, 2005). Further, signs of inflammatory effects in nasal lavage were not observed, i.e. no increase of polymorphonuclear cells, total protein, IL-6 and IL-8 ( Laumbach et al., 2005). This agrees with the lack

of inflammatory effects in bronchoalveolar lavage in mice exposed repeatedly to reaction products of limonene ( Wolkoff et al., 2012). A similar outcome was obtained by exposure of rats for 3 h to reaction products of 6 ppm limonene and 0.8 ppm ozone, though a marginal decrease in isolated type II cells was observed ( Sunil et al., 2007). However, histopathology showed an up regulation of inflammatory markers (TNF-α, cyclooxygenase-2 and an antioxidant enzyme (superoxide dismutase)) Nutlin-3a concentration in lung macrophages and type II lung cells together with histological changes. In another

study, eye blink frequencies increased significantly in male subjects (n = 8–10), as a physiological measure of trigeminal stimulation, during 20 min exposure to reaction products of limonene in comparison with the reactants and clean air ( Klenø and Wolkoff, 2004 and Nøjgaard et al., 2005). The findings coincided with qualitative reporting of weak eye irritation symptoms. In the present study we have tested the hypothesis that common terpene reaction products cause acute eye and airway effects from indoor climate exposures. We studied the airway effects of five common terpene reaction products by use a mouse bioassay, see Table 3. We previously showed that Obeticholic Acid formaldehyde and a residual high concentration of limonene explained about 75% of the sensory irritation from 16 s old mixture of reaction products from limonene, while moderate effects in the conducting airways remained unexplained in a mouse

bioassay (Wolkoff et al., 2008). The contribution of formaldehyde, however, may be somewhat underestimated in view of the general difficulty obtaining accurate analytical data from dinitrophenylhydrazine sampled aldehydes, Bumetanide cf. (Wisthaler et al., 2008), thus implying that an even greater fraction of formaldehyde might have been responsible for the decrease of the respiratory frequency due to sensory irritation. The critical effect of IPOH was sensory irritation by the TB elongation, which caused the decrease in the respiratory frequency. A 2–4% molar yield corresponding to 0.08–0.15 ppm IPOH was generated in our previous standard experimental set-up of ozone (∼4 ppm) and limonene (44 ppm) using the mouse bioassay to measure the airway effects (Clausen et al., 2001). Thus, IPOH in this experiment would contribute ≤10% to sensory irritation in view of its NOEL of 1.6 ppm. Its human RF value is twice that of the official indoor air guideline for formaldehyde by the World Health Organization (2010). To the best of our knowledge measurements of IPOH in offices have not been reported.