Document ID: EPA-HQ-OPP-2007-0833-0003
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-10-10T04:00Z

SEQ CHAPTER \h \r 1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

 OFFICE OF                  

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES        

October 1, 2007			

MEMORANDUM			

SUBJECT:	Revised Occupational and Residential/Bystander Assessment of
the Antimicrobial Use (Remedial Wood Treatment) of Sodium Fluoride for
the Reregistration Eligibility Decision (RED) Document.  Case Number
3132.  PC Code 075202.

FROM:		Tim Leighton, Environmental Scientist

				Antimicrobials Division

TO:			Sanyvette Williams, Chemical Review Manager

				Antimicrobials Division

				

This document  SEQ CHAPTER \h \r 1  is a review of the occupational
applicator and residential bystander assessment for the antimicrobial
remedial wood treatment use of sodium fluoride to support the
Reregistration Eligibility Decision (RED) document.  It has been revised
to include comments from the Phase 1 “error comment” period.

  SEQ CHAPTER \h \r 1 EXECUTIVE SUMMARY

	

The Antimicrobials Division (AD) assessed the occupational and potential
bystander risks to the remedial wood treatment uses of sodium fluoride. 
The remedial wood treatment is used to treat poles, crossties,
structural timbers such as bridge pilings and posts, etc., against decay
producing fungi. Based on label directions, two distinct application
types were assessed including predrilled hole treatments as well as
groundline treatments.  The pre-drilled hole treatments that are applied
using an automated rail tie application technique as well as the solid
stick product are expected to result in minimal exposure that can be
mitigated with personal protective equipment (PPE) are not assessed
quantitatively.  PPE should be required for these products to mitigate
potential exposure for leaks, etc.  The inhalation risks for the
pre-drilled hole spray applications using the mechanical pressure pumps
are not of concern.  However, dermal risks are triggered for this
application scenario for the treatment of distribution and transmission
poles.  Additionally, all of the dermal MOEs are below the target MOE
for the groundline brush-on treatments (MOEs less then or equal to 1). 
The brush-on treatment also represents the high-end exposures for the
trowel-on and impregnated wraps.  Inhalation exposure is expected to be
minimal for the groundline treatments because of the viscosity of the
product as well as its low vapor pressure.

The potential bystander inhalation exposure to sodium fluoride is
minimized by the extremely low vapor pressure.  The potential for dermal
exposure to bystanders (i.e., children playing in the vicinity of
treated poles) is minimized by the enclosure of the application site
(i.e., capping of pre-drilled holes and groundline applications covered
with dirt).

1.0		Introduction

	

  SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1  		1.1	Purpose  tc \l2 "1.1
Purpose  

		In this document, the Antimicrobials Division (AD) presents the
results of its review of the potential human health effects of
occupational and residential exposure to sodium fluoride. This
information is for use in EPA's development of the sodium fluoride
Reregistration Eligibility Decision (RED) document. 

		1.2	Criteria for Conducting Exposure Assessments tc \l2 "1.2	Criteria
for Conducting Exposure Assessments 

		An occupational and/or residential exposure assessment is required for
an active ingredient if (1) certain toxicological criteria are triggered
and (2) there is potential exposure to handlers (mixers, loaders,
applicators, etc.) during use or to persons entering treated sites after
application is complete.  For sodium fluoride, both criteria are met.
Toxicological endpoints were selected for short-, intermediate-, and
long-term dermal and inhalation exposures to sodium fluoride.  There is
the potential for occupational exposure to some of the application
methods used in the remedial wood treatment (e.g., brush-on, pressurized
sprays, etc).  Therefore, risk assessments are required for occupational
uses.

	In this document, handler scenarios were assessed by using unit
exposure data to estimate occupational exposures. Unit exposures are
estimates of the amount of exposure to an active ingredient a handler
receives while performing various handler tasks and are expressed in
terms of micrograms or milligrams of active ingredient per pounds of
active ingredient handled.  A series of unit exposures have been
developed that are unique for each scenario typically considered in
assessments (i.e., there are different unit exposures for different
types of application equipment, job functions, and levels of
protection).  The unit exposure concept has been established in the
scientific literature and also through various exposure monitoring
guidelines published by the USEPA and international organizations such
as Health Canada and OECD (Organization for Economic Cooperation and
Development).  Using surrogate unit exposure data, maximum application
rates from labels, and EPA estimates of daily amount handled, exposures
and risks to handlers were assessed.

