.0 00:00 Toxicity Testing in Sediments Affected By Residues from Former Manufactured Gas Plant Wastes. Cura JJ*, Piccard C, Occhialini J; Woods Hole Group, Falmouth, MA; Smithers Viscient, Wareham, MA; Alpha Labs, Mansfield, MA firstname.lastname@example.org|
Abstract: The residues of discharges from Former Manufactured Gas Plants in sediments are detectable as increased PAH concentrations, visible sheens upon disturbance of sediments, odors in disturbed sediments, and visible tar fragments. These residues may be due to past direct discharges to water bodies, leaching of tars from river banks, or groundwater discharge of tars or associated PAHs. These residues are persistent and often obvious when sediments are disturbed. These studies assess the potential sediment toxicity based on three endpoints (survival, growth, and reproduction) of the freshwater test organism, Hyalella azteca.
The tests were conducted in four very different hydrologic regimes from water bodies in Massachusetts and New Hampshire: a broad, slowly flowing outlet to a large lake; a rapidly flowing medium size urbanized river reach; a small, erosive rural stream; and a high flow major river. The sediment types ranged from fine grained sandy silt to medium sand. The PAH concentrations ranged from the parts per billion level to high parts per million levels. The evidence of MGP impacts in the samples included odors, visible sheens, and fine grained tar fragments. These tests, conducted in different years, and over widely varying hydrologic and sedimentological conditions demonstrate that there is no apparent correlation between toxicity and the presence of any of these MGP residues (PAH concentrations, odors, sheens, tar fragments). In most cases, there were no statistical differences between the presence or, in the case of PAHs, the magnitude of any of these residues and toxic response in Hyallela azteca.
.0 00:00 Assessing the noncancer chemical risk of 1,3-dibromobenzene: Preliminary surrogate approaches and QSAR models employing long-term LOAELs and chemical structures of halogenated benzenes . Collar CJ*, Wang NCY; ORISE / US EPA 404-593-6050|
Abstract: Halogenated benzenes (HBs) are used as solvents, herbicides, antiseptics, and pesticides. Due to high environmental persistence and often associated adverse effects, these compounds are chemicals-of-concern at Superfund waste sites. There is not enough toxicity data for a traditional risk assessment of 1,3-dibromobenzene (1,3-DiBB), a HB chemical-of-concern. Hence, we employed two alternative methods to assess the chemical risk of 1,3-DiBB: (1) a surrogate approach, and (2) a quantitative structure-activity relationship (QSAR) approach. The surrogate approach considered four bromobenzenes (BBs) in relation to supporting data including toxicokinetic and chemical class-specific toxicity data. Deductive reasoning was used to identify a suitable representative compound, and the toxicity value of the identified compound could serve as the surrogate value for 1,3-DiBB. Through our analysis, hepatotoxicity was found to be an endpoint of greatest concern amongst BBs. The specific endpoint permits the subsequent QSAR approach to quantitatively correlate 13 HBs, including the four BBs used in approach (1), and toxicity data, assuming similar mode of action and effect. Peer-reviewed hepatotoxic long-term lowest-observed-adverse-effect levels (LOAELs) of 13 HBs were acquired from public databases (e.g., IRIS), and these were employed for both (1) and (2) to assess the chemical risk of 1,3-DiBB. These two alternative methods to assessing chemical risk led to the following conclusions: (1) based on the trend of increasing toxicity with the number of bromine atoms and observation that ortho- and meta- positions are generally more toxic, the point-of-departure (POD) of 1,2,4-triBB could serve as a surrogate POD for 1,3-diBB and (2) a hepatotoxicity QSAR model (r2 > 0.8 and q2 > 0.7) was developed and used to predict a reasonable liver-specific LOAEL for 1,3-DiBB. The views expressed in this presentation are those of the presenters and do not necessarily reflect US EPA policy.