Titanium oxide nanoparticles in the freshwater ecosystem: <em>Atya lanipes</em> shrimp as a nanotoxicological model

Abstract

This dissertation specializes in studying and determining the environmental concentrations of an emerging pollutant of which we do not fully know, titanium oxide nanoparticles (TiO₂ NPs). Although we are aware of the extensive use and commercial production of this nanoparticle in the US and that there are various sources of contamination and their entry into rivers, we are almost completely unaware of the environmental concentrations that exist in Puerto Rico. There is little knowledge of the toxicological effects that could be associated with ecologically susceptible species. To date, there are no federal or state regulations for acceptable environmental concentrations in our rivers. This study aims to determine the actual status of urban and rural rivers in Puerto Rico related to the presence/absence of TiO₂ NPs and the specific fate and behavior in a laboratory-controlled environment. Also, we want to understand and measure how the presence of these nanoparticles in the freshwater ecosystem results in lethal and sublethal effects due to the toxicity of the TiO₂ NPs, on the life cycle of an endemic shrimp in Puerto Rico, <em>Atya lanipes</em>. The objectives of this dissertation are: 1) Determine the environmental concentrations of titanium oxide nanoparticles and the fate and behavior laboratory assessment, 2) Describe the early larval development description of the freshwater shrimp <em>Atya lanipes</em> Holthuis, 1963 (Decapoda: Caridea: Atyidae), 3) Establish titanium oxide nanoparticles as emerging aquatic pollutants evaluating the nanotoxicity in the freshwater shrimp larvae <em>Atya lanipes</em>, and 4) Determine the neurotoxicity and oxidative stress development in adult <em>Atya lanipes</em> shrimp exposed to titanium oxide nanoparticles. Through field and laboratory studies, we obtained for the first time the concentrations of titanium oxide nanoparticles in sediment and dissolved titanium in water from the Rio Piedras and Sabana rivers. Also, we were able to elucidate the first nine (9) larval stages of the <em>Atya lanipes</em> shrimp. Then, after acute and chronic exposures, we evaluated lethal and sublethal toxic effects in both larval and adult stages of the <em>Atya lanipes</em> shrimp. This study is an innovative one that contributes significantly to our scientific knowledge of the magnitude of the concentration of TiO₂ NP that we are facing. It provides a starting point to begin public policy and better management in the use and discharge of this type of nanomaterial.