		1.3	 tc \l2 "1.3	Chemical Identification 	Physical/Chemical Properties
tc \l2 "1.4	Physical/Chemical Properties 

		Table 1.2 shows physical/chemical characteristics that have been
reported for sodium fluoride.

Table 1.2.  Physical/Chemical Properties of Sodium Fluoride

Parameter	

Sodium Fluoride

Molecular Weight	42

Density	2.55 g/cm3 

Boiling Point	1704 °C

Water Solubility	

4.1 g/100 ml at 15 °C

Vapor Pressure	5.43 x 10-26 mmHg at 25 °C (EPI Suite)

2.0	 USE INFORMATION tc \l1 "2.0	 USE INFORMATION 

		2.1	 Formulation Types and Percent Active Ingredient tc \l2 "2.1	
Formulation Types and Percent Active Ingredient 

		The products containing sodium fluoride as the active ingredient (a.i)
are formulated as liquid ready-to-use, soluble concentrate, wraps, and
rods. Concentrations of sodium fluoride range from 8.39% to 97.5%.  

		2.2	 Summary of Use Pattern 

	The Agency determines potential exposures to handlers of the product by
identifying exposure scenarios from the various application methods that
are plausible, given the label uses.  Based on a review of product
labels, sodium fluoride is the active ingredient in remedial wood
treatments.  Specific application techniques are presented in Section 4
below. 

3.0		  SEQ CHAPTER \h \r 1 Toxicological Endpoints of Concern

	Table 3.1 presents the acute toxicity categories (USEPA 2007). 

Table 3.1. Acute Toxicity Categories for Sodium Fluoride

Study Type	Toxicity Category

Acute Oral Toxicity	II

Acute Dermal Toxicity	III

Acute Inhalation Toxicity	III

Primary Eye Irritation	II

Primary Dermal Irritation	IV

Dermal Sensitization	negative

	

	Table 3.2 summarizes the toxicological endpoints for sodium fluoride
(USEPA 2007). 

Table 3.2.  Summary of Sodium Fluoride Toxicological Endpoint Selection.

Exposure

Scenario	Dose (mg/kg/day) 	Level of Concern 	Study and Toxicological
Effects

Dietary Risk Assessments

Acute Dietary

(general population and females 13-49)

	No appropriate endpoints were identified that represent a single dose
effect.

Therefore, this risk assessment is not required.

Chronic Dietary

	No appropriate endpoints were identified.

Therefore, this risk assessment is not required.

Non-Dietary Risk Assessments

Short -Term Dermal 

(1 - 30 Days)

	

LOAEL = 20 mg/kg/day

	

Target MOE=300 

(10x inter-species extrapolation, 10x intra-species variation, 3x for
use of LOAEL)

	

Oral Subchronic Toxicity – Rat (Sodium Fluoride)

LOAEL = 20 mg/kg/day, based on significant reductions in body weight
gain and suppressed spontaneous motor activity.

Intermediate -Term Dermal 

(30 Days- 6 months)

	

NOAEL = 1.5 mg/kg/day 	

Target MOE=100 

(10x inter-species extrapolation, 10x intra-species variation)

	

6-month NTP oral toxicity study-mouse

LOAEL = 7.5 mg/kg/day based on  histopathology observed in bone with
degeneration in tibias and femurs of animals

Long-Term Dermal (> 6 months)

	LOAEL = 1.3 mg/kg/day	TARGET MOE = 300 (10x inter-species
extrapolation, 10x intra-species variation, and 3x for use of  LOAEL)

	2-year NTP chronic toxicity/carcinogenicity study in rats

LOAEL = 1.3 mg/kg/day, based on   dentine dysplasia in males and
females, and ameloblast degeneration in males

Short-term Inhalation 

(1-30 days)	LOAEL = 20 mg/kg/day

	Target MOE=300 

(10x inter-species extrapolation, 10x intra-species variation, and 3x
for use of LOAEL)  

Note:  10x route extrapolation for confirmatory inhalation study.

	Oral Subchronic Toxicity – Rat (Sodium Fluoride)

LOAEL = 20 mg/kg/day, based on significant reductions in body weight
gain and suppressed spontaneous motor activity.

