(1) Common Elements

The post-application exposure scenarios address servicemembers who were exposed to ULV mist downwind of spraying operations for 30 min. The only consequential exposure route was inhalation. While it is possible limited post-application dermal contact occurred, investigators presumed this to have been inconsequential. There would have been few outdoor surfaces conducive to frequent and/or prolonged and/or extensive dermal contact (i.e., small skin surface area exposed); primarily, there would have been little high vegetation that servicemembers would have been frequently rubbing against. Some mist undoubtedly drifted indoors, and there was undoubtedly some dermal contact, but with ULV fog application the surface concentrations should have been very low.

Two reports, from non-applicators, will serve to illustrate pesticide product fogging operations during the Gulf War in a way which is relevant for post-application exposure assessment. Although the reports appear to address HV fogging, some of the information is useful in the assessment of post-application ULV fog exposure. The first report describes fogging with malathion at an Air Force base in Saudi Arabia with over 5,000 servicemembers.^[370] According to the report, the entire camp was fogged with a mixture of malathion in diesel fuel at least twice a week from March 1991 through early July 1991 to control flies. The trucks drove along all the streets of the base between the rows of tents. Prior to fogging, the troops were warned via a public address system to stay away, although the announcements were not necessarily always audible to everyone, and some servicemembers may have ignored the announcements. The second report (also Air Force) describes the fogging of a base in the United Arab Emirates.^[371] The report states that the base was fogged by truck twice a day every day for 6 months. During the fogging operations the entire camp was reported to be completely engulfed in mist. The latter contact did not know what pesticide product was used, and did not know whether the fogging was done by US servicemembers or local contractors.

Based on the two reports described above, and the PM exposure interviews (Table 13), investigators selected exposure frequencies (EFs) of 1, 4, and 16 days per month for low, medium, and high exposure for evaluation of ULV fogs. Some of the PM interviews indicated that fogging occurred but was rare. Investigators consider the second report above, indicating an EF of 60 times per month as unique and unrepresentative of the majority of ULV fog exposures. It is noteworthy that the reported exposure durations (EDs) of 5-6 months from the two non-applicator reports are close to the average values for ULV fogs from the PM interviews. It is also noteworthy that the two non-applicator reports describe a readily visible fog, and presumably servicemembers would be more likely to see this, and move to an upwind location. In the case of a ULV mist, it is less likely that servicemembers would be aware of its presence if they did not observe the applicator's truck or missed instructions to change location.

(2) Chlorpyrifos, 19% Liquid (ULV)

Table 82 presents the formulation-specific assumptions used for the post-application exposure assessment of chlorpyrifos, 19% liquid (ULV).

Table 82. Chlorpyrifos ULV Assumptions for post application

(3) Malathion, 91% Liquid (ULV)

Table 83 presents the formulation-specific assumptions used for the post-application exposure assessment of malathion, 91% liquid (ULV).

Table 83. Malathion ULV assumptions for post application

(4) Air Modeling for ULVs

For the purpose of air modeling, investigators assumed that a 400,000-square-meter (99-acre) area is treated with the insecticide formulation sprayed as an aerosol or mist from a ULV fogging truck. The treated area is assumed to be rectangular (1,000 meters long x 400 meters wide). The truck traverses the area, gradually applying the formulation in four, sequential, 100-meter wide swaths until the entire area is treated. The direction of source movement alternates oppositely for each swath (e.g., north, south, north, south). The entire application takes 30 minutes (450 seconds per swath).

Two different formulations were applied. One formulation was 19% chlorpyrifos, consistent with the label for a representative chlorpyrifos ULV concentrate.^[376] Investigators assumed chlorpyrifos to be applied at the rate recommended in Armed Forces technical guidance^[377] for a similar 25% chlorpyrifos ULV formulation (1.6 ounces per acre). The other formulation was 91% malathion, consistent with the material safety data sheet (MSDS) for a representative malathion ULV concentrate^[378] and Armed Forces technical guidance.

Exposure to insecticides applied via ULV fogging is a potential concern for individuals downwind of the application area. To estimate air concentrations downwind of the application area, investigators made the following assumptions:

• The formulation is uniformly discharged over the entire application area, both in terms of application rate per unit area and unit time.
  
  
• The formulation is sprayed from one or more nozzles mounted on the truck approximately 1 m above the ground with the truck traveling at 5 miles per hour.
  
