-
[show abstract]
[hide abstract]
ABSTRACT: The presence of pyrethroids in both urban and agricultural sediments at levels lethal to invertebrates has been well documented. However, variations in bioavailability among sediments make accurate predictions of toxicity based on whole sediment concentrations difficult. A proposed solution to this problem is the use of bioavailability-based estimates, such as solid phase microextraction (SPME) fibers and Tenax beads. This study compared three methods to assess the bioavailability and ultimately toxicity of pyrethroid pesticides including field-deployed SPME fibers, laboratory-exposed SPME fibers, and a 24-h Tenax extraction. The objective of the current study was to compare the ability of these methods to quantify the bioavailable fraction of pyrethroids in contaminated field sediments that were toxic to benthic invertebrates. In general, Tenax proved a more sensitive method than SPME fibers and a correlation between Tenax extractable concentrations and mortality was observed.
Environmental pollution (Barking, Essex: 1987) 11/2012; 173C:47-51. · 3.43 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Recent studies have determined that techniques, such as solid phase microextraction (SPME) fibers and Tenax beads, can predict bioaccumulation and potentially could predict toxicity for several compounds and species. Toxicity of bifenthrin was determined using two standard sediment toxicity tests with the benthic species Hyalella azteca and Chironomus dilutus in three reference sediments with different characteristics. The objectives of the current study were to establish bioavailability-based median lethal concentrations (LC50) and median effect concentrations (EC50) of the pyrethroid insecticide bifenthrin, compare their ability to assess toxicity to the use of whole sediment concentrations, as well as to make comparisons of the concentrations derived using each method in order to make assessments of accuracy and extrapolation potential. Four metrics were compared including SPME fiber concentration, pore water concentration derived using SPMEs, 6h Tenax extractable concentration, and 24h Tenax extractable concentration. The variation among the LC50s and EC50s in each sediment derived using bioavailability-based methods was comparable to variation among organic carbon normalized sediment concentrations, but improved over whole sediment concentrations. There was a significant linear relationship between SPME or Tenax and organic carbon normalized sediment concentrations. Additionally, there was a significant relationship between the SPME and Tenax concentrations across sediments. The significant linear relationship between SPME and Tenax concentrations further demonstrates that these bioavailability-based endpoints are interrelated. This study derived bioavailability-based benchmarks that may prove to be more accurate than sediment-based ones in predicting toxicity across sediment types.
Chemosphere 10/2012; · 3.21 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In the companion paper, solid phase microextraction (SPME) fiber concentrations were used as a dose metric to evaluate the toxicity of hydrophobic pesticides, and concentration-response relationships were found for the hydrophobic pesticides tested in the two test species. The present study extends the use of fiber concentrations to organism body residues to specifically address biotransformation and provide the link to toxic response. Test compounds included the organochlorines p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT), p,p'-dichlorodiphenyldichloroethane (p,p'-DDD), and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE); two pyrethroids, permethrin and bifenthrin; and an organophosphate, chlorpyrifos. Toxicity, body residues, and biotransformation of the target compounds were determined for the midge Chironomus dilutus and the amphipod Hyalella azteca. Significant regression relationships were found without regard to chemical, extent of biotransformation, or whether the chemical reached steady state in the organisms. The equilibrium SPME fiber concentrations correlated with the parent compound concentration in the biota; however, the regressions were duration specific. Furthermore, the SPME fiber-based toxicity values yielded species-specific regressions with the parent compound-based toxicity values linking the use of SPME fiber as a dose metric with tissue residues to estimate toxic response.
Environmental Toxicology and Chemistry 07/2012; 31(9):2168-74. · 2.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Use of solid-phase microextraction (SPME) fibers as a dose metric for toxicity testing was evaluated for hydrophobic pesticides to the midge Chironomus dilutus and the amphipod Hyalella azteca. Test compounds included p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT), p,p'-dichlorodiphenyldichloroethane (p,p'-DDD), p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), permethrin, bifenthrin, tefluthrin, and chlorpyrifos. Acute water toxicity tests were determined for 4- and 10-d exposures in both species. Median lethal and sublethal concentrations were expressed both on a water concentration (LC50 and EC50) and on an equilibrium SPME fiber concentration (LC50(fiber) and EC50(fiber)) basis. A significant log dose-response relationship was found between log fiber concentration and organism mortality. It has been shown in the literature that equilibrium SPME fiber concentrations reflect the bioavailable concentrations of hydrophobic contaminants, so these fiber concentrations should be a useful metric for assessing toxic effects from the bioavailable contaminant providing a framework to expand the use of SPME fibers beyond estimation of bioaccumulation.
