Degradation of Fipronil (Termidor®) in Aqueous Solution Stored in Polyethylene Tanks Exposed to Sunlight or Shade

Bull Environ Contam Toxicol (2009) 82:605609 DOI 10.1007/s00128-009-9651-6

Degradation of Fipronil (Termidor) in Aqueous Solution Stored in Polyethylene Tanks Exposed to Sunlight or Shade

T. J. Husen N. A. Spomer S. T. Kamble

Received: 5 July 2008 / Accepted: 8 January 2009 / Published online: 21 January 2009 Springer Science+Business Media, LLC 2009

Abstract Pest Management Professionals commonly use polyethylene or berglass tanks for mixing and applying termiticides. We investigated the stability of pronil (Termidor SC) (0.06%, 0.09% and 0.125% active ingredient) in aqueous solutions stored in polyethylene tanks under sun and shade for 2 week. Chemical analysis of tank-mixed solutions sampled at 0, 24, 48, 72, 168 and 336 h indicated that pronil remained stable. Our data indicated that polyethylene tanks prevent pronil from photodegradation and these tanks can be safely used for short term storage (up to 2 week) of liquid termiticides.

Keywords Fipronil Stability Polyethylene tanks

Photolysis

Subterranean termites are commonly controlled and excluded from structures by creating a subsoil chemical barrier adjacent to the exterior and/or interior of the structural foundation (Kamble 2006). In the past, control of subterranean termites relied on using chlorinated hydro-carbon, organophosphate, carbamate, and pyrethroid soil termiticides which persisted in the environment and had moderate to high mammalian toxicities (Gold et al. 1996). Currently, non-repellent termiticides with novel modes of action and considerably low mammalian toxicity are being used for termite control. These termiticide AIs and their classes include: imidacloprid and acetamiprid (neonicotinoids), pronil (phenyl pyrazole), chlorfenapyr (pyrazole), and indoxacarb (oxadiazine). Termidor (pronil) Soluble

Concentrate (SC) was registered in 2000 for termite control and it continues to be the most effective and widely used termiticide today.

Fipronil [()-5-amino-1-(2,6-dichloro-a,a,a-triuoro-ptolyl)-4-triuoromethyl sulnyl-pyrazole-3-carbonitrile], a broad-spectrum, interferes with the passage of chloride ions through gamma-aminobutyric acid (GABA) regulated chloride ionophore thereby disrupting inhibitory post synaptic neuron activity, resulting in uncontrolled central nervous system function, and eventually causing death (Cole et al. 1993; Tingle et al. 2003). Fipronil is slightly water soluble with solubility ranges from 1.92.4 mg/L at 20C, very low vapor pressure (3.7 9 10-4 mPa @ 25C), and a low Henrys law constant (3.7 9 10-5 Pa m3/mol) (Hainzl and Casida 1996; Connelly 2006; Tingle et al. 2003). Fipronil degrades to its major metabolites by reduction to sulde, oxidation to...