Environ. Sci. Techno/. 1995, 29, 673-676
Simulated Air levels of Volatile Organic Compounds followinsDaerent Methods of Indoor Insecticide Application J O H N A . B U K O W S K I * AND LEROY W. MEYER New lersey Department of Environmental Protection, Pesticide Control Program, 380 Scotch Road, CN 411, Trenton, New Jersey 08625-0411
Many general health complaints that may be attributed to indoor insecticide exposure are also consistent with exposure to the volatile organic compounds (VOCs) used as inert ingredients in insecticidal formulations. However, f e w indoor insecticide labels make ventilation or reentry recommendations that would help to limit exposure to these compounds. The Indoor Air Quality Model developed by the U.S. EPA was used to simulate potential VOC air levels following hypothetical indoor application of emulsifiable concentrate (EC), broadcast aerosol, and aerosol fogger formulations. Estimated VOC levels were highest for foggers and lowest for EC sprays (peak concentrations of 328 and 20.5 mg/m3, respectively). However, all three application methods produced indoor air levels that were in the range of values expected to produce health complaints among certain individuals. Three hours of enhanced ventilation decreased air levels by as much as 75-80%. However, enhanced ventilation was most effective when vigorously applied immediately after application.
Background and Significance Indoor pesticides are typically applied as 0.5-5% solutions of active ingredient, with the remaining 95-99.5% of the solution consisting of water and inert ingredients. These inerts include emulsifiers, organicsolvents, and propellants. The term “inert” indicates that these ingredients have no pesticidal properties, not that they are nonreactive or without potential health effects. Various public and governmental organizations have voiced concern over the potential health effects of the inert ingredients used in pesticides. The U.S. EPA initially identified 50 inerts of toxicologic concern and later developed a toxicity categorization system for inerts. The EPA also instituted a policy requiring manufacturers to either replace targeted toxic inerts with less hazardous ones or print hazard warnings on product labels. (1-3). Many indoor formulations, especially emulsifiable concentrate (EC) sprays, include a mixture of eight- and ninecarbon solvents such as xylene, mesitylene, methyl ethyl benzene, and cumene ( 4 ) . Some aerosol sprays are over 45% kerosene and other solvents (5). These volatile organic compounds have vapor pressures that are much higher than those of the active agents. Therefore, there is a much greater potential for acute airborne exposure to these constituents than to the active ingredients following indoor applications. However, few indoor product labels contain recommendations or requirements regarding reentry times or enhanced ventilation to reduce exposure to either VOCs or active ingredients. Many of the general symptoms attributed to indoor pesticides (i.e., headache, irritation, nausea, tightness in the chest, etc.) are also compatible with solvent exposure (6‘). Volatile organics also contribute to a perception of poor air quality. The odor and/or irritant properties of VOCs may trigger a variety of reactions ranging from mild annoyance to a disabling symptom complex frequently referred to as “multiple chemical sensitivity” (7). Little information is available on the air levels of VOCs following pesticide applications. Maddy et al. reported ethylene glycol monoethyl ether concentrations of approximately 10 mg/m3 in a nonventilated apartment 1 h after broadcast application of Safrotin. No levels were detected inventilated rooms, although the level of detection was only 2-4 mg/m3 (8). Mulrennan et al. failed to detect any methylene chloride or trichloroethylene following a crack and crevice application of Baygon aboard a submarine. However, the level of detection in that study was approximately 80-130 mg/m3 (9). This paper models the levels of volatile organics that could be expected over time following hypothetical indoor applicationswithaerosolor emulsifiable concentrate sprays. The effects of different ventilation rates are also examined. This is intended to examine the generalmagnitude of indoor VOC pollution associated with these applications and to determine if the estimated levels are in the range of values that could be expected to result in health complaints.
