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Christoph van Thriel

Publications and source records attributed to Christoph van Thriel.

12 recordsLinked to original sources
PubMed2006

Human experimental exposure study on the uptake and urinary elimination of N-methyl-2-pyrrolidone (NMP) during simulated workplace conditions.

A human experimental study was carried out with 16 volunteers to examine the elimination of N-methyl-2-pyrrolidone (NMP) after exposure to the solvent under simulated workplace conditions. The NMP concentrations were 10, 40 and 80 mg/m(3) for 2 x 4 h with an exposure-free interval of 30 min. Additionally, a peak exposure scenario (25 mg/m(3) baseline, 160 mg/m(3) peaks for 4 x 15 min, time-weighted average: 72 mg/m(3)) was tested. The influence of physical activity on the uptake and elimination of NMP was studied under otherwise identical exposure conditions but involving moderate workload on a bicycle ergometer (75 W for 6 x 10 min). The peak times and biological half-lives of urinary NMP and its main metabolites 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) in urine were analysed as well as the interrelationships between exposure and biomarkers. All analytes showed a close correlation between their post-shift peak concentrations and airborne NMP. An exposure to the current German workplace limit value of 80 mg/m(3) under resting conditions resulted in urinary peak concentrations of 2,400 microg/L NMP, 117 mg/g creatinine 5-HNMP and 32 mg/g creatinine 2-HMSI (workload conditions: 3,400 microg/L NMP, 150 mg/g creatinine 5-HNMP, 44 mg/g creatinine 2-HMSI). Moderate workload enhanced the total uptake of NMP by approximately one third. Differences between the estimated and the observed total amount of urinary metabolites point to a significant contribution of dermal absorption on the uptake of NMP. This aspect, together with the influence of physical workload, should be considered for the evaluation of a biological limit value for NMP.

Administration, Inhalation↗
PubMed2006

Odor and irritation thresholds for ammonia: a comparison between static and dynamic olfactometry.

Odor and lateralization (irritation) thresholds (LTs) for ammonia vapor were measured using static and dynamic olfactometry. The purpose of the study was to explore the test-retest reliability and comparability of dynamic olfactometry methodology, generally used to determine odor thresholds following European Committee for Standardization guidelines in the context of odor regulations to outside emissions, with static olfactometry. Within a 2-week period, odor and LTs for ammonia were obtained twice for each method for 24 females. No significant differences between methods were found: mean odor detection thresholds (ODTs) were 2.6 parts per million (ppm) for either method (P = 0.96), and mean LTs were 31.7 and 60.9 ppm for the static and dynamic method, respectively (P = 0.07). Test-retest reliability was higher for the dynamic than for the static method (r = 0.61 vs. 0.14 for ODTs and r = 0.86 vs. 0.45 for LTs). The choice of optimal method for any application, however, depends not only on psychometric factors but also on practical factors such as physicochemical properties of the compound, availability of equipment and expertise, task efficiency, and costs.

Ammonia↗
PubMed2006

From neurotoxic to chemosensory effects: new insights on acute solvent neurotoxicity exemplified by acute effects of 2-ethylhexanol.

Historically, acute solvent neurotoxicity was strongly related to reversible narcotic states that could be detected by neurobehavioral tests (e.g., simple reaction time). Nowadays, the occupational exposure to chemicals is markedly reduced and the avoidance of chemosensory effects is more important for the regulation of solvents. Exemplarily, this study examines if the chemosensory perception of 2-ethylhexanol is capable to distract performance in demanding neurobehavioral tasks. In two experiments three time-weighted average concentrations of 2-ethylhexanol (C(TWA): 1.5, 10, and 20 ppm) were investigated. In experiment A (n=24) variable concentrations over time (4h) were used, experiment B (n=22) investigated constant concentrations. The experiments were conducted in a 29 m3 exposure laboratory. Cross-over designs with randomized sequences of exposures were used. Among the 46 male participants 19 subjects reported enhanced chemical sensitivity; the other 27 subjects did not show this personality feature. During the exposure periods neurobehavioral tests were presented twice (beginning; end), the intensity of chemosensory perceptions were rated thrice. The intensity of chemosensory perceptions showed a clear dose-dependency. Subjects' performance in the vigilance test was not affected by the different exposures. Moreover, the results of neurobehavioral tests measuring executive function were neither affected by the C(TWA) concentration nor by the exposure peaks. With increasing C(TWA), a subgroup of the chemically sensitive subjects showed deteriorated accuracy in a divided attention task. Especially the 20 ppm conditions were very annoying. Only during the constant 10 ppm condition the time courses of the annoyance and nasal irritation ratings indicated some adaptation. In general, with the applied neurobehavioral tests distractive effects of acute 2-ethylhexanol exposures up to 20 ppm could not be confirmed. In sensitive groups such distractive effects of irritating solvents might be conceivable and moreover, in cooperation with researchers from cognitive neuroscience more sensitive functions and tests should be developed and incorporated.