  
• The majority of the spray settles and adheres to the ground or plants; 10% of the spray remains airborne.
  
  
• The receptor of concern is located 10 m downwind of the application area at the location with the highest modeled air concentration. The breathing zone of this individual is 1.25 m (4 ft, 1 in) above ground.
  
  
• The duration of exposure to bystanders to the modeled concentration of the active ingredient in the mist is comparable to the application time (30 minutes). The residual air concentration after application is complete, and after the suspended material has blown away, is negligible relative to the exposure during application.
  
  

Investigators estimated the ambient air concentrations resulting from these scenarios using the EPA INPUFF dispersion model (Version 2.5).

(5) General Model Description

Investigators conducted the modeling of ULV fogging impacts downwind of the treatment area using the EPA's INPUFF model. INPUFF is a Gaussian integrated puff model that was designed to simulate dispersion from semi-instantaneous or continuous point sources. Source emissions are treated as a series of individual puffs. Wind direction, speed, and atmospheric stability class are assumed to be constant during each time step, and the Gaussian puff diffusion equation is used to calculate the contribution to the concentration at each receptor from each puff for every time step.

The EPA developed the INPUFF model in response to requests for modeling impacts downwind of moving incineration ships. Investigators selected INPUFF for use for estimating impacts downwind of a ULV fogging truck since it was the only available model that captured the intrinsic nature of the source term (i.e., a moving point source). For this analysis, the ULV fogging truck was simulated as a moving point source within a spatially constant wind field.

Other models investigators considered were less appropriate. Although investigators conducted some initial analysis using the EPA SCREEN model, the representation of the source in SCREEN as a continuous area source did not conform as well to the scenario under consideration. In addition, SCREEN is a Gaussian plume model (rather than a puff model) that assumes a release at a constant rate for a period of an hour and was not able to account directly for the more limited duration (30 minutes) of the spraying and subsequent exposure. Other puff models, such as CalPUFF, are designed for mesoscale analyses and do not incorporate the capability of simulating moving sources. Models such as CalPUFF are more appropriate for analyzing the long-range transport of pollutants rather than for the more limited microscale analysis for the ULV fog application.

The INPUFF model is documented in its computer code (available from EPA) and, in part, in a user’s guide^[379] for an earlier version of the model.

(6) Model Application

Each of the four swaths was represented by a moving point source that emits the insecticide formulation only during the 450-second interval representing the coverage of the particular swath. Each source started at one end of a swath and traveled towards the other end of the swath at a rate of 2.222 m/s (5 miles per hour).

Investigators assigned each point source an emission height of 1 m. Investigators also assigned nominally small parameter values for stack gas temperature, stack diameter, stack gas velocity, and stack gas volume flow rate in order to minimize any modeled plume rise. In essence, the model treats the release as inert and nonbuoyant. Investigators set deposition and settling velocities both to zero, so that the model neglected any depletion of the airborne portion of plume material.

Investigators assigned initial horizontal and vertical dispersion parameters for the point sources based on the user’s guide for sources located near the ground. Investigators defined the initial horizontal dispersion parameter by dividing the initial horizontal scale (100 meters) by 4.3, and defined the initial vertical dispersion parameter by dividing the initial vertical scale (1 meter) by 2.15. Investigators set the source update parameter so that a new puff was emitted each second.

Investigators defined the modeling domain as a sufficiently large area to ensure that the model would continue tracking emitted puffs over the area in which source impacts were of interest.

An emission rate was calculated for and assigned to each source for the period when the particular swath was being treated. The calculated emission rate was consistent with the recommended insecticide application rate and the assumption that 10% of the applied material remained airborne. Table 84 presents the emission rate calculated.

The assumption that 10% of the applied material remains airborne is based on the droplet size description provided in military guidance^[380] as follows:

• "... an aerosol for ULV dispersal will generally fall between 5 and 25 microns. A large number of very small or very large droplets outside the 5-25 micron range indicates incorrect atomization. If a large number of droplets five microns or less is produced, and they constitute a small percentage (less than 10%) of the volume (mass), the remaining droplets will normally produce effective control."
  
  
• "Aerosol droplets must not be less than 5 microns in size, as the smaller droplets do not impinge readily on adult mosquitoes."
  
  
• "Droplets should not exceed 32 microns in size. Three percent can exceed 32 microns ... and no droplets exceed a maximum of 48 microns."
  