Methods The Indoor Air Quality (IAQ) Model developed by the U S . EPA was used to simulate solvent air levels over time (10). This model assumes a seven-room test house with a total
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air volume of 293 m3, 122 m2 of living area, and 100 m of interior perimeter distance. The default parameters associated with the model are those that have been studied by the EPA using this seven-room test house. Since these represent the actual conditions in the test house, they were used whenever possible. The default settings that allow for a total of 12 chemical sinks, one to two per room, were unchanged for the simulations. The default high volume air conditioning ( W A C ) system characteristics were also unchanged. Four interior insecticide application techniques were simulated. These were perimeter (crack and crevice) application using an emulsifiable concentrate (EC) spray, broadcast (totalsurface area) application using an EC spray, broadcast application using an aerosol spray, and fogging (total-release aerosol application). In each case, it was assumed that the entire perimeter distance, surface area, or volume was treated. There are literally thousands of products available for indoor application, and it would be impossible to adequately address them all. For the purposes of the simulations, commonly used, commercially available products were selected as representative of those typically used for indoor applications. The formulation chosen to represent emulsifiable concentrate (EC) applications was a commonly used chlorpyrifos product that is available as a 40-mL concentrate containing 41% active ingredients (59%inert ingredients). This is diluted to a 0.5% pesticide spray by the addition of 1 gal of water. Approximately 0.69 gal of finished spray would be needed to treat the entire 122 m2of the test house via broadcast application. This represents approximately 16 g of inert ingredients. The above formulation was also selected for the hypothetical perimeter treatment. The total amount of inert ingredients deposited via perimeter application was estimated from an article by Wright and Leidy (11). These investigators estimated that a 14.6-mperimeter application of a 0.5% chlorpyrifos spray to a dormitory room deposited an average of 2 g chlorpyrifos. Assuming that the concentrate formulation was 59% inert, this represents approximately 2.9 g of inert ingredients. A similar application to the entire EPA test house would deposit approximately 20 g of inerts. Since this is very similar to the 16 g deposited by the broadcast spray, 20 g was used to represent both perimeter and broadcast application methods. A commercially available flea premise spray was chosen to represent aerosol broadcast applications. This product contains greater than 99% inert ingredients and is typical of most indoor aerosols, which usually contain 95-99.5% inerts. One can of this product contains approximately 450 g of inert ingredients and treats approximately222 m2. Treatment of the EPA test house would release approximately 240 g of inert ingredients. A commercially available flea fogger was chosen to represent total-release aerosol applications. One can of this product (approximately 335 g of inert ingredients), which treats up to 10 000 ft3 (370 m3),would be needed to treat the entire EPA test house. The EPA model calculates an emission rate (ER) for the source that is equal to Roe-krs,where Ro is the emission rate at time 0 (in mg/h), k is the decay constant, tis time, and s is the size of the source (10). This model is typically used to examine more complicated exposures from solid or semisolid sources (wax,polishes, painted surfaces, treated fabric, wood paneling, etc.)that degas VOCs gradually over 074
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time. The model parameters were simplified in order to address the indoor application scenario, which assumes an even layer of liquid material that releases VOCs rapidly to the air. For the purposes of this study, it was assumed that the inert ingredients consisted wholly of VOCs. Since volatile organics will vaporize rapidly, the decay constant ( k ) for the model was set at 1.2 to force all the inerts to vapor over a several hour period. The total amount of chemical liberated indoors was controlled by altering the initial emission rate (Ro). The ROfor the EC spraywas set at 25 000 and resulted in the estimated release of 19.4g ofVOCs.The Ro’s for the aerosol applications were set at 300 000 for the broadcast spray and at 400 000 for the fogger, so as to liberate 235 and 314 g of VOCs, respectively. The IAQ model allows the pollutant sources to be placed in different rooms. As a simplifylng assumption for this investigation, half of the total amount of calculated VOCs was placed in the den (thelargest room),and the remainder was equally divided among the three bedrooms. Air level estimates were calculated at 1 h intervals for each application method. Levels in the different rooms were similar, so only air concentrations in the den (room 1)were recorded. The simulations were performed under three levels of ventilation. The baseline ventilation rate was set at 0.5 air changes per hour (ACH),which is similar to the model default of 0.4 ACH. To approximate passive ventilation, such as open doors and windows,the ventilation rate was arbitrarily doubled to 1 ACH. Active ventilation, such as exhaust fans, was approximated by doubling the ventilation rate yet again to 2 ACH. Enhanced ventilation for the emulsifiableconcentrate and aerosol broadcast spray situations was assumed to begin immediately after application and to continue for 3 h. Enhanced ventilation for fogging ran for 3 h, but began 2 h after fogger placement as per label directions. Enhancedventilation was generally limited to 3 h because this seemed like a reasonable recommendation for homeowners. Also, it is consistent with drying studies that indicate that it takes approximately 3 h for carpets to dry completely following spray application (4).
