A rare case of Holmes tremor in a worker with occupational carbon monoxide poisoning.

Parkinsonism and encephalopathy are frequently seen in patients who survive carbon monoxide (CO) poisoning. Neurological findings associated with CO poisoning can emerge immediately after cessation of exposure or following a brief period of pseudo-recovery. When present, the tremor associated with CO poisoning is typical of the postural/intention type. Here, we report on a rare case of toxic encephalopathy with a dominant-hand Holmes-type tremor, characterized by resting, as well as postural and kinetic/intentional components, in a previously healthy 53-year-old man exposed to CO while actively engaged in the process of performing a physically demanding skilled labor task. The unique neuropathological and functional changes that give rise to Holmes-type tremor and how this relates to the selective vulnerability of the inhibitory indirect pathway of the basal ganglia to glutamatergic excitotoxicity mediated by tissue hypoxia are discussed.

Posttraumatic Stress Trajectories in World Trade Center Tower Survivors: Hyperarousal and Emotional Numbing Predict Symptom Change.

There is a paucity of knowledge concerning the underlying symptomatology of heterogeneous posttraumatic stress symptom (PTSS) trajectories following mass trauma, such as a terrorist attack. This study examined longitudinal PTSS trajectories using latent growth mixture modeling in 2,355 World Trade Center (WTC) tower survivors surveyed by the WTC Health Registry an average of 2.5, 5.5, and 10.5 years after the September 11, 2001 terrorist attacks. Covariates included sociodemographic characteristics, WTC-related exposure, and other traumas/stressors. Four curvilinear PTSS trajectories were identified: low symptom (74.9%), recovering (8.0%), worsening (6.7%), and chronic (10.4%). The majority of WTC survivors (85.3%) maintained stable symptom trajectories over time, with PTSS changes occurring less often. Although WTC-related exposure was associated with initial PTSS severity, exposure was not associated with chronicity or change of PTSS over time. Male gender and a higher number of post-WTC disaster life-stressors were associated with worsening symptom severity over time. Individuals with more severe hyperarousal symptoms at Wave 1, particularly of anxious arousal, were more likely to have PTSS that worsened over time, adjusted odds ratio (aOR) = 1.55. Less severe emotional numbing symptoms, particularly of dysphoria, at Wave 1, were marginally significantly associated with subsequent PTSS recovery, aOR = 0.75. Interventions that target hyperarousal and emotional numbing symptoms may mitigate a worsening of symptoms and facilitate posttraumatic recovery following future mass traumas, such as terrorist attacks. Further clinical implications are discussed.

Spanish Abstracts by Asociación Chilena de Estrés Traumático (ACET) Trayectorias de estrés postraumático en sobrevivientes de la torre del World Trade Center: Hiperactivación y adormecimiento emocional predicen un cambio en los síntomas TRAYECTORIAS DE TEPT RELACIONADAS CON EL WORLD TRADE CENTER Existe una escasez de conocimientos sobre la sintomatología subyacente de las trayectorias heterogéneas de los síntomas de estrés postraumático (TEPT) después de un trauma masivo, como un ataque terrorista. Este estudio examinó las trayectorias longitudinales de TEPT utilizando modelos de mezcla de crecimiento latente en 2.355 sobrevivientes de las torres del World Trade Center (WTC), encuestados por el Registro de Salud de WTC con un promedio de 2.5, 5.5 y 10.5 años después de los ataques terroristas del 11 de septiembre de 2001. Las covariables incluyeron características sociodemográficas, exposición relacionada con el WTC y otros traumas/factores estresantes. Se identificaron cuatro trayectorias curvilíneas de TEPT: síntomas bajos (74.9%), recuperación (8,0%), empeoramiento (6,7%) y crónico (10,4%). La mayoría de los sobrevivientes del WTC (85.3%) mantuvieron trayectorias de síntomas estables a lo largo del tiempo, con cambios en TEPT que ocurren con menos frecuencia. Aunque la exposición relacionada con el WTC se asoció con la gravedad inicial del TEPT, la exposición no se asoció con la cronicidad o el cambio del TEPT a lo largo del tiempo. El género masculino y un mayor número de factores estresantes de vida después del WTC se asociaron con el empeoramiento de la gravedad de los síntomas con el tiempo. Las personas con síntomas de hiperactivación más severos en la primera evaluación (1), particularmente de agitación ansiosa, tenían más probabilidades de tener TEPT, el cual empeoró a través del tiempo, la razón de probabilidades ajustada (aOR) = 1.55. Los síntomas de adormecimiento emocional menos severos, particularmente de disforia, en la primera evaluación (1), se asociaron marginalmente de manera significativa con la recuperación subsecuente de TEPT, aOR = 0.75. Las intervenciones dirigidas a los síntomas de hipersensibilidad y adormecimiento emocional pueden mitigar el empeoramiento de los síntomas y facilitar la recuperación postraumática después de futuros traumas masivos, como los ataques terroristas. Se discuten las implicaciones clínicas.