Adult↗
PubMed2006

From chemosensory thresholds to whole body exposures-experimental approaches evaluating chemosensory effects of chemicals.

OBJECTIVES: To ensure safety and health the avoidance of adverse chemosensory effects is essential at workplaces where volatile chemicals are used. The present study describes psychophysical approaches that provide information for the evaluation of such effects. METHODS: By means of a modified staircase procedure the odor (OT) and irritation thresholds (IT) of 15 irritants were determined. These basic chemosensory properties, confining the chemosensory effect range, were investigated in a random sample of 144 persons stratified for gender and age. Those irritants exhibiting high chemosensory potency were selected for the second psychophysical part of the study. Forty-eight persons, again stratified for gender and age, rated the intensity of 13 trigeminal and olfactory perceptions elicited by nine ascending concentrations of the irritants, ranging from the odor to the irritation threshold of the respective substances. RESULTS: Across the investigated chemicals the transition from concentrations eliciting pure olfactory stimulation (OT) to trigeminal stimulation (IT) differed markedly. The carboxylic acids yielded narrow ranges from odor to irritation thresholds, while for the amines (cyclohexylamine, dimethylamine, and trimethylamine) and the esters (ethyl formate and ethyl acetate) these ranges were somewhat wider. The two chemosensory thresholds of ethyl acrylate and ammonia were farthest from each other. Gender and age had only weak impact on the chemosensory thresholds. At present, the results of the intensity ratings could be given for six substances. Among them, the rated pungency for cyclohexylamine, formic acid, and ethyl acetate increased strongest across the nine applied concentrations. CONCLUSIONS: By means of these psychophysical approaches a diverse class of chemicals can be described and compared with respect to their chemosensory potency. This information can be used twofold (a) for the evaluation of existing studies reporting sensory irritations and (b) for the design of experimental exposure studies.

Adolescent↗
PubMed2003

Neurobehavioural test results and exposure to inorganic mercury: in search of dose-response relations.

The aim of the analysis was, in general, to find a way to summarise results of studies in search of exposure-response relationships and, in particular, to ask whether an exposure-response relationship can be ascertained for neurobehavioural studies on occupational mercury exposure. Eighteen studies dealing with human mercury exposure and examining 1,106 exposed and 1,105 control subjects were included in the analysis. Effect sizes were calculated for each of the single neuropsychological test results on cognitive and motor performance and were considered in relation to mean current concentrations of exposure. The total of effect sizes demonstrated a correlation to exposure in the range of r=0.50. Additional analyses showed that the influence of mercury on psychological functions was different and that results on motor performance compared with memory and attention revealed the greatest impairment in mercury-exposed workers. Implications for the reversibility of impairments could be discussed because three of the studies examined subjects whose exposure had ceased. Besides the usefulness of the approach, it became obvious that the available 18 studies are a small sample, even when non-dimensional effect-sizes are used; hence, not all psychological domains covered by tests could be analysed.

Attention↗
PubMed2003

Toluene exposure below 50 ppm and cognitive function: a follow-up study with four repeated measurements in rotogravure printing plants.

OBJECTIVE: There are findings of cross-sectional studies on slight cognitive effects due to toluene exposure below 50 ppm. The critical points of the earlier studies will be scrutinised by a follow-up study with four examinations in 5 years. METHODS: Employees from 14 magazine rotary printing plants were classified into groups of "high" (printing area) vs "low" (end-processing) and "short" vs "long" exposure. The sample size of 333 in examination 1 decreased to 216 in examination 4. A repeated-measurement design could be applied for 192 persons. Current exposure was measured by personal air sampling (n=2,521). Data for past exposure (lifetime weighted average exposure, LWAE) were based on job exposure matrices. High-exposure and low-exposure groups were characterised by 26 ppm vs 3 ppm (current exposure) and 45 ppm vs 9 ppm (LWAE). For long-exposure and short-exposure groups 21 vs 6 years were ascertained. Attention (symbol digit substitution, switching attention, simple reaction), memory (digit span forward and backwards, immediate and delayed reproduction of pictures), and psychomotor functions (steadiness, line tracing, aiming, tapping, peg board) were measured as dependent variables. RESULTS: Separate stepwise regressions for examinations 1 to 4, which included the co-variables age, level of education, carbohydrate-deficient transferrin as an alcohol marker, and trait anxiety as personality characteristic, did not exhibit remarkable exposure impacts on the performance variables. Repeated-measures analyses of covariance, which included all examination periods, also did not exhibit significant impacts of LWAE or current exposure on the functions measured. Age and education were the dominant factors for the variability of the data. Additionally, carbohydrate-deficient transferrin and trait anxiety showed sporadic impacts on the test results. CONCLUSION: Evidence for psychological performance effects due to long-term toluene exposure below 50 ppm could not be proved.