Environmental Toxicology and Chemistry 07/2012; 31(9):2159-67. · 2.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Recent studies recognize the ability of chemical techniques such as solid phase microextraction (SPME) fibers and Tenax extraction to predict bioavailability more effectively than exhaustive chemical extractions for sediment-associated organic contaminants. While the majority of research using these techniques studied legacy compounds such as PCBs and PAHs, there is great potential for these methods to work well for highly toxic, rapidly biotransformed compounds such as pyrethroid insecticides. The current study compared the ability of the two techniques to predict the bioavailability of permethrin and bifenthrin to two benthic invertebrates (Lumbriculus variegatus and Hexagenia sp.). In addition, variations in the application of the two techniques, specifically duration and conditions of exposure of the SPME fibers and duration of extraction with Tenax, were explored. The SPME fiber concentrations correlated strongly to both 6 and 24 h Tenax concentrations. The SPME fiber concentrations and 6 h and 24 h Tenax extractable concentrations correlated with both the parent permethrin and bifenthrin concentrations in the tissues of both species at steady state. Parent compound tissue concentrations for both species could be predicted with a single relationship for individual pyrethroids. This demonstrated the potential value of these methods to predict the bioavailability of compounds subject to biotransformation and application to multiple species.
Environmental Science & Technology 02/2012; 46(4):2413-9. · 4.80 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The ability of polydimethlysiloxane coated solid phase microextraction (SPME) fibers to predict bioavailability has been documented for a number of species and compounds. There are also a variety of established methods for establishing SPME-based bioavailability estimates; however, factors such as time until equilibrium and exposure regimen could affect fiber concentrations and have not yet been thoroughly tested. Exposure time may influence SPME fiber concentrations at equilibrium. Co-exposure of the fibers with different animals or the invertebrate species used could yield different estimates than those acquired using a shaker table system to achieve equilibrium between the sediment and SPME fibers. The current study examined the effects of time and exposure method (shaker table versus co-exposure with test species) on SPME fiber concentrations for two hydrophobic compounds: permethrin and p,p'-dichlorodiphenyldichloroethylene (DDE). An additional experiment with permethrin determined whether animal densities or fiber number influenced fiber concentrations. There were significant differences between the time required for SPME fibers to reach equilibrium when co-exposed with different species or separately, but fiber concentrations at equilibrium among treatments for both compounds were similar. Furthermore, among the 12 variations in species and fiber densities, there were no significant differences among treatments indicating that neither the route of exposure, animal density, nor fiber volume influenced SPME fiber estimates. This demonstrated that SPME fiber concentrations at equilibrium were not affected by exposure conditions, increasing their versatility in environmental assessments.
Chemosphere 11/2011; 86(5):506-11. · 3.21 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Multiple factors can influence bioavailability, which can make predictions of toxicity in natural systems difficult. The current study examined the potential use of solid-phase microextraction fibers as a matrix-independent approach to predict the toxicity of permethrin to Daphnia magna across various water sources, including a laboratory reconstituted water, two natural waters, and a modified natural water. Water source strongly affected the toxicity of permethrin as well as the concentration-response relationships. Although permethrin concentrations in the water were predictive of toxicity to D. magna for individual water sources, there was no relationship between permethrin concentrations among water sources and mortality. This indicated that compositional differences among water sources can greatly influence toxicity, suggesting that benchmarks established using reconstituted water may be overly conservative for some natural waters. In addition, although permethrin tissue residues were predictive of mortality for individual waters, the correlation among waters was not as clear. Finally, both 48-h and equilibrium-based SPME fiber concentrations adequately predicted toxicity independent of water properties. This demonstrated that bioavailability-based estimates provided a more accurate prediction of toxicity than water concentrations and that SPME fibers could be used in environmental monitoring as a rapid and accurate means of predicting toxicity in natural waters.
Archives of Environmental Contamination and Toxicology 10/2011; 62(3):438-44. · 1.93 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The traditional approach for predicting the risk of hydrophobic organic contaminants (HOCs) in sediment is to relate organic carbon normalized sediment concentrations to body residues or toxic effects to organisms. However, due to the multiple variables controlling bioavailability, this method has limitations. A matrix independent method of predicting bioavailability needs to be used in order to be universally applicable. Both chemical activity (freely dissolved chemical concentrations) measured by solid-phase microextraction (SPME) and bioaccessibility (rapidly desorbing fraction) estimated by Tenax extraction have been developed to predict bioavailability of sediment-associated HOCs. The objectives of this review are to summarize a number of studies using matrix-SPME or Tenax extraction to estimate bioavailability and/or toxicity of different classes of HOCs and evaluate the strengths and weakness of these two techniques. Although the two chemical techniques assess different components of the matrix, estimates obtained from both techniques have been correlated to organism body residues. The advantages of SPME fibers are their applicability for use in situ and their potential usage for a wide array of contaminants by selection of appropriate coatings. Single time-point Tenax extraction, however, is more time- and labor-effective. Tenax extraction also has lower detection limits, making it more applicable for highly toxic contaminants. This review also calls for additional research to evaluate the role of sequestrated contaminants and ingestion of sediment particles by organisms on HOC bioavailability. The use of performance reference compounds to reduce SPME sampling time and linking chemical based bioavailability estimates to toxicological endpoints are essential to expand the applications of these methods.
