Grantee Research Project Results
1998 Progress Report: Assessing Levels of Organophosphorus Insecticides Which Could Expose Children From Pets Treated with Flea Control Insecticides
EPA Grant Number: R825170Title: Assessing Levels of Organophosphorus Insecticides Which Could Expose Children From Pets Treated with Flea Control Insecticides
Investigators: Chambers, Janice E. , Boone, J. Scott , Tyler, John W.
Institution: Mississippi State University
EPA Project Officer: Aja, Hayley
Project Period: October 1, 1996 through September 30, 1999
Project Period Covered by this Report: October 1, 1997 through September 30, 1998
Project Amount: $597,804
RFA: Exposure of Children to Pesticides (1996) RFA Text | Recipients Lists
Research Category: Pesticides , Children's Health , Human Health , Safer Chemicals
Objective:
The objective of this project is to determine the levels of dislodgable insecticide residues that could be transferred to humans from dogs treated with flea control dips or collars.Progress Summary:
During the first grant year, the project completed 12 replications of a chlorpyrifos dip-no-shampooing protocol, 12 replications of a chlorpyrifos dip-shampooing protocol, and initiated a phosmet dip protocol.During this second year, 24 replications of the phosmet dip-no-shampooing protocol were completed, and a protocol using a tetrachlorvinphos collar has been initiated. The project was continued with the phosmet dip using the procedures and protocols developed during the first year. Because of the rapid decline in the chlorpyrifos residues observed during the initial study of the first year, it was decided to obtain two additional early samples (1 day and 3 days) to better characterize the availability of dislodgable residues when they were showing the largest changes; therefore, samplings were performed at 4 hours and at 1, 3, 7, and 14 days after treatment. Twenty-four dogs were recruited and initially shampooed and sampled for residues and plasma cholinesterase activity. The experiment was conducted in four sets with six dogs per set. None of the dogs showed evidence of phosmet contamination or cholinesterase inhibition. The dogs then were dipped, dried, and sampled at 4 hours after the initial dipping. Fur sampling consisted of rubbing with a white cotton glove along the midline of the back for a measured distance of 10 inches for a 5-minute period. Blood samples were collected into ethylene diamine tetra-acetic acid (EDTA) by venipuncture, and the samples were centrifuged to separate plasma. Fur and blood samples again were collected at 1, 3, 7, and 14 days following dipping, at which point the dogs were dipped again. This procedure was repeated for a total of four dips. Both acetylthiocholine (the most appropriate substrate for acetylcholinesterase, AChE) and butyrylthiocholine (the most appropriate substrate for butyrylcholinesterase, BChE) were assayed using the cholinesterase inhibitor eserine and the BChE inhibitor iso-OMPA to characterize activity. Plasma was diluted as necessary to ensure that activities stayed within the linear range of the assay. All data from this experiment have been obtained and are undergoing statistical analysis.
The second protocol conducted during this grant year is sampling for dislodgable residues of tetrachlorvinphos from a nonprescription collar. This procedure was not part of the original grant proposal. The elimination during the first grant year of the second set of 12 replications in the chlorpyrifos dip protocols because of the withdrawal of chlorpyrifos dips from the market by the manufacturer made funds available to conduct additional experiments. Collars containing tetrachlorvinphos were assayed. The protocol involves sampling at 0 and 4 hours and at 3, 7, 14, 28, 56, 84, and 112 days for fur and blood samples. Fur sampling involved collecting three samples on each occasion: on the back of the dog distant from the collar to determine migration of insecticide over the surface of the dog, on the back of the neck with the collar removed to determine residues transferred to immediately adjacent fur, and the back of the neck with the collar back in place to determine residues dislodgable from the collar itself. Preliminary results were similar to those obtained during the first grant year with the chlorpyrifos dips, where a large amount of variability exists among animals (see table). This variability may be of particular value to EPA if probabilistic methods of exposure assessment are used in the risk characterization process.
Residue on | Percent Inhibition | |||
Time | Glove ( g) | Range ( g) | BChE | AChE |
4 h | 2,841 ? 339 | 79?11,620 | 14.6 ? 3.8 | 0.8 ? 4.0 |
1 day | 1,103 ? 157 | 57?6,066 | ? | ? |
3 days | 602 ? 110 | 1?3,405 | 9.8 ? 4.0 | 8.3 ? 3.7 |
7 days | 164 ? 29 | 1?895 | 12.2 ? 4.3 | 9.5 ? 4.0 |
14 days | 48 ? 13 | 0.3?386 | 10.2 ? 4.0 | 6.2 ? 3.3 |
Data evaluation indicates that, similar to the results seen with the chlorpyrifos dip during the first grant year, the dislodgable residues from the phosmet dip also were high initially and dissipated rapidly. The residues from the phosmet dip were higher than those from the chlorpyrifos dip probably because the concentration of active ingredient in the dipping solution was higher for phosmet than for chlorpyrifos. Dissipation of residues was rapid in that very little residue remained at the time of the next prescribed dipping, and no buildup of residues appeared with repeated dippings. Unlike chlorpyrifos, there was little or no AChE or BChE inhibition following phosmet treatment, suggesting little internalization of the active ingredient by the dogs.
Data on residues resulting from the tetrachlorvinphos collar treatment are incomplete at this time; however, the preliminary results indicate that milligram quantity levels of the insecticide can be dislodged by a 5-minute rubbing over the collar shortly after administration of the collar. Peak residues were observed at 3 to 7 days after collar administration, with the highest residue samples obtained by rubbing over the collar itself and the next highest residues observed on the neck fur nearest or in direct contact with the collar. Measurable residues were dislodged from the back of the dog, indicating that these residues can migrate from the collar to distant parts of the dog. Appreciable residues are still being obtained at 28 days after collar administration. It is estimated that the project is nearly two-thirds complete.
Future Activities:
Complete the tetrachlorvinphos collar experiment. Initiate the protocol with the chlorpyrifos collar for a 6-month period, as described in the original proposal. Prepare manuscripts describing the chlorpyrifos and phosmet dip data for peer-review literature.Journal Articles:
No journal articles submitted with this report: View all 5 publications for this projectSupplemental Keywords:
children, chlorpyrifos, dog, exposure assessment, flea collar, flea dip, insecticide, organophosphorous, phosmet, tetraclorvinphos., RFA, Health, Scientific Discipline, Toxics, Environmental Chemistry, Health Risk Assessment, pesticides, Risk Assessments, Susceptibility/Sensitive Population/Genetic Susceptibility, Children's Health, genetic susceptability, health effects, pesticide exposure, risk assessment, sensitive populations, dermal exposure, adult reference dose, Phosmet, health risks, infants, age-related differences, chlorpyrifos, dermal contact, dogs, measuring childhood exposure, exposure, pets, air pollution, children, assessment of exposure, children's vulnerablity, susceptibility, toxicity, human exposure, insecticides, pesticide residues, exposure pathways, harmful environmental agents, dietary exposure, flea control insecticides, organophosphate pesticidesRelevant Websites:
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.