Effect of race on fine particle deposition for oral and nasal breathing.

Nasal efficiency for removing fine particles from inhaled air may be affected by variations in nasal structure associated with race. In 11 African American and 11 Caucasian adults (age 18-31 yr) we measured the fractional deposition (DF) of fine particles (1 and 2 mum mass median aerodynamic diameter) (MMAD) for oral and nasal breathing using individual breathing patterns previously measured by respiratory inductance plethysmography during a graded exercise protocol. DF for both nasal and mouth breathing was measured separately by laser photometry at the same tidal volume and breathing rate for resting and light exercise (20% of maximum work load) conditions. From these DF measures, nasal deposition efficiency (NDE) was calculated for each condition. For light exercise conditions, NDE for both 1- and 2-microm particles was less in African Americans versus Caucasians, 0.15 +/- 0.07 (SD) versus 0.24 +/- 0.11 for 1-microm particles (p = .03), and 0.29 +/- 0.13 versus 0.44 +/- 0.11 for 2-microm particles (p = .006). The racial differences in NDE were associated with racial differences in nasal resistance and nostril shape. These race-dependent nasal efficiencies are dosimetric factors that should be considered in modeling and assessing particulate dose from human exposure to air pollutants.