  

Thus, investigators assumed that a maximum of 10% of all ULV droplets would be less than 5 microns in diameter. We estimated the deposition (settling) rates of malathion ULV droplets of various sizes under the modeled conditions (400 m x 1,000 m application area, 1 m release height, 1 m/s wind speed). This analysis indicated that the 5 micron droplets would tend to remain airborne downwind of the application area, but the larger droplets would tend to deposit. Based on these results, 10% of the ULV aerosol released was estimated to remain airborne downwind of the application area (similar to the total maximum acceptable mass of 5 micron droplets).

The actual model runs used a unit emission rate of 1.0 g/s. The investigators scaled model estimates in the output files scaled to account for the emission rates for chlorpyrifos (0.046 g/s) and malathion (1.46 g/s), respectively. This approach is valid since the estimated concentration is directly proportional to the emission rate.

Table 84. Calculation of emission rate of ULV fogs for air modeling^a

The modeling considered a range of standard screening meteorological conditions. Table 85 presents the combinations of stability class and wind speed for each as analyzed in a separate model execution. These combinations fully span the range of conditions that would yield maximum concentrations near the surface. Higher wind speeds would only yield lower concentrations due to the increased dilution effect of the wind. Wind speeds lower than about 1 m/s are considered to be calm and are not appropriate for Gaussian models.

Table 85. ULVs, meteorological parameters for air modeling

Investigators set the anemometer height to a standard 10-meter level for screening purposes. Given the low level of the release and the definition of source release parameters to minimize any estimate of plume rise, the effect of mixing height on estimates will be negligible.

Investigators modeled two wind directions: one parallel to the long axis of the treatment area and one parallel to the short axis of the treatment area.

Investigators placed model receptors downwind of the treatment area. The closest model receptors were located 10 meters beyond the downwind edge of the last swath. Receptors were also placed at various lateral positions beyond the downwind edge of the last swath.

Investigators assigned a receptor height of 1.25 meters above ground level to represent a typical breathing zone height.

Investigators ran the model for a total duration of 1-hour beginning at the onset of insecticide application and ending 30 minutes after the application was completed. For each modeled meteorological condition, the model provided concentrations at each model receptor for each of two 30-minute averaging periods as well as 1-hour concentrations for the entire period of modeling. For most wind speeds and receptors, most of the insecticide exposure was estimated to occur during the first 30-minute averaging period. However, for the lowest modeled wind speeds, comparable exposure was estimated to occur during the second 30-minute period at more distant receptors.

The model estimated maximum concentrations for light wind (1 m/sec), stable (class F) conditions. These are the conditions that typically yield maximum estimated concentrations for ground-level or low level releases without appreciable plume rise.

For the scenario in which winds were perpendicular to the direction of insecticide application (Condition A), the model estimated maximum concentrations at the nearest receptors (i.e., those located 10 meters beyond the downwind edge of the application area) and varied laterally. The maximum 1-hour average concentration estimated for the modeled unit emission rate was 98.3 mg/m³, and the maximum 30-minute average concentration was approximately 196.6 mg/m³. After adjusting for emission rates, this corresponds to maximum average 30-minute concentrations of 9.0 mg/m³ for chlorpyrifos and 287.0 mg/m³ for malathion.

For the scenario in which winds were parallel to the direction of insecticide application (Condition B), the model again estimated maximum concentrations to occur at the nearest receptors (i.e., those located 10 meters beyond the downwind edge of the application area) and varied laterally. The maximum 1-hour average concentration estimated for the modeled unit emission rate was 199.2 mg/m³, and the maximum 30-minute average concentration would be no greater than 398.4 mg/m³ (assuming that the entire 1-hour exposure occurred within a 30-minute period). After adjusting for emission rates, this corresponds to maximum average 30-minute concentrations of 18.3 mg/m³ for chlorpyrifos and 581.7 mg/m³ for malathion.

INPUFF model output files for the maximum estimated impact conditions (F stability with 1 m/second winds) were generated. These conditions would generally be expected to only occur in the period after sunset until shortly after sunrise. Solar heating of the surface and the lower atmosphere would lead to more unstable atmospheric conditions and lower estimated concentrations.

Investigators assumed all chlorpyrifos and malathion that remains airborne to have existed in the vapor phase (or as fine droplets which behave similarly) during exposure. Therefore, separate particulate modeling was not conducted.