Intermediate-term Inhalation	NOAEL = 1.5 mg/kg/day 	Target MOE=100 

(10x inter-species extrapolation, 10x intra-species variation)

 Note:  10x route extrapolation for confirmatory inhalation study.
6-month NTP oral toxicity study-mouse

LOAEL = 7.5 mg/kg/day based on  histopathology observed in bone with
degeneration in tibias and femurs of animals

Long-term Inhalation	LOAEL = 1.3 mg/kg/day	TARGET MOE =300 (10x
inter-species extrapolation, 10x intra-species variation, and 3x for use
of LOAEL)

Note:  10x route extrapolation for confirmatory inhalation study.	2-year
NTP chronic toxicity/carcinogenicity study in rats

LOAEL = 1.3 mg/kg/day, based on   dentine dysplasia in males and
females, and ameloblast degeneration in males

Cancer

	Sodium fluoride has been classified as a “Group D” (inadequate
evidence of carcinogenicity).  This conclusion is consistent with the
recent report by the National Academy of Sciences which concluded that
‘the evidence on the potential of fluoride to initiate or promote
cancers, particularly of the bone, is tentative and mixed.’ 

4.0		Remedial Wood Treatment

4.1		Exposure Scenarios

	Sodium fluoride is used as a remedial wood treatment for the protection
against decay producing fungi.  Table 4.1 summarizes the various sodium
fluoride label parameters used in this assessment including EPA Reg.
No., percent active ingredient, signal word, personal protective
equipment, and use directions/application methods.  Application
techniques include a product-specific dispenser, grease/caulking guns,
pressurized sprayers, preservative cartridges, brush-on and/or trowel-on
applications.  The personal protective equipment (PPE) listed on the
label range from a minimum protection of goggles to a maximum protection
of goggles, gloves, and respirators.  Label PPE should be reviewed for
accuracy and consistency.

Table 4.1.  Summary of Sodium Fluoride Labels.

EPA Reg No.	% ai	Signal Word	PPE	Label Directions

(e.g., application techniques, rates,etc)

3008-58	97.5	Danger	Respirator, goggles	Includes a non pesticide
statement

75340-2

	54.92	Warning	Gloves	TIE-GARD dispenser; grease gun; pressurized
applicator; Apply to drilled holes to “fill” and cap; Used on rail
road ties and structural timbers such as bridge pilings and posts.

75341-6	92.6	Danger	Gloves	FLURODS (i.e., preservative cartridges, solid
sticks) placed into drilled holes and capped.  For treating poles,
posts, timbers, crossties, etc.  Rate:  39.2 grams/cubic foot wood.

75341-4	70.6	Danger	Gloves, goggles	PoleWrap.  Groundline treatment. 
Dig 20 inches around pole, wrap down to 18 inches below groundline to 2
inches above groundline and cover with dirt.

75341-5	44.4	Danger	Goggles	Used in combination with copper naphthenate.
 Brush-on, trowel-on, grease gun.  1/16th of an inch rate 18 inches
below and 3 inches above groundline and covered with a wrap.  Also used
in drilled holes applied by a grease gun and capped (paste density 12
lbs/gallon).

75341-12	8.39	Danger	Gloves, goggles, respirator, and respirator when
spraying for continued or prolonged use or frequent use	Used in
combination with copper naphthenate.  Mix 1 gallon of product with 1.5
gallons of water.  Apply using air or mechanical pressure pump into
prepared opening (assume pre-drilled).  Rate:  1 gallon of treatment
solution per cubic foot of wood.

75341-13	44.42	Warning	Goggles, face shield or safety glasses,
protective clothing, and chemical resistant-gloves	Used in combination
with copper naphthenate.  Brush-on, trowel-on, grease gun.  1/16th of an
inch rate 18 inches below and 3 inches above groundline and covered with
a wrap.  Also used in drilled holes applied by a grease gun and capped.

Chemical-specific exposure data were not submitted to support the
remedial wood applications.  Therefore, AD developed a screening-level
assessment using surrogate data to determine the potential risks
associated with remedial wood treatment.  Based on the label review
listed in Table 4.1 above, there are two basic remedial applications: 
(1) applying product into pre-drilled holes; and (2) applying product
around the circumference of poles at or below the groundline.  Each
remedial application can be applied using various techniques.  Surrogate
exposure data are not available for all application techniques specified
on the label.  Representative exposure scenarios (i.e., application
techniques) are used to represent the potential worker short-,
intermediate, and in some cases long-term durations of inhalation and
dermal exposures.  Table 4.2 presents the representative exposure
scenarios used to assess the labeled remedial wood treatment uses.

