Occupational Exposure to Manganese and Fine Motor Skills in Elderly Men: Results from the Heinz Nixdorf Recall Study

Objectives

Exposure to manganese (Mn) may cause movement disorders, but less is known whether the effects persist after the termination of exposure. This study investigated the association between former exposure to Mn and fine motor deficits in elderly men from an industrial area with steel production.

Methods

Data on the occupational history and fine motor tests were obtained from the second follow-up of the prospective Heinz Nixdorf Recall Study (2011-2014). The study population included 1232 men (median age 68 years). Mn in blood (MnB) was determined in archived samples (2000-2003). The association between Mn exposure (working as welder or in other at-risk occupations, cumulative exposure to inhalable Mn, MnB) with various motor functions (errors in line tracing, steadiness, or aiming and tapping hits) was investigated with Poisson and logistic regression, adjusted for iron status and other covariates. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated for substantially impaired dexterity (errors >90th percentile, tapping hits <10th percentile).

Results

The median of cumulative exposure to inhalable Mn was 58 µg m-3 years in 322 men who ever worked in at-risk occupations. Although we observed a partly better motor performance of exposed workers at group level, we found fewer tapping hits in men with cumulative Mn exposure >184.8 µg m-3 years (OR 2.15, 95% CI 1.17-3.94). MnB ≥ 15 µg l-1, serum ferritin ≥ 400 µg l-1, and gamma-glutamyl transferase ≥74 U l-1 were associated with a greater number of errors in line tracing.

Conclusions

We found evidence that exposure to inhalable Mn may carry a risk for dexterity deficits. Whether these deficits can be exclusively attributed to Mn remains to be elucidated, as airborne Mn is strongly correlated with iron in metal fumes, and high ferritin was also associated with errors in line tracing. Furthermore, hand training effects must be taken into account when testing for fine motor skills.

Effects of Manganese Exposure on Olfactory Functions in Teenagers: A Pilot Study

Long-term exposure to environmental manganese (Mn) affects not only attention and neuromotor functions but also olfactory functions of a pre-adolescent local population who have spent their whole life span in contaminated areas. In order to investigate the effect of such exposure at the level of the central nervous system we set up a pilot fMRI experiment pointing at differences of brain activities between a non-exposed population (nine subjects) and an exposed one (three subjects). We also measured the volume of the olfactory bulb as well as the identification of standard olfactory stimuli. Our results suggest that young subjects exposed to Mn exhibit a reduction of BOLD signal, subjective odor sensitivity and olfactory bulb volume. Moreover a region of interest SPM analysis showed a specifically reduced response of the limbic system in relation to Mn exposure, suggesting an alteration of the brain network dealing with emotional responses.

Embryonic stem cell-based screen for small molecules: cluster analysis reveals four response patterns in developing neural cells

Neural differentiation of embryonic stem cells (ESC) is considered a promising model to perform in vitro testing for neuroactive and neurotoxic compounds. We studied the potential of a dual reporter murine ESC line to identify bioactive and/or toxic compounds. This line expressed firefly luciferase under the control of the neural cell-specific tubulin alpha promoter (TUBA1A), and renilla luciferase under the control of the ubiquitous translation elongation factor 1-alpha-1 (EEF1A1) promoter. During neural differentiation, TUBA1A activity increased, while EEF1A1 activity decreased. We first validated our test system using the known neurotoxin methyl mercury. This compound altered expression of both reporter genes, with ESC-derived neural precursors being affected at markedly lower concentrations than undifferentiated ESCs. Analysis of a library of 1040 bioactive compounds picked up 127 compounds with altered EEF1A1 and/or TUBA1A promoter activity, which were classified in 4 clusters. Cluster 1 (low EEF1A1 and TUBA1A) was the largest cluster, containing many cytostatic drugs, as well as known neurodevelopmental toxicants, psychotropic drugs and endocrine disruptors. Cluster 2 (high EEF1A1, stable TUBA1A) was limited to three sulfonamides. Cluster 3 (high EEF1A1 and TUBA1A) was small, but markedly enriched in neuroactive and neurotoxic compounds. Cluster 4 (stable EEF1A1, high TUBA1A) was heterogeneous, containing endocrine disruptors, neurotoxic and cytostatic drugs. The dual reporter gene assay described here might be a useful addition to in vitro drug testing panels. Our two-dimensional testing strategy provides information on complex response patterns, which could not be achieved by a single marker approach.

Neurobehavioral effects of experimental exposures to low levels of styrene

Two experimental studies were conducted with the intention to simulate exposure characteristics of work places with styrene exposure and to investigate the risk for neurobehavioral impairments. In experiment I 16 volunteers (8 in the morning, 8 in the afternoon) were exposed to 0.5 and 20 ppm styrene on a constant level for 3h. In experiment II 24 volunteers (12 in the morning, 12 in the afternoon) were exposed for 4h to 0.5 and 20 ppm styrene on a constant level as well as to a changing exposure between 0.5 and 40 ppm with a TWA of 14 ppm. Simple reaction, choice reaction, attention, acute symptoms, and ratings for well-being were measured. Exposure related performance effects could not be detected. However, 6h time change resulted in delayed choice reactions in the morning hours. Analysing acute symptoms and the state of well-being the impact of styrene did not reach adverse extents of impaired well-being.

Nasal function in self-reported chemically intolerant individuals

Nasal function has not yet been investigated under controlled exposures in individuals with self-reported Multiple Chemical Sensitivity (sMCS). Therefore, anterior rhinomanometry and acoustic rhinometry were applied in 12 individuals with sMCS, and 12 age-matched controls. The sMCS individuals and controls were selected on the basis of a standardized questionnaire. Controlled 4-hr exposures to ethylbenzene and 2-butanone were performed during 4 sessions. Exposures were close to the current German threshold limit values, and they approximated odor thresholds. Subjects with sMCS had a significant decrease in the flow value in anterior rhinomanometry, independent of substance and doses, compared with controls. This result suggests somatic reactions to the exposure. The result must be confirmed in additional studies, and pathophysiological examinations must be performed. For these investigations, anterior rhinomanometry was usable, but acoustic rhinometry can be recommended only after sufficient standardization has occurred. Furthermore, biochemical parameters of nasal mucosa must be considered.