Quantitative biokinetics over a 28 day period of freshly generated, pristine, 20 nm silver nanoparticle aerosols in healthy adult rats after a single 11/2-hour inhalation exposure

There is a steadily increasing quantity of silver nanoparticles (AgNP) produced for numerous industrial, medicinal and private purposes, leading to an increased risk of inhalation exposure for both professionals and consumers. Particle inhalation can result in inflammatory and allergic responses, and there are concerns about other negative health effects from either acute or chronic low-dose exposure. To study the fate of inhaled AgNP, healthy adult rats were exposed to 11/2-hour intra-tracheal inhalations of pristine .sup.105Ag-radiolabeled, 20 nm AgNP aerosols (with mean doses across all rats of each exposure group of deposited NP-mass and NP-number being 13.5 [+ or -] 3.6 [mu]g, 7.9 [+ or -] 3.2*10.sup.11, respectively). At five time-points (0.75 h, 4 h, 24 h, 7d, 28d) post-exposure (p.e.), a complete balance of the [.sup.105Ag]AgNP fate and its degradation products were quantified in organs, tissues, carcass, lavage and body fluids, including excretions. The biokinetics of inhaled [.sup.105Ag]AgNP is relatively complex since the dissolving [.sup.105Ag]Ag-ions (a) form salt layers on the [.sup.105Ag]AgNP surface which retard dissolution and (b) the [.sup.105Ag]Ag-ions released from the [.sup.105Ag]AgNP surface form poorly-soluble precipitates of [.sup.105Ag]Ag-salts in ELF. Therefore, hardly any [.sup.105Ag]Ag-ion clearance occurs from the lungs but instead [.sup.105Ag]AgNP and nano-sized precipitated [.sup.105Ag]Ag-salt are cleared via the larynx into GIT and, in addition, via blood, liver, gall bladder into GIT with one common excretional pathway via feces out of the body.