Results and Discussion This study demonstratesthat indoor pesticide applications may produce significant VOC air concentrations. Potential VOC levels produced by the EC spray were small compared to the aerosol formulations (Figure 11,because of the relative weight of inert ingredients among these formulations. Maximum levels for the EC spray reached about 21 mg/m3 (2 h postapplication) and declined to less than 1 mg/mg3 by24 h. Air levelsfollowingthe aerosol fogger and broadcast applications peaked at around 328 (2 h postapplication) and 234 (1h postapplication) mg/m3,respectively,and were approximately 8 and 6 mg/m3, respectively, at 24 h. Generally, VOC levels following broadcast aerosol and fogger applications were 12 and 16 times higher, respectively, than following emulsion sprays. While this general ratio was maintained throughout the simulation, the absolute differencebetween methods changed dramatically with time. The largest differential was noted during approximately the first 6- 12 h. The actual amount of inert ingredients liberated by the two aerosol products would have probably been very similar if the test house had been closer to the maximum treatment volume listed on the fogger label (10 000 ft3). However,
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FIGURE 3. Simulated air levels of volatile organic compounds under different ventilation scenarios, following indoor application of a broadcast aerosol insecticide spray. Baseline ventilation is set at 0.5 ACH. Enhanced ventilation begins immediately.
FIGURE 1. Simulated air levels of volatile organic compounds following indoor application of emulsifiable concentrete (EC), broadcast aerosol (BcA), or total release (TR) insecticidal preparations. Ventilation is set at 0.5 ACH.
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FIGURE 2. Simulated air levels of volatile organic compounds under different ventilation scenarios, following indoor application of an emulsifiable concentrate insecticide spray. Baseline ventilation is set at 0.5 ACH. Enhanced ventilation begins immediately.
FIGURE 4. Simulated air levels of volatile organic compounds under different ventilation scenarios, following indoor application of a total-release insecticide spray. Baseline ventilation is set at 0.5 ACH. Enhanced ventilation begins at 2 h.
fogging requires a total release of the entire contents, even if this is more than is needed. Furthermore, the fogger label recommends additional units for remote rooms or where a free flow of mist is not assured, thereby liberating even more VOCs into the indoor environment. These factors needs to be considered when choosing between total release and other application methods. Three hours of enhanced ventilation decreased air levels under all indoor application scenarios by 75-80% (Figures 2-4). However, the effect was greatest when begun soon after application,when airlevels were highest. For example, the average VOC concentration over the first 12 h postbroadcast aerosol application was approximately 41 mgl m3, when 3 h of active ventilation (2 ACH) was begun immediately, but rose to approximately 93 mg/m3 when active ventilation was delayed 6 h. Active ventilation was also more effective than passive ventilation, even if the passive ventilation was operating longer. When the duration of passive ventilation increased to 6 h, the 12-haverage (62 mg/m3)was still higher than that observed under 3 h of active ventilation. The 24-h average concentration was approximately 1.4 times greater for fogging (78 mg/m3) than for broadcast aerosol (58 mg/m3)under no enhanced ventilation. This
mirrored the relative difference in VOCs liberated by the two application methods. However, this ratio increased to approximately 1.5 with 3 h of passive ventilation and 1.9 with 3 h of active ventilation. This is probably because enhanced ventilation was begun later for fogging than for broadcast aerosol, causing air levels to decrease more rapidly following the broadcast aerosol application. Furthermore, the delay may have caused more VOCs to distribute to sinks (furniture, carpeting, etc.), thereby slowing elimination. These factors caused ventilation to be more effective followingbroadcast aerosol than following fogging. The VOC air levels estimated by the model are in the range of values expected to produce health complaints among certain individuals. Exposure of normal healthy adults to only 25 mglm3 of total VOCs has been shown to produce significantly increased eye, nose, and throat irritation; headache; and drowsiness (12). Other investigators have recorded symptoms at even lower levels (13).The simulations suggest that this general level of exposure is present for at least several hours followingunventilated EC applicationsand for the better part of 1 day followingaerosol applications.
