap-interval values, shows temporal variation as the number of tapping increases. Curve fitting applications indicate that the variation has a biphasic nature.

CONCLUSION

The measures obtained in this study reflect the complex nature of the finger-tapping task and are suggested to provide reliable information regarding hand performance. Moreover, the equation reflects both the variations in and the general patterns associated with the task.

Structural Magnetic Resonance Imaging in an adult cohort following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water

This population-based retrospective cohort study examined Structural Magnetic Resonance Imaging (MRI) of the brain in relation to prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using pipe network information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling software, and Geographic Information System (GIS) methodology. Brain imaging was performed on 26 exposed and 16 unexposed subjects. Scans were acquired on a Philips 3T whole body scanner using the ADNI T1-weighted MP-RAGE scan. The scans were processed by FreeSurfer version 4.3.1 software to obtain measurements of specific brain regions. There were no statistically significant differences between exposed and unexposed subjects on the measures of white matter hypointensities (β: 127.5mm(3), 95% CI: -259.1, 1514.0), white matter volumes (e.g. total cerebral white matter: β: 21230.0mm(3), 95% CI: -4512.6, 46971.7) or gray matter volumes (e.g. total cerebral gray matter: β: 11976.0mm(3), 95% CI: -13657.2, 37609.3). The results of this study suggest that exposure to PCE during gestation and early childhood, at the levels observed in this population, is not associated with alterations in the brain structures studied.

Adult neuropsychological performance following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water

This population-based retrospective cohort study examined adult performance on a battery of neuropsychological tests in relation to prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using pipe network information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling software, and a Geographic Information System (GIS). Results of crude and multivariate analyses among 35 exposed and 28 unexposed subjects showed no association between prenatal and early postnatal exposure and decrements on tests that assess abilities in the domains of omnibus intelligence, academic achievement or language. The results were suggestive of an association between prenatal and early postnatal PCE exposure and diminished performance on tests that assessed abilities in the domains of visuospatial functioning, learning and memory, motor, attention and mood. Because the sample size was small, most findings were not statistically significant. Future studies with larger sample sizes should be conducted to further define the neuropsychological consequences of early developmental PCE exposure.

Occurrence of mental illness following prenatal and early childhood exposure to tetrachloroethylene (PCE)-contaminated drinking water: a retrospective cohort study

BACKGROUND

While many studies of adults with solvent exposure have shown increased risks of anxiety and depressive disorders, there is little information on the impact of prenatal and early childhood exposure on the subsequent risk of mental illness. This retrospective cohort study examined whether early life exposure to tetrachloroethylene (PCE)-contaminated drinking water influenced the occurrence of depression, bipolar disorder, post-traumatic stress disorder, and schizophrenia among adults from Cape Cod, Massachusetts.

METHODS

A total of 1,512 subjects born between 1969 and 1983 were studied, including 831 subjects with both prenatal and early childhood PCE exposure and 547 unexposed subjects. Participants completed questionnaires to gather information on mental illnesses, demographic and medical characteristics, other sources of solvent exposure, and residences from birth through 1990. PCE exposure originating from the vinyl-liner of water distribution pipes was assessed using water distribution system modeling software that incorporated a leaching and transport algorithm.

RESULTS

No meaningful increases in risk ratios (RR) for depression were observed among subjects with prenatal and early childhood exposure (RR: 1.1, 95% CI: 0.9-1.4). However, subjects with prenatal and early childhood exposure had a 1.8-fold increased risk of bipolar disorder (N = 36 exposed cases, 95% CI: 0.9-1.4), a 1.5-fold increased risk post-traumatic stress disorder (N = 47 exposed cases, 95% CI: 0.9-2.5), and a 2.1-fold increased risk of schizophrenia (N = 3 exposed cases, 95% CI: 0.2-20.0). Further increases in the risk ratio were observed for bipolar disorder (N = 18 exposed cases, RR; 2.7, 95% CI: 1.3-5.6) and post-traumatic stress disorder (N = 18 exposed cases, RR: 1.7, 95% CI: 0.9-3.2) among subjects with the highest exposure levels.