(7) ULV Doses - Post Application

Table 86 presents doses potentially resulting from the post-application inhalation exposure to ULV fogs, for evaluation of noncarcinogenic effects. Toxicity values were not available for the assessment of the potential carcinogenic effects of chlorpyrifos and malathion (Tab D, Section D, "Toxicity Assessment"), so investigators did not calculate LADDs.

Table 86. ULV fogs, dose rates - post application, for evaluation of noncarcinogenic effects^a

Formulation	Exposure Group	Exposure Point	ABS	PDRD (mg/kg/d)	ADD (mg/kg/d)	PDRI (mg/kg/d)
Chlorpyrifos, 19% liquid (ULV)	Low	Outdoor	0.03	-	-	1.03E-04
	Medium	Outdoor	0.03	-	-	1.03E-04
	High	Outdoor	0.03	-	-	2.09E-04
Malathion, 91% liquid (ULV)	Low	Outdoor	0.1	-	-	3.28E-03
	Medium	Outdoor	0.1	-	-	3.28E-03
	High	Outdoor	0.1	-	-	6.65E-03
Formulab PDRI = (CA x IRA x ET)/BW

a)	ABS = dermal absorption factor. PDRD = potential dose rate for dermal contact ADD = absorbed dermal dose PDRI = potential dose rate for inhalation A dash (-) indicates that the item is not applicable.
b)	BW = body weight. CA = a.i. concentration in air from modeling IRA = inhalation rate ET = exposure time

10. Lindane Dust

Investigators evaluated only lindane, 1% dust.

a. Application Scenarios

Lindane, 1% dust was the only form of lindane available through the military supply system. An important use of lindane dust was in the delousing of enemy prisoners of war (EPWs) as part of their initial processing at detention camps. It was supplied for mass delousing in 25 lb cans. Lindane dust was also issued in 2 oz containers to US servicemembers for their own use. According to the RAND survey, 7% of servicemembers used or witnessed the use of lindane dust (Table 8). The majority of personal use was clearly in the Army (10% of servicemembers) vs. the other services. The survey percentages almost certainly refer mainly to personal use, although some may be referring to EPW delousing. However, there is little doubt that the exposure levels encountered by servicemembers conducting delousing activities were far higher than the levels encountered by other servicemembers. This being the case, delousing is the use of lindane evaluated in detail. Doses and risks associated with the personal use of lindane would be substantially lower.

The servicemembers who carried out the delousing operations were exclusively or almost exclusively military police (MPs), although other servicemembers probably were in the vicinity during operations. Application of lindane to EPWs was reported to be conducted both at outdoor stations and inside tents.

US forces captured the bulk of the EPWs from the onset of the ground war (February 24, 1991) through about April 30, 1991; a period of about 9 weeks. US forces took relatively few EPWs before the ground war. US servicemembers processed approximately 70,000 EPWs (including some displaced civilians) at four camps, with peak processing rates of 1500 EPWs per day, per camp.^[381] Investigators estimate the overall average processing rate to be about 195 EPWs per day per camp, given 70,000 EPWs processed over the course of 3 months. Reportedly there was a 3 to 4-week interval where 44,000 EPWs were processed, yielding a processing rate of about 440 EPWs per day at each of the four camps. Investigators assumed the delousing treatment to have been part of the in-processing of every one of the EPWs.

According to directions for applying the lindane powder to clothed individuals, ^{[382,] [383,] [384]} between 1 and 2 ounces of powder is sprayed beneath the clothing at various entry points (e.g., neck, sleeves, waist). Also, the person’s head is dusted until the hair is whitened with the dust and the inside of the hat is dusted. The powder can be applied by means of a plunger-type hand duster or a portable gasoline-powered dusting device. The power duster is designed to allow delousing of 600 people per hour; however, due to various limitations such as equipment failure, it is unlikely that many EPWs were processed at anywhere near this rate. The delousing dust contained 1% lindane by weight.

An important determinant of the level of absorbed pesticide active ingredient dose is the level of PPE worn by applicators. A review of military guidance and the delousing interviews led to use of the following scenarios for applicators:

• Low exposure: long pants, long-sleeve shirt, gloves, half-face respirator with dust/mist cartridges (respiratory protection factor = 80%).^[385]
  
  
• Medium exposure: long pants, long-sleeve shirt, gloves.
  
  
• High exposure: long pants, long-sleeve shirt ("single layer, no gloves" from the PHED Guide).
  
