In vivo evidence of intestinal lead dissolution from lead dioxide (PbO2) nanoparticles and resulting bioaccumulation and toxicity in medaka fish

Abstract

Nanoscale lead (Pb) dioxide particles (nPbO₂) are a newly identified corrosion product formed inside lead-bearing pipes or lead-containing faucets in drinking water distribution systems. These particles can release toxic lead ions, which cause drinking-water contamination and lead poisoning in humans, especially children. nPbO₂ may be dislodged from pipes into drinking water; however, little research has focused on the bioavailability and toxicity of nPbO₂in vivo. In this study, we used adult medaka fish (Oryzias latipes) as an animal model to investigate the uptake, lead dissolution, bioaccumulation and toxic effects of nanoscale [nPbO₂] and microscale bulk [bPbO₂] Pb dioxide and Pb(II)_aq (Pb²⁺) in vivo upon acute to sub-chronic aqueous exposure. Both types of PbO₂ particles were chemically stable in dechlorinated tap water with low water solubility. However, the X-ray absorption near-edge structure (XANES) analysis and analytical quantification of lead speciation showed that both nPbO₂ and bPbO₂ could be reductively dissolved into Pb(II)_aq in both the intestine (major uptake route) and gills of the fish; thereby, enhancing hepatic Pb accumulation. The fish brains exhibited greater Pb accumulation and acetylcholinesterase inhibition with Pb(II)_aq treatment than all the PbO₂ treatments. The Pb content was greater in the gills, liver and brain with nPbO₂ than bPbO₂. This in vivo evidence implies the possibility of increased risk of exposure to Pb dissolution from PbO₂ particles in the digestive system via drinking water, which can enhance the bioavailability of Pb uptake and toxicity in humans.