Monitoring of cholinesterase-inhibiting activity in water from the Tone canal, Japan, as a biomarker of ecotoxicity

Abstract

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.

Effect of hypochlorite oxidation on cholinesterase-inhibition assay of acetonitrile extracts from fruits and vegetables for monitoring traces of organophosphate pesticides

“…A sample volume of 1 μl was splitlessly injected into the GC-MS at 270°C. The confirmation and determination of organophosphorus and carbamate pesticides tested in the present study were carried out according to the methods described in previous papers (Kawakami et al, 2008;Kanno et al, 2010Kanno et al, , 2012.…”

“…The combination method of ChE assay and hypochlorite oxidation was used to monitor the inhibitors present in environmental samples, according to previous papers (Onodera et al, 1992;Kawakami et al, 2008;Kanno et al, 2012). The organic concentrates obtained from fruit and vegetable samples that had been spiked with organophosphorus pesticides, followed by hypochlorite oxidation (1,000 mg active Cl/l), were tested at three doses for their ChE-inhibiting activity.…”

Enhancement of anti-cholinesterase activity of aqueous samples by hypochlorite oxidation for monitoring traces of organophosphorus pesticides in water

“…This river is typically to the Kamihanawa purification plant and then distributed to the Northwest district of Chiba Prefecture, including to our laboratory. Chlorinated water was prepared from the river sample after treatment with hypochlorite, which produced 10 mg-Cl/l in the water sample, at 20°C for 1 hr with slow stirring, according to the procedure described in previous paper (Kawakami et al, 2008). Drinking water sample (2000 l), containing 0.5 mg/l of residual chlorine, was also obtained from the water tap in the laboratory during period of June 20 th to 21 th 2008.…”

“…The electron ionization conditions were as follows: ion energy, 70 eV; ion source temperature, 200°C ; and m/z = 50-600 full scan for qualitative analysis. The confirmation and determination of organophosphorus and carbamate pesticides tested in the present study were carried out according to the methods described in previous papers (Kawakami et al, 2008;Kanno et al, 2010). …”

Cholinesterase-inhibiting Potentials of Amberlite XAD-2 Resin Extracts Collected from River and Drinking Waters in Northwest District of Chiba Prefecture, Japan

“…We considered these periodic variations to be due to periodic application of the herbicides described in the previous studies. 10,16,17,20,21) Several insecticides, such as diazinon, DDVP, fenitrothion, isoxathion, and pyridaphention, applied to paddy fields were also frequently detected in river water during the investigation period, and others were either not or detected in traces. The total insecticide levels in the river water ranged from 0.26 to 1.33 µg/l with a mean value of 0.91 µg/l ( Table 3).…”