Indoor Airborne Residues of Methyl Bromide and Sulfuryl Fluoride Following Aeration of Fumigated Houses

Abstract

Residual airborne concentrations of methyl bromide (MB) were measured in 10 houses after fumigation with MB at a mean exposure of 53, 369 ppm. hr to control drywood termites. Sulfuryl fluoride (SF) residues were measured in 10 and 3 houses after SF fumigation at 59,161 and 33,531 ppm. hr, respectively. Prior to sampling, all 23 houses were aerated to MB and SF threshold limit values (TLVs) of 5 ppm following label-directed procedures. Immediately following aeration, doors and windows of houses were closed and ventilation system deactivated. During this initial 2-h closure period, the mean concentration among MB-fumigated houses increased to 17.5 ppm MB at 90 min with room means of all 10 MB houses exceeding TLV. Residue means at 120 min among SF-fumigated houses were 4.6 and 5.0 ppm SF with 3 and 2 houses exceeding TLV for the high and low SF exposures, respectively. After a second aeration and closure, levels exceeded TLV in 5 of 6 MB houses monitored during this period, but not in any of the 9 SF houses sampled. Post-aeration residues tended to be higher in bedrooms and bathrooms. Because of the excessive transient desorption and diffusion of both fumigants revealed by this study, modified aeration procedures are needed to ensure that occupant exposure levels do not exceed safety standards.