No abstract

Respiratory absorption factors (AFs) are important parameters for assessing human health risks of long-term inhalation exposure to low-level hazardous air pollutants. However, it is uncertain whether previously measured respiratory AFs for high-level exposures could be directly applied. Here we measured real-time respiratory AFs using proton transfer reaction time-of-flight mass spectrometry for 50 subjects (20–30 years of age; 24 females and 26 males) exposed in a normal office room with aromatic hydrocarbons (AHs) at concentrations of several parts per billion by volume. The mean respiratory AFs of benzene, toluene, and C8-aromatics (ethylbenzene and xylenes) from all subjects were 28.2, 63.3, and 66.6%, respectively. No gender difference in the respiratory AFs of AHs was observed. Correlation analysis revealed that exposure concentration, rather than physiological parameters like body mass index or body fat ratio, was the dominant factor influencing the AFs of AHs. The results also demonstrated that respiratory AFs decreased in a logarithmic way when exposure levels of AHs were decreased. The decreased respiratory AFs at lowered exposure levels suggest the dual effect of reducing ambient air toxics like AHs with a decrease in human inhalation intake.