Joint toxicity of fluoranthene and pentachlorobenzene to Hyalella azteca and Chironomus dilutus

Louisiana Tech University, Ruston, LA 71272, USA.
Chemosphere (Impact Factor: 3.34). 09/2009; 77(3):399-403. DOI: 10.1016/j.chemosphere.2009.07.001
Source: PubMed


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.

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    • "We recognize that there are myriad studies that could have been selected as case studies, but we have limited the number of studies so that specific, key issues such as establishing doseresponse and causality are emphasized. Case study one: Binary mixture Two freshwater arthropods, Hyalella azteca and Chironomus dilutus (previously named C. tentans), were exposed to mixtures of fluoranthene and pentachlorobenzene in aqueous exposures without changing or measuring the water concentrations (Schuler et al. 2009). The 2 chemicals have similar log octanol–water partition coefficients (K OW , 5.18–5.20) "
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    ABSTRACT: Experimental designs for evaluating complex mixture toxicity in aquatic environments can be highly variable and, if not appropriate, can produce and have produced data that are difficult or impossible to interpret accurately. We build on and synthesize recent critical reviews of mixture toxicity using lessons learned from 4 case studies, ranging from binary to more complex mixtures of primarily polycyclic aromatic hydrocarbons and petroleum hydrocarbons, to provide guidance for evaluating the aquatic toxicity of complex mixtures of organic chemicals. Two fundamental requirements include establishing a dose-response relationship and determining the causative agent (or agents) of any observed toxicity. Meeting these 2 requirements involves ensuring appropriate exposure conditions and measurement endpoints, considering modifying factors (e.g., test conditions, test organism life stages and feeding behavior, chemical transformations, mixture dilutions, sorbing phases), and correctly interpreting dose-response relationships. Specific recommendations are provided.
    Integrated Environmental Assessment and Management 04/2012; 8(2):217-30. DOI:10.1002/ieam.277 · 1.38 Impact Factor
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    • "Because of the almost infinite number of mixture-combinations, and the many different targeted organisms, every individual case cannot be investigated. It is therefore crucial to have models that can predict mixture effects, which can be based on toxic units or critical body residues (Di Toro and McGrath, 2000; Verbruggen et al., 2008; Schuler et at., 2009). It has been suggested that chemical activity could be used in the assessment of chemicals that elicit their toxicity by interfering with membrane fluidity, a term called baseline toxicity (Ferguson, 1939; Reichenberg and Mayer, 2006). "
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