Adult↗
PubMed2003

Breathing and heart rate during experimental solvent exposure of young adults with self-reported multiple chemical sensitivity (sMCS).

This paper deals with the assumption that young adults with self-reported multiple chemical sensitivity (sMCS) show a heightened sensitivity of autonomic functions during experimental solvent exposure. Male sMCS-subjects were selected (out of n=274) on the base of a German questionnaire on chemical and environmental sensitivity (CGES). Two independent experiments were carried out, each with 12 sMCS-subjects and 12 age-matched control-subjects. In experiment I two concentrations of the solvents ethyl benzene (10 and 98 ppm) and 2-butanone (10 and 189 ppm) were used. Experiment II investigated 2-propanol (35 and 190 ppm) and 1-octanol (0.1 and 6.4 ppm). The low concentrations correspond nearly to the olfactory thresholds while the high concentrations correspond to the German occupational threshold limit values (MAC). The exposure duration under each condition was 4h. The sequence of the four exposure conditions was random including intervals of at least 2 days without exposure. During the exposure physiological changes of breathing rate and heart rate were recorded. Two 30 min intervals with a sedentary position of the subjects at the beginning and end of exposure were chosen for analyses. Neither in experiment I nor in experiment II significant specific reactions to the type or level of the exposures were found. The autonomic functions in both experiments revealed alterations within the exposure sessions. The heart rate in experiment II and the breathing rate in both experiments decreased significantly during the analyzed 30 min intervals. Furthermore, in both experiments the heart rates decreased significantly from beginning to end of exposure. Only in experiment I the mean breathing rate of sMCS-subjects was generally higher compared to the control-subjects. Regarding the assumption of a heightened sensitivity of sMCS-subjects the two experiments yielded controversial results. Thus, the hypothesis of stronger responses of autonomic functions of sMCS-subjects provoked by various exposure scenarios remains open.

Adult↗
PubMed2003

Neurobehavioral effects during experimental exposure to 1-octanol and isopropanol.

OBJECTIVES: The study examined acute neurobehavioral effects provoked by controlled exposure to 1-octanol and isopropanol among male volunteers. METHODS: In a 29-m3 exposure laboratory, 24 male students (mean age 25.8 years) were exposed to 1-octanol and isopropanol. Each substance was used in two concentrations (0.1 and 6.4 ppm for 1-octanol; 34.9 and 189.9 ppm for isopropanol:). In a crossover design, each subject was exposed for 4 hours to the conditions. Twelve subjects reported enhanced chemical sensitivity; the other 12 were age-matched controls. At the onset and end of the exposures neurobehavioral tests were administered and symptoms were rated. RESULTS: At the end of the high and low isopropanol exposures the tiredness ratings were elevated, but no dose-dependence could be confirmed. For both substances and concentrations, the annoyance ratings increased during the exposure, but only for isopropanol did the increase show a dose-response relation. The subjects reported olfactory symptoms during the exposure to the high isopropanol and both 1-octanol concentrations. Isopropanol provoked no sensory irritation, whereas high 1-octanol exposure slightly enhanced it. Only among the subjects with enhanced chemical sensitivity were both 1-octanol concentrations associated with a stronger increase in annoyance, and lower detection rates were observed in a divided attention task. CONCLUSIONS: Previous studies reporting no neurobehavioral effects for isopropanol (up to 400 ppm) were confirmed. The results obtained for 1-octanol lacked dose-dependency, and their evaluation, is difficult. The annoying odor of 1-octanol may mask sensory irritation and prevent subjects with enhanced chemical sensitivity from concentrating on performance in a demanding task.

2-Propanol↗
PubMed2002

Psychological reactions related to chemosensory irritation.

