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Bioaccumulation and Depuration of Nanoparticules by Marine Bivalves: Potential Foodborne Hazards and Implications for Shellfish Safety


The proposed research will examine an emerging food safety issue by characterizing the uptake and depuration of an emerging pollutant (i.e., manufactured nanoparticles) by several species of commercially important marine bivalves, including: 1) the blue mussel, Mytilus edulis; 2) the eastern oyster, Crassostrea virginica; and 3) the quahog clam, Mercenaria mercenaria. These benthic suspension feeders are among the most important bivalve species on the East and Gulf Coasts of the US, supporting large aquaculture and fisheries industries (USDA 2005). The study will determine the bioaccumulation and depuration of two different types of nanoparticles that are commonly used for industrial applications and in a variety of consumer products, including: titanium dioxide (TiO2) and plastic (polystyrene). Specifically, we will investigate how feeding limitations and the form of delivery (freely suspended or incorporated in marine aggregations) affects nanoparticle bioavailability, ingestion, and thus internal exposure. Informed by these results, we will then expose bivalves to nanoparticles for several weeks and determine net bioaccumulation, and after exposure ceases, quantify the rate of elimination during depuration. To accomplish these goals, we have developed several lines of research to investigate nanoparticles as an emerging food safety issue:• Initiative 1: Determine bioavailability by quantifying the rates at which freely suspended nanoparticles and nanoparticles incorporated within marine aggregates are ingested;• Initiative 2: Quantify the bioaccumulation of nanoparticles during a chronic exposure of several weeks;• Initiative 3: Define the depuration rate and residual concentrations (if any) of nanoparticles over a post-exposure period, and estimate the overall bioaccumulation factors.

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Manufactured nanomaterials are being used in a variety of consumer products including sunscreens, cosmetics, personal-care products, and paints. Nanomaterials are extremely small compounds having at least one dimension less than 100 nanometers. For comparison, one typical hair from a human head or a single sheet of paper has a thickness of approximately 100,000 nanometers. These tiny particles are smaller than the cells of a human body and, in fact, smaller than the nucleus inside of those cells. With an increasing presence in household goods, the demand for and the production of nanomaterials composed of carbon, metal oxides, polystyrene and silica has also increased. For example, to fill product needs the world-wide production of titanium-dioxide nanoparticles is projected to exceed 200,000 tons/year by 2016. As the production of nanomaterials increases, so too does the likelihood of release into the environment as a result of spills, use of products, post-consumer degradation of material, leaching from septic tanks and landfills, or outflow from wastewater treatment facilities. Many questions regarding the environmental safety of nanomaterials have been raised. Toxicological effects of nanoparticles in humans are well studied and include inflammation, oxidative stress and DNA damage. Even particles made of low-toxicity material (e.g., polystyrene) can be harmful when delivered in their nano form, presumably due to their high surface area. Comparatively little research has focused on the effects of nanomaterials on marine ecosystems, or whether this class of emerging pollutants could be transferred through marine food webs to humans. Coastal ecosystems near densely populated, industrialized regions are particularly vulnerable to the infiltration of man-made materials such as nanoparticles. Filter-feeding bivalves, such as clams, mussels and oysters, which are harvested or cultured for human consumption, are particularly susceptible to nanoparticle exposure given their abundance in coastal waters and their particle feeding behavior. Few studies, however, have addressed how these animals encounter nanoparticles in the environment and little is known about the accumulation and elimination of nanoparticles by bivalves. In this project, we will investigate whether nanoparticles could be a foodborne hazard in shellfish. Specifically, we will study: 1) the way in which bivalves encounter and ingest nanoparticles; 2) whether they accumulate nanoparticles during chronic exposure; and 3) if bivalves can eliminate the nanoparticles from their body after exposure ceases, and if so how long does it take. Results will provide realistic estimates of exposure and bioaccumulation of nanoparticles in shellfish, and help elucidate the potential for nanoparticles to be passed to higher trophic levels including humans. Ultimately, new knowledge generated by our research will inform decision makers, and guide strategies for the management of this class of emerging pollutants, and help ensure and improve shellfish safety. Through outreach and dissemination activities, we will educate and deliver science-based knowledge to scientists, shellfish growers, managers, and the general public in order to inform decision making. Such actions will serve to enhance the environmental quality of coastal ecosystems and help protect the living marine resources on which aquaculture and fisheries rely. Protecting fish and shellfish resources is important for both long-range improvement and sustainability of the aquaculture and fisheries industries. Determining the extent to which nanoparticles are an emerging food safety issue is also critical for ensuring the quality and safety of seafood collected by recreational activities. Such activities have been shown to enhance human health and the well-being of society.

Ward, Evan
University of Connecticut
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