TOXICOKINETICS OF SEDIMENT-SORBED BENZO[a]PYRENE AND HEXACHLOROBIPHENYL USING THE FRESHWATER INVERTEBRATES HYALELLA AZTECA, CHIRONOMUS TENTANS, AND LUMBRICULUS VARIEGATUS

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156

101

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.

Section: Statisticsmentioning

confidence: 99%

Temperature as a toxicity identification evaluation tool for pyrethroid insecticides: Toxicokinetic confirmation

Harwood¹,

You²,

Lydy³

2009

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156

101

“…The k u , k ep , k em , and k m values from the two temperature tests were compared using an asymptotic test based on point estimates and standard errors of these quantities [25]. The k u , k ep , k em , and k m values from the two temperature tests were compared using an asymptotic test based on point estimates and standard errors of these quantities [25].…”

Section: Toxicokinetic Studiesmentioning

confidence: 99%

Whole sediment toxicity identification evaluation tools for pyrethroid insecticides: III. Temperature manipulation

Weston

You

Harwood

et al. 2009

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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.

“…It is well known that chemical bioavailability, or the fraction of the total chemical in the system that is available for uptake, complicates this use of external media concentrations as a surrogate of the dose and muddles interpretation of the analytical results [5,6]. It is well known that chemical bioavailability, or the fraction of the total chemical in the system that is available for uptake, complicates this use of external media concentrations as a surrogate of the dose and muddles interpretation of the analytical results [5,6].…”

Section: Introductionmentioning

confidence: 99%

Response spectrum of fluoranthene and pentachlorobenzene for the fathead minnow (Pimephales promelas)

Schuler

Landrum

Lydy

2007

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Internal body residue has been recognized as a potential dose metric for toxicological assessments. This relationship between body residue and biological effects, including both lethal and sublethal effects, is critically important for determining environmental quality in risk assessments. The present study identified the toxic equivalent body residues for fluoranthene (FLU) and pentachlorobenzene (PCBz) associated with mortality, reduced growth, and decreased hatchability in the fathead minnow. The toxic equivalent body residue was defined as the total of the parent compound and the organically extractable metabolites for FLU and of the parent compound only for PCBz, because no biotransformation was measurable. The lethal body residues corresponding to 50% mortality were 0.80 and 1.26 micromol/g wet weight for FLU and PCBz, respectively. As expected, residues associated with sublethal effects generally are 2- to 40-fold lower than the lethal residues for FLU and PCBz. Juvenile fish growth was the most sensitive endpoint examined for both compounds. The maximum allowable toxicant residues were 0.02 and 0.43 micromol/g wet weight for FLU and PCBz, respectively. The information collected from the present study will permit a greater understanding of residue-response relationships, which will be useful in risk assessments.