Correlating Agricultural Use with Ambient Air Concentrations of Methyl Isothiocyanate During the Period of 2011–2014
Abstract
In February 2011, as part of the Department of Pesticide Regulation’s (DPR) mandate for continuous evaluation of currently registered pesticides, DPR implemented an Air Monitoring Network (AMN) for measuring pesticides in three agricultural communities. The AMN monitors for 32 pesticides, including methyl isothiocyanate (MITC), on a weekly basis. In this report, we explored the relationship between AMN-measured ambient MITC concentrations and reported use in each of the three AMN sampling locations during the period of 2011-2014. The spatial distribution of MITC-producing pesticide applications and local meteorological parameters were analyzed as part of this work.
Results showed that all three AMN sites possess unique detection-use profiles. Data showed that ambient MITC concentrations were not statistically correlated to the weekly use applied within 5 miles of the AMN sampling sites. Furthermore, detections of MITC during weeks without any reported use, particularly in Salinas and Shafter, could indicate that some number of detections may have occurred from MITC applications made further than 5 miles from the sampling sites. The data also suggests that methods of fumigant application which are designed to mitigate off-site movement of MITC and local weather at the time of application may have influenced the quantity of positive MITC detections.