Nose-only exposure model

Nose-only Exposure Model for Controlled Respiratory Uptake in Aninml Studies in Vivo... 

In support of inhalation studies, blood samples are taken after a 4- to 6-hour whole-body or nose-only exposure period. The steady-state plasma concentration and the elimination rate are determined. The steady-state concentrations are plotted versus exposure concentration to make the determination of dose proportionality. A kinetic model is developed and used to predict steady-state concentrations and the time to reach steady state. 

From a methodological perspective, it is particularly challenging to investigate the effects of low-level exposure of long duration in animal models and compromises are inevitable. Nose-only exposures have been used by Benschop et al. (1998) to determine the toxicokinetics of soman stereoisomers in atropinized guinea-pigs and subsequently, related studies have been undertaken in marmosets (van Helden et al., 2005). Hulet et al. (2006) have investigated the effects of exposure concentration and duration on pupil... 

We routinely use nose-only inhalation exposure of B(a)P aerosol to evaluate the consequence of prenatal exposure to this toxicant on physiological and behavioral endpoints. The properties of this B(a)P aerosol are shown in Figure 17.4. The aerosol typically exhibits a trimodal distribution with a 93% cumulative mass less than 5.85 pm, 89% cumulative mass less than 10 pm, 55.3% cumulative mass less than 2.5 pm, and 38% less than 1 pm. Fifty-five percent of the aerosol generally has a cumulative mass less than PM2.5 and the mass median aerodynamic diameter (MMAD) + geometric standard deviation for this mode is consistently 1.7 =E 0.085 pm. For several years we employed a rat model exposing timed pregnant dams to inhalation concentrations of 25, 75, and 100 pg/m. ... 

---