  

The low exposure level represents proper handling and application of lindane, use of appropriate PPE, and adequate hygienic measures, such as washing up prior to engaging in hand-to-mouth activities including eating, drinking, smoking, or chewing gum. Additionally, investigators assumed that lindane dust did not settle inside mess facilities, or break areas, or on eating utensils, etc. The medium exposure level represents proper handling and application of lindane, inadequate PPE, and adequate hygienic measures. The high exposure level represents proper handling and application of lindane, but inadequate PPE, and inadequate hygienic measures.

Table 87 presents the assumptions for application of lindane dust during EPW delousing. As shown in Table 17, 23% of the servicemembers in the delousing interviews indicated that delousing was conducted outdoors, while 50% indicated that it was conducted indoors. In this analysis, investigators considered application and post-application exposure considered together. The majority of exposure would certainly have been to the applicators, with little to non-applicators. Application is further broken down into two steps as "mixing/loading" and "dispersal." Inhalation and dermal exposure during the mixing/loading step is assessed using PHED. Inhalation exposure during the dispersal step is estimated based on air modeling. Dermal exposure during the dispersal step is estimated by combining several factors presented in Table 87, including CS, CF, SA, AF, events, and BW. See Table 87 for definitions of exposure factors. The PHED unit exposure factors are incorporated to derive a total dermal exposure (PDR_D).

Table 87. Lindane, 1% dust assumptions for application

Factor	Units	Definition/Explanation	Assumptions by Level			Source/Rationale
			Low	Medium	High
Exp. Point	-	Exposure point - place where exposure occurred	Outdoors	Indoors	Indoors	Delousing interviews: 23% said outdoors; 50% said indoors.
UE	mg/lb a.i.	Unit dermal exposure for mixing/loading	0.17	0.17	3.7	1998 PHED Guide[386]
UIE	mg/lb a.i.	Unit inhalation exposure for mixing/loading	0.0043	0.043	0.043	1998 PHED Guide[387]
CPR	EPWs/d	Camp processing rate	350	350	1,500	US DoD;[388]
AC	-	Number of applicators working per day per camp	10	10	10	US Army [389,] [390]
APR	EPWs/d	Applicator processing rate	35	35	150	See notea
Equipment	-	Equipment used to apply lindane	Manual pump	Manual pump	Power duster	Delousing Interviews: 50% used pumps and other manual; 25% used power duster.
AMT	oz/EPW	Average amount of lindane applied to each EPW.	1.0	1.2	2.0	EPA;[391] US Army/US Navy[392]Octagon[393]
WA	lb a.i./d	Weight of a.i. handled	0.022	0.026	0.19	Equation[394]
CA	mg/m3	Inhaled air concentration of lindane during application	0.0075	0.0559	0.889	Air modeling (see text)[395]
CS	mg/kg	Concentration of a.i. in the formulation	10,000	10,000	10,000	1% = 10,000 mg/kg
CF	kg/mg	Unit conversion factor	1E-06	1E-06	1E-06	Standard
Events	d-1	Dermal exposure events	1	1	1	See text
SA	cm2	Skin surface area available for contact	2,000	5,000	20,000	EPA[396]; USAEHA;[397]
AF	mg/cm2	Dust-to-skin adherence factor	0.0021	0.022	0.13	EPA[398]
ET	h/d	Exposure time	4	9	12	Delousing interviews
EF	d/mo	Exposure frequency	6	17	30	Delousing interviews
ED	mo	Exposure duration	1.0	1.9	3.0	Delousing interviews; see noteb
IR	mg/d	Ingestion rate	-	-	480	EPA[399] ; see notec
ABS	-	Dermal absorption factor	0.1	0.1	0.1	ATSDR[400]

a)	APR = CPR/AC. Assumes that there were 10 applicators per camp. At 5 minutes per EPW, the 90th percentile value, this translates to 12.5 hours per day, which is nearly the 90th percentile exposure time reported by veterans.
b)	The high value of 3 months is based on the fact that the bulk of the EPWs were taken between February 24, 1991 and April 30, 1991.
c)	Many personnel described high levels of lindane dust in the immediate vicinity of personnel engaged in EPW delousing.