Posttraumatic Stress Disorder, Gender, and Risk Factors: World Trade Center Tower Survivors 10 to 11 Years After the September 11, 2001 Attacks.

Ten to eleven years after the September 11, 2001 terrorist attacks, probable posttraumatic stress disorder (PTSD) was evaluated in 1,755 World Trade Center (WTC) evacuees based on data from the WTC Health Registry. Characteristics of men and women were compared and factors associated with PTSD symptom severity were examined using the PTSD Checklist (PCL). Compared with men (n = 1,015, 57.8%), women (n = 740, 42.2%) were younger and of lower socioeconomic status. Ten to eleven years after September 11, 2001, 13.7% of men and 24.1% of women met criteria for PTSD. Results indicated that when considered with all other variables (i.e., demographic, socioeconomic and social resources, exposure to the attacks, life events), gender was not a significant predictor of PTSD symptom severity. Being younger on September 11, 2001, unemployed, less educated, and/or having higher exposure to the attacks, unmet mental health care needs, and less social support predicted higher PCL scores for both genders (ßs = .077 to .239). Demographic characteristics and socioeconomic resources (ΔR2 = .113) accounted for the largest amount of variance in PCL scores over and above exposure/evacuation, mental healthcare needs, and social support variables (ΔR2 = .093 to .102). When trends of unmet mental healthcare needs were analyzed, the most prevalent response for men was that they preferred to manage their own symptoms (15.1%), whereas the most prevalent response for women was that they could not afford to pay for mental health care (14.7%). Although the prevalence of probable PTSD in women tower survivors was approximately twice as high as it was for men, this is attributable largely to demographic and socioeconomic resource factors and not gender alone. Implications for treatment and interventions are discussed.

A PTSD symptoms trajectory mediates between exposure levels and emotional support in police responders to 9/11: a growth curve analysis.

BACKGROUND: Exposure to the terrorist attack on the World Trade Center (WTC) on 9/11/2001 resulted in continuing stress experience manifested as Posttraumatic Stress Disorder (PTSD) Symptoms in a minority of the police responders. The WTC Health Registry has followed up a large number of individuals, including police officers, at three waves of data collection from 2003 to 2011. This analysis examines the relationship between initial exposure levels, long-term PTSD symptoms, and subsequent emotional support among police responders. METHODS: The study population included police responders who had reported their 9/11 exposure levels at Wave 1 (2003/4), provided three waves of data on PTSD symptoms using the 17-item PCL scale, and rated their received emotional support at Wave 3 (N = 2,204, 1,908 men, 296 women, mean age: 38 years at exposure). A second-order growth curve reflected a PTSD symptom trajectory which was embedded in a structural equation model, with exposure level specified as an exogenous predictor, and emotional support specified as an endogenous outcome. RESULTS: Exposure had a main effect on mean symptom levels (intercept) across three waves but it made no difference in changes in symptoms (slope), and no difference in emotional support. The symptom trajectory, on the other hand, had an effect on emotional support. Its intercept and slope were both related to support, indicating that changes in symptoms affected later emotional support. CONCLUSIONS: Initial trauma exposure levels can have a long-term effect on mean symptom levels. Emotional support is lower in police responders when PTSD symptoms persist over seven years, but becomes higher when reduction in symptoms occurs.

