Ultrafine Airborne Particle Deposition and Clearance in an Avian Lung under Ecologically Relevant Conditions.

Air pollutants, such as particulate matter, are known to contribute to disease in humans, but their impact on wildlife remains understudied. A contributing factor to this health impact is the fraction of inhaled particles depositing in the respiratory system. Compared to humans, birds are equipped with a very different respiratory system, which may render them more or less susceptible to air pollution. Although evidence for adverse pollution effects in birds has emerged, little is known about particle dynamics inside the avian lungs. To elucidate this, we exposed zebra finches (Taeniopygia guttata) to ambient-like ultrafine model particles under controlled conditions and quantified deposition in the lungs and, in a smaller subset, also the heart, liver and red blood cells. Birds were exposed to 50 or 100 nm particles at air temperatures of 5 or 25 °C, all of which fall within environmentally relevant exposure conditions. Lung deposition was highest for the smallest particles, in line with the size dependence of particle diffusion rate. While deposited fraction in the lung remained unaffected, deposited dose rate (DR) increased at the lower temperature, indicating that the effect was driven solely by elevated minute ventilation (oxygen consumption). Particle clearance measurements 2 weeks after exposure revealed that 44% of the initially deposited 100 nm particles remained in the avian lungs. We found no evidence that particles translocated to the heart, liver or red blood cells in the analyzed subsets. These findings provide an ecologically relevant foundation for understanding particle exposure dynamics in an avian model and support future work assessing health effects of particulate pollution in birds.