Urinary excretion half life of trichloroacetic acid as a biomarker of exposure to chlorinated drinking water disinfection by-products.

AIMS: To measure accurately urinary elimination half life of trichloroacetic acid (TCAA). METHODS: A longitudinal pilot exposure/intervention study measured the elimination half life of TCAA in urine. Beverage consumption was limited to a public water supply and bottled water of known TCAA concentration, and ingestion volume was managed. The five participants limited fluid consumption to only the water provided. Consumption journals were kept by each participant and their daily first morning urine (FMU) samples were analysed for TCAA and creatinine. TCAA elimination half life curves were generated from a two week washout period using TCAA-free bottled water. RESULTS: Individual elimination half lives ranged from 2.1 to 6.3 days, for single compartment exponential decay, the model which fit the data. CONCLUSION: Urinary TCAA is persistent enough to be viable as a biomarker of medium term (days) exposure to drinking water TCAA ingestion within a range of realistic concentrations.

Acute ecotoxicity of creosote-contaminated soils to Eisenia fetida: a survival-based approach.

Quantification of risks to the ecosystem is necessary for cost-effective remediation strategies. Contaminant endpoints need to be established that consider the bioavailability of toxicants in soil. The challenge is to develop methods that assign risk to the bioavailable toxic contaminants, thereby protecting ecosystems, while balancing remediation costs. Our objective was to evaluate changes in bioavailability of creosote constituents in soils to earthworms. An acute ecotoxicological investigation of three weathered creosote-contaminated and two slurry-phase-biotreated soils was conducted using a 14-d earthworm (Eisenia fetida) survival bioassay. Soil characterization (physical and chemical) and contaminant concentration data (polycyclic aromatic hydrocarbons [PAH] and total dichloromethane extractable organics [DEO]) were also determined. The toxicity of the soils could not always be predicted based on chemical concentrations alone. Soils having a low PAH:DEO ratio had higher cumulative earthworm survival times as measured by earthworm-days. We propose that the DEO fraction may regulate toxicity by altering bioavailability of toxicants.

Comparison of Ah receptor-mediated luciferase and ethoxyresorufin-O-deethylase induction in H4IIE cells: implications for their use as bioanalytical tools for the detection of polyhalogenated aromatic hydrocarbons.

A recombinant H4IIE rat hepatoma cell line (H4L1.1c4, H4IIE-luc), containing a luciferase reporter gene under control of dioxin-responsive enhancers, was examined for responsiveness to several polyhalogenated aromatic hydrocarbons (PHAHs). The recombinant cell system was compared with the widely used wild-type cell line (H4IIE-wt), which expresses Ah receptor-mediated cytochrome P450 1A induction. We also report an improved and down-scaled method for the H4IIE-wt bioassay which allows for the rapid screening of environmental samples for Ah-active PhAHs. This method employs 96-well plates, a plate-reading spectrofluorometer, and a fluorescence-based protein assay that enables the simultaneous measurement of resorufin and protein. Both cell lines demonstrated a dose-dependent increase in Ah receptor-mediated response upon exposure to a number of known Ah receptor agonists, including Halowax 1014. H4IIE-luc cells were 3-fold more sensitive than H4IIE-wt cells to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The detection limit and ED50 for EROD induction by TCDD were 0.6 and 4.9 fmol/well (2,4 and 20 pM), respectively; for luciferase induction they were 0.2 and 1.4 fmol/well (0.8 and 5.6 pM). The detection limit for EROD induction in H4IIE-wt cells was a 50-fold improvement over that reported previously (Tillitt et al., Environ. Sci. Technol. 25, 87-92, 1991) and comparable to that of a chicken embryo primary hepatocyte bioassay (Kennedy et al., Anal. Biochem. 211, 102-112, 1993). The tested PHAHs exhibited a similar structure-activity relationship in H4IIE-luc as in H4IIE-wt cells. Binary mixtures of TCDD, PCB-126, and PCB-77 showed no departure from additivity in their combined responses when tested in H4IIE-wt cells. PCB-153 at the highest tested dose of 14 nmol/well (56 microM) significantly reduced the potency of TCDD and PCB-126 without affecting their efficacy in both H4IIE-wt and H4IIE-luc cells. These findings support the use of H4IIE-luc cells as an alternative bioanalytical tool to the wild-type cells for the detection of Ah agonists in environmental samples.