Police officers who responded to 9/11: Comorbidity of PTSD, depression, and anxiety 10-11 years later.

BACKGROUND: After the 9/11/2001 World Trade Center (WTC) attack, many police-responders developed PTSD and might be vulnerable to develop depression and/or anxiety. Comorbidity of PTSD, depression, and/or anxiety is examined. METHOD: Police enrollees (N = 1,884) from the WTC Health Registry were categorized into four groups based on comorbidity of PTSD, depression, and anxiety. DSM-IV diagnostic criteria for PTSD were used. Depression (PHQ-8) and anxiety (GAD-7) were assessed with standardized psychometric inventories. Multinomial logistic regression was used to identify putative risk factors associated with comorbidity of PTSD. RESULTS: Of 243 (12.9% of total) police with probable PTSD, 21.8% had probable PTSD without comorbidity, 24.7% had depression, 5.8% had anxiety, and 47.7% had comorbid depression and anxiety. Risk factors for comorbid PTSD, depression, and anxiety include being Hispanic, decrease in income, experiencing physical injury on 9/11, experiencing stressful/traumatic events since 9/11, and being unemployed/retired. CONCLUSION: Nearly half of police with probable PTSD had comorbid depression and anxiety. Am. J. Ind. Med. 59:425-436, 2016. © 2016 Wiley Periodicals, Inc.

Medication use associated with exposure to manganese in two Ohio towns.

This report describes the use of medications as a proxy when medical record reviews are unavailable, to study the health effects of residents environmentally exposed to air-manganese (n = 185) compared to unexposed residents (n = 90). Participants' current medication lists and medication questionnaire responses were collected in clinical interviews and categorized into 13 domains. Exposed participants reported fewer hours of sleep than controls (6.6 vs. 7.0). The exposed used significantly more medications than unexposed participants (82.2 % vs. 67.8 %) and, when adjusting for age, education, and personal income, also for pain (aOR = 2.40) and hypothyroidism (aOR = 7.03). Exposed participants with higher air-Mn concentrations, monitored for 10 years by the U.S. Environmental Protection Agency, were 1.5 times more likely to take pain medications. The exposed participants take significantly more medications than unexposed participants in the categories of hypothyroidism, pain, supplements, and total medications.

Chronic probable PTSD in police responders in the world trade center health registry ten to eleven years after 9/11.

BACKGROUND: Police enrolled in the World Trade Center Health Registry (WTCHR) demonstrated increased probable posttraumatic stress disorder (PTSD) after the terrorist attack of 9/11/2001. METHODS: Police enrollees without pre-9/11 PTSD were studied. Probable PTSD was assessed by Posttraumatic Stress Check List (PCL). Risk factors for chronic, new onset or resolved PTSD were assessed using multinomial logistic regression. RESULTS: Half of police with probable PTSD in 2003-2007 continued to have probable PTSD in 2011-2012. Women had higher prevalence of PTSD than men (15.5% vs. 10.3%, P = 0.008). Risk factors for chronic PTSD included decreased social support, unemployment, 2+ life stressors in last 12 months, 2+ life-threatening events since 9/11, 2+ injuries during the 9/11 attacks, and unmet mental health needs. CONCLUSION: Police responders to the WTC attacks continue to bear a high mental health burden. Improved early access to mental health treatment for police exposed to disasters may be needed.

Characterization of air manganese exposure estimates for residents in two Ohio towns.