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The air levels calculated by the model are also near or above the odor threshold for many aromatic compounds (4). Therefore, general health complaints may represent either irritation from exposure to the VOCs or a physical reaction to their odors. In a survey of 643 healthy college students without clinical syndromes or occupational exposures, Bell et al. found that 66% reported moderate to marked illness related to the odor of either pesticides, paint, automobile exhaust, new carpet, or perfumes. These illness symptoms included fatigue,irritability,indigestion, muscle/ joint pain, headache, trouble sleeping, and difficulty concentrating. Of the 90 students classified as severely affected by odors, 98% reported that the odor of pesticide preparations was a problem for them. Furthermore, pesticide odors were significantlycorrelated with elevations in all but two symptoms (14). Currently, very few indoor insecticide labels contain adequate ventilation or reentry requirements or recommendations. A review of the labels for 126 chlorpyrifos or propetamphos formulations registered for indoor use in New Jersey revealed that 26 (21%) contained no recommendations whatsoever. Only 14 (11%) of the labels contained specific references to reentry times, and only 12 (9.5%) had references to ventilation. Furthermore, most of these references were quite general and gave only nonspecific recommendations such as “adequate ventilation”, “ventilate thoroughly”, and “allow to dry before reentry”. This modeling study was designed to provide a rough estimate of potential VOC air levels following indoor applications and to provide guidance regarding reentry recommendations. It was not meant to provide an in-depth or comprehensive quantitative picture of indoor VOC pollution under all possible application conditions. Therefore, the model parameters were simplified when appropriate. One simplifymg assumption, that all inerts are VOCs, is probably an overestimation, since the label designation of “inert”may include water, other nonvolatile substances, or aerosol propellants (propane, butane, etc.) that are relativelyharmless VOCs. However,VOCs probably represent a considerable percentage of the formulation. Furthermore, the types and amounts of inert ingredients used in indoor pesticide formulations are difficult to define accurately because they vary widely and are often considered proprietary information by the manufacturer. Therefore, this conservative assumption seemed appropriate. Specificproducts were chosen to represent the different application methods, and other products would give slightly different results. Similarly, active and passive ventilation were defined somewhat arbitrarily, and actual air exchange
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rates would be expected to vary widely among structures. The decision to partition the source among the different rooms was also somewhat arbitrary. However, these choices should not have a dramatic impact on the general trends and potential magnitude of exposure demonstrated by the study due to the simplified nature of the simulation. In conclusion, aerosol preparations have a much greater potential for VOC exposure than do emulsifiable concentrates. Ventilation can greatly decrease the VOC levels resulting from all types of indoor applications. However, to be most effective, enhanced ventilation should be vigorous and should be instituted as soon as possible after application. Individuals should be advised to delay reoccupying treated rooms untilventilation has been performed.
Acknowledgments We would like to thank Dr. Leslie Sparks of the U S . EPA for his help in defining the model parameters. We would also like to thank Mr. David Rich for his valuable assistance in compiling pesticide label information.
literature Cited (1) Pestic. Toxic Chem. News 1985, 13 (33),20-22. (2) Fed. Regist. 1987, 52, 13305. (3) Fed. Regist. 1989, 54, 48314. (4) Vaccaro, J. R. In Pesticides in Urban Environments: Fate and Significance; Racke, K. D., Leslie, A. R., Eds.; ACS Symposium Series 522;American Chemical Society: Washington, DC, 1993; pp 297-306. (5) Pauluhn, J.;Machemer, L.; Kimmerle, G.; Eban,A.J. Appl. Toxicol. 1988, 8 (61, 431. (6) Rosenberg,J. In OccupationalMedicine;LaDou,J., Ed.;Appleton and Lange: Nonvalk, CT, 1990; Chapter 27. (7) Samet, J. M. Indoor Air 1993, 3, 1. (8) Maddy, K. T.; Lowe, J.; Saini, N. Indoor Air Concentrations of Ethylene Glycol Monoethyl Ether Following Application of Propetamphos Insecticide Emulsifiable Concentrate; California Department of Food and Agriculture, Worker Health and Safety Unit, Division of Pest Management, California Environmental Protection Agency: Sacramento, CA, Jan 4, 1985; HS-1264. (9) Mulrennan, J. A.; Lamdin, J. M.; Bolton, H. T.; Hammond, C. L. J. Econ. Entomol. 1975, 68, (61, 755. (10) Sparks, L. E.. ComputerModelforAnalysis ofIndoorAirPollutant Sources on Individual Exposures. Exposure Version2; EPAReport EPA-60018-91-013;U.S. EPA ResearchTrianglePark, NC, 1991. (11) Wright, C. G.; Leidy, R. B. Bull. Enuiron. Contam. Toxicol. 1978, 19, 340. (12) Hudnell, H. K.; Otto, D.A.;House, D. E.; Molhave,L.Arch. Enuiron. Health 1992, 47 ( l ) ,31. (13) Morrow, L. A. Otolaryngol. Head Neck Surg. 1992, 106 (61, 649. (14) Bell, I. R.; Schwartz, G. E.; Peterson, J. M.; Amend, D. Arch. Enuiron. Health 1993, 48 (11, 6.
Received f o r review June 9,1994. Revised manuscript received November 10, 1994. Accepted November 16, 1994.@
ES940360K @Abstractpublished in Aduance ACS Abstracts, January 1, 1995.
