SULFURYL FLUORIDE (VIKANE): A REVIEW OF ITS USE AS A FUMIGANT
MICHELE R. DERRICK, HELEN D. BURGESS, MARY T. BAKER, & NANCY E. BINNIE
VIKANE IS an odorless, colorless gas that is not irritating to the eyes or skin. This inability to cause human sensory recognition is dangerous since sulfuryl fluoride can be lethal to humans in a single exposure to normal fumigation concentrations of Vikane in air (Dow Chemical Co. 1989). For safety reasons, Dow recommends that trace amounts of chloropicrin, a highly acrid, lachrymal gas, be released in the structure prior to fumigation as a warning agent. (The effect of chloropicrin on museum materials is not known. Thus, when possible, artifacts should be treated in a safe manner that does not require the presence of chloropicrin.) Since Vikane, in liquid and gaseous form, is not absorbed through the skin, the most likely route of exposure and overexposure is inhalation. The lethal dose by inhalation (LC50) for rats is in the range of 1000-4000 ppm for 1-4-hour exposures (Dow Chemical Co. 1989; Nitschke et al. 1986). Rats and rabbits exposed to 100 ppm of sulfuryl fluoride for 6 hours per day, 5 days per week for 13 weeks had mottled teeth and slightly diminished sensory functions, while animals exposed to 30 ppm exhibited no treatment effects (Mattson et al. 1988; Eisenbrandt and Nitschke 1989).
Some deaths have been attributed to sulfuryl fluoride. In two cases, individuals, despite numerous warning signs, entered tented houses during the Vikane containment period. Both inhaled lethal doses of the fumigant. Autopsies revealed higher than normal levels of fluoride in both the plasma and urine (Scheuerman 1986). Another case was reported recently in Art Hazards News(McCann 1987) in which an elderly couple died after returning to their house, which had been fumigated with sulfuryl fluoride, aerated, and certified safe for reentry (Morbidity and Mortality Weekly Report 1987). Although autopsy information was lacking and the death profiles were atypical for sulfuryl fluoride, the exterminator in the case was held liable for the deaths because the recommended procedures for Vikane fumigation, such as checking the fumigant concentration with proper instrumentation prior to permitting the occupant to enter, were not followed (New York Times 1988).
The recommended exposure levels are 5 ppm TLV (maximum exposure for 8 hours a day, 5 days a week) and 10 ppm STEL (maximum short term exposure limit) (Dow Chemical Co. 1989). Overexposure may cause abdominal pains, nausea, vomiting, convulsions, or chemical pneumonia. Some possible chronic effects from exposure are lung and kidney damage, central nervous system damage, and teeth and bone defects from fluorosis. Vikane was found to be teratogenic in animals only when it reached levels at which the mother was injured or killed. Serious long-term mutagenic, carcinogenic, and reproduction effects of sulfuryl fluoride are unknown. Using animals, sulfuryl fluoride was shown to be one-half to one-third as toxic as methyl bromide (Torkelson, Hoyle, and Rowe 1966).
No studies have investigated the long-term exposure effects of Vikane on humans. However, one study, on the effects of methyl bromide on the neurobehavioral functions of professional fumigators, selected as a control group some fumigators who solely used sulfuryl fluoride (Anger et al. 1986). This study found that the group consistently using Vikane had both higher sensitivity levels and higher cognitive performances than the group using methyl bromide. However, all fumigators tested exhibited some slower responses than another control group that contained people who were not exposed to fumigants. Overall, the size of the study group for sulfuryl fluoride was too small to allow investigators to draw statistically significant conclusions on the long-term effects on humans of using Vikane fumigant.