Journal of Environmental Monitoring 03/2011; 13(4):792-800. · 1.99 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A statewide investigation of insecticide presence and sediment toxicity was conducted in Illinois, USA, from June to August 2008. Twenty sediment samples were collected from urban areas throughout Illinois, and 49 sediment samples were collected from 14 agriculture-dominated counties in central and southern Illinois. Ten-day sediment toxicity tests were conducted using the amphipod Hyalella azteca, and 59% of the urban sites and 2% of the agricultural locations sampled caused significant mortality in the amphipods. The field sediments were analyzed for 29 pesticides, including 19 organochlorines, one organophosphate, and nine pyrethroids. The detection frequencies of organochlorines, chlorpyrifos, and pyrethroids were 95, 65, and 95%, respectively, for urban sites, and 45, 6.1, and 47%, respectively, for agricultural sites. Based on toxic unit analysis, bifenthrin was the main contributor to the detected mortality in urban sediments. The present study provides the first broad assessment of pesticide prevalence in both urban and agriculture areas in Illinois.
Environmental Toxicology and Chemistry 01/2010; 29(1):149-57. · 2.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Nonpolar organic chemicals such as polycyclic aromatic hydrocarbons and chlorobenzenes are expected to act additively when exposed as a mixture. The present study examined the toxicity of fluoranthene (FLU) and pentachlorobenzene (PCBz) individually and in a binary mixture using the whole-body residue as the dose metric. Body residues were based on the toxic equivalent body residue, which included the parent compound plus the organically extractable metabolites for FLU and the parent compound only for PCBz. Using a toxic unit (TU) approach, the binary mixtures of FLU and PCBz following 4- and 10-d water-only exposures acted additively. The lethal residue (LR50) values for mixtures of the compounds for Hyalella azteca were 1.26 (1.19-1.33) TU and 1.27 (1.20-1.34) TU for 4- and 10-d exposures, respectively. For Chironomus dilutus, the 4-d and 10-d values were 0.93 (0.90-0.97) TU and 1.01 (0.96-1.06) TU. Additionally, the total molar sum of PCBz and FLU whole-body residues in a mixture were compared to residues from single compound exposures. For both species tested, the LR50 values based on the total molar sum fell within the range of those determined from the single compound tests; providing additional support for molar additivity for nonpolar narcotic compounds. Assuming that residue-effects data among narcotic compounds (e.g., LR50) are similar, applying the molar sum methodology to narcotic compounds in tissues determined from routine biomonitoring programs and risk specific sampling may be a valuable tool to assess potential effects to biota in the field.
Chemosphere 09/2009; 77(3):399-403. · 3.21 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The current study measured the degradation of fipronil in laboratory-spiked silt loam sediment under anaerobic conditions at different aging times. The half-life of fipronil in anaerobic sediments spiked at 5.8+/-0.049 and 21+/-1.4microg/kg dry weight (dw) was 21+/-0.22 and 15+/-0.11d, respectively. Fipronil-sulfide was the primary degradation product with fipronil-sulfone detected at lower concentrations. No degradation occurred to fipronil-sulfide and fipronil-sulfone over 200d in separate systems. A concurrent decline in sediment concentrations resulted in a decline of fipronil in sediment porewater with an increase in fipronil-sulfide and fipronil-sulfone measured by matrix-solid phase microextraction (matrix-SPME). Equilibrium among sediment, porewater, and matrix-SPME fiber occurred within 138d for fipronil and fipronil-sulfone; however, fipronil-sulfide did not reach equilibrium during the test, and modeling predicted upwards of 1083d to reach equilibrium. Regardless of the time to reach equilibrium, the rapid degradation of fipronil has little ecological significance given that fipronil-sulfide and fipronil-sulfone have equal or greater toxicity, and exhibit greater environmental stability in both the sediment and porewater, thereby becoming bioavailable.
