Elucidation of Fipronil Photodegradation Pathways

Ngim, Kenley K.; Mabury, Scott A.; Crosby, Donald G.

doi:10.1021/jf9913007

Cited by 49 publications

(44 citation statements)

References 18 publications

(31 reference statements)

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“…Fipronil can undergo degradation in water and soil through abiotic and biotic processes. reduction, hydrolysis, photolysis and oxidation respectively 3, 6, 8–15. Fipronil sulfide, fipronil sulfone and desulfinyl are all biologically active against insect pests 16.…”

Section: Introductionmentioning

confidence: 99%

Adsorption, transport and degradation of fipronil termiticide in three Hawaii soils

Shuai

Chen²,

Ray

2011

Pest Management Science

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BACKGROUND: The behavior of the termiticide fipronil in soils was studied to assess its potential to contaminate ground and surface water. This study characterizes (1) adsorption of fipronil in three different soils, (2) transport of fipronil through leaching and runoff under simulated rainfall in these soils and (3) degradation of fipronil to fipronil sulfide and fipronil sulfone in these soils. RESULTS: The adsorption experiments showed a Freundlich isotherm for fipronil with Koc equal to 1184 L kg−1. In the leaching experiments, the concentration of fipronil and its metabolites in leachate and runoff decreased asymptotically with time. The concentration of fipronil in the leachate from the three soils correlated inversely with soil organic carbon content. The degradation experiment showed that the half‐life of fipronil in the soils ranged from 28 to 34 days when soil moisture content was 75% of field capacities, and that 10.7–23.5% of the degraded fipronil was transformed into the two metabolites (fipronil sulfide and fipronil sulfone). CONCLUSION: Fipronil showed large losses through leaching but small losses via runoff owing to low volumes of runoff water generated and/or negligible particle‐facilitated transport of fipronil. The half‐life values of fipronil in all three soils were similar. Copyright © 2011 Society of Chemical Industry

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Section: Introductionmentioning

confidence: 99%

Adsorption, transport and degradation of fipronil termiticide in three Hawaii soils

Shuai

Chen²,

Ray

2011

Pest Management Science

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“…Fipronil transforms to several degradates in the environment. Fipronil is stable in aqueous solutions under mildly acidic or neutral conditions [2,3] but undergoes transformation through hydrolysis under basic conditions [2,3], photolysis [3][4][5][6], and oxidation or reduction in water, soil, or sediment [7][8][9][10][11][12][13][14]. The main degradates ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Persistence and sorption of fipronil degradates in urban stream sediments

Lin

Haver²,

Oki

et al. 2009

Enviro Toxic and Chemistry

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Fipronil, an increasingly popular insecticide used for urban pest control, is known to readily transform into several degradates that generally have similar or greater toxicity to aquatic organisms than the parent compound. However, knowledge on the fate of these degradates in the environment is obscure. In the present study, degradation kinetics and sorption of desthiofipronil, fipronil sulfide, and fipronil sulfone were investigated in urban stream sediments. All degradates showed enhanced persistence in sediments compared to fipronil under facultative or anaerobic conditions. Under facultative conditions, the estimated half-lives of desthiofipronil, fipronil sulfide, and fipronil sulfone were 217 to 497, 195 to 352, and 502 to 589 d, respectively. Under anaerobic conditions, the corresponding half-lives were over one year in one sediment, while no detectable degradation occurred in the other two sediments after 280 d. Sorption isotherms of fipronil and its degradates in the sediments were linear, with mean K(OC) values of 802, 1,296, 3,684, and 3,543 L/kg for fipronil, desthiofipronil, fipronil sulfide, and fipronil sulfone, respectively, suggesting that the degradates generally have a higher sorption capacity than fipronil. Sorption coefficient K(d) increased up to fourfold over 280 d, suggesting an aging effect on sorption. The inherent toxicity, long persistence, and strong sorption potential highlight the importance for a better understanding of the sediment toxicity of fipronil degradates in surface water bodies.

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“…Under normal use conditions, fipronil can be degraded mainly to fipronil sulfone via biotic/abiotic oxidation and to a desulfinyl photoproduct via photolysis (Environmental Protection Agency, 1996;Bobe et al, 1998;Ngim et al, 2000;Fenet et al, 2001;Tingle et al, 2003). Fipronil sulfone is rapidly formed through cytochrome P450 NADPH-dependent oxidation in human recombinant CYP3A4 system and in human liver microsomes in vitro.…”

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confidence: 99%

Sulfone Metabolite of Fipronil Blocks γ-Aminobutyric Acid- and Glutamate-Activated Chloride Channels in Mammalian and Insect Neurons

Zhao

Yeh²,

Salgado³

et al. 2005

J Pharmacol Exp Ther

103

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Fipronil sulfone, a major metabolite of fipronil in both insects and mammals, binds strongly to GABA receptors and is thought to play a significant role in poisoning by fipronil. To better understand the mechanism of selective insecticidal action of fipronil, we examined the effects of its sulfone metabolite on GABA-and glutamate-activated chloride channels (GluCls) in cockroach thoracic ganglion neurons and on GABA A receptors in rat dorsal root ganglion neurons using the whole-cell patch-clamp technique. Fipronil sulfone blocked both desensitizing and nondesensitizing GluCls in the cockroach. Activation was required for block and unblock of desensitizing GluCls. In contrast, activation was not prerequisite for block and unblock of nondesensitizing channels. After repetitive activation of the receptors, the IC 50 of fipronil sulfone to block the desensitizing GluCls was reduced from 350 to 25 nM and that for blocking nondesensitizing GluCls was reduced from 31.2 to 8.8 nM. This use-dependent block may be explained by its slow unbinding rate. In cockroach and rat neurons, fipronil sulfone blocked GABA receptors in both activated and resting states, with IC 50 values ranging from 20 to 70 nM. In conclusion, although fipronil sulfone is a potent inhibitor of cockroach GABA receptors, desensitizing and nondesensitizing GluCls, and rat GABA A receptors, its selective toxicity in insects over mammals appears to be associated with its potent blocking action on both desensitizing and nondesensitizing GluCls, which are lacking in mammals.

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Elucidation of Fipronil Photodegradation Pathways

Cited by 49 publications

References 18 publications

Adsorption, transport and degradation of fipronil termiticide in three Hawaii soils

Adsorption, transport and degradation of fipronil termiticide in three Hawaii soils

Persistence and sorption of fipronil degradates in urban stream sediments

Sulfone Metabolite of Fipronil Blocks γ-Aminobutyric Acid- and Glutamate-Activated Chloride Channels in Mammalian and Insect Neurons

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