The value for exposure events is one per day (Table 87). The rationale for assuming one exposure event per day is that there is a maximum amount of lindane dust that can adhere to the skin per day for each exposure group under the conditions defined. Investigators assumed that the maximum amount cannot be exceeded. For example, the assumed maximum amount of 1% lindane dust that can adhere to the skin for the high exposure group is as follows:

PDR_DMAX = SA_H x AF_H
PDR_DMAX = (20,000 cm²) x (0.13 mg/cm²) = 2,600 mg dust = 26 mg a.i.

where,

PDR_DMAX = maximum potential dose rate for dermal contact
SA_H = skin surface contact area, high exposure
AF_H = adherence factor, high exposure

The dermal exposure event lasts for a time equal to the exposure time (ET). During this event, the skin surface contact area (SA) is covered with 1% lindane dust, adhering per the adherence factor (AF).

The investigators justify the assumption of a single exposure event because servicemembers were not bathing during the day, and then receiving new potential doses of lindane dust. This assumption is combined with two additional assumptions. First, investigators assumed that the entire potential dermal dose of lindane active ingredient was available for absorption. The latter assumption is highly conservative since the 99% talc^[401] in the formulation would in fact significantly retard absorption due to layering of the pesticide formulation on the skin surface. Second, investigators assumed the high-exposure receptor received whole-body exposure based on the significant penetration of clothing determined by USAEHA^[402] for power-driven delousing equipment. The 12-fold protection factor determined by USAEHA means that, under very dusty conditions, substantial amounts of lindane will reach the skin through BDUs.

At first glance, the assumption of 100% absorption of lindane active ingredient from talc, when taken alone, may appear overly conservative. However, it is combined with two non-conservative assumptions, first, that there is one exposure event per day, and second, that the total lindane dust directly contacting the skin can be no higher than 2.6 g in a day. Also, the USAEHA study reported total dermal exposure to lindane dust of 6.3 g/h (0.063 g of lindane active ingredient per hour), which, if directly extrapolated, would be 75.6 g of dust in 12 h. The USAEHA value is based on the amount trapped in dermal pads placed on exposed skin and under BDUs rather than the amount shown to directly contact the skin. Therefore, investigators rejected 75.6 g as being a reasonable estimate for total exposure in 12 h.

Investigators evaluated oral exposure due to the conditions described by applicators during the delousing interviews. Servicemembers frequently worked long days under very dusty conditions, with much of the dust being specifically lindane powder. Since data are not available on the levels of lindane powder ingested, published assumptions regarding soil and dust ingestion were evaluated for use as potential surrogate values.^[403]

Many interviewees described high levels of lindane dust in the immediate vicinity of servicemembers engaged in EPW delousing. Many veterans described lindane dust as typically visible in the air, visible on US servicemembers, and visible on surfaces associated with hand-to-mouth activities. Furthermore, lack of appropriate PPE coupled with poor personal hygiene would have contributed to a high ingestion rate. There can be little doubt under such conditions that significant amounts of lindane powder were ingested. Therefore, the highest value listed by the EPA for soil ingestion by adults (480 mg/day) was selected, despite the fact that this value is referred to by the EPA as "conjectural." It should be noted that the high ingestion rate used is not really that much mass: 480 mg = 0.017 oz. Finally, even the lower adult ingestion values provided by the EPA of 50 mg/day and 100 mg/day are associated with a low level of confidence, and are intended to reflect fairly routine soil ingestion rates throughout the year in the US at residential and industrial locations.

b. Air Modeling for Lindane

(1) Low Exposure Scenario

The low exposure scenario involves the treatment of EPWs outdoors using a manual pump. Investigators estimated concentrations to which applicators were exposed based on an adjustment of concentrations reported in a 1986 study conducted by the US Army Environmental Hygiene Agency (USAEHA).^[404] The USAEHA study simulated delousing operations using mannequins as recipients of lindane dust applied via a power duster and provides measured air concentrations of dust to which applicators were exposed during application. The application in the USAEHA study should represent a reasonable surrogate for the defined low exposure scenario. The measured concentrations reported in the USAEHA study were adjusted to account for the different (lower) pesticide formulation application rate assumed for the low exposure scenario.

For the low exposure scenario, 1.0 oz (28.35 g) of the pesticide formulation with 1% lindane active ingredient is applied to each EPW, yielding an application rate of 0.2835 g of lindane per EPW. The investigators assumed an applicator treated 35 EPWs for approximately 5 minutes each over a period of 4 hours. During application to an individual EPW, the average lindane application rate (AR) is given by:

AR = (0.2835 g/EPW)(EPW/5 minutes) = 0.0567 g lindane/minute.

