Drywood termites and other wood-destroying insects can cause significantdamage as they feed on materials con-taining cellulose found in structures, suchas wood, paper, texti les, furnishings, andworks of art. Because these insects l ivemost of their l i fe cycle within their foodsource. the exact distribution and extent ofinfestation is often diff icult to determine.Therefore. localized treatments usingphysical methods or conventional insecti-cides may not eradicate all wood-destroy-ing insects infesting a structure. To solvethis problem The Dow Chemical Companydeveloped sulfuryl f luoride, the activeingredient of Vikane. gas fumigant, to beused exclusively by professional fumiga-tors (DowElanco 1992). '

Research conducted during the develop-ment of sulfuryl f luoride demonstrated thatthis fumigant possesses highly desirablecharacteristics for the eradicatron of struc-ture-infesting insects (Derrick et al. 1990).Sulfuryl f luoride is nonflammable, non-cor-rosive. and does not cause undesirableodors. It quickly penetrates structural mate-rials, is effective against a variety of struc-tural pests, and dissipates rapidly duringaeration (Kenaga 1957; Stewart 1957).Since f irst marketed as Vikane in 1961 ,sulfuryl f luoride has been used to fumigatemore than one mi l l ion bui ld ings, inc ludingmuseums, historical landmarks, such asthe Hearst Castle in California (PestControl 1977) and the Flagler Museum inFlorida (Moon 198'l ), rare book l ibraries,government archives, scientif ic and med-ical research laboratories. and food-han-dling facil i t ies.

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Vikane has been demonstrated to reduceoxygen uptake in insect eggs (Outram'l 970). Vikane also prevents insects f rommetabolizing the stored fats they need tomaintain a sufficient source of energy forsurvival by disrupting the glycolysis cycle(Meik le et a l . 1963). This metabol ic imbal-ance may delay mortality of insects forseveral days or more following fumigation(Osbr ink et a l . 1987). For th is reason,insects that have received a lethal exoo-sure to Vikane may sti l l be alive immedi-ately following fumigation.The activity of Vikane depends on the con-centration reaching the target pest and theduration of exposure. Therefore, thedosage of Vikane required for a specifictarget pest is calculated in "ounce-hours,"ounces of Vikane multiplied by hours ofexposure. Insect eggs require a higherounce-hour dosage of Vikane compared tolater life stages. Control of the egg stage ofsocial insects, such as termites and ants, isnot necessary because newly hatched ter-mites and ants cannot survive without adultcare.Higher dosages required to control eggsof insects, such as wood-boring beetles,can be obtained by increasrng the expo-sure time, increasing the concentration ofVikane, or a combination of both.Fumigators use the Fumiguide- calcula-tion system, which was developed specifi-cally for Vikane, to determine the amountof Vikane requrred for specific pests andfumigation conditions.Vikane has also been successfully usedsince 1961 to control a wide variety ofhousehold pests, including cockroaches,clothes moths, rodents, bedbugs and car-pet beetles. The eradication of eggs ofcarpet beetles requires very high dosagesof Vikane (Su and Scheffrahn 1990)which are not economically practical.Therefore, two fumigations are required toeradicate carpet beetles using Vikane.The second fumigation is conducted afterall beetle larvae have hatched from eggssurv iv ino the f i rs t fumioat ion.

