Exposure to lawn herbicides and pesticides has been associated with increased risk for invasive urinary bladder cancer in pet dogs. There is concern of potential risks for humans as well. Among many steps to further investigate this finding, two were addressed here. The purpose of this work was to determine: (1) length of time for potential exposure to chemicals after lawn treatment, i.e. residence time of chemicals on grass, and (2) lawn chemical concentrations in the urine of pet dogs and children living in households that used commercial lawn products. Marker chemicals commonly used in lawn products were selected to track potential exposures. Methods: The work included 2 parts. 1. Residence chemical times were studied in experimental grass plots to define methods and sampling times for the subsequent work. Briefly, a product containing 0.169% 2,4‐dichlorophenoxyacetic acid (2,4‐D), 0.045% 4‐chloro‐2‐methylphenoxypropionic acid (MCPP), and 0.015% Dicamba was applied by calibrated sprayer at manufacturer recommended amounts under different lawn conditions (green, dry brown, wet, recently mowed grass). Chemicals in the dislodgeable residue were measured by LC‐MS (0.17, 24, 48, 72 hrs post treatment). 2. A household study was conducted in which chemical (2,4‐D, MCPP) residence times and chemical concentrations in urine of children and dogs were determined at 0, 24, and 48 hrs post lawn treatment. Questionnaires regarding lawn exposure for dogs and children were completed for treated and for untreated (control) households. Results: In the experimental grass plot study, minimal amounts of 2,4‐D, MCPP, and dicamba were still detected at 48 hours post chemical application to green lawns, although chemical residence time was prolonged (P < 0.05) on dry brown grass. In the household study, chemical concentrations were more than 5 fold higher in some lawns, and chemical residence times were considerably longer (up to 196 µg/m2 of 2,4‐D at 48 hrs) than for the experimental grass plot study. No chemicals were detected in the urine of children, although children in this study spent little time on the lawn. Chemicals (0.69 – 6.12 mg/g creatinine 2,4‐D, 0.20 – 0.68 mg/g creatinine MCPP) were detected in the urine of dogs in 4 of 9 treated households. No chemicals were detected in the urine of dogs in 5 control households. Conclusions: The findings of much higher concentrations and longer residence times (>48 hrs) of chemicals on commercially treated lawns compared to experimental grass plots treated with recommended amounts of herbicide suggest that excessive amounts of chemicals are applied in some commercial settings, thun increasing exposure potential. Detection of chemicals in the urine of dogs in 4 of 9 treated households confirms that chemical uptake and internalization occurs, and that a clear exposure risk exists for pet animals. Further study is needed to assess the exposure risk to humans.

Citation Information: Cancer Prev Res 2010;3(1 Suppl):A40.