The USAEHA study involved the application of 600 g of pesticide formulation (with 1% active ingredient) to 10 mannequins over a period of 14 minutes by each applicator. The average lindane application rate (AR) for this study for a single applicator is given by:

AR = (600 g formulation/EPW)(0.01g lindane/g formulation)/(14 minutes),

= 0.429 g lindane/minute.

The USAEHA study provides lindane concentrations measured in respiratory field samples from applicator collar filters and collar impingers for each of eight individual runs. After adjusting the measured data to substitute one-half the level of detection for a single non-detect sample, the resulting average air concentration to which the applicator was exposed during the application was calculated by dividing the total mass collected (13.05 m g) by the number of samples (8) and by the average sample size (21 liters), yielding a concentration of 78 mg/m³.

Since the application rate for the defined low exposure scenario is lower, the concentration from the USAEHA study was adjusted by the ratio of the application rates:

(78 mg/m³)(0.0567 g lindane/minute)/(0.429 g lindane/minute) = 10.3 mg/m³.

This is an estimate of the concentration to which the applicator would be exposed during the application process in the low exposure scenario. The average concentration to which the applicator would be exposed during the exposure time (4 hours) would then be given by multiplying the concentration during application by the ratio of the application time (35 EPW x 5 minutes/EPW) by the exposure time (240 minutes), yielding:

(10.3 mg/m³)(175 minutes/240 minutes) = 7.5 mg/m³.

(2) Medium and High Exposure Scenarios

The medium exposure scenario involves the indoor treatment of EPWs via a manual pump. Investigators assumed ten applicators each treated 35 EPWs over a period of 9 hours. Investigators assumed each EPW received 1.2 oz (34.02 g) of the pesticide formulation containing 1% lindane. Investigators assumed the application occurred within a GP medium tent with a volume of 4350 ft³ (128.13 m³).

The high exposure scenario involves the indoor treatment of EPWs via a power duster. Investigators assumed ten applicators each treated 150 EPWs over a period of 12 hours. Investigators assumed each EPW received 2 oz (56.70 g) of the pesticide formulation containing 1% lindane. Investigators assumed the application occurred within a GP medium tent.

To estimate air emissions in the treatment area (within the tent), the following assumptions were employed:

• 25% of the powder applied to an EPW was applied to the head and the hat (consistent with an illustration of proper application showing eight points of application, two of which are the head and the hat that has been removed from the individual’s head);^[405]
  
  
• clothing effectively suppresses dust emission at the six beneath-clothing application points; most of the powder that becomes airborne is from the spraying of the individual’s head and hat; and
  
  
• 2.5% of the powder applied to the head and hat remains airborne, with the remainder adhering to the EPW or hat or settling to the ground.
  
  

Based on these assumptions and the scenario definitions, emission rates of lindane within the tent for these scenarios are presented in Table 88, as calculated by the mass balance equation shown.

Table 88. Lindane, calculation of emission rates for air modeling^a

Parameter	Units	Medium Exposure	High Exposure
AMT	grams	34.02	56.70
fa	dimensionless	0.25	0.25
APR	EPWs treated /applicator	35	150
AC	applicators	10	10
P	dimensionless	0.01	0.01
f	dimensionless	0.025	0.025
t	hours	9	12
E	mlligrams/hour	82.7	443.0

a)

E = (AMT)(1,000)(fa)(APR)(AC)(p)(f)/t E = emission rate of lindane, mg/h. AMT = amount of pesticide formulation applied to each subject, grams. fa = fraction of pesticide formulation applied above clothing. APR = treatment rate, number of EPWs treated per applicator. AC = number of applicators. p = fraction by weight of active ingredient in pesticide formulation unitless. f = fraction of pesticide formulation which becomes airborne, unitless. t = duration of application period, hours.

Indoor air concentrations were calculated inside the tent using a standard box model approach as described for permethrin. For the case where the initial concentration is zero, where contribution from outside is zero, and where the active ingredient is assumed to be nonreactive, the concentration within the tent is given by:

C_ai = [E/(I)(V)][1-exp{-(I)(t)}] where,

C_ai = concentration in air inside tent (mg/m³)
E = emission rate (mg/h)
V = volume of air inside tent (m³)
I = air changes per hour in tent
t = time (h)

This equation asymptotically approaches an equilibrium concentration (C_eq) given by:

C_eq = E/(I)(V)

The average concentration over the duration of the lindane application in the tent can be approximated by the equilibrium concentration.

