Triclosan, which is used widely as an antibacterial agent, was ubiquitously found in the water samples collected from the Tone Canal, Chiba, Japan. The concentrations of triclosan ranged from 11 to 31 ng/L. Higher concentrations of triclosan were observed in water samples collected from downstream, as compared to in the water samples collected upstream. The daily monitoring of a selected point from where the domestic wastewater inflow occurs showed that the triclosan levels in the water samples ranged from 55 to 134 ng/L; the levels of the loading amounts peaked from 10:00 to 12:00.

Amberlite XAD-2 resin extracts of river and drinking water sampled in each month during the period from January to December 2008 from the Northwest district of Chiba Prefecture were investigated to characterize and determine their cholinesterase (ChE)-inhibiting potentials and pesticide levels. The XAD-2 extracts from river water collected during the mid-spring to mid-summer periods exhibited strong inhibition effect to horse serum ChE, reflecting the application of organophosphorus and carbamate pesticides to paddy fields. Gas chromatographicmass spectrometric (GC/MS) determinations of the XAD-2 extracts of the river water collected during spring to summer periods also showed to be comparatively high levels of agricultural chemicals, such as herbicides, insecticides and fungicides, as compared with those detected in the drinking water. Although a considerable reduction in the ChE-inhibiting potentials and in the GC/MS detectable compound levels was observed for the river water samples, it is particularly interest that ChE-inhibiting potentials still remained in the drinking water.

The cholinesterase (ChE)-inhibiting activity of water and the concentrations of representative inhibitors were monitored in the Tone canal, Japan, during April to December 2006. The ChE-inhibiting activity, measured by using horse serum as enzyme source, increased from late April to early June, and from September to October. Although the trends in the ChE-inhibiting activity of the samples were consistent with concentration changes of organophosphorus pesticides, ChE-inhibiting activity was not observed in samples replicated on the basis of the chemical concentrations detected. The water samples were treated with chlorine to enhance the ChE-inhibiting activity by conversion of thiophosphate pesticides to phosphate pesticides. The ChE-inhibiting activity increased in almost all the chlorine-treated samples, although organophosphorus pesticides were either not detected or detected in traces in the samples by gas chromatographic-mass spectrometric analysis. These results suggested that assay of ChE-inhibiting activity is important for evaluating the ecotoxicity of environmental water, because toxicological investigations based solely on inhibitor concentrations may underestimate the contamination. Furthermore, the combined method of oxidation by chlorination and the ChE assay is very effective for screening and monitoring of organophosphorus pesticides in environmental water.

Cyclooxygenase (COX) plays an important role in eicosanoid metabolism. Nonsteroidal anti-inflammatory drugs (NSAIDs) function as COX inhibitors and are frequently detected in the aquatic environment. Here, we measured the in vitro COX-inhibiting activity of the surface water and domestic wastewater in the Tone Canal, Japan. The concentrations of several NSAIDs in the some samples were also determined using gas chromatography-tandem mass spectrometry for confirming the validity of the assay. The target compounds were extracted from the samples using a solid-phase extraction cartridge. A dose-response relationship between the inhibiting activity and sample volume were observed in the wastewater sample. The higher COX-inhibiting activities were observed in the wastewater sample, as compared with the samples of the surface water in the canal. These inhibiting activities reflected the trends of NSAIDs distribution in the canal. However, the inhibiting activities of the water samples could not be entirely explained by the NSAIDs that were selected for instrumental analysis in this study. Other compounds that were not measured by instrumental analysis in this study might contribute to the inhibiting activities. Therefore, the COX-inhibiting assay would be effective for evaluating inclusive ecotoxicity in the aquatic environment.

This investigation was undertaken to determine the effect of the bromide concentration on the formation of polyhalogenated ethylphenoxyethylphenols (PXEPEPs), including predioxins, during the chlorination of 4-ethylphenol in solution. An aqueous solution of 4-ethylphenol was treated with hypochlorite in the presence of various concentrations of bromide ions. The changes in the compositions of the halogenated products in hexane extracts of the chlorinated solution were analyzed by gas chromatograph (GC) and a flame ionization detector (FID) and mass spectrometry (MS). 4-ethylphenol was shown to from several halogenated compounds, including PXEPEPs, as by-products of chlorination. The number of substituted chlorine or bromine atoms ranged from 0 to 4. The formation of bromine-substituted PXEPEPs was observed in the presence of 0.1 equivalents of bromide ions per mole of 4-ethylphenol. The number of substituted bromine atoms increased with the amount of co-existing bromide ions. In the presence of more than one equivalent of bromide ions per mole of 4-ethylphenol, the number of bromine atoms substituted in the PXEPEPs increased, whereas the number of chlorine atoms substituted in the PXEPEPs decreased. GC-MS total ion chromatograms confirmed the formation of polybrominated and polychlorinated predioxins during the aqueous chlorination of 4-ethylphenol in the presence of bromide ions. However, at ten equivalents of bromide ions per mole of 4-ethylphenol, no predioxins were observed in the hexane extract obtained from the aqueous 4-ethylphenol solution after being treated with chlorine. The formation of PXEPEPs during the chlorination of 4-ethylphenol in the presence of bromide ions was also influenced by the reaction pH.