Sulfuryl f luoride, the active ingredient ofVikane, is a gas at temperatures above-67"F. Vikane is packaged in white cylin-ders as a l iquid under pressure, containing99.5% sulfuryl f luoride with no other pesti-cides, solvents or additives. Vikane has ahigh vapor pressure; it evaporates 20,000times more readily than mothballs andtherefore disperses rapidly from structures.Vikane does not react with commonhousehold furnishings. This is why fumiga-tion with Vikane is an established methodused to eradicate pests infesting delicateand rare biological and historical museumartifacts. Food must be protected fromexposure to Vikane during fumigationbecause no residue tolerances have beenset for any food product (see PREPARA-TION). Vikane does not form toxic surfaceresidues in household rtems, and thusdishes, clothes, and other items do notneed to be washed followino fumioationwith Vikane.Watering soil around exterior perimeterbuilding foundations is recommended toreduce both loss of fumigant through thesoil and exoosure of olant roots to Vikaneduring fumigation. The solubil ity of sulfurylf luoride in water is very low, 0.075% byweight at 77"F (Meikle and Stewart 1962).Vikane is nonflammable and relatively sta-ble; however, it wil l react to form hydrogenfluoride at extremely high temperaturesexceeding 752'F. This acid can etch met-als, glass, ceramic ti le, or china near theheat source. Thus, prior to structural fumi-gation, all open tlames and glowing heat f i l-aments are turned off or disconnected.Vikane is odorless at concentrations usedto fumigate structures and is not irritatingas a gas to the eyes or skin. For these rea-sons, a trace amount of the warning agent,chlorooicrin. is introduced in the structureprior to fumigation to warn people and ani-mals that the structure is being fumigated.Chloropicrin acts as a warning by causingirritation of the eyes, tears, discomfort, andhas a noticeable disagreeable pungentodor even at very low concentrations, lessthan 1 paft per mill ion (ppm).

Chloropicrin diffuses from structures moreslowly than Vikane. Thus, occupants mayexperience some eye irritation after all ofthe Vikane has aerated from the structure.The fumigator should be contacted to takeremedial measures if this occurs. A trainedfumigator wil l use an approved clearancedevice, such as an Interscanl or Miran2, todetermine that the concentration of Vikanewithin the structure is 5 ppm or less prior toallowing anyone to reoccupy the structure.

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The label for Vikane requires that the follow-ing preparations be completed prior toreleasing the fumigant into the structure.1. Al l an imals ( inc luding f ish) and p lants

must be removed from the structure toho { r rmina lo r i

2. Mattresses and pil lows completelyenveloped in water-proof covers (notincluding waterbeds) must be removedfrom the area to be fumigated if thecovers can not be removed. Thewater-proof covers restrict dispersionof fumigant dur ing aerat ion.

3. All f lames such as pilot l ights and elec-tric heating elements must be turnedoff for reasons previously described3.

4. The fo l lowing should be opened pr iorto fumigation: internal doors, rnternalopenings to attics and sub-areas, stor-age chests, cabinets, drawers, closets,and appliances such as washers, dry-ers and ovens. In tarpaul in fumiga-tions, operable windows are opened.These procedures assist in rapid dis-pers ion of Vikane dur ing fumigat ionand aeration.

5. Food, feed, drugs and medic inals ,including items in refrigerators andfreezers, must be removed from thefumigat ion s i te or sealed in h ighlyresistant containers such as glass,metal or plastic or enclosed in specialbags according to label directions.

This is required because exposure ofunprotected foodstuffs to Vikane mayresult in the formation of temporary sul-furyl f luoride residues and permanentfluoride residues. However, experimen-tal exposure of food commodities pro-tected in tvvo nylon bags to 10xdosages of Vikane resulted in nodetectable sulfuryl fluoride or added flu-oride residues. Two nylon bagsreduced the exposure of protectedfoodstuffs to Vikane by 99.99%(Scheffrahn et al. 1990). Excessiveexposure to fluoride can have toxico-logically significant effects, althoughlongterm human intake of water con-taining up to 1 mg/l (1 ppm) fluoride isgenerally considered not to result inadverse effects. (National ResearchCounci l 1977).

Because of a multitude of structural. envi-ronmental, and fumigation variations,there are no two fumigation jobs that areidentical. The required dosage of Vikaneis influenced by the temperature at thesite of the pest, the length of the exposureperiod and the susceptibil i ty of the pest tobe controlled. Consequently, the dosagesvary, but the typ ical s ingle fami ly homefumigat ion involves the use of 6-16ounces/1000 cubic f t (1440-3850 ppm).The length of the exposure period is crit i-ca l to accumulate suf f ic ient ounce-hoursarequired for the temperature at the site ofthe pest . The ounce-hours requi red tocontrol target insect pests have beendetermined from laboratorv and field test-ing

