Journal of Pesticide Science

The current risk assessment of human exposure to low-level pyrethroids (PYRs) is generally based on the estimation of residue intake from diets. Limited data are available on individual exposure levels in human studies, which is partly attributable to the difficulty in biological monitoring of PYR exposure. This obstacle has been overcome in recent years due to the evolution of analytical chemistry. Separation and sensitive identification and quantitation of urinary PYR metabolites are today reliably made with liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. This article gives an overview of the biological monitoring of urinary PYR metabolites, reviews PYR metabolite levels in general populations, and discusses future research perspectives in the field of environmental health.

View full abstract

Show abstractHide abstract

Pyribencarb is a novel benzylcarbamate-type fungicide, which is active against a wide range of plant pathogenic fungi. In this paper, the inhibitory effects of this fungicide on the electron transport system of fungi, plants, rat and carp were examined to elucidate its mode of action and selectivity. Pyribencarb potently inhibited succinate-cytochrome c reductase (SCR) activities of Botrytis cinerea (cucumber gray mold), Corynespora cassiicola (leaf spot) and decylubiquinol-cytochrome c reductase (UCR) activity of B. cinerea. Pyribencarb inhibited the UCR of B. cinerea in an uncompetitive manner with respect to decylubiquinol, which was the same as strobilurin fungicides, and the substrate-dependent inhibition constant was found from calculation to be 13 nM. These results suggested that the target site of pyribencarb is cytochrome b of complex III in the electron transport system of the respiratory chain. On the other hand, the inhibitory potency of pyribencarb on SCR activities of plants, rats and carp was relatively weak compared with that of strobilurin fungicides, indicating that pyribencarb is a Qo inhibitor of cytochrome b, whose properties are superior to well-known Qo inhibitor fungicides in terms of target. The binding site of pyribencarb on cytochrome b was assumed to be a little different from that of strobilurin fungicides, because pyribencarb inhibited SCRs of strobilurin fungicide-resistant strains of B. cinerea and C. cassiicola with relatively low concentrations. The binding site was also discussed through comparison of amino acid sequences of plants, rats, carp, yeast and fungi, including B. cinerea, which was elucidated in this paper.

View full abstract

Download PDF (942K)

To investigate the intrinsic bioavailability of heptachlor to various plant species, the root of each test plant was treated with hydroponic solution containing ¹⁴C-heptachlor for 72 hr. The levels and nature of ¹⁴C-residues in roots and shoots of treated plants were determined to estimate the values of the root concentration factor (RCF) and the transpiration stream concentration factor (TSCF). RCF and TSCF values ranged from 126 (corn) to 4086 (lettuce) and 0.052 (Chinese cabbage) to 0.494 (zucchini), respectively. In pumpkin and zucchini, unmetabolized heptachlor itself was translocated from the root to the shoot via a transpiration stream and no further extensive metabolism was observed. cis-Heptachlor epoxide was the predominant metabolite in the shoots of tomato, cabbage, Chinese cabbage and lettuce. Less metabolism of cis-heptachlor epoxide was suggested in the shoots of these plants.

View full abstract

Thirty-nine paddy pesticides and 11 of their metabolites were monitored in the Sakura River during the rice cultivation season in 2007 and 2008. Pesticide concentrations in the river water depended on the timing of pesticide application. Herbicides that were shipped to Ibaraki Prefecture in large amounts or had high water solubility, a low soil adsorption constant value, or large usage rates were detected at high peak concentrations. The concentrations of nursery-box-applied fungicides and insecticides peaked immediately after transplanting. The concentrations of pesticide metabolites, such as bromobutide-desbromo, cafenstrol-descarbamoyl, clomeprop-propionic acid, carbofuran, and fenthion-sulfoxide depended on the degradation rates and metabolic pathways of the parent compounds and on the stability of the metabolites in water and soil. Clomeprop-propionic acid, carbofuran, and fenthion-sulfoxide, which were formed from rapidly degradable pesticides, were detected at much higher peak concentrations than the parent compounds.

View full abstract

Register with J-STAGE for free!