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Changes in Agglomeration of Fullerenes During Ingestion and Excretion in Thamnocephalus Platuyrus
Patra, M., X. Ma, D. BOUCHARD, H. POYNTON, J. M. LAZORCHAK, AND K. R. ROGERS. Changes in Agglomeration of Fullerenes During Ingestion and Excretion in Thamnocephalus Platuyrus. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 30(4):828-8335, (2011).
The National Exposure Research Laboratory′s (NERL) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA′s mission to protect human health and the environment. HEASD′s research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA′s strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
The crustacean Thamnocephalus platyurus was exposed to aqueous suspensions of fullerenes C60 and C70. Aqueous fullerene suspensions were formed by stirring C60 and C70 as received from a commercial vendor in deionized water (termed aqu/C60 and aqu/C70) for approximately 100 d. The Z-average (mean hydrodynamic) diameters of aqu/C60 and aqu/C70 aggregates as measured by dynamic light scattering were 517 ± 21nm and 656 ± 39nm (mean ± 95% confidence limit), respectively. Exposure of T. platyurus to fullerene suspensions resulted in the formation of dark masses in the digestive track visible under a stereomicroscope (x 40 magnification). Fullerene ingestion over 1 h of exposure was quantitatively determined after extraction and analysis by high-performance liquid chromatography mass spectrometry (HPLC-MS). One-hour exposures (at 3mg/L and 6mg/L) resulted in aqu/C60 burdens of 2.7 ± 0.4 µg/mg and 6.8± 1.5µg/mg wet weight, respectively. Thin-section transmission electron microscopy (TEM) images of aqu/C60-exposed T. platyursushowed the formation in the gut of fullerene agglomerates (5–10µm) that were an order of magnitude larger than the suspended fullerene agglomerates. Upon excretion, the observed fullerene agglomerates were in the 10- to 70-µm size range and settled to the bottom of the incubation wells. In contrast to the control polystyrene microspheres, which dispersed after depuration, the aqu/C60 agglomerates (greater than two orders of magnitude larger than the suspended fullerenes) remained agglomerated for up to six months. When exposed to fullerenes, T. platyurus shows the potential to influence agglomerate size and may facilitate movement of these nanoparticles from the water column into sediment.
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