Five to ten minutes pr ior to in t roducingVikane into the st ructure, the fumigatorwi l l p lace a warning agent . ch loropicr in , inthe st ructure. This warning agent isrequired to warn any person or animalthat may have entered the structure afterthe final inspection by the fumigator. Oncethe building is determined to be cleared ofa l l people and anrmals, the fumigator wi l lrelease the Vikane into the structure.Vikane is packaged in 125 lb. cy l indersthat fumigators transpon on their vehicles.The fumigator introduces Vikane throughtubing into the air stream of a fan thathelps d isperse the fumigant throughoutthe structure. Once the appropriateamount of Vikane is introduced. the fumi-gator turns off the cylinder valve andremoves the tubing from the cylinder.

Vikane is usually held in the structure forapproximately 16-30 hours. Fumigat iontime is deoendent uoon the factors men-tioned previouslys. When the fumigationexposure period is complete, the fumiga-tor wil l return to the structure to conductthe aeration procedure.

Aeration is the final step of a fumigation.Aeration involves orooer ventilation andclearance of Vikane and the warningagent , ch loropicr in , f rom a st ructure.The Occupational, Safety & HealthAdministration (OSHA) established aPermiss ib le Exposure Level (PEL) of 5par ts per mi l l ion (ppm) for Vikane. A PELis the Time Weighted Average (TWA)exDosure to which it is believed that mostmembers of a healthy working populationcan be exposed 40 hours/week for awork ing l i fe t ime.The fumigator must aerate a structure sothat the concentration of Vikane in the airis 5 ppm or less pr ior to a l lowing reentry.This 5 ppm PEL is substant ia l ly lowerthan the level that may affect people andpets following even long-term exposure.Unl ike l iqu id and sol id insect ic ides,Vikane is a gas possessing a very highvapor pressure (potential to escape froman area) and low boil ing point (it is a gasabove -67"F). During aeration of the fumi-gated structure, Vikane wil l quickly diffusefrom high concentrations within a struc-ture to the outside air where it rapidly dis-sioates to nondetectable levels.Degassing is the process of fumigant dif-

fusing out of materials when the concen-tration of gas is less around the obleclthan within the object. Required aerationprocedures a l low the fumigant t ime to d i f -fuse from structural voids and householdmaterials and be ventilated out of thestructure. The fumigator wil l use powerfulfans and open cabinets, doors, and win-dows to speed the process of aeration.Many structures have been tested by uni-versity researchers and DowElanco'sci-entists with the goal of developing newaeration procedures. The aeration proce-dures have been vigorously tested toensure that even under ooor ventilationconditions concentrations of Vikane wil lnot increase after occuoants return.Only specially trained and state-l icensedicertif ied orofessionals can deter-mine that a structure can be reoccuoied.Unique equipment, such as the Interscanand Miran, must be used to test the con-centrations of Vikane within structures.The Interscan is specially designed todetect levels of Vikane down to 1 oom.

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When Vikane is aerated from a structureit rapidly dissipates into the atmospherebecause of its high vapor pressure.Vikane is broken down mainly throughhydrolysis to release fluoride and fluoro-sulphate ions. Ultraviolet radiation andreactions with solid particles in the atmos-phere may also catalyze the breakdownof Vikane.

The re lat ive ly smal l amounts of Vikanereleased are calculated to have virtuallyno impact on global atmosphere/environ-ment . Sul fury l f luor ide is fu l ly ox id ized,and thus is not expected to interact orcontribute to local ozone formation (suchas Los Angeles smog) because of its lowreactivity in the atmosphere. The relativecontr ibut ion of Vikane to ac id ra in is in f i -nitely small compared to the massrveamount of sulfur released into the atmos-phere from industry. Vikane contains nochlor ine or bromine and thus can notreact to deplete stratospheric ozone bythe known mechanisms (Bai ley 1992).

