Toxicity of Biosolid Elutriates from Different Wastewater Treatment Processes to Ceriodaphnia Dubia

Proceedings of the 2003 Georgia Water Resources Conference, held April 23-24, 2003, at the University of Georgia.Biosolids from wastewater treatment plants (WWTPs) have a high content of nutrients and organic matter and are used as a land fertilizer constituent. However, biosolids can contain many toxic chemicals, including heavy metals and synthetic organic chemicals. Thus, land application of biosolids may introduce these toxicants to water resources through runoff or soil leachate. The objective of this study was to assess the toxicity of biosolid elutriates from different WWTP processes to Ceriodaphnia dubia. Class B biosolids and composted biosolids (Class A) were collected from six southeastern WWTPs. Elutriate from each biosolid sample was used as the test solution in 48 hour acute toxicity tests. Results indicated that elutriates were highly toxic (LC50 range 11.2%-35.5%) to C. dubia. A decrease in toxicity (completely alleviated) was observed for one elutriate from a composted biosolids sample, but an increase in toxicity was observed in the other. Reductions in dissolved oxygen concentrations in some tests confounded toxicity results. Elevated concentrations of 4-nonylphenol (4-NP) were found in several biosolid samples that had high elutriate toxicity. Additional chemical analyses are being conducted to identify other toxic compounds in elutriates and biosolids. Anticipated benefits include selection of different treatment and disposal methods of biosolids to reduce potential for toxicants to enter surface waters

Integration of Metabolomics and In Vitro Metabolism Assays for Investigating the Stereoselective Transformation of Triadimefon in Rainbow Trout

Triadimefon is a systemic agricultural fungicide of the triazole class whose major metabolite, triadimenol, also a commercial fungicide, provides the majority of the actual fungicidal activity, i.e., inhibition of steroid demethylation. Both chemicals are chiral: triadimefon has one chiral center with two enantiomers while its enzymatic reduction to triadimenol produces a second chiral center and two diastereomers with two enantiomers each. All six stereoisomers of the two fungicides were separated from each other using a chiral BGB-172 column on a GC-MS system so as to follow stereospecificity in metabolism by rainbow trout hepatic microsomes. In these microsomes the S-(+) enantiomer of triadimefon was transformed to triadimenol 27% faster than the R-(-) enantiomer, forming the four triadimenol stereoisomers at rates different from each other. The most fungi-toxic stereoisomer (1S,2R) was produced at the slowest rate; it was detectable after 8 h, but below the level of method quantitation. The triadimenol stereoisomer ratio pattern produced by the trout microsomes was very different from that of the commercial triadimenol standard, in which the most rat-toxic pair of enantiomers (known as ‘‘Diastereomer A’’) is about 85% of the total stereoisomer composition. The trout microsomes produced only about 4% of ‘‘Diastereomer A’’. Complementary metabolomic studies with NMR showed that exposure of the separate triadimefon enantiomers and the racemate to rainbow trout for 48 h resulted in different metabolic profiles in the trout liver extracts, i.e., different endogenous metabolite patterns that indicated differences in effects of the two enantiomers

Bioaccumulation and biotransformation of chiral triazole fungicides in rainbow trout (Oncorhynchus mykiss)

