Assessing Levels of Intermittent Exposures of Children to Flea Control Insecticides from the Fur of DogsEPA Grant Number: R828017
Title: Assessing Levels of Intermittent Exposures of Children to Flea Control Insecticides from the Fur of Dogs
Investigators: Chambers, Janice E. , Boone, J. Scott , Boyle, Carolyn R. , Tyler, John W.
Institution: Mississippi State University
EPA Project Officer: Saint, Chris
Project Period: April 10, 2000 through April 9, 2003 (Extended to August 9, 2005)
Project Amount: $712,010
RFA: Children's Vulnerability to Toxic Substances in the Environment (1999) RFA Text | Recipients Lists
Research Category: Health , Children's Health , Health Effects
There are reported insecticide residues present in food, water, and surfaces such as carpets treated for flea control. However, no studies (except those we currently have in place) have quantified the transferable flea control insecticide residues which occur on pets (the majority of which are dogs) that could be transferred to children. These dermal exposures could easily become oral exposures when children place their contaminated hands in their mouths. Organophosphorus insecticides or synthetic pyrethroids are among the most common types of insecticides used for flea control. Our calculations have estimated that transfer of these residues could result in exposure levels approaching the adult reference dose (RfD), which does not contain the I 0-fold safety factor to account for the greater sensitivity of children. There are a very large number of dog-owning households in the United States (about 37%) and about half of pet-owning households have children in them. The opportunity for large numbers of children to contact flea control insecticides on pets is high. Because of this lack of information and the likelihood of appreciable insecticide residues being present on pet fur, we propose to test the following hypothesis: The residues of insecticides available for intermittent transfer to children from the fur of dogs treated by either a spot treatment or a collar for flea control will be appreciable and of a magnitude necessitating inclusion in cumulative risk assessments of pesticides to children; and, secondly, that the fur rubbing procedure developed to quantify transferable residues provides a useful estimate of insecticide residues which could be transferred from the fur of dogs to children.
This project will generate unique and much needed information by determining the amount of residues which may be obtained from pets which are treated with flea control insecticides. Treatment of the dogs with either the synthetic pyrethroid permethrin in a spot treatment, or the organophosphates tetrachlorvinphos (TCVP) or chlorpyrifos in a flea collar will be performed according to label directions. All three products are over-the-counter and readily available to the public. Dogs will be sampled before and periodically after treatment by rubbing the fur with white cotton gloves using a standardized protocol currently used in our laboratories. The current fur rubbing protocol will be expanded to include the analysis of residues of tee shirts worn by children aged 3-12 in the households of these dogs to determine the amount of these insecticides actually removed by the children's interaction with their pets. These gloves and insecticide-laden shirts will be extracted with organic solvents by standard methods used for pesticide residue analysis, and the extract will be analyzed by gas chromatography with electron capture detection. Correlation analysis will be conducted on the glove and tee shirt data to determine whether the rubbing protocol is an effective surrogate for the children's exposure. Additionally, urinary metabolites will be quantified at these same sampling times from the child and from one adult in the household to determine how these transferable residues compare to estimates of internal exposure. This approach will be conducted in three specific aims: 1) to determine the exposure of children to permethrin resulting from residues from the fur of dogs from a permethrin spot treatment; 2) to determine the exposure of children to TCVP resulting from residues from the fur of dogs treated with a TCVP flea collar; and 3) to determine the exposure of children to chlorpyrifos resulting from residues from the fur of dogs treated with a chlorpyrifos flea collar. These exposure estimates will indicate whether appreciable residues are available from common flea control strategies, which could yield significant intermittent exposures of children to pesticides.
It is our prediction, based on the transferable residues we are currently measuring from flea dips and collars (which are in the mg range) that these exposure estimates will be substantial and will warrant being included in cumulative risk assessments of pesticides with respect to the safety of children. We expect that, based on our current data on flea control dips, initial residues will be very high shortly after application of the flea control product, but that these residues will dissipate relatively quickly. Thus, we predict that flea control products will yield intermittent exposures of children to insecticides at levels, which must be considered in cumulative risk assessments.
Improvements in Risk Assessment/Risk Management:
The 1996 Food Quality Protection Act mandates that cumulative risk assessments be performed on multiple insecticides from multiple sources (dietary and non-dietary) if they display a common mechanism of toxicity. The flea control insecticides are very likely to fall under this mandate along with others in their chemical classes when concurrent exposures occur. At present, there is no information, except what we are generating, which indicates how great insecticide exposure from flea control insecticides on pets would be. This project proposes to obtain information on transferable residues from dog fur together with concurrent biomonitoring of urine from children and adults in contact with the dog to give much needed information of the levels of intermittent exposure. This information will fill a prominent data gap in the field of pesticide exposure assessment and will enable future cumulative risk assessments to be appropriately and more accurately conducted.