^aCenter for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi, USA

Correspondence: Dr. J.E. Chambers, Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, P.O. Box 6100, Mississippi State, MS 39762, USA. Tel.: +662 325 1255; Fax: +662 325 1031; E-mail: chambers@cvm.msstate.edu

¹Current address: United States Environmental Protection Agency, Environmental Chemistry Branch, John C. Stennis Space Center, Mississippi, USA.

²Current address: Western University of Health Sciences, College of Veterinary Medicine, Pomona, California, USA.

Received 5 March 2007; Revised 5 October 2007; Accepted 5 November 2007; Published online 2 January 2008.

Abstract

Fleas are a persistent problem for pets that require implementation of control measures. Consequently, pesticide use by homeowners for flea control is common and may increase pesticide exposure for adults and children. Fifty-five pet dogs (23 in study 1; 22 in study 2) of different breeds and weights were treated with over-the-counter flea collars containing tetrachlorvinphos (TCVP). During study 1, fur of treated dogs was monitored for transferable TCVP residues using cotton gloves to pet the dogs during 5-min rubbings post-collar application. Plasma cholinesterase (ChE) activity was also measured in treated dogs. Average amounts of TCVP transferred from the fur of the neck (rubbing over the collar) and from the back to gloves at 3 days post-collar application were 23,7002100 and 26050 g/glove, respectively. No inhibition of plasma ChE was observed. During study 2, transferable TCVP residues to cotton gloves were monitored during 5-min rubbings post-collar application. Transferable residues were also monitored on cotton tee shirts worn by children and in the first morning urine samples obtained from adults and children. Average amounts of TCVP transferred to gloves at 5 days post-collar application from the neck (over the collar) and from the back were 22,4002900 and 8020 g/glove, respectively. Tee shirts worn by children on days 7–11 contained 1.80.8 g TCVP/g shirt. No significant differences were observed between adults and children in urinary 2,4,5-trichloromandelic acid (TCMA) levels; however, all TCMA residues (adults and children) were significantly greater than pretreatment concentrations (=0.05). The lack of ChE inhibition in dogs and the low acute toxicity level of TCVP (rat oral LD₅₀ of 4–5 g/kg) strongly suggest that TCVP is rapidly detoxified and excreted and therefore poses a very low toxicological risk, despite these high residues.