There are very little data on the bioaccumulation and biotransformation of current-use pesticides (CUPs) despite the fact that such data are critical in assessing their fate and potential toxic effects in aquatic organisms. To help address this issue, juvenile rainbow trout (Oncorhynchus mykiss) were exposed to dietary concentrations of a mixture of chiral triazole fungicides (bromuconazole, cyproconazole, metconazole, myclobutanil, penconazole, propiconazole, tebuconazole, tetraconazole, and triadimefon) and a chiral legacy pesticide [α-hexachlorocyclohexane (α-HCH)] to study the bioaccumulation and biotransformation of these CUPs. Fish accumulated all triazoles rapidly during the 8 day uptake phase, and was followed by rapid elimination, which was estimated by taking accelerated sampling times during the 16 day depuration period. Half-lives (t1/2s) and times to 95% elimination (t95s) ranged from 1.0 to 2.5 and 4.5 to 11.0 days, respectively. Chiral analysis suggested no significant selectivity in biotransformation for most of the compounds based on statistically unaltered enantiomer fractions (EFs) in the fish compared to food values; exceptions were a change in EF of myclobutanil and changes in diastereomer fractions (DFs) of propiconazole and cyproconazole. No biotransformation was observed for α-HCH based on consistent EFs in the fish throughout the experiment and a t1/2 (15.8 days) that fell within the 95% confidence interval of a log Kow-log t1/2 relationship developed for assessing biotransformation of organic contaminants. This relationship did show that biotransformation accounted for the majority (ranging from 59.9 to 90.4%) of the elimination for all triazoles, and that triazole compounds with oxygen and hydroxyl functional groups were more easily biotransformed. This research indicated that chiral analysis may potentially miss biotransformation of CUPs and other potential non-persistent organic contaminants and shows the utility of the log Kow-log t1/2 relationship as a mechanistic tool for quantifying biotransformation. Based on the rapid biotransformation of the triazoles, future research should focus on formation of metabolites and their fate and possible effects in the environment. © 2006 Elsevier B.V. All rights reserved

Bioaccumulation, biotransformation, and metabolite formation of fipronil and chiral legacy pesticides in rainbow trout

To assess the fate of current-use pesticides, it is important to understand their bioaccumulation and biotransformation by aquatic biota. We examined the dietary accumulation and enantioselective biotransformation of the chiral current-use pesticide fipronil, along with a mixture of selected chiral [α-hexachlorocyclohexane(α-HCH), heptachlor epoxide (HEPX), polychlorinated biphenyls (PCBs) 84,132,174, o,p′-DDT, and o,p′-DDD] and nonchiral (p,p′-DDT, p,p′-DDD) organochlorine compounds in juvenile rainbow trout (Oncorhynchus mykiss). Fish rapidly accumulated all compounds, as measured in the carcass (whole body minus liver and GI tract) during the 32 d uptake phase, which was followed by varying elimination rates of the chemicals (half-lives (t1/2s) ranging from 0.6 d for fipronil to 77.0 d for PCB 174) during the 96 d depuration period. No biotransformation was observed for α-HCH, HEPX, PCB 174, o,p′-DDT, or o,p′-DDD based on consistent enantiomeric fractions (EFs) in the fish and their t 1/2s falling on a log Kow - log t1/2 relationship established for recalcitrant contaminants in fish. p,p′-DDT and PCBs 84 and 132 were biotransformed based on the former\u27s t1/2 position below the log Kow - log t1/2 relationship, and the PCBs change in EF. Fipronil was rapidly biotransformed, based on a change in EF, a t1/2s that fell below the log Kow - log t 1/2 relationship, which accounted for 88% of its elimination, and the rapid formation of fipronil sulfone, a known metabolite. Fipronil sulfone was found to persist longer (t1/2 ∼ 2 d) than its parent compound fipronil (t1/2 ∼ 0.6 d) and needs to be considered in fate studies of fipronil. This research demonstrates the utilities of the log K ow - log t1/2 relationship as a mechanistic tool for quantifying biotransformation and of chiral analysis to measure biotransformation in fish. © 2006 American Chemical Society

Acute enantioselective toxicity of fipronil and its desulfinyl photoproduct to Ceriodaphnia dubia

Fipronil is a phenylpyrazole insecticide increasingly used in applications such as rice culture, turf grass management, and residential pest control, with a high probability to contaminate aquatic environments. As a chiral pesticide, fipronil is released to the environment as a racemic mixture (equal amounts of optical isomers called enantiomers). Enantiomers can have different toxicological and biological activity; however, information on these differences, which is necessary for accurate risk assessment of chiral pesticides, is limited. Here we examine the acute toxicity of fipronil enantiomers, the racemate, and its photoproduct (desulfinyl fipronil) to Ceriodaphnia dubia. The 48-h median lethal concentration (LC50) values based on measured concentrations of each compound indicate the (+) enantiomer (LC50 = 10.3 ± 1.1 μg/L, mean ± standard error [SE]) was significantly more toxic to C. dubia than either the (-) enantiomer (LC50 = 31.9 ± 2.2 μg/L) or racemate (LC50 = 17.7 ± 1.3 μg/L). To account for any potential loss of fipronil through photolysis, tests were performed under light (fluorescent) and dark exposure conditions, and no significant differences in toxicity were observed. Desulfinyl fipronil, the major photodegradation product, which is not chiral, was detected at \u3c1% of each parent compound in test solutions after 48 h. Separate toxicity tests with desulfinyl fipronil found a \u3e20-fold higher LC50 (355 ± 9.3 μg/L) compared to the fipronil racemate, suggesting lower adverse effects to C. dubia as a result of fipronil photolysis. The present results suggest selection of the (-) enantiomer in fipronil production for lower impacts to C. dubia; however, the consistency and relevancy of fipronil\u27s enantiomer-specific activity at both acute and chronic levels of concern to additional target and nontarget species needs further consideration. © 2005 SETAC