CONCLUSIONS

The results of this study provide evidence against an impact of early life exposure to PCE on the risk of depression. In contrast, the results provide support for an impact of early life exposure on the risk of bipolar disorder and post-traumatic stress disorder. The number of schizophrenia cases was too small to draw reliable conclusions. These findings should be confirmed in investigations of other similarly exposed populations.

Affinity for risky behaviors following prenatal and early childhood exposure to tetrachloroethylene (PCE)-contaminated drinking water: a retrospective cohort study

BACKGROUND

Many studies of adults with acute and chronic solvent exposure have shown adverse effects on cognition, behavior and mood. No prior study has investigated the long-term impact of prenatal and early childhood exposure to the solvent tetrachloroethylene (PCE) on the affinity for risky behaviors, defined as smoking, drinking or drug use as a teen or adult.

OBJECTIVES

This retrospective cohort study examined whether early life exposure to PCE-contaminated drinking water influenced the occurrence of cigarette smoking, alcohol consumption, and drug use among adults from Cape Cod, Massachusetts.

METHODS

Eight hundred and thirty-one subjects with prenatal and early childhood PCE exposure and 547 unexposed subjects were studied. Participants completed questionnaires to gather information on risky behaviors as a teenager and young adult, demographic characteristics, other sources of solvent exposure, and residences from birth through 1990. PCE exposure was estimated using the U.S. EPA's water distribution system modeling software (EPANET) that was modified to incorporate a leaching and transport model to estimate PCE exposures from pipe linings.

RESULTS

Individuals who were highly exposed to PCE-contaminated drinking water during gestation and early childhood experienced 50-60% increases in the risk of using two or more major illicit drugs as a teenager or as an adult (Relative Risk (RR) for teen use = 1.6, 95% CI: 1.2-2.2; and RR for adult use = 1.5, 95% CI: 1.2-1.9). Specific drugs for which increased risks were observed included crack/cocaine, psychedelics/hallucinogens, club/designer drugs, Ritalin without a prescription, and heroin (RRs:1.4-2.1). Thirty to 60% increases in the risk of certain smoking and drinking behaviors were also seen among highly exposed subjects.

CONCLUSIONS

The results of this study suggest that risky behaviors, particularly drug use, are more frequent among adults with high PCE exposure levels during gestation and early childhood. These findings should be confirmed in follow-up investigations of other exposed populations.

Risk of learning and behavioral disorders following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water

This population-based retrospective cohort study examined the association between developmental disorders of learning, attention and behavior and prenatal and early postnatal drinking water exposure to tetrachloroethylene (PCE) on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling software, and a Geographic Information System (GIS). Mothers completed a questionnaire on disorders of attention, learning and behavior in their children and on potential confounding variables. The final cohort consisted of 2086 children. Results of crude and multivariate analyses showed no association between prenatal exposure and receiving tutoring for reading or math, being placed on an Individual Education Plan, or repeating a school grade (adjusted Odds Ratios (OR)=1.0-1.2). There was also no consistent pattern of increased risk for receiving a diagnosis of Attention Deficit Disorder (ADD) or Hyperactive Disorder (HD), special class placement for academic or behavioral problems, or lower educational attainment. Modest associations were observed for the latter outcomes only in the low exposure group (e.g., adjusted ORs for ADD were 1.4 and 1.0 for low and high exposure, respectively). (All ORs are based on an unexposed referent group.) Results for postnatal exposure through age five years were similar to those for prenatal exposure. We conclude that prenatal and early postnatal PCE exposure is not associated with disorders of attention, learning and behavior identified on the basis of questionnaire responses and at the exposure levels experienced by this population.

State-of-the-science review: Does manganese exposure during welding pose a neurological risk?

