Volatile and Dislodgeable Residues Following Triadimefon and MCPP Application to Turfgrass and Implications for Human Exposure

Abstract

Volatilization can be a major route of pesticide loss following application to turfgrass areas. Consequently, a significant portion of applied pesticide may be available for human exposure via volatile and dislodgeable residues. In this study, volatile and dislodgeable residues were determined following application of triadimefon [1‐(4‐chlorophenoxy)‐3,3‐dimethyl‐l‐(1H‐1,2,4‐triazol‐l‐yl) butanone], and MCPP [( +/−)‐2‐(4‐chloro‐2‐methylphenoxy) propionic acid], to established plot of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.). For each application, a 10‐m radius plot was sprayed and the Theoretical Profile Shape (TPS) method of Wilson was used to estimate volatile flux. Dislodgeable residues were concurrently determined by wiping treated turfgrass with a water dampened piece of cheesecloth. Less than 8% of the total applied triadimefon was measured as volatile residues with nearly all volatilization loss occurring within 5 to 7 d of application. Diurnal patterns of triadimefon volatilization were evident. Mid‐day (1100–1500 h) triadimefon volatile flux on Days 2 (4.6 g ha−2 h−1 ) and 3 (2.4 g ha−2 h−1) was 2 and 1.4 times, respectively, greater than the average of morning and late afternoon volatile flux on these respective days. Less than 1% of the total applied MCPP was measured as volatile residue. Volatile MCPP residues decreased over time to nondetectable levels by Day 5. Both triadimefon and MCPP dislodgeable residues were greatest on Day 1 following application and dissipated over time. By Day 5, triadimefon dislodgeable residues decreased to 0.04% of the initial residue level immediately following application and MCPP dislodgeable residues were nondetectable. Inhalation and dermal exposures to humans were estimated from measured air concentrations and dislodgeable residues, respectively. Hazard quotients (HQs) were calculated for both volatile and dislodgeable residues of each pesticide. Exposures (i.e., doses) divided by reference doses (Rfds) resulted in hazard quotients (HQs). Triadimefon and MCPP volatile and dislodgeable residues resulted in HQs below 1.0 throughout the entire 15‐d experimental period indicating that exposures were below any level expected to cause adverse health effects.