Eight percent of the PM exposure interviews cited use of d-phenothrin, 2% aerosol (Table 13). The survey (Table 8) indicated that up to 28% of servicemembers may have used d-phenothrin; however, this is probably a significant overestimate. The value of 28% includes an unknown portion of other aerosol products. d-Phenothrin was used to control sand flies, filth flies, and mosquitoes. The predominant use of d-phenothrin was as an area spray inside tents and other structures (Table 13). In the PM exposure interviews, 79% of interviewees who mentioned d-phenothrin indicated that it was used mainly indoors. The military supplied the formulation in a 2-oz aerosol spray can containing a mixture of the active ingredient, and various inert ingredients such as solvents and/or propellants.

1.  Application Scenarios

It is most likely that the majority of servicemembers who used d-phenothrin aerosol did so without using personal protective equipment such as gloves and respirator. PPE would not normally have been required. d-Phenothrin was widely available to servicemembers, and was not restricted to servicemembers trained in pesticide product application. In the PM exposure interviews, 74% of the interviewees who mentioned d-phenothrin did not even respond to the question on PPE. The label directs the user to ventilate buildings, vans, and tents before re-entry.^[182] We have no way of knowing the extent to which troops followed this direction. Table 33 presents the assumptions for application of d-phenothrin, 2% aerosol.

Table 33. d-Phenothrin assumptions for application

2.  d-Phenothrin Dose Rates – Application

Table 34 presents the doses potentially resulting from application exposure to d-phenothrin, 2% aerosol. As noted previously, only the inhalation exposure route is relevant for d-phenothrin; thus, only one type of dose is presented in Table 34 for the evaluation of noncarcinogenic effects: PDR_I. EPA has not associated d-phenothrin with carcinogenic activity, so investigators did not calculate LADDs (see Section B.4,  Toxicity Assessment).

3.  Post-Application Scenarios

Table 35 presents the assumptions for post-application exposure to d-phenothrin, 2% aerosol. The only relevant post-application exposure route is inhalation.^[187] Dermal and oral exposure would almost certainly have been inconsequential. The amount of dislodgeable residue remaining on treated surfaces would have been very low, and the opportunity for contact of large surface areas of skin minimal.

4.  Air Modeling for d-Phenothrin

The air modeling procedure used for d-phenothrin, 2% aerosol is the same as that described for permethrin; most of the assumptions are the same as well. The details may be found in the permethrin air modeling subsection. The inputs which differ from permethrin are described below. The calculations are presented in Table 36.

Investigators calculated the emission rate of d-phenothrin to the indoor air according to the same mass balance equation used for permethrin.

The recommended application rate is 10 g per 1,000 ft³ (Table 36). The product label states that the time required to discharge 10 g is 10 seconds.^[188] Thus, a GP medium tent would require 43 seconds (0.72 min) to treat. Additionally, investigators assumed that 90% of the material discharged goes into the air, while 10% is deposited on surfaces, since the label directs the user to spray into the air. Investigators calculated the emission rate as follows:

p = 0.02 (2%)
S = 43 g
f = 0.90 (90%)
t = 0.72 min
E = 0.5573 mg/min

Table 37 summarizes the average d-phenothrin concentrations estimated within the tent for each modeled scenario for the assumed 8-hour exposure period following the onset of spraying.

5.  d-Phenothrin Dose Rates – Post Application

Table 38 presents the doses potentially resulting from post-application exposure to d-phenothrin, 2% aerosol. As noted previously, only the inhalation exposure route is relevant for d-phenothrin; thus, only one type of dose is presented in Table 38 for the evaluation of noncarcinogenic effects: PDR_I. EPA has not associated d-phenothrin with carcinogenic activity, so investigators did not calculate any LADDs (see Section B.4,  Toxicity Assessment).

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