OBJECTIVES: For risk assessments of solvents the knowledge on chemosensory irritation effects is important, but the methodological base for that is incomplete. The psychological approach measuring chemosensory irritations leans on perceived symptoms and self-reported changes of well being. Characteristics assessing the validity of such psychological approaches are presented. METHODS: The article is based on 14 experimental inhalation studies with (mostly) 4-h exposures to acetone, 2-butanone, ethanol, ethyl acetate, ethyl benzene, iso-propanol, 1-octanol, and styrene. The profiles of exposure include constant and changing concentrations using the range of the German maximum concentrations at the workplace (MAK) list. Irritations (eyes and nose), olfactory symptoms (odour), and annoyance are the dependent variables measured by ratings. Young and healthy subjects ( n=160), - partially, subjects with self-reported odour sensitivity (measured by items from the questionnaire on chemical and general environmental sensitivity) - were investigated. RESULTS: The reliability of ratings is sufficient. Dose-response relationships for perceived odour and annoyance are stronger than those for irritations. A ranked order of the size of effect (related to the values before exposure) for the substances investigated shows correspondence between odour and annoyance; that for irritation differs. Within the limits of the MAK list, perceived irritations are not correlated to annoyance, whereas perceived bad smell correlates significantly to annoyance. Reversibility of the self-reported effects to approximately the pre-exposure level can be shown 1 h after cessation of the experimental exposure for the "normal" subjects. Influences of trait anxiety and chemical sensitivity on reports of annoyance, bad odour or irritation are only weak. CONCLUSION: The psychological approach of repeated measurements for self-reported irritation includes distinctive advantages compared with other methods, the simple and repeated availability during exposure, the sufficient reliability and dose-response relationship, and the comparability between substances by means of effect size. The extension of the concept of "chemosensory irritations" on reports for annoyance and bad smell can be recommended.

Air Pollutants, Occupational↗
PubMed2002

Time courses of sensory irritations due to 2-butanone and ethyl benzene exposure: influences of self-reported multiple chemical sensitivity (sMCS).

The individually different effects of exposure to comparable levels of chemicals might be partly explained by dissimilar response sensitivity towards chemicals. Multiple chemical sensitivity (MCS) might be the clinical endpoint of this altered sensitivity. Concerning a subclinical range of chemical sensitivity, 'challenge studies' with people reporting chemical sensitivity are needed to improve the knowledge about such differences. The chemical and general environmental sensitivity questionnaire (CGES) is a standardized screening tool for the selection of this group. In the present study 24 healthy male volunteers, half of them classified as sMCS-subjects, were experimentally exposed to 2-butanone and ethyl benzene at different levels (TLV-level vs. odor threshold). The strength of self-reported sensory irritations (nasal and ocular) and symptoms of bad smell were assessed, prior, during, and after the 4 hours of exposure. The time courses of sensory irritations were affected by sMCS. Across all exposure periods sMCS-subjects showed increasing symptom scores while control-subjects did not. Symptoms of bad smell were affected by three exposure-related factors (substance, level, duration) without any additional influence from the sMCS factor. Starting from these results it could be concluded that the time-depending influence of reported chemical sensitivity is most prominent for subjective data of sensory irritations.

Adult↗
PubMed2002

Psychophysiological functions of subjects with self-reported multiple chemical sensitivity (sMCS) during experimental solvent exposure.

The study examined the assumption of a higher sensitivity of autonomic functions of subjects with self-reported multiple chemical sensitivity (sMCS) during environmental exposure. The hypothesis was tested in a laboratory study with standardized exposures. Twelve healthy male subjects (26.4 +/- 5.4 y) with and 12 male control subjects (25.7 +/- 3.8 y) without self-reported multiple chemical sensitivity (sMCS), selected by a questionnaire, were included in the experimental study. At four different days the subjects were exposed in a random order to solvents for four hours: 10 ppm or 98 ppm ethyl benzene, 10 ppm or 189 ppm 2-butanone. Heart rate and breathing rate were analysed for two 30-minutes periods of vigilance testing at the beginning and end of exposure. In sMCS-subjects both functions were elevated at the beginning of the testing periods with a tendency to decrease over the 30-minutes periods. Control subjects revealed a relatively constant level (breathing rate) and a small increase (heart rate) during the periods. These group differences were obvious for all experimental conditions across substances and levels of exposures. Furthermore, the mean of the breathing rate of sMCS-subjects was generally higher compared to the control subjects. While the assumption of a generally altered sensitivity of autonomic functions of sMCS-subjects to environmental changes seems to be supported, no specific reactions to the type or level of the chemical exposure were found.

Adult↗