Recent studies report that exposure to manganese (Mn), an essential component of welding electrodes and some steels, results in neurotoxicity and/or Parkinson's disease (PD) in welders. This "state-of-the-science" review presents a critical analysis of the published studies that were conducted on a variety of Mn-exposed occupational cohorts during the last 100 yr, as well as the regulatory history of Mn and welding fumes. Welders often perform a variety of different tasks with varying degrees of duration and ventilation, and hence, to accurately assess Mn exposures that occurred in occupational settings, some specific information on the historical work patterns of welders is desirable. This review includes a discussion of the types of exposures that occur during the welding process--for which limited information relating airborne Mn levels with specific welding activities exists--and the human health studies evaluating neurological effects in welders and other Mn-exposed cohorts, including miners, millers, and battery workers. Findings and implications of studies specifically conducted to evaluate neurobehavioral effects and the prevalence of PD in welders are also discussed. Existing exposure data indicate that, in general, Mn exposures in welders are less than those associated with the reports of clinical neurotoxicity (e.g., "manganism") in miners and smelter workers. It was also found that although manganism was observed in highly exposed workers, the scant exposure-response data available for welders do not support a conclusion that welding is associated with clinical neurotoxicity. The available data might support the development of reasonable "worst-case" exposure estimates for most welding activities, and suggest that exposure simulation studies would significantly refine such estimates. Our review ends with a discussion of the data gaps and areas for future research.

Self-reported symptoms and their effects on cognitive functioning in workers with past exposure to solvent-based glues: an 18-year follow-up

OBJECTIVES

To examine to what extent exposure to organic solvents during the working life affects general well-being in the long term, and to explore the relationship between self-reported symptoms and cognitive functioning in previously solvent-exposed floor layers.

METHODS

The study included 41 solvent-exposed floor layers and 40 unexposed referents participating in a longitudinal follow-up study 18 years after the baseline assessment. Symptom prevalence and level of spare time activities were studied using the same methods as in the initial study. These include a general health examination, the Q16 symptom questionnaire, and a questionnaire for spare time activities. Relationships between symptoms and cognitive functioning were analysed based on recently published data on cognitive functioning of the participants at follow-up.

RESULTS

At follow-up neuropsychiatric symptoms such as need to check things, depressive mood, and abnormal fatigue, were more prevalent among floor layers, particularly the most exposed individuals, than among referents. In addition, the most highly exposed floor layers reported more concentration difficulties and irritability. Fatigue and depressive mood increased over the follow-up time in the most exposed floor layers but not in the referents. Memory difficulties, although more frequent among floor layers than among referents, had decreased in floor layers while increased in referents. Floor layers also reported some negative effects on intimate relations and activity level. Neuropsychiatric symptoms were related to poorer performance chiefly in memory tasks and tests of complex attention and perceptual speed, more seldom in visuospatial tasks.

CONCLUSIONS

Findings of exposure-related, long-lasting, partly deteriorating neuropsychiatric complaints indicate that general well-being later in life has been affected in floor layers with past heavy solvent exposure. We also found frequent associations between symptom prevalence and the cognitive functioning. Together with previous findings of dose-related cognitive decrements, the present results strengthen the evidence that long-term heavy occupational solvent exposure may negatively interact with the normal ageing process.

Sequelae of fume exposure in confined space welding: a neurological and neuropsychological case series

Welding fume contains manganese (Mn) which is known to be bio-available to and neurotoxic for the central nervous system. Although an essential metal, Mn overexposure may cause manganism, a parkinsonian syndrome. The present welder study sought to improve the clinical portrait of manganism and to determine dose-effect relationships. The welders were employed in the construction of the new Bay Bridge (San Francisco) and welded in confined spaces for up to 2 years with minimal protection and poor ventilation. Neurological, neuropsychological, neurophysiological, and pulmonary examinations were given to 49 welders. Clinical cases were selected on the basis of apriori defined criteria pertaining to welding history and neurological/neuropsychological features. Among the 43 eligible welders, 11 cases of manganism were identified presenting with the following symptoms: sleep disturbance, mood changes, bradykinesia, headaches, sexual dysfunction, olfaction loss, muscular rigidity, tremors, hallucinations, slurred speech, postural instability, monotonous voice, and facial masking. Significant associations between outcome variables and cumulative exposure index (CEI) or blood Mn (MnB) were obtained with CEI for variables implicating attention and concentration, working and immediate memory, cognitive flexibility, and verbal learning; and with MnB for executive function, cognitive flexibility, visuo-spatial construction ability, and visual contrast sensitivity. This study strongly suggests that neuropsychological features contribute in a dose-effect related way to the portrait of manganism usually characterized by tremor, loss in balance, diminished cognitive performance, and signs and symptoms of parkinsonism.

