The high NOELs for DHC indicate that the contribution of sensory irritation and airflow limitation are insignificant in our previous animal set-up with reaction products of limonene (Clausen et al., 2001); similarly, the relatively high RFs suggest that the impact of DHC would be minor or insignificant in offices. The derived RFs for 4-AMCH showed Selleckchem BIBW2992 that airflow limitation was the critical effect. Its concentration in our previous ozone-limonene set-up was 0.1–0.12 ppm (Clausen et al., 2001); thus, its contribution to effects in the conducting airways is considered negligible in this mouse bioassay

experiment. To our knowledge measurements of 4-AMCH in offices have not been reported. The derived RFs for 6-MHO showed that both sensory irritation and airflow limitation may be critical effects. 6-MHO has been measured in office air from 0.8 ppb (Salonen et al., 2009) to 2.3 ppb

in a simulated office (28.5 m3, air exchange rate: 1 h−1) with two subjects and an initial ozone concentration of 33 ppb (Wisthaler and Weschler, 2010), and in an occupied and simulated aircraft cabin exposed to ozone (60–70 ppb; air exchange rate: 4.4–8.8 h−1) to 3–6 ppb (Weschler et al., 2007). For sensory irritation, the hazard index is ≤0.02; thus, indicating that 6-MHO can be ruled out as a significant sensory irritant or bronchoconstrictor at indoor buy Ulixertinib air concentrations. Effects in Carnitine palmitoyltransferase II the conducting airways of mice were reported in previous studies about the ozone-limonene system (Rohr et al., 2002 and Wolkoff et al., 2008). However, the concentration of 4-OPA was less than 0.02 ppb in these studies (unpublished) and thus, would not be expected

to affect the lower airways in view of its NOEL value (Table 3). Downstream 4-OPA concentration of 10 ppb has been measured from used ozone exposed ventilation filters (Destaillats et al., 2011) and concentrations from 2 to 6 ppb have been measured in aircraft cabin and office air (Weschler et al., 2007 and Wisthaler and Weschler, 2010); slightly lower concentrations have been measured in forest environments (Matsunaga et al., 2004). These levels at their maximum still provide a hazard index ≤0.3; thus, indicating that lower airway effects would not be expected. High limonene (and other precursors) concentrations would be prerequisite together with an ozone concentration ≥0.1 ppm, if lung effects should be developed, in agreement with human exposure studies, cf. (Wolkoff et al., 2012). In view of its low RF value, conditions that promote the production of 4-OPA should be considered precautionary. Further precautionary actions would be cleaning, that removes human and animal skin debris, and to avoid crowded spaces with low ventilation. The airflow limitation of 4-OPA could be caused by inflammatory reactions.