Table 4.2.  Respresentative Exposure Scenarios for Remedial Wood
Treatments.

Remedial Applications	High-end Exposure Scenarios	Application Techniques
Represented by the High-end Exposure Scenario

Pre-drilled holes	Closed systems (PPE mitigation)	TIE GARD dispenser for
rail ties; FLURODS (solid sticks)

	Sprays	Grease/caulking gun; air or mechanical pressure pump

Groundline	Brush-on	Brush; Trowel; PoleWrap (dry wrap)

4.1.1	Pre-Drilled Hole Treatments

TIE-GARD and FLURODS:

TIE-GARD and FLURODS are sodium fluoride products that are inserted into
pre-drilled holes and capped are expected to result in minimal
inhalation and dermal handler exposure because the products are
engineered to be closed systems.  The FLURODS are solid sticks that are
placed in the pre-drilled holes.  TIE-GARD is a gel product containing
sodium fluoride.  The automated rail tie use is packaged in 30 gallon
PVC closed head drums.  It is applied from high capacity rubber track
machinery that rides on railroads and automatically injects the gel
product into rail ties.  Any potential for exposure from leaks/spills
from these products (i.e., TIE GARD and FLURODS) is believed to be best
mitigated by the label requirement of PPE such as chemical resistant
gloves, goggles, long pants, and long sleeved-shirts.  Therefore, the
handler risks to pre-packaged products are not quantified.

Spray/Injection Applications:

Although EPA does not have a specific surrogate exposure scenario for
injection of pesticides into wooden poles, similar exposure data for
hand-held application equipment exist.  The spray application is
believed to represent the high end of exposure to the grease gun.  The
exposure data for hand-held applications that are available to EPA
include data from the Pesticide Handlers Exposure Database (PHED) and
the Outdoor Residential Exposure Task Force (ORETF).  The data available
from these sources are for garden hose-end sprayers, low pressure
hand-wands, backpack sprayers, high pressure handwands, and rod shank
termiticide applications.  The most representative data available for an
injection-type hand-held devise is the rod shank termiticide application
from PHED.  Other equipment types are not believed to be as
representative because each one involves a spray and the injection into
the pole will minimize spray.  

The rod shank termiticide injection data in PHED are used to develop a
screening-level assessment for the pole use.  The dermal unit exposure
(UE) for combined liquid pour and termiticide injection is based on 17
replicates with the test subjects wearing a single layer of clothing and
chemical resistant gloves with AB grades (i.e., guideline
recommendations for analytical quality).  The dermal UE is 0.36 mg/lb
ai.  The inhalation UE is based on the same 17 replicates and the grades
are also AB.  The inhalation UE is 0.0022 mg/lb ai.  Although not all of
the labels currently specify the use of chemical resistant gloves (e.g.,
EPA Reg. No. 75341-5), the “gloved” clothing scenario is the only
one available to assess risks.  

Groundline Treatments

Groundline treatments consist of brush and trowel-on applications as
well as impregnated wraps around poles.  Once applied, the pole
treatment is covered with dirt.  The most representative surrogate
exposure data available to assess the high-end of the exposure potential
are for painting with a paint brush.  The product is expected to have a
much higher viscosity then paint.  Because of the high viscosity and low
vapor pressure, inhalation exposure is expected to be minimal.  Dermal
unit exposure values for paint brush applications from PHED were used
(single layer of clothing).  The dermal unit exposure is 24 mg/lb a.i.
for the painting scenario for a test subject wearing long pants,
long-sleeved shirt, and chemical resistant gloves.

4.2		Application Rates and Amounts Handled

Label directions indicate that sodium fluoride is applied into poles,
timbers, etc, via four different formulations; paste, bandage or wrap,
liquid and solid rods. The application for these formulations is very
different from each other due to the physical properties and percentage
of sodium fluoride present in each formulation. Typically paste
formulations are applied by brush-on application around the groundline
area of pole and then wrapped with a protective barrier before being
backfilled with dirt. The dry impregnated wrap is applied around the
groundline portion of the pole. Liquid formulations are normally applied
to internal voids through means of pressurized injection and rods are
applied by drilling application holes, inserting the rods into the holes
and then plugging them.

Labeled application rates for pastes are to apply by brush to a
thickness of 1/16th inch.  The dry wrap is applied by cutting the wrap
to match the circumference of the pole. Liquid application instructions
include filling application holes to refusal and more specific
instructions such as 1 gallon of diluted solution per cubic foot of
wood.  However, label directions are not provided to determine neither
the number of holes per pole nor the number of cubic feet per pole to be
treated with sodium fluoride. Therefore, for this assessment 1 cubic
foot of wood per pole is assumed to be treated for the spray/injection
application.  