The severity of toxicological effects isdependent on the exoosure concentrationand exposure duration. The mode ofaction by which Vikane produces its toxic-ity in humans depends on the exposureconcentration. In general, the effects ofoverexposure to high concentrations arecentral nervous system depression andrespiratory irritation followed by pul-monary edema, which is the accumulationof f lu ids in the lungs and can resul t indeath. Humans exposed to high concen-trations of Vikane may expect to experi-ence symptoms s imi lar to drunkenness.Speech and movements may be slowed,and fingers, hands, and toes may becomenumb.Animal studies may indicate that some sul-furyl fluoride is converted to fluoride ion inthe body. Chronic exposure may result influoride binding to the teeth and bones,causing fluorosis, which is manifested asmottled teeth.Applicators who work with Vikane canhave their urine checked for f luoride.However, high fluoride levels in the urinecould be due to chemicals other than sul-furyl f luoride, for example, f luorides indrinking water, f luorinated tooth paste, andsome medicines.

Another factor to be considered in the safeuse of Vikane is the length of t ime in whicha person might have "escape capabil ity"during exposure to high levels of Vikane.Researchers have investigated this bydetermining the length of t ime that rats areable to maintain coordinated activity whenexposed to very high concentrations ofVikane. The time to incapacrtation of labo-ratory rats for various exposure concentra-tions were (Nitschke et al. 1986):

42 minutes at 4,000 ppm16 minutes at 10,000 ppm10 minutes at 20,000 ppm6 minutes at 40,000 ppm

Exoosures were terminated when inca-pacitation occurred. All rats died or weremor ibund wi th in 3 hours fo l lowing the endof exposure. Theretore, the above expo-sures can be considered to oroduce100'2" mortality in rats. For comparison.typical init ial concentrations in single fami-ly homes are 1440-3850 ppm and mustbe reduced to 5 oom or less beforehumans can enter dwel l inqs wi thout resoi -ratory protection.

lManufactured by Interscan Corporation, Chatsworth, CA 9131 12Manufactured by The Foxboro Company, East Bridgewater, MA 02333 I3See the Section on FORMULATION AND PROPERTIESaSee the section on EFFICACY5See the secl ion on Vikane FUMIGANT DOSAGE DETERMINATjON

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RepeatedExposureToxicity Studies Offspring

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Rats, rabbits, and dogs have been stud-ied lollowing daily repeated exposures toVikane. Exposures of 30 ppm 6hours/day, 5 days/week for 13 weeks hadno etfects on rats or rabbits, while dogsshowed no effects from 100 ppm in a sim-ilar exposure regimen. Rats exposed to300 ppm had decreased body weights,mottled teeth, and microscopic evidenceof brain and kidney injury and respiratoryirritation. Rabbits exposed to 100 or 300ppm showed decreased body weightsand microscopic changes in brain andnasal tissues. Dogs exposed to 200 ppmshowed nervous system effects, includingmicroscopic changes in the brain.

Mutagenicity StudiesVikane has been tested in a battery ofmutagenicity tests that serve as a screenfor identifying chemicals that affect genet-ic mechanisms. All test results have beennegative, indicating that Vikane is notmutagenic in standard testing. Lifetimestudies in which rats and mice wereexposed to Vikane to assess whether ornot the chemical has potential to causecancer were also negative.

Neurological EffectsRats exposed for 6 hours a day for 2 daysto 100 ppm and 300 ppm showed nosigns of neurotoxicity.

Other Routes OfExposure To VikaneInhalation is the primary route of exposureto Vikane. lngestion is highly unlikelysince the material is a gas at tempera-tures higher than -67"F. Laboratory ani-mals maintained for 66 days on feeddirectly fumigated at 2lbl1000 cubic ft(7700 ppm) showed no adverse effects.Typical structural fumigation concentra-tions are 1 lb/1000 cubic ft (3850 ppm) orless. Feed exposed to abnormally highapplication rates (10-200 lb/1000 cubic ft;38,500 to 770,000 ppm) and fed to testanimals caused decreased body weightgains and fluorosis of the teeth. The gasis not absorbed through the skin in acute-ly toxic amounts; rats exposed dermallyfor 4 hours to concentrations of 9599 ppmdid not show evidence of toxicitv.

