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

Nanoscale lead (Pb) dioxide particles (nPbO 2 ) 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. nPbO 2 may be dislodged from pipes into drinking water; however, little research has focused on the bioavailability and toxicity of nPbO 2 in 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 [nPbO 2 ] and microscale bulk [bPbO 2 ] Pb dioxide and Pb( ii ) aq (Pb 2+ ) in vivo upon acute to sub-chronic aqueous exposure. Both types of PbO 2 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 nPbO 2 and bPbO 2 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 PbO 2 treatments. The Pb content was greater in the gills, liver and brain with nPbO 2 than bPbO 2 . This in vivo evidence implies the possibility of increased risk of exposure to Pb dissolution from PbO 2 particles in the digestive system via drinking water, which can enhance the bioavailability of Pb uptake and toxicity in humans. Nanoscale lead (Pb) dioxide particles (nPbO 2 ) are a newly identified corrosion product formed inside lead-bearing pipes or lead-containing faucets in drinking water distribution systems.