Specific amounts of sodium fluoride applied by workers daily are not
available.  Therefore, in addition to the number of cubic feet treated
per pole, the number of poles treated per day (i.e., pre-drilled
treatments, not groundline applications) with sodium fluoride was also
estimated.  

The amount of paste applied to each pole for groundline treatments is
estimated to be 0.167 gallons/pole for distribution poles and 0.255
gallons per transmission pole (i.e., 21 inch wide treatment x up to 34
inch circumference for distribution poles and 50 inches for transmission
poles x 1/16 inch thickness of product treatment).

Distribution Poles - the smaller diameter wooden distribution poles
(~140 million distribution poles in service) are treated at a rate of
~24 per day. Workers treat these types of poles as their main work
function, treating 5 days per week, on a yearly basis (i.e., 250
days/year).  This scenario is represented by the short-, intermediate-
and long-term exposure durations.

Transmission Poles - the larger wooden transmission poles are treated at
a rate of 30 per day. Workers treat these types of poles as their main
work function, treating 5 days per week, on a yearly basis (i.e., 250
days/year).  This scenario is represented by the short-, intermediate-
and long-term exposure durations.

4.3		Exposure and Risk Estimates

Table 4.3 presents the potential dermal and inhalation short-,
intermediate-, and long-term exposures and risks for the remedial pole
treatment uses of sodium fluoride.   The exposure and risks to handlers
of the TIE-GARD product used in the automated rail tie treatment system
and the solid stick FLURODS are expected to be minimal and are not
quantified.  

The spray applications into pre-drilled holes indicate no dermal risks
of concern for the short-term duration for the distribution poles. 
Dermal risks, however, are triggered fro the intermediate- and long-term
durations.  The intermediate- and long-term dermal MOEs are 26 and 22,
respectively, with a target MOE of 300.  No inhalation risks are
triggered for the distribution poles at any timeframe.

For the spray applications into pre-drilled holes for the transmission
poles, the inhalation (all durations) and short-term dermal risks are
not of concern.  However, the short-, intermediate- and long-term dermal
risks for the transmission poles are of concern.  The short-,
intermediate- and long-term dermal MOEs are 280, 21 and 18,
respectively, with a target MOE of 300 for short-term and 100 for
intermediate-term.

All of the dermal MOEs are below the target MOE for the groundline
brush-on treatments (MOEs less then or equal to 1).  The brush-on
treatment also represents the high-end exposures for the trowel-on and
impregnated wraps.  Inhalation exposure is expected to be minimal for
the groundline treatments because of the viscosity of the product as
well as its low vapor pressure.

Table 4.3.  Dermal and Inhalation Exposure and Risks for Remedial
Applications of Sodium Fluoride to Poles.

 Application

 	Dermal UE

(mg/lb ai)	Inhalation UE

(mg/lb ai)	Rate

(gal/pole)	Rate

(lb ai/gal)	 

# poles	Dermal dose

(mg/kg/day)	Inhalation dose

(mg/kg/day)	Dermal MOEs	Inhalation MOEs

ST (300)	IT (100)	LT (300)	ST (300)	IT (100)	LT (300)

Spray (Distribution Poles)

 	0.36	0.0022	1	0.47	24	0.058	0.00035	350	26	22	56,000	4,200	3,700

	Spray (Transmission Poles)

 	0.36	0.0022	1	0.47	30	0.073	0.00044	280	21	18	45,000	3,400	2,900

	Brush-on (Distribution Poles)

 	24	NA	0.225	5.33	24	9.87	NA	2	<1	<1	NA

	Brush-on (Transmission Poles)

 	24	NA	0.368	5.33	30	20.2	NA	1	NA	NA	NA

	NA = not applicable (e.g., short-term (ST) MOEs are only applicable for
the high treatment frequency of poles).

ST = short-term; IT = intermediate-term; LT = long-term.

UE are from PHED for termiticide MLAP, liquid pour, rod shank injection

	Dermal unit exposure represents workers wearing is single layer of
clothing and chemical resistant gloves.

