Implications of Silver Nanoparticle (Nano Ag) Exposure on Respiratory Physiology

Silver has been one of the most commonly used materials for various applications. As the level of production and use of engineered silver nanoparticles (Nano Ag) increases, the exposure risk to Nano Ag at both occupational and non-occupational settings has become real. Despite the availability of many cellular toxicology studies, few studies have been conducted to understand the physiological impacts on respiratory system. In this study, Nano Ag of various sizes and concentrations (size ranging between 10 and100nm at varying concentrations between 10 and 1000 ppb) was homogenized in representative environmental and physiological conditions by using bovine surfactant (Calfactant) at room temperature. Both control and experimental groups of suspension/solutions were used to measure the contact angles for each sample by using a goniometer. The measured contact angles, then, were used for surface tension as a way of indirect measurement of physiological impacts. The results show that:

1. Nano Ag at 100nm size range (compared to 15nm size) causes more significant change in surface tension in a representative environmental condition without having the effects of surfactants, 
2. The effect of Nano Ag exposure in terms of change in surface tension reduction was more prominent by smaller size Nano Ag (i.e. 15nm in this case) than larger size Nano Ag (i.e., 100nm) in a physiological environment, 
3. Size effect on surface tension at 15 and 100nm is less distinctive in the concentration ranges between 50 and 100ppb of Nano Ag, while smaller Nano Ag (15nm) causes more dramatic increment of surface tension at a higher exposure concentration (1000ppb) than larger size Nano Ag (100nm). 

From the results it is concluded that:

1. human respiratory physiology can be more easily compromised by smaller Nano Ag in a size and concentration dependent manner, and 
2. it might be possible to implement preventive measures in nanomaterial induced toxicity at manufacturing facilities by better understanding the correlation between the size in nano scale and pathophysiological conditions.