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Data of a follow up study with four examinations were summarized by odds ratio statistics in order to scrutinize the results of the earlier studies with cross sectional approaches. For a "high"- (n=106) and a "low"-exposed group (references, n=86) current toluene exposures of 26ppm versus 3ppm and lifetime weighted average exposures of 45ppm versus 9ppm were ascertained. As measures of sensory functions vibration thresholds, colour discrimination, and auditory thresholds were used. Measures of psychological performances were attention (symbol-digit substitution, switching attention, simple reaction), memory (digit span forward, delayed reproduction of pictures), and psychomotor functions (steadiness, line tracing, aiming, tapping, peg board). Additionally, the frequency of diseases and symptoms were ascertained. By odds ratio statistics including relevant cofactors no significant increase of "cases with impaired functions" among the high-exposed workers was found. Evidence for neurobehavioral effects due to long-term toluene exposure below 50ppm was not established.

Even at low concentrations airborne chemicals can excite olfactory and trigeminal receptors and inform the organism about the presence of airborne chemicals. Acutely, malodors or sensory irritations might trigger symptoms (e.g., bad air quality, eye irritations) and in the long-run functional impairment of chemoreception might occur. In humans, knowledge about short-term adaptational processes and effects of exposure peaks on these systems is limited. Therefore, two different experiments with human volunteers were conducted. In experiment A exposures (4h) with fluctuating concentrations of 2-ethylhexanol (1.5, 10, 20ppm C(TWA)) were investigated, experiment B used similar but constant vapor concentrations. Olfactory- and trigeminal-mediated symptoms and intensities of odor, eye, and nasal irritations were recorded. All measures showed a dose-dependent response and peak exposure effects. In the course of the 4h exposures solely olfactory symptoms decreased. Nasal irritations remained nearly unchanged across the 4h, eye irritations slightly increased. Inter-individual differences related to the personality trait of self-reported chemical sensitivity had only minor effects on chemosensory symptoms in experiment B and no effect on intensity ratings in both experiments. Chemosensory effects seem to be amplified by exposure peaks and less adaptive than assumed.

During inhalational exposure to irritants stimulation of the trigeminal nerve endings in the nasal mucosa or other biochemical mechanisms might initiate inflammatory processes. Increased sensitivity of this physiological system in response to chemical stimulation is postulated in subjects reporting chemical intolerance. In the present study 12 subjects reporting chemical sensitivity and 12 controls were exposed to different concentrations of the industrial solvents ethyl benzene and methyl ethyl ketone (MEK). Concentrations of various inflammatory biomarkers, namely eosinophil cationic protein (ECP), myeloperoxidase (MPO), interleukin 1β (IL-lβ), substance P (SP), and neurokinin A (NKA) were measured in nasal secretion after exposures. Before, during, and after the exposures subjects rated the severity of nasal irritations. The biomarker concentrations and reported irritations were not affected by the exposures. Regardless of substance and concentration sensitive subjects reported more nasal irritations. In conclusion, the investigated substances might possess weaker potency to elicit intranasal irritative effects than postulated.