An observational study of the potential for human exposures to pet-borne diazinon residues following lawn applications

Abstract

This study examined the potential for pet dogs to be an important pathway for transporting diazinon residues into homes and onto its occupants following residential lawn applications. The primary objectives were to investigate the potential exposures of occupants and their pet dogs to diazinon after an application to turf at their residences and to determine if personal contacts between occupants and their pet dogs resulted in measurable exposures. It was conducted from April to August 2001 before the Agency phased out all residential uses of diazinon in December 2004. Six families and their pet dogs were recruited into the study. Monitoring was conducted at pre-, 1, 2, 4, and 8 days post-application of a commercial, granular formulation of diazinon to the lawn by the homeowner. Environmental samples collected included soil, indoor air, carpet dust, and transferable residues from lawns and floors. Samples collected from the pet dogs consisted of paw wipes, fur clippings, and transferable residues from the fur by a technician or child wearing a cotton glove(s). First morning void (FMV) urine samples were collected from each child and his/her parent on each sampling day. Diazinon was analyzed in all samples, except urine, by GC-MS. The metabolite 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMPy) was analyzed in the urine samples by HPLC-MS/MS. Mean airborne residues of diazinon on day 1 post-application were at least six times higher in both the living rooms (235+/-267 ng/m(3)) and children's bedrooms (179+/-246 ng/m(3)) than at pre-application. Mean loadings of diazinon in carpet dust samples were at least 20 times greater on days 2, 4, and 8 post-application than mean loadings (0.03+/-0.04 ng/cm(2)) at pre-application. The pet dogs had over 900 times higher mean loadings of diazinon residues on their paws on day 1 post-application (88.1+/-100.1 ng/cm(2)) compared to mean loadings (<0.09 ng/cm(2)) at pre-application. The mean diazinon loadings on the fur clippings were at least 14 times higher on days 1, 2, 4, and 8 post-application than mean loadings (0.8+/-0.4 ng/cm(2)) at pre-application. For transferable residues from dog fur, the mean loadings of diazinon on the technician's cotton glove samples were the lowest before application (0.04+/-0.08 ng/cm(2)) and the highest on day 1 post-application (10.4+/-23.9 ng/cm(2)) of diazinon to turf. Urinary IMPy concentrations for the participants ranged from <0.3 to 5.5 ng/mL before application and <0.3-12.5 ng/mL after application of diazinon. The mean urinary IMPy concentrations for children or adults were not statistically different (p>0.05) at pre-application compared to post-application of diazinon to turf. The results showed that the participants and their pet dogs were likely exposed to low levels of diazinon residues from several sources (i.e., air, dust, and soil), through several pathways and routes, after lawn applications at these residences. Lastly, the pet dog appears to be an important pathway for the transfer and translocation of diazinon residues inside the homes and likely exposed occupants through personal contacts (i.e., petting).