Neuropsychiatric symptoms and past manganese exposure in a ferro-alloy plant

INTRODUCTION

Psychiatric manifestations have been reported in cases of manganism, and mood disorders are often observed in manganese (Mn) exposed workers. We examined neuropsychiatric symptoms among formerly Mn-exposed workers 14 years after cessation of exposure.

MATERIALS AND METHODS

A study was conducted in 1990 among workers from a ferro- and silico-Mn plant and unexposed working men referents from the same region in South-West Quebec. At follow-up in 2004, 77 former Mn-workers and 81 referents agreed to participate and responded to a neuropsychiatric symptom checklist, the Brief Symptom Inventory (BSI); scores were transformed into T-scores based on a normative population. Cumulated exposure indices (CEI) were computed for each former Mn-worker. Linear and logistic regression analyses were used.

RESULTS

Mean T-scores were significantly higher among former Mn-workers than referents on scales of Depression and Anxiety. Mean T-scores of psychological distress increased with the CEI tertiles, with significant associations for the scales Somatization, Depression, Anxiety and Hostility. Former Mn-workers in the two highest tertiles of CEI showed a higher risk for T-scores >or=63 for Hostility (OR, 7.5; 95% CI, 1.5-38.9), Depression (OR, 2.6; 95% CI, 1.1-8.4) and Anxiety (OR, 3.0; 95% CI, 1.1-8.4).

CONCLUSION

These results suggest that past exposure to Mn may have lasting consequences on neuropsychiatric symptoms.

Mental Health in F-111 Maintenance Workers: The Study of Health Outcomes in Aircraft Maintenance Personnel (SHOAMP) General Health and Medical Study

OBJECTIVE

We sought to contrast mood disorder symptoms in F-111 aircraft Deseal/Reseal maintenance personnel with appropriate comparisons.

METHODS

Participants completed a comprehensive health assessment, including measures of mood disorder, self-reported mood symptom questionnaire items, and review of anxiolytic and depression medication. Multiple logistic regression was conducted for each outcome using exposure group and potential confounders as explanatory variables.

RESULTS

There was high agreement between self-reported mood disturbance and objective tests. The exposed group was more likely to self-report previous diagnoses of depression/anxiety, had higher use of antidepressant medications, and had increased risk of diagnosis of depression/anxiety. Results were consistently strong against both comparison groups, with the exposed more likely to have mental distress and social dysfunction when compared with the Australian population.

CONCLUSIONS

There is robust evidence for an association between F-111 Deseal/Reseal exposure and impaired mental health.

Manganese exposure: neuropsychological and neurological symptoms and effects in welders

Manganese exposure reportedly may have an adverse effect on CNS function and mood. Sixty-two welders with clinical histories of exposure to manganese were compared to 46 matched regional controls chosen at random from a telephone directory. The following tests were given: Wechsler Adult Intelligence Scale (WAIS-III), Wechsler Memory Scale (WMS-III), Boston Naming, WRAT-3, Cancellation H, Trail Making Tests A and B, Auditory Consonant Trigrams, Stroop, Rey-Osterreith, Animal Naming, Controlled Oral Word Association (COWAT), Test of Memory Malingering, Rey 15-item, Fingertapping, Grooved Pegboard, Dynamometer, Visual Attention Test, Lanthony d-15 Color Vision, Vistech Contrast Sensitivity, and Schirmer strips. The controls were administered a shorter battery of tests and the Rey-Osterreith, Animal Naming and some of the subtests of the WAIS-III, WMS-III were not administered. Mood tests, given to both groups, included the Symptom Checklist-40, Symptom Checklist-90-R, Profile of Mood Scale, Beck Depression Inventory II, and Beck Anxiety Inventory. Forty-seven welders and 42 controls were retained for statistical analysis after appropriate exclusions. Results showed a high rate of symptom prevalence and pronounced deficits in motor skills, visuomotor tracking speed and information processing, working memory, verbal skills (COWAT), delayed memory, and visuospatial skills. Neurological examinations compared to neuropsychological test results suggest that neuropsychologists obtain significantly more mood symptoms overall. Odds ratios indicate highly elevated risk for neuropsychological and neurological symptomatology of manganism. Mood disturbances including anxiety, depression, confusion, and impaired vision showed very high odds ratios. Neurological exams and neuropsychological tests exhibit complementarity and differences, though neuropsychological methods may be more sensitive in detecting early signs of manganism. The present study corroborates the findings of our previous study in another group of welders.