Concentrations and patterns of perfluoroalkyl acids in Georgia, USA surface waters near and distant to a major use source

Perfluoroalkyl acids (PFAAs) are widespread contaminants emanating from, among other sources, the production/degradation of fluorinated chemicals used in surface repellant applications, such as carpet manufacturing. The goal of the present study was to assess the concentrations of PFAAs, including perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUA), and perfluorooctane sulfonamide (PFOSA), in surface waters both near a wastewater land application system (LAS) in Dalton (GA, USA), home to North America\u27s largest carpet manufacturing site, and distant to this location (Altamaha River, GA, USA) to understand the fate of PFAAs in freshwater. Levels of PFAAs were high in the Conasauga River (GA, USA) downstream of the LAS (PFOA, 253-1,150 ng/L; PFOS, 192-318 ng/L; PFNA, 202-369 ng/L; PFDA, 30.1-113 ng/L; PFUA, 58.0-99.2 ng/L; PFOSA, 162-283 ng/L) and in streams and ponds in Dalton (PFOA, 49.9-299 ng/L; PFOS, 15.8-120 ng/L), and were among the highest measured at a nonspill or directrelease location. Perfluoroalkyl acids in the Altamaha River were much lower (PFOA, 3.0-3.1 ng/L; PFOS, 2.6-2.7 ng/L), but were a source of PFAAs to Georgia\u27s estuaries. A preliminary hazard assessment indicated that concentrations of PFOS at two sites in the Conasauga River exceeded the threshold effect predicted for birds consuming aquatic organisms that are exposed continuously to the PFOS levels at these sites. Assuming that toxicity for all PFAAs quantified is equal to that of PFOS, the sum total PFAAs at two sites within the Conasauga River exceeded PFOS thresholds for aquatic and avian species, warranting additional research. © 2008 SETAC Printed in the USA

Integration of metabolomics and in vitro metabolism assays for investigating the stereoselective transformation of triadimefon in rainbow trout

Triadimefon is a systemic agricultural fungicide of the triazole class whose major metabolite, triadimenol, also a commercial fungicide, provides the majority of the actual fungicidal activity, i.e., inhibition of steroid demethylation. Both chemicals are chiral: triadimefon has one chiral center with two enantiomers while its enzymatic reduction to triadimenol produces a second chiral center and two diastereomers with two enantiomers each. All six stereoisomers of the two fungicides were separated from each other using a chiral BGB-172 column on a GC-MS system so as to follow stereospecificity in metabolism by rainbow trout hepatic microsomes. In these microsomes the S-(+) enantiomer of triadimefon was transformed to triadimenol 27% faster than the R-(-) enantiomer, forming the four triadimenol stereoisomers at rates different from each other. The most fungi-toxic stereoisomer (1S,2R) was produced at the slowest rate; it was detectable after 8 h, but below the level of method quantitation. The triadimenol stereoisomer ratio pattern produced by the trout microsomes was very different from that of the commercial triadimenol standard, in which the most rat-toxic pair of enantiomers (known as Diastereomer A ) is about 85% of the total stereoisomer composition. The trout microsomes produced only about 4% of Diastereomer A . Complementary metabolomic studies with NMR showed that exposure of the separate triadimefon enantiomers and the racemate to rainbow trout for 48 h resulted in different metabolic profiles in the trout liver extracts, i.e., different endogenous metabolite patterns that indicated differences in effects of the two enantiomers. © 2009 Wiley-Liss, Inc