This study was conducted to derive receptor-specific outdoor exposure concentrations of total suspended particulate (TSP) and respirable (dae ≤ 10 µm) air manganese (air-Mn) for East Liverpool and Marietta (Ohio) in the absence of facility emissions data, but where long-term air measurements were available. Our "site-surface area emissions method" used U.S. Environmental Protection Agency's (EPA) AERMOD (AMS/EPA Regulatory Model) dispersion model and air measurement data to estimate concentrations for residential receptor sites in the two communities. Modeled concentrations were used to create ratios between receptor points and calibrated using measured data from local air monitoring stations. Estimated outdoor air-Mn concentrations were derived for individual study subjects in both towns. The mean estimated long-term air-Mn exposure levels for total suspended particulate were 0.35 µg/m³ (geometric mean [GM]) and 0.88 µg/m³ (arithmetic mean [AM]) in East Liverpool (range: 0.014-6.32 µg/m³) and 0.17 µg/m³ (GM) and 0.21 µg/m³ (AM) in Marietta (range: 0.03-1.61 µg/m³). Modeled results compared well with averaged ambient air measurements from local air monitoring stations. Exposure to respirable Mn particulate matter (PM10; PM <10 µm) was higher in Marietta residents.

Longitudinal mental health impact among police responders to the 9/11 terrorist attack.

BACKGROUND: Among police responders enrolled in the World Trade Center Health Registry (WTCHR), Post-traumatic Stress Disorder (PTSD) was almost twice as prevalent among women as men 2-3 years after the 9/11 attacks. METHODS: Police participants in the WTCHR Wave 1 survey 2-3 years after 9/11/01, were reassessed for probable PTSD at Wave 2, 5-6 years after 9/11/01, using PCL DSM-IV criteria. RESULTS: Police participants in the Wave 2 survey included 2,527 men, 413 women. The prevalence of "Probable PTSD" was 7.8% at Wave 1 and 16.5% at Wave 2. Mean PCL scores increased from 25.1 to 29.9 for men and 28.6 to 32.2 for women. Prevalence of PTSD was higher for women than for men at Wave 1 (χ(2) = 10.882, P = 0.002), but not Wave 2 (χ(2) = 2.416, P = 0.133). Other risk factors included losing one's job after 9/11 and being disabled. CONCLUSIONS: Prevalence of probable PTSD among police doubled between 2003-2004 and 2006-2007. After the 2-year time span, the gender difference was no longer significant; prevalence of PTSD symptoms increased and there was a substantial amount of co-morbidity with other mental health problems. Further development of prevention and intervention strategies for police responders with symptoms of PTSD is needed. The observed upward trend in PCL scores over time in police officers with PCL scores less than 44, suggests that PTSD prevention and intervention strategies should be applied to all police affected by the 9/11 attacks, not limited just to those with PTSD symptoms.

Gender differences in probable posttraumatic stress disorder among police responders to the 2001 World Trade Center terrorist attack.

BACKGROUND: Police responders to the 2001 World Trade Center (WTC) disaster were previously reported to have an increased prevalence of probable posttraumatic stress disorder (PTSD). METHODS: Four thousand seventeen police responders (3,435 men and 582 women) were interviewed 2-3 years after 9/11/01 as part of the World Trade Center Health Registry. Demographic, occupational, and event-specific risk factors were evaluated for probable PTSD, determined by DSM-IV criteria using the Posttraumatic Stress Checklist (PCL). RESULTS: Overall prevalence of probable PTSD was 8.3% (women: 13.9%; men: 7.4%, P < 0.001). Risk factors for both genders included 9/11-related injury and older age. For men, specific risk factors were: presence in WTC Towers on 9/11 and Hispanic ethnicity; and for women, witnessing horror and education less than a college degree. CONCLUSIONS: Significantly higher prevalence of probable PTSD was found for female police responders. Although consistent with civilian populations, this finding contrasts with other studies of PTSD and WTC rescue and recovery workers, and police prior to 9/11.

