Estimating Sulfuryl Fluoride Emissions During Structural Fumigation of Residential Houses

The California Department of Pesticide Regulation conducted indoor air monitoring to estimate sulfury fluoride (SO2F2) emissions that bystanders around fumigated houses were potentially exposed to during structural fumigation of residential houses. Monitoring was conducted for 23 fumigations between September 2014 and March 2015. The SO2F2 indoor concentrations were measured from four locations inside the fumigated houses once an hour. The decreases of indoor concentrations are due to gas leakage (treatment period) and aeration (aeration period) from the structure to the outdoor environment. Analysis on the monitoring data showed considerable variability of half loss time (11-60h) and mass loss (22-81%) during treatment periods. The decline of indoor concentrations followed the first-order kinetics; therefore, the hourly flux (g/m(2)s) of a treatment period can be calculated using initial SO2F2 concentration, treatment period mass loss, and house height. Although the California Aeration Plan requires a minimum 12-24h of aeration after a treatment, the monitoring data showed that 93 +/- 5% of the mass at the end of the treatment periods was emitted through the ducting system within the first 2h. The average ratio of the loss amount in the first hour to the loss in the second was 6:1. These monitoring results provided the critical input for the computer modeling to estimate bystander exposure during structural fumigations of residential houses.