Abstract: Nanoscale lead dioxide (nPbO2(s)) is an attractive nanomaterial with high potential being used in industrial manufactures and electrochemical wastewater treatment processes. It is also a newly identified corrosion product formed inside lead-bearing pipes or lead-containing faucets as a tetravalent solid in the drinking water distribution system when free chlorine is used as the disinfectant. A dramatic increase of lead concentration in drinking water is reported due to a change in disinfectant from free chlorine to chloramine, thus causing lead poisoning for residents especially for children. The nPbO2(s) particles may enter the surface water via direct or indirect pathways. The stability of nPbO2 plays a key role in determining lead pollution in drinking water and receiving water bodies. Lead is a toxic metal and possible human carcinogen that can cause a variety of adverse health effects including neurotoxicity, nephrotoxicity, genotoxicity etc. However, the toxicity of nPbO2, its environmental fate associated with water matrices and impact to human health and wildlife safety remain unknown. The goal of this project is to establish a systematic in vitro/in vivo detection system that can effectively assess casual toxicity of nPbO2 and its associated species. We propose a two-stage study that comprises of high throughput in vitro cell culture system with the human and in vivo biomarker assays using medaka fish (Oryzias latipes) as an alternative animal model to examine the toxic effects of three lead species including nPbO2 (<100 nm), bulky PbO2 (bPbO2, 200 nm) and Pb2+ ion (the positive control). Stage I (including task 1-3) studies focus on development of a bio-analytical approach to understand the causal toxicity of three lead species at environmentally relevant levels. Stage II (including task 4-6) studies aim to understand all fundamental research questions regarding to bioasscessibility/bioaccumulation (the first year aim), nanotoxicity mechanisms (the second year aim) and bioavailability/ecological risk (the third year aim) of nPbO2 and related lead species, based on results obtained from in vitro and in vivo studies. The research scheme for a three-year span is illustrated in Figure 1. Overall, we envision that results from this project will provide scientific and regulatory communities with integrated information about nPbO2 regarding to (1) modes of toxic action; (2) the fate and toxic impact on human health and ecosystems; (3) the use of fish as an alternative model for nanotoxicology. These results identify an appropriate strategy and critical endpoints for evaluating toxic impact or ecological risk of nPbO2 particles on human health and aquatic life. The outcome can not only accelerate the replacement of lead pipes or lead-containing materials from the drinking water system, but also establish a regulatory guideline of preventing lead contamination in drinking water and aquatic ecosystems.
Nanoscale Lead Dioxide (nPbO2)