Background:
Sensory irritations and odor annoyance are the most prominent acute effects
of occupationally used chemicals. The perception is mediated by the trigeminal
(CN V) and olfactory nerve (CN I). Effects elicited by these chemosensory perceptions
have different significance with regard to health impairment and only a differentiating
consideration allows for an adequate setting of occupational exposure limits
for local irritants. Odor sensations are transient effects that are liable to
adjustment processes (adaptation) and up to certain quantities no consequences
on health can be expected. Irritations however, particularly those indicated
by psychophysical effects, point to patho-physiological processes acting at
the mucous membranes of the upper airway tract and the eyes.
Research questions:
(a) How can - on the level of single substances - the olfactory and trigeminal
potency of local irritants be differentially assessed and described adequately?
(b) How can olfactory and trigeminal effects of local irritants be multidimensionally
assessed by behavioural, perceptual, and physiological outcome measures?
(c) Does chemosensory information processing during acute exposure to irritants
interfere with other cognitive functions and which are the underlying mechanisms?
Recent research:
The project 'chemosensory effects during acute exposures to n-methyl-2-pyrrolidone
(NMP)' was conducted in cooperation with the Hanover Medical School. NMP
is used as a substitute for dichloromethane. Moreover, in this experimental
exposure study the problem of adequate biomonitoring of this chemical was addressed.
During 8 hours exposures simulating a whole work shift the highest permitted
concentration (20 ppm, 82 mg/m³) - even with peak exposures of 160 mg/m³
- did not result in upper airway or eye irritations, neither subjectively nor
physiologically assessed. This was true even during the 15 minutes of peak exposure.
Therefore, the current German MAC value (Maximum Allowable Concentration) appears
to be adequate to protect workers from chemosensory effects.
The joint project 'Delineation and differentiation of irritative and annoying effects of hazardous substances' performed in collaboration with regional research institutes (IPA; bis zum 20.11.09 , IGF) has developed an integrative approach for the evaluation of local irritants. The chemosensory effects for four local irritants (ethyl acetate, cyclohexylamine, acetic and propionic acid) could be evaluated conclusively. For other irritants, basic chemosensory data were obtained that require further investigations of some of the irritants, while for others the occupational exposure limits seem to be adequate to avoid adverse chemosensory effects.