Chemosphere 08/2009; 77(1):22-8. · 3.21 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Toxicity identification evaluation (TIE) methods can be used to identify toxic compounds in environmental samples using a variety of laboratory techniques. Whereas TIEs exist for nonpolar organics, relatively few methods are established for individual contaminant classes. Toxicity identification evaluations have shown pesticides to be the cause of toxicity in agricultural waters and effluents, and more recent studies have shown that the insecticide class of concern is pyrethroids. The primary objectives of the present study were to confirm a temperature TIE model and mechanistically explain these trends. This was achieved by comparing the relative toxicity and influence of temperature (13 vs. 23 degrees C) on Chironomus dilutus exposed to four insecticides, including two pyrethroids, an organophosphate, and an organochlorine, and then explaining these changes using toxicokinetics. A 10 degrees C temperature decrease increased the toxicity of pyrethroids and DDT but decreased the toxicity of chlorpyrifos. The decrease in chlorpyrifos toxicity was driven primarily by the reduction of the formation of more toxic products via decreased biotransformation. The increase in DDT toxicity, in contrast, can be attributed to increased nerve sensitivity at 13 versus 23 degrees C. The pyrethroid toxicity change, however, resulted from a combination of increased accumulation of parent compound and increased nerve sensitivity, exacerbating the toxicity of pyrethroids at 13 degrees C. These trends also held true in sediment exposures with chlorpyrifos and permethrin, indicating that water-only exposures were adequate substitutes for examining this mechanism.
Environmental Toxicology and Chemistry 01/2009; 28(5):1051-8. · 2.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Since the toxicity of pyrethroid insecticides is known to increase at low temperatures, the use of temperature manipulation was explored as a whole-sediment toxicity identification evaluation (TIE) tool to help identify sediment samples in which pyrethroid insecticides are responsible for observed toxicity. The amphipod Hyalella azteca is commonly used for toxicity testing of sediments at a 23 degrees C test temperature. However, a temperature reduction to 18 degrees C doubled the toxicity of pyrethroids, and a further reduction to 13 degrees C tripled their toxicity. A similar response, though less dramatic, was found for 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT), and dissimilar temperature responses were seen for cadmium and the insecticide chlorpyrifos. Tests with field-collected sediments containing pyrethroids and/or chlorpyrifos showed the expected thermal dependency in nearly all instances. The inverse relationship between temperature and toxicity provides a simple approach to help establish when pyrethroids are the principal toxicant in a sediment sample that could be used as a supplemental tool in concert with chemical analysis or other TIE manipulations. The phenomenon appears to be, in part, a consequence of a reduced ability to biotransform the toxic parent compound at cooler temperatures. The strong dependence of pyrethroid toxicity on temperature has important ramifications for predicting their environmental effects, and the standard test temperature of 23 degrees C dramatically underestimates risk to resident fauna during the cooler months.
Environmental Toxicology and Chemistry 09/2008; 28(1):173-80. · 2.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Pyrethroids and fipronil insecticides partition to sediment and organic matter in aquatic systems and may pose a risk to organisms that use these matrices. It has been suggested that bioavailability of sediment-sorbed pesticides is reduced, but data on toxicity of sediment-associated pesticides for pyrethroids and fipronil are limited. In the current study, 10-d sediment exposures were conducted with larval Chironomus tentans for bifenthrin, lambda-cyhalothrin, permethrin, fipronil, fipronil-sulfide, and fipronil-sulfone, the last two being common fipronil metabolites. Sublethal endpoints included immobilization, instantaneous growth rate (IGR), body condition index, and growth estimated by ash-free dry mass (AFDM). Pyrethroid lethal concentrations to 50% of the population (LC50s) were 6.2, 2.8, and 24.5 microg/g of organic carbon (OC) for bifenthrin, lambda-cyhalothrin, and permethrin, respectively; with the former two lower than previously published estimates. Fipronil, fipronil-sulfide, and fipronil-sulfone LC50 values were 0.13, 0.16, and 0.12 microg/g of OC, respectively. Ratios of LC50s to sublethal endpoints (immobilization, IGR, and AFDM) ranged from 0.90 to 9.03. The effects on growth observed in the present study are important because of the unique dipteran life cycle involving pupation and emergence events. Growth inhibition would likely lead to ecological impacts similar to mortality (no emergence and thus not reproductively viable) but at concentrations up to 4.3 times lower than the LC50 for some compounds. In addition, C. tentans was highly sensitive to fipronil and metabolites, suggesting that dipterans may be important for estimating risk and understanding effects of phenylpyrazole-class insecticides on benthic macroinvertebrate communities.
Environmental Toxicology and Chemistry 09/2008; 27(12):2582-90. · 2.81 Impact Factor
