Investigators evaluated only lindane, 1% dust.

1.  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.^[342] 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,^{[343,344,345]} 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%).^[346]

• 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

The value for exposure events is 1 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:

The dermal exposure event lasts for a time equal to ET (exposure time). 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^[362] 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^[363] 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.^[364]

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 EPA for soil ingestion by adults (480 mg/day) was selected, despite the fact that this value is referred to by 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 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.

2.  Air Modeling for Lindane

a.  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).^[365] 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:

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:

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 �g) by the number of samples (8) and by the average sample size (21 liters), yielding a concentration of 78 �g/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 �g/m³)(0.0567 g lindane/minute)/(0.429 g lindane/minute) = 10.3 �g/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 �g/m³)(175 minutes/240 minutes) = 7.5 �g/m³.

b.  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);^[366]

• 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

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^a

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.

3.  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

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

4.  Post-Application Scenarios

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

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