Assessing transferable residues from intermittent exposure to flea control collars containing the organophosphate insecticide chlorpyrifos

Abstract

Children can be exposed to pesticides from numerous residential sources such as carpet, house dust, toys and clothing from treated homes, and flea control remedies on pets. In the present studies, 48 pet dogs (24 in each of two studies) of different breeds and weights were treated with over-the-counter flea collars containing chlorpyrifos (CP), an organophosphorus insecticide. Transferable insecticide residues were quantified on cotton gloves used to rub the dogs for 5 min and on cotton tee shirts worn by a child (Study 2 only). First morning urine samples were also obtained from adults and children in both studies for metabolite (3,5,6-trichloro-2-pyridinol) quantification. Blood samples were obtained from treated dogs in Study 1 and plasma cholinesterase (ChE) activity was monitored. Transferable residues on gloves for all compounds were highest near the neck of the dogs and were lowest in areas most distant from the neck. Rubbing samples (over the collar) at two weeks post-collar application contained 447757 mg CP/glove while samples from the fur of the back contained 872 mg CP/glove. In Study 2, cotton tee shirts worn by children at 15 days post-collar application for 4 h showed CP levels of 134766 ng/g shirt. There were significant differences between adults and children in the levels of urinary metabolites with children generally having higher urinary levels of metabolites than adults (grand mean7SE; 11.671.1 and 7.970.74 ng/mg creatinine for children and adults, respectively, compared to 9.470.8 and 6.970.5 ng/mg creatinine before collar placement). Therefore, there was little evidence that the use of this flea collar contributed to enhanced CP exposure of either children or adults.

Assessing intermittent pesticide exposure from flea control collars containing the organophosphorus insecticide tetrachlorvinphos

“…The selection and care of pet dogs used in these studies were in accordance with our earlier studies (Chambers et al, 2007). Dogs were of a variety of breeds (including both short and long hair breeds) and sizes (range 8-85 lb).…”

“…One child and one adult were selected from each participating family (study 2 only) as previously described by Chambers et al (2007). A copy of the protocol was distributed to each participating household and informed consent was obtained from the adults.…”

“…During study 1, plasma ChE activity was determined spectrophotometrically from blood samples taken from each dog at the same time as rubbing samples (Chambers et al, 2007).…”

“…Samplers utilized during both studies were students enrolled in the veterinary medicine curriculum at the College of Veterinary Medicine, Mississippi State University. Preparation of gloves and sampling procedures described by Chambers et al (2007) were employed. Rubbing samples were obtained prior to collar placement (day 0) and at 4 h, and 3, 7, 14, 28, 56, 84, and 112 days post-collar application during study 1 and prior to collar placement (0), and again at 5 and 12 days following collar placement in study 2.…”

“…Pesticide exposures to infants and children from food, water, and residential sources have been well documented (Woody, 1984;Zwiener and Ginsburg, 1988;Fenske et al, 1990;Morgan et al, 2001;Castorina et al, 2003;Colt et al, 2003;Rohrer et al, 2003;Hore et al, 2005;Boone et al, 2006;Chambers et al, 2007). However, one area that does not seem to have been appreciably explored is the possibility that residues of insecticides remaining on pet fur from flea control treatments could be a significant source of pesticide exposure in children.…”