Titanium dioxide (TiO2) nanoparticles (NPs) are one of the most widely used manufactured nanomaterials in industrial and consumer products, with predicted environmental loads as high as 2,000,000 to 6,000,000 tons in the next 10 years. Toxicologically, engineered TiO2 NPs have been well studied with most work being performed on cell lines, bacteria, and rodents. The reported effects include inflammation, oxidative stress, and DNA damage, but are highly dependent on exposure method, and the concentration and physicochemical characteristics of the NPs. Other research has examined the photocatalytic properties of TiO2 NPs as a way of oxidizing contaminants, disinfecting drinking water, or treating tumors. These studies have reported various phototoxic effects, but typically use irradiances much higher than those found in aquatic settings. A few studies have examined the phototoxicity of TiO2 on freshwater organisms under natural light regimes, but work on near-shore marine communities is largely lacking. We argue that the phototoxicity of TiO2 NPs on shallow-water marine organisms is an overlooked area of research which is critical for a full assessment of the environmental safety of nanotechnology. Based on our extensive experience with a marine biology, metal chemistry and ocean optics, we have developed several lines of research that examine the photocatalytic effects of TiO2 under environmentally-relevant conditions. Our projects fit within the budgetary constraints of the Environmental Health and Safety of Nanotechnology program, and represent an exciting area of research in which students and PIs will work. Specifically, we will investigate: 1) incorporation of nanoscale TiO2 into naturally occurring hetero-aggregations (i.e., marine snow); 2) phototoxicity on important groups of microorganisms that live within the marine-snow complex; 3) trophic transfer efficiency via marine snow to two species of near-shore, benthic filter feeders; 4) subsequent photocatalytic effects on the physiology and cellular processes of these two animals (one translucent, one opaque).
Intellectual Merit : The proposed work represents the first comprehensive study to consider common oceanographic processes (e.g., formation of marine snow) and environmentally-relevant light regimes in assessing 1) photocatalytic impacts of TiO2 NPs on microbial communities and benthic filter feeders that play key roles in marine ecosystems, and 2) trophic transfer and bioavailability to benthic organisms. Determining the potential deleterious effects of NPs on key groups of benthic organisms is not only important for comparative purposes, but also to determine how such materials might produce community level impacts. For example, toxic effects on filter feeders would compromise their capacity for benthic-pelagic coupling and, in turn, greatly impact the surrounding environment. Knowledge generated by our research will be of interest to monitoring agencies concerned with seafood safety, regulators who are developing risk-assessment protocols, scientists who study the distribution of emerging pollutants, and engineers who are designing "green" nanotechnology. As we are at the forefront of such research it is likely that our results will immediately yield important data for marine systems, and contribute to the debate regarding the potential safety of NPs in the environment.
Broader Impacts : As a natural extension of our work we will train undergraduate and graduate students in concepts and techniques that cross the disciplines of biology, chemistry, and optics. Our research program will be used as a vehicle to engage educators and students in discussions about near-shore ecosystem processes, and the benefits and potential hazards of nanotechnology. Offering positive and entertaining learning opportunities for scientific discovery at an early age is crucial to capturing the enthusiasm for learning. Consequently, we will focus on developing and implementing innovative teaching materials that advocate the importance of marine environments to human health. The teaching materials will be designed in collaboration with New England Science & Sailing (NESS), a non-profit marine-science educational organization. In collaboration with NESS we will: 1) Develop lesson plans that demonstrate, in an engaging and understandable way, basic principles that drive coastal ecosystems, and explore the links between emerging pollutants and oceans and human health; 2) Train NESS senior staff to use these lessons to foster ecological literacy and draw students into science and engineering.