Studies For EffectsOn ReproductionAnd Development Of Carcinogenicity And

The results of the studies described hereindicate that Vikane is not likely to haveany effects on reproduction or develop-ment of offspring. Groups of pregnant ratsand rabbits were exposed to Vikane atthree different concentrations: 25, 75, or225 ppm for 6 hours/day during themajority of the gestaiion period. Althoughthe highest level of 225 ppm was toxic tothe maternal animals (as would beexpected), there was no evidence thatVikane was teratogenic (causing birthdefects in otfspring of exposed females).The only effects on the felus werereduced body weights in the rabbits at thehighest level, probably associated withthe maternal weight loss. In a reproduc-tion study, male and female,rats wereexposed to concentrations of 5, 20, or150 ppm throughout two generations.The highest level of 150 ppm was toxic tothe parent animals, producing effects sim-ilar to those seen in the 13-week studydescribed in the preceding section. Parentanimals exposed to 5 ppm were withoutevidence of effects. Decreased weights ofthe offspring were observed at 150 ppmthat may have been secondary todecreased maternal growth. The onlyeffect observed at 20 ppm was mild lungirritation in parental rats, with no evidenceof toxicity in offspring. There were noeffects on reproductive performance inany exposure group.

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REFERENCES

Bailey, R. 1992. Sulfluryl f luoride: Fate in the atmosphere. Dow Chemical Company.DECO-ES Report 2511. Midland, Michigan.Derrick, M. R., H. D. Burgess, M. T. Baker, and N. E. Binnie. 1990. Sulfurylf luoride(Vikane-): A review of its use as a fumigant. JAIC 29: 77-90.

DowElancoJ 1992. Fumigation manual for Vikane gas fumigant. DowElanco,'Indianapolis. Indiana,Kenaga, E, E. 1957. Some biological, chemical, and physical properties of sulfurylf luoride as an insecticidal fumigant. J. Econ. Entomol. 50: 1-6.Meikle, R^ W., D. Stewart, and O. A. Globus. 1963. Drywood termite metabolism ofVikane gas fumigant as shown by labeled pool technique. J. Agric. Food Chem. 11:226-230Meikle, R. W. and D. Stewart. 1962. Structural fumigants, the residue potential ofsulfuryl f luoride, methyl bromide, and methane-sulfonyl f luoride in structural fumiga-tions. J. Ag. and Food Chem. 12:464-467.

Moon, B. L. 1981 . Vikane gas helps save the Taj Mahal of North America. Ind. Veg.Pest Management. 13(1) : 12-15.

National Research Council. Drinking Water and Health, 1977. National Academy ofSciences, Washington, D.C.Nitschke, K, D., R. R. Albee, J. L. Mattsson, and R. R. Miller. 1986" Incapacitationand treatment of rats exposed to a lethal dose of sulfuryl fluoride. Fund. and Appl.Tox. 7: 664-670.Outram, l. 'l 970. Some effects of the fumigant sulphuryl fluoride on the gross metab-olism of insect eggs. Fluoride 3: 85-91Osbrink, W. L^ A^, R. H. Scheffrahn, N.-Y. Su, and M. K. Rust. 1987. Laboratorycomparisons of sulfuryl fluoride toxicity and mean time of mortality among ten termitespecies (lsoptera: Hodotermitidae, Kalotermitidae, Rhinotermitidae). J. Econ.Entomol. 80:1Q44-1O47Pest Control. 1977. Dewey defends Hearst Castle against lyctus beetles. PestControl 45(6): 30, 31, 48.

Scheffrahn, R. H., R.-C. Hsu, and N.-Y. Su. 1990. Evaluation of polymer fi lm enclo-sures as protective barriers for commodities from exposure to structural fumigants. J.Agric. Food Chem. 38;904-908.Stewart, D. 1957. Sulfuryl fluoride - A new fumigant for control of the Drywood ter-mite Kalotermes minor Hagen. J. Econ. Entomol. 50: 7-11.Su, N.-Y. and R. H. Scheffrahn. 1990. Efficacy of sulfuryl fluoride against four beetlepests of museums (Coleoptera: Dermestidae, Anobiidae). J. Econ, Entomol. 83: 879-882.

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