PTSD and comorbid depression: Social support and self-efficacy in World Trade Center tower survivors 14-15 years after 9/11.

OBJECTIVE: Following the World Trade Center (WTC) terrorist attack in New York City, prevalence rates of posttraumatic stress disorder (PTSD) and depression remain elevated. Although social support and self-efficacy have been associated with PTSD, little is known about their differential effect on PTSD and depressive comorbidity. METHOD: WTC tower survivors (n = 1,304) were assessed at Wave 1 (2003-2004), Wave 2 (2006-2007), Wave 3 (2011-2012), and Wave 4 (2015-2016). RESULTS: At Wave 4, 13.0% of participants had probable PTSD, a decrease from 16.5% at Wave 1. In addition, 4.1% (54) were identified as having PTSD alone, 6.8% (89) had depression alone, and 8.9% (116) had comorbid PTSD and depression. Of those with PTSD, 68.2% also had comorbid depression. WTC tower survivors with PTSD and comorbid depression reported greater PTSD symptom severity and were more likely to have had greater exposure to the events of 9/11 (adjusted odds ratio [aOR] = 1.14) and lower self-efficacy (aOR = 0.85) than those with depression alone. Less perceived social support predicted only depression and not PTSD, whereas less perceived self-efficacy equally predicted having PTSD or depression (aOR = 0.76). CONCLUSIONS: Findings indicate that self-efficacy may be more important to the severity and chronicity of PTSD symptoms than social support. Multivariate comparisons suggest that PTSD with comorbid depression is a presentation of trauma-dependent psychopathologies, as opposed to depression alone following trauma, which was independent of trauma exposure and may be secondary to the traumatic event and posttraumatic response. Implications for assessment and treatment are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

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.

Dose-effect relationships between manganese exposure and neurological, neuropsychological and pulmonary function in confined space bridge welders.

BACKGROUND: Although adverse neuropsychological and neurological health effects are well known among workers with high manganese (Mn) exposures in mining, ore-processing and ferroalloy production, the risks among welders with lower exposures are less well understood. METHODS: Confined space welding in construction of a new span of the San Francisco-Oakland Bay Bridge without adequate protection was studied using a multidisciplinary method to identify the dose-effect relationship between adverse health effects and Mn in air or whole blood. Bridge welders (n = 43) with little or no personal protection equipment and exposed to a welding fume containing Mn, were administered neurological, neuropsychological, neurophysiological and pulmonary tests. Outcome variables were analysed in relation to whole blood Mn (MnB) and a Cumulative Exposure Index (CEI) based on Mn-air, duration and type of welding. Welders performed a mean of 16.5 months of welding on the bridge, were on average 43.8 years of age and had on average 12.6 years of education. RESULTS: The mean time weighted average of Mn-air ranged from 0.11-0.46 mg/m(3) (55% >0.20 mg/m(3)). MnB >10 microg/l was found in 43% of the workers, but the concentrations of Mn in urine, lead in blood and copper and iron in plasma were normal. Forced expiratory volume at 1s: forced vital capacity ratios (FEV(1)/FVC) were found to be abnormal in 33.3% of the welders after about 1.5 years of welding at the bridge. Mean scores of bradykinesia and Unified Parkinson Disease Rating Scale exceeded 4 and 6, respectively. Computer assisted tremor analysis system hand tremor and body sway tests, and University of Pennsylvania Smell Identification Test showed impairment in 38.5/61.5, 51.4 and 88% of the welders, respectively. Significant inverse dose-effect relationships with CEI and/or MnB were found for IQ (p

Validity of self-reported concentration and memory problems: Relationship with neuropsychological assessment and depression.