Neuropsychological sequelae of exposure to welding fumes in a group of occupationally exposed men

This study compares the neuropsychological function, emotional status, visual function, and illness prevalence of 76 former and current chemical industry welders primarily involved in steel welding, and exposed to welding fumes for an average of 24.9 years with that of 42 unexposed, non-welder controls. Health and occupational history questionnaires were administered, as were the neuropsychological tests included in the World Health Organization Neurobehavioral Core Test Battery, Luria Motor Test, and selected tests from the WAIS-III, and WMS-III. Emotional status tests included the BSI, POMS, BAI, and BDI, and vision tests included the Snellen near visual acuity, Lanthony d-15 color vision, Vistech Contrast Sensitivity, and Schirmer strips. While welders and controls performed similarly on tests of verbal skills, verbal retention, and auditory span, welders performed worse than controls on tests of verbal learning, working memory, cognitive flexibility, visuomotor processing speed, and motor efficiency. Welders had poorer color vision and emotional status, and increased prevalence of illnesses and psychiatric symptoms. The increased symptoms in welders were related to decreased scores on tasks measuring verbal learning, visuomotor abilities, visuospatial abilities, and information processing, and motor efficiency. Within the group of welders, the number of hours welding was negatively related to scores on verbal learning, auditory span, working memory, cognitive flexibility, and motor efficiency.

Methodological Problems in the Neuropsychological Assessment of Effects of Exposure to Welding Fumes and Manganese

Recently, Kaiser (2003) raised concerns over the increase in brain damage claims reportedly due to exposure to welding fumes. In the present article, we discuss methodological problems in conducting neuropsychological research on the effects of welding exposure, using a recent paper by Bowler et al. (2003) as an example to illustrate problems common in the neurotoxicity literature. Our analysis highlights difficulties in conducting such quasi-experimental investigations, including subject selection bias, litigation effects on symptom report and neuropsychological test performance, response bias, and scientifically inadequate casual reasoning.

Neuropsychological effects of ethylene dichloride exposure

Production of 1,2-dichloroethane (EDC) has increased and exposure to it has been reported to produce adverse effects in animals and CNS effects in humans. A group of 221 EDC exposed hazardous clean-up workers incurred chronic exposure to EDC without protective equipment. A clinical history and the following tests were administered: the WHO Adult Environmental Neurobehavioral Test Battery (AENTB), Wechsler Adult Intelligence Scale (WAIS-III), Wechsler Memory Scale (WMS-III); WRAT 3 Reading, Cancellation H, Trail Making, Stroop, Rey Osterreith, Animal Naming, COWAT, TOMM, Rey 15, Lanthony d-15 Color Vision, and Vistech Contrast Sensitivity. Mood and symptoms were assessed with the SCL90-R, BDI, BAI and IES. The clinical neuropsychological evaluation of these workers indicates lower neuropsychological functioning in the domains of processing speed; attention; cognitive flexibility; motor coordination and speed; verbal memory; verbal fluency; and visuo-spatial abilities. These workers also showed disturbed mood and impaired vision. Dose/response relationships between exposure to EDC and test scores are shown.

Intermanual transfer in a simple motor task

The present study examines the effects of a four-week training session in a pegboard task on uni- and bimanual performance. Of particular interest was whether practice transfer from the trained to the untrained hand takes place. Twenty-five consistently right-handed subjects were trained to perform the task with the dominant hand, or the subdominant hand, or with both hands. After this training, the learning effects for the trained and untrained hands were analysed. To summarise, we obtained the following findings: (1) After training, movement times were considerably reduced for all hands and for all training conditions (practice effects); (2) practice effects were found for the hand trained and also for the untrained hand; (3) there was not a great difference in the size of the practice effects for the right hand after left hand training or for the left hand after right hand training; (4) task difficulty had no clear influence on the practice effect; (5) and finally, we discovered that bimanual movements not only profit from bimanual training but also from unimanual training and conversely unimanual movements benefit from bimanual training. These findings are discussed in the context of different motor control models and in the light of recent brain imaging findings.