Sensory irritation - time extrapolation, intra- and inter-individual differences

Status:

completed 06/2016

Aims:

The current research project continues the scientific work of the previous projects (FP0228A and FP0267 "Measuring irritative and inconvenience causing effects"). Many local irritants include chemical properties (e.g. fat solubility) playing an essential role for operating applications or product quality. Because of rarely available alternatives the group of local irritants is of particular importance.

Activities/Methods:

Four experimental exposure studies were conducted using the work substances ethyl acrylate, ammonia (2x), and propionic acid. 139 subjects participated in these studies with 2 (109 subjects) or 10 (30 subjects) test days respectively. Furthermore in 2 psychophysical studies, (a) the influence of stress on the odor threshold of 2-mercaptoethanol and (b) the breathing depth during exposure to different concentrations of two local irritants (2-ethyl-1-hexanol and ammonia) were investigated. Another 58 subjects participated in these studies. Moreover, 321 individuals were screened regarding self-reported generalized sensitivity for odors (GSO) using an online questionnaire.

Results:

The research module "accumulation" revealed that ethyl acrylate during 5 successive days did not result in an accumulation of adverse effects from day to day. As already shown in FP267, exposure peaks proved to play an important role in eliciting adverse effects. Despite difficulties in recruiting subjects with GSO (only 23 of 321 screened persons match the strict criteria), 14 sensitive subjects were exposed to ammonia in the research module ExpoLab “Sensi" with GSO subjects. Sensitive and control subjects did not differ with regard to physiological and behavioral effects of ammonia exposure. When using a second group of subjects with a potentially increased sensitivity (subjects sensitized to environmental allergens), differences between subjects with seasonal allergic rhinitis and controls in a behavioral task could be demonstrated. Comparing subjects with seasonal allergic rhinitis and controls regarding physiological measures showed altered inflammation processes in seasonal allergic rhinitis subjects that were not modified by the ammonia exposure. The research module "Breathing" failed to show a significant reduction in breathing depth during short exposures with 2-ethyl-1-hexanol and ammonia up to concentrations corresponding to the irritation threshold. Using flow-olfactometry it was shown that stress improved the odor thresholds of subjects (research module DynOlf "Breathing"). The research module ExpoLab "Emotion" investigated the influence of stress in working environments. Physiological data confirmed the stress response, which only had slight effects on behavioral and rating tasks.

The conducted experiments reduced existing knowledge deficits about local effects of irritants and established new areas of research, which are of high importance for setting healthbased occupational exposure limits. Temporal extrapolations remain important as experimental studies with more than 10 exposure days are technically almost infeasible. Those studies should be complemented by epidemiologic data to predict effects of longer exposure periods. Though stress responses could be confirmed, there is a difference between stress in the lab and stress at real work places. Again, other research methods should be used to consider the effects of stress at work places. All things considered, statistically reliable results concerning different work substances could be achieved.

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