BACKGROUND: This study investigated the validity of self-reported concentration and memory problems (CMP) in residents environmentally exposed to manganese (Mn). METHOD: Self-report of CMP from a health questionnaire (HQ) and the Symptom Checklist-90-Revised (SCL-90-R) was compared to neuropsychological assessment (Trails A&B; Digit Span; Digit Symbol; Similarities; Auditory Consonant Trigrams, ACT; NAB Memory; Rey-Osterrieth, Rey-O, Delayed). Participants included 146 residents from Ohio exposed to air-Mn, with a modeled average concentration of 0.55 µg m-3 (range = 0.01-4.58). RESULTS: Residents were primarily White (94.5%), aged 30-64 years (M = 51.24), with a minimum of 10 years of residence (range = 10-64). Ninety-four (65.3%) participants reported concentration problems, and 107 residents (73.3%) reported memory problems. More participants endorsed CMP on the SCL-90-R than on the HQ. The prevalence of self-reported CMP was higher for women than for men (88.4% vs. 68.3%). Point-biserial and Pearson's correlations between self-reported CMP and neuropsychological test scores were nonsignificant and weak for both the HQ (rpb = -.20 to rpb = .04) and the SCL-90-R (r = -.12 to r = .007). Greater levels of depression, anxiety, and female sex predicted having more self-reported CMP on both the HQ and the SCL-90-R. Air-Mn and blood-Mn were not associated with self-reported CMP. Residential distance from the Mn source accounted for a small proportion of variance (sr2 = .04), although depression remained the largest predictor (sr2 = .21). CONCLUSION: These results indicate that self-report of CMP in Mn-exposed residents appear to be invalid when compared to neuropsychological test scores. The participants' misperception of having CMP is associated with less education and higher levels of depression. Neuropsychological assessment is recommended to attain valid results.

Parkinsonism due to manganism in a welder: neurological and neuropsychological sequelae.

A 33-year-old welder with 3 years of exposure to manganese (Mn) bearing welding fumes was seen by neurologists for cognitive and motor complaints. He exhibited signs and symptoms of Parkinson's disease, including tremor, bradykinesia, gait disturbance and cogwheel rigidity. However, he was young and had significant inattention and forgetfulness, had found levodopa unhelpful and moved with a cock-walk gait, all of which suggested manganism. His serum and urine levels of Mn were, in fact, elevated, and his brain MRI had increased T1-weighted signal intensities in the basal ganglia bilaterally (globus pallidus) consistent with Mn deposition. Two years later, he underwent comprehensive neuropsychological testing. Clinical history indicated a mild tremor and emotional dysfunction with irritability, anxiety, and depression with psychotic features. He showed deficits in cognitive flexibility, information processing and speed, and greatly reduced motor speed, which are consistent with a fronto-subcortical process. These findings support a diagnosis of early onset parkinsonism from welding.

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.

Issues in neurological risk assessment for occupational exposures: the Bay Bridge welders.

The goal of occupational risk assessment is often to estimate excess lifetime risk for some disabling or fatal health outcome in relation to a fixed workplace exposure lasting a working lifetime. For sub-chronic or sub-clinical health effects measured as continuous variables, the benchmark dose method can be applied, but poses issues in defining impairment and in specifying acceptable levels of excess risk. Such risks may also exhibit a dose-rate effect and partial reversibility such that effects depend on how the dose is distributed over time. Neurological deficits as measured by a variety of increasingly sensitive neurobehavioral tests represent one such outcome, and the development of a parkinsonian syndrome among welders exposed to manganese fume presents a specific instance. Welders employed in the construction of piers for a new San Francisco-Oakland Bay Bridge in San Francisco were previously evaluated using a broad spectrum of tests. Results for four of those tests (Rey-Osterrieth Complex Figure Test, Working Memory Index, Stroop Color Word Test and Auditory Consonant Trigrams Test) were used in the benchmark dose procedure. Across the four outcomes analyzed, benchmark dose estimates were generally within a factor of 2.0, and decreased as the percentile of normal performance defining impairment increased. Estimated excess prevalence of impairment, defined as performance below the 5th percentile of normal, after 2 years of exposure at the current California standard (0.2 mg/m3, 8 h TWA), ranged 15-32% for the outcomes studied. Because these exposures occurred over a 1-2-year period, generalization to lifetime excess risk requires further consideration of the form of the exposure response and whether short-term responses can be generalized to equivalent 45-year period. These results indicate unacceptable risks at the current OSHA PEL for manganese (5.0 mg/m3, 15 min) and likely at the Cal OSHA PEL as well.

