The high NOELs for DHC indicate that the contribution of sensory

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 However, the concentration of 4-OPA was less than 0.02 ppb in these studies (unpublished) and thus, would not be expected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.

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