Article

Influence of humic acid on bioavailability and toxicity of benzo[k]fluoranthene to Japanese medaka.

State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
Environmental Science and Technology (impact factor: 5.23). 01/2009; 42(24):9431-6. pp.9431-6
Source: PubMed

ABSTRACT Japanese medakas (Oryzias latipes) and triolein-embedded cellulose acetate membranes (TECAMs) were exposed simultaneously to benzo[k]fluoranthene (BkF) in the static exposure system containing different concentrations of humic acid (HA). The concentration-response relationships of induced hepatic 7-ethoxysorufin-o-deethylase (EROD) activity were established in regard to the nominal water concentration of BkF and the free concentration estimated using TECAM, as well as the body residues, respectively. In general, bioaccumulation of BkF and EROD activity in medaka were reduced with an increase of HA concentration in the exposure medium. The concentration-response relationships varied with HA concentration when expressed in nominal concentration. However, these relationships overlapped completely and partially when expressed in body BkF residue and in free BkF concentration estimated by TECAM, respectively. HA treatments were slightly beyond the 0.95 confidence band of HA-free control thereby indicating the participation of BkF-HA complex to the bioavailability and toxicity. On the basis of the bioavailability model, it was estimated that approximately 17-22% and 13-18% of BkF-HA complex contributed to the bioaccumulation and/or to the induced toxic effect, correspondingly.

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    Article: Maintaining the Constant Exposure Condition for an Acute Caenorhabditis elegans Mortality Test Using Passive Dosing.
    Hyuck-Chul Kwon, Ji-Yeon Roh, Dongyoung Lim, Jinhee Choi, Jung-Hwan Kwon
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    ABSTRACT: Maintaining the constant exposure to hydrophobic organic compouds in acute toxicity tests is one of the most difficult issues in the evaluation of their toxicity and corresponding risks. Passive dosing is an emerging tool to keep constant aqueous concentration because of the overwhelming mass loaded in the dosing phase. The primary objectives of this study were to develop the constant exposure condition for an acute mortality test and to compare the performance of the passive dosing method with the conventional spiking with co-solvent. A custom cut polydimethylsiloxane (PDMS) tubing loaded with benzyl butyl phthalate (BBP) was placed in each well of a 24-well plate containing assay medium. The rate of the release of BBP from PDMS was evaluated by measuring the change in the concentration of BBP in the assay medium. The efficiency of maintaining constant exposure condition was also evaluated using a simple two-compartment mass transport model employing a film-diffusion theory. An acute mortality test using 10 C. elegans in each well was conducted for the evaluation of the validity of passive dosing and the comparative evaluation of the passive dosing method and the conventional spiking method. Free concentration in the assay medium reached 95% steady state value within 2.2 hours without test organisms, indicating that this passive dosing method is useful for an acute toxicity test in 24 hours. The measured concentration after the mortality test agreed well with the estimated values from partitioning between PDMS and the assay medium. However, the difference between the nominal and the free concentration became larger as the spiked concentration approached water solubility, indicating the instability of the conventional spiking with a co-solvent. The results in this study support that passive dosing provides a stable exposure condition for an acute toxicity test. Thus, it is likely that more reliable toxicity assessment can be made for hydrophobic chemicals using passive dosing.
    Environmental health and toxicology. 01/2011; 26:e2011015.
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Keywords

0.95 confidence band
 
BkF
 
BkF-HA complex
 
body BkF residue
 
concentration-response relationships
 
concentration-response relationships varied
 
different concentrations
 
free BkF concentration
 
free concentration
 
HA
 
HA-free control
 
induced hepatic 7-ethoxysorufin-o-deethylase
 
induced toxic effect
 
Japanese medakas
 
nominal concentration
 
nominal water concentration
 
relationships overlapped
 
static exposure system
 
TECAMs
 
triolein-embedded cellulose acetate membranes
 

Shan Chen