Introduction

The development of a numerical modeling tool for the soil fumigant 1,3-dichloropropene (1,3-D) started several decades ago using the Industrial Source Complex Short Term (ISCST3) air dispersion model. 1 Early work was extended by incorporating a soil fate modeling tool, the Pesticide Root Zone Model (PRZM3), to simulate the source strength used in ISCST3 air dispersion calculations. 2 This initial work was the forerunner of the SOil Fumigant Exposure Assessment (SOFEA) modeling system, a stochastic numerical modeling tool developed by Dow AgroSciences as a regulatory tool to evaluate and manage human inhalation exposure potential associated with the use of soil fumigants and other semi-volatile or volatile compounds.

The original SOFEA model was first described in 2005 3 in addressing the need to model chemical concentrations in ambient air in basins spanning several California townships and assess long-term human inhalation exposures and potential human health risks associated with 1,3-D. Originally a pre- and post-processor for the ISCST3 air dispersion model, SOFEA was updated in 2016 to incorporate the AMS/EPA Regulatory Model (AERMOD). SOFEA allows users to probabilistically generate input files using over 20 discrete and continuous probability distributions for input parameters, and it provides graphical tools for analyzing weather data, creating flux profiles, importing source geometry from Geographic Information System (GIS) data, generating receptors using computational geometry methods, and high-performance post-processing of results using the NetCDF scientific data format incorporated directly into AERMOD.

SOFEA has exceptional attributes and functionality compared to other similar modeling tools for addressing the exposure and risk from the use of volatile (or semi-volatile) pesticides. In a collaborative effort between Dow AgroSciences and Exponent, Inc. (an Engineering and Scientific Consulting company), SOFEA was upgraded to modern software engineering standards, and a new graphical interface was developed with C++ and Qt to provide users an Integrated Development Environment (IDE)-like experience in creating new simulation projects. Summary statistics, moving averages, and quantiles can be calculated efficiently over millions of data points, comprising hourly concentrations over several years and thousands of receptors.

Multiple publications using SOFEA have been documented since SOFEA was first developed. 4 5 6 7 8

References

1

Cryer SA, van Wesenbeeck IJ. Predicted 1,3-dichloropropene air concentrations resulting from tree and vine applications in California. Journal of Environmental Quality. 2001;20:1887-1895

2

Cryer SA, van Wesenbeeck IJ, Knuteson JA. Predicting regional emissions and near-field air concentrations of soil fumigants using modest numerical algorithms: A case study using 1,3-dichloropropene. Journal of Agricultural and Food Chemistry. 2003;51:3401-3409

3

Cryer SA. Predicting soil fumigant acute, sub-chronic, and chronic air concentrations under diverse agronomic practices. Journal of Environmental Quality. 2005;34:2197-2207

4

de Cirugeda Helle O, van Wesenbeeck IJ, Cryer SA. SOFEA modeling of 1,3-Dichloropropene concentrations in ambient air in high fumigant use areas of the United States. American Chemical Society (ACS). 255th National meeting. Boston, MA. August 19-23, 2018

5

USEPA Agency Scientific Advisory Panel 2004. Fumigant Bystander Exposure Model Review: Soil Fumigant Exposure Assessment System (SOFEA) Using Telone as a Case Study. Available from: https://archive.epa.gov/scipoly/ sap/meetings/web/html/090904_mtg. html [Accessed: September 10, 2004]

6

Cryer SA, van Wesenbeeck IJ. Coupling field observations, soil modeling, and air dispersion algorithms to estimate 1,3-dichloropropene and chloropicrin flux and exposure. Journal of Environmental Quality. 2011;2011(40):1450-1461. (Invited Paper for Special Submissions: Agricultural Air Quality)

7

van Wesenbeeck IJ, Cryer SA, de Cirugeda Helle O, Li C, Driver J. Comparison of regional air dispersion simulation and ambient air monitoring data for the soil fumigant 1,3-dichloropropene. Science of the Total Environment. 2016:569-570 603-610

8

van Wesenbeeck IJ, Cryer SA, Havens PL, Houtman BA. Use of SOFEA to predict 1,3-D concentrations in air in high use regions of California. Journal of Environmental Quality. 2011;40:1462-1469