	Treatment solution for spray from EPA Reg. No. 75341-12 (i.e., 1 gal
product x 8.34 lb/gal x 8.39% ai / 1.5 gallons water = 0.47 lb ai/gal
treatment solution)

	Brush-on rate EPA Reg No 75341-5 is 44.4% ai; density of 12 lb/gal =
5.33 lb ai/gallon

# poles = registrant estimate during the reregistration phase 1 error
comment period (Distribution is 24 poles per day and transmission is 30
poles per day). 

Dermal (mkd) = Dermal UE x rate x # poles x 1/70kg

	Inhalation dose (mkd) = Inhalation UE x rate x #poles x 1/70kg

MOE ST Dermal & inhalation = LOAEL 20 mkd / dose;  UF = 300

MOE IT Dermal & Inhalation = NOAEL 1.5 mkd / dose; UF = 100

MOE LT Dermal & Inhalation = LOAEL 1.3 mkd / dose; UF = 300

5.0		Bystander/Residential Exposure and Risks

In general, remedial wood treatment for poles and beams on bridges do
not occur in high traffic areas for bystanders.  However, distribution
poles are numerous and often located in people’s front yards.  The
vapor pressure of sodium fluoride is negligible (i.e., 5.43x 10-26 mmHg
at 25 °C), and therefore, no vapor will be released in the vicinity of
treated poles.  Additionally, label directions to cap treated holes
after application will minimize any potential for dermal contact. 
Likewise, groundline treatments are also covered (i.e., brush-on and
wrap treatments are below the groundline and then covered with dirt) and
will minimize potential dermal contact to children playing in areas of
treated poles.  

6.0		Conclusions

Applications of sodium fluoride include pre-drilled hole treatments and
groundline treatments.  The pre-drilled hole treatments are applied with
pre-packaged insert products and also mechanical pressure pumps. 
Exposure to the automated TIE-GARD and solid stick FLURODS are expected
to be negligible and is not assessed quantitatively.  PPE should be
required for these products to mitigate potential exposure for leaks,
etc.  The inhalation (all durations) and short-term dermal risks for the
pre-drilled hole spray applications for the distribution poles using the
mechanical pressure pumps are not of concern.  However, the dermal risks
for the intermediate- and long-term dermal risk for the distribution
poles are of concern (i.e., MOEs are 26 and 22, respectively, with a
target MOE of 100 and 300, respectively).  For the transmission poles,
no inhalation risks were identified for any duration.  However, the
dermal risks for the short-, intermediate- and long-term durations for
the transmission poles are of concern (i.e., MOEs are 280, 21, and 18,
respectively, with a target MOE of 300, 100, and 300, respectively). 
All of the dermal MOEs are below the target MOE for the groundline
brush-on treatments (MOEs less then or equal to 1).  The brush-on
treatment also represents the high-end exposures for the trowel-on and
impregnated wraps.  Inhalation exposure is expected to be minimal for
the groundline treatments because of the viscosity of the product as
well as its low vapor pressure.

EPA has used the best available surrogate exposure data from PHED and
CMA to develop a screening-level assessment for the handlers of sodium
fluoride.  The following uncertainties should be considered by the
regulatory risk managers during the decision making process:

Unit exposures are not available for the scenarios that are prescribed
for remedial pole injection.  Nonetheless, the data from PHED for
combined mixing/loading/injecting a liquid termiticide is a reasonable
surrogate for the pole treatment as the label for the remedial wood
treatment indicates to apply a spray into predrilled holes with an air
or mechanical pressure pump.  The PHED termiticide scenario is
considered to be of “high confidence” (i.e., 17 replicates of Grade
AB data – indicating the analytical portion of the study meets EPA
exposure test guidelines). 

Sodium fluoride is used to treat both poles and timbers.  The assessment
for the remedial wood treatments is based on applications to
distribution and transmission poles as representative of all the
remedial treatments.  Although it is unknown how many timbers in a
bridge or other structure are treated, the pole use is believed to be
representative of the high end use.

The use information for the remedial pole treatments is based on the
registrant’s response during the error comment period.  The
individuals contacted have experience in these operations and their
estimates are believed to be the best available without undertaking a
statistical survey of the uses.  

The potential bystander inhalation exposure to sodium fluoride is
minimized by the extremely low vapor pressure.  The potential for dermal
exposure to bystanders (i.e., children playing in the vicinity of
treated poles) is minimized by the enclosure of the application site
(i.e., capping of pre-drilled holes and groundline applications covered
with dirt). 

Reference

USEPA.  2007.   Toxicological endpoint selection memorandum.   

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