For the tents used for lindane application, indoor concentrations have been estimated for a range of air exchange rates (4, 8, and 12 air changes per hour). These rates are believed to be reasonable given reports that strong winds readily penetrated the structures under consideration and given the frequent foot traffic in and out of the tent associated with individuals being treated. The estimated concentrations for a range of air exchange rates are summarized in Table 89.

Table 89. Lindane air modeling results

Parametera	Units	Ib	Medium Exposure	High Exposure
E	mg/h	4, 8, 12	82.69	443.0
V	m3	4, 8, 12	123.18	123.18
Ceq	mg/m3	4	0.168	0.889
		8	0.0839	0.450
		12	0.0559	0.300

a)	E = emission rate (mg/h).. Ceq = equilibrium concentration.	V = volume of air inside tent (m3)
b)	I = air changes per hour in tent.

The release of lindane vapor directly to the air constitutes an inconsequential exposure pathway, since lindane is probably strongly adsorbed to the dust and has a relatively low vapor pressure. Thus, air modeling for lindane vapor was not conducted.

c. Lindane Doses - Application

Tables 90 and 91 present doses potentially resulting from exposure to lindane during EPW delousing operations. There are four types of doses presented in Table 90 for the evaluation of noncarcinogenic effects: PDR_O, PDR_D, AD_D, and PDR_I. Table 91 presents three types of doses for the evaluation of carcinogenic effects for lindane: LADD_O, LADD_D, and LADD_I. The LADD_O is calculated based on the high-exposure level since an oral dose was not calculated for lower exposure levels.

Table 90. Lindane, dose rates - application, for evaluation of noncarcinogenic effects^a

Formulation	Exposure Group	Exposure Point	ABS	PDRO (mg/kg/d)	PDRD (mg/kg/d)	ADD (mg/kg/d)	PDRI (mg/kg/d)
Lindane 1% dust	Low	Outdoors	0.1	-	6.53E-04	6.53E-05	6.87E-04
	Medium	Indoors	0.1	-	1.58E-02	1.58E-03	1.15E-02
	High	Indoors	0.1	6.86E-02	3.81E-01	3.81E-02	2.44E-01
Formulas: (1) PDRO = (0.01 x IR)/BW (2) PDRD = ((UE x WA)+(CS x CF x SA x AF x events))/BW (3) ADD = PDRD x ABS (4) PDRI = ((UIE x WA)+(CA x IRA x ET))/BW

a)

ABS = dermal absorption factor. PDRO = potential dose rate for ingestion. PDRD = potential dose rate for dermal contact. ADD = absorbed dermal dose. PDRI = potential dose rate for inhalation. A dash (-) indicates that the item is not applicable. IR = ingestion rate. BW = body weight. UE = unit dermal exposure. WA = weight of a.i. handled. CS = a.i. concentration in dust. CF = conversion factor. SA = skin surface contact area. AF = dermal adherence factor. events = dermal exposure events. UIE = unit inhalation exposure. CA = a.i. concentration in air. IRA = inhalation rate. ET = exposure time.

Table 91. Lindane, lifetime average daily doses - application, for evaluation of carcinogenic effects^a

Formulation	Exposure Group	Exposure Point	LADDO (mg/kg/d)	LADDD (mg/kg/d)	LADDI (mg/kg/d)
Lindane 1% dust	Low	Outdoors	-	-	-
	Medium	Indoors	-	1.99E-06	1.46E-05
	High	Indoors	2.42E-04	-	-
Formulas: LADDO = (PDRO x EF x ED)/AT LADDD = (ADD x EF x ED)/AT LADDI = (PDRI x EF x ED)/AT

a)

LADDO = lifetime average daily absorbed dose via ingestion. LADDD = lifetime average daily absorbed dose via dermal contact. LADDI = lifetime average daily potential dose via inhalation. A dash (-) indicates that the item is not applicable. PDRO = potential dose rate for ingestion. EF = exposure frequency. ED = exposure duration. AT = averaging time. ADD = absorbed dermal dose. PDRI = potential dose rate for inhalation.

 

d. Post-Application Scenarios

Application and post-application exposure are evaluated together under application.