Environmental exposure to manganese in air: Associations with tremor and motor function.

BACKGROUND: Manganese (Mn) inhalation has been associated with neuropsychological and neurological sequelae in exposed workers. Few environmental epidemiologic studies have examined the potentially neurotoxic effects of Mn exposure in ambient air on motor function and hand tremor in adult community residents. Mn exposed residents were recruited in two Ohio towns: Marietta, a town near a ferro-manganese smelter, and East Liverpool, a town adjacent to a facility processing, crushing, screening, and packaging Mn products. METHODS: Chronic (≥ 10 years) exposure to ambient air Mn in adult residents and effects on neuropsychological and neurological outcomes were investigated. Participants from Marietta (n=100) and East Liverpool (n=86) were combined for analyses. AERMOD dispersion modeling of fixed-site outdoor air monitoring data estimated Mn inhalation over a ten year period. Adult Mn-exposed residents' psychomotor ability was assessed using Finger Tapping, Hand Dynamometer, Grooved Pegboard, and the Computerized Adaptive Testing System (CATSYS) Tremor system. Bayesian structural equation modeling was used to assess associations between air-Mn and motor function and tremor. RESULTS: Air-Mn exposure was significantly correlated in bivariate analyses with the tremor test (CATSYS) for intensity, center frequency and harmonic index. The Bayesian path analysis model showed associations of air-Mn with the CATSYS non-dominant center frequency and harmonic index; while the Bayesian structural equation model revealed associations between air-Mn and lower Finger Tapping scores. Household income was significantly associated with motor dysfunction but not with tremor. CONCLUSION: Tremor and motor function were associated with higher exposure to airborne Mn.

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.

Blood metal concentrations of manganese, lead, and cadmium in relation to serum ferritin levels in Ohio residents.

The objectives of this study were to assess ferritin-specific profiles of blood metal concentrations such as manganese, lead, and cadmium and to evaluate whether ferritin may affect the behavior of the blood metals in relation to menstruation, menopause, or sex in Ohio residents. Recruited participants included residents from Marietta, East Liverpool, and Mt. Vernon, OH, USA, who were aged 30-75 years and lived at least 10 years in their respective town. The levels of the neurotoxic metals such as manganese, cadmium, and lead were assayed in whole blood. Serum was analyzed for ferritin level [as a biomarker of iron (Fe) status]. An association between blood metal concentrations and independent variables (age, serum ferritin, manganese exposure status, and sex) by multiple regression analysis was assessed, controlling for various covariates such as BMI, educational level, smoking, and alcohol drinking status. Overall, the geometric means of blood manganese, cadmium, and lead levels of all participants (n = 276) were 9.307 µg/L, 0.393 µg/L, and 1.276 µg/dL, respectively. Log serum ferritin concentrations were inversely associated with log blood manganese concentration (ß = -0.061 log ferritin and ß = 0.146 categorical ferritin) and log blood cadmium concentrations (ß = -0.090 log ferritin and ß = 0.256 categorical ferritin). Log serum ferritin concentrations were not associated with log blood lead concentrations. Variables of age, sex, and exposure status were not associated with log manganese concentrations; however, log blood cadmium concentrations were higher in older population, women, and smokers. Log blood lead concentrations were higher in older population, men, and postmenopausal women. Our study showed that iron deficiency is associated with increased levels of blood manganese and cadmium, but not blood lead, in Ohio residents. These metals showed different toxicokinetics in relation to age, sex, and menopausal status despite similar relationships between ferritin and metal concentrations.