Document ID: EPA-HQ-OPP-2008-0347-0009
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-10-29T04:00Z

DRAFT  Policy 013

Science Advisory Council for Exposure

Policy #:	Draft

Regarding:	Postapplication Exposure Assessment For Children From Pet
Treatments

Date:		January xx, 2002

Index terms:	Post-application, pet treatments, dips, shampoos, collars,
dusts, activity, residential exposure, children, dermal exposure

Contacts:	Jeff Dawson, Tim Leighton

ISSUE:

Many types of chemicals can be used to control pests on companion
animals such as dogs and cats.  These pests can include fleas, ticks,
and other disease carrying insects or parasites.  The Agency has
addressed these exposures since the advent of the Food Quality
Protection Act and the issuance of the first version of its Standard
Operating Procedures For Residential Exposure Assessment in 1997.  Since
1997, little more has become known about how these exposures might take
place.  Even so, it is important to make incremental changes in the
approaches used and to consider new data as it becomes available so that
assessments reflect the most current information.  The products that are
used to control pests on animals are varied and can include dusts, dips
and shampoos, collars, spot-ons, and feed-throughs.   The Agency is
interested in the use of any of these that results in exposure to
children although the Agency generally is not concerned about
feed-throughs and spot-ons based on how they are used.  It is believed
that small children (e.g., toddlers) potentially have the highest
exposures associated with the use of these types of products compared to
adults or older children because of the time spent with animals and the
nature of the contact they have with animals.  For example, a small
child might be more prone to put their hands in their mouth after
petting a dog without washing their hands.  This policy illustrates how
the Agency addresses exposures from different types of animal treatment
products.

BACKGROUND:

The Agency began considering exposures from pet treatment products
routinely based on the 1997 version of the SOPs For Residential Exposure
Assessment after the passage of the Food Quality Protection Act.  Dermal
exposures at this point in time were calculated based on a percentage of
the total amount of active ingredient applied.  Hand-to-mouth exposures
were calculated using the older SOP approaches.  In September of 1999,
the Agency proposed a number of modifications to the manner in which it
calculated residential exposures to the FIFRA Science Advisory Panel for
review.  Among the proposals were a number of changes that impacts how
the Agency calculated exposures from treated pets.  The major changes 
included the use of a hug approach for calculating dermal exposures and
modifications to the manner in which hand-to-mouth exposures were
calculated (e.g., addition of a saliva extraction factor, modification
to the frequency and surface area factors used for hand-to-mouth
exposures).  More detailed information concerning these changes can be
found in the document Overview of Issues Related to the Standard
Operating Procedures For Residential Exposure Assessment available at
www.EPA.Gov (link to SAP Archives).  The approaches outlined in this
document were adopted at that point by the Agency for calculating
exposures from treated pets. 

The scientific data in this area are very limited but the Agency has
attempted to use the available information to formulate policies that
are protective without being unreasonable.  Much of the scientific
research related to this topic is being completed or has been done at
the Center For Environmental Health Sciences, College of Veterinary
Medicine, Mississippi State University with funding through Agency STAR
grants (Science to Achieve Results) by researchers such as Boone and
Chambers.  In one of their recent publications (Boone, 2001), they put
the potential for exposure in the general population in perspective:

(A demographic survey of companion animals by the American Veterinary
Medical Association indicated that in 1991 approximately 34.6 million
households (36.5%) in the United States owned a dog or dogs, a number
essentially unchanged from 1987.  More households had dogs as pets than
other types of animals.  There was a mean of 1.52 dogs per  dog-owning
household, yielding an estimated national population of 52.5 million
dogs.  Fifty percent of pet-owning households were parental households
with children; in comparison, 40% of total households have children. 
The authors of that study projected that there would be 53.6 million
dogs in the United States in 1998.  These dogs would be a source of
exposure to millions of children who live in the same environment and
come into direct contact with dogs treated with flea control products.(

This current policy summarizes the changes that were made to the SOPs
For Residential Exposure Assessment based on the 1999 presentation at
the FIFRA SAP.  Additionally, since that time, there have been proposed
refinements over and above those presented.  Many of these have been
discussed and approved at routine Exposure SAC meetings.  These changes
are also included below.

POLICY:

Exposures from treated pets are thought to occur as a result of dermal
contact with their fur and from young children (i.e., toddlers) putting
contaminated hands in their mouth.  Because children are believed to
have the highest exposures because of their behaviors, the Agency
completes its risk assessments using toddlers as the model or sentinel
population for exposure.  The  approach that is used in the calculations
can be summarized very concisely in that it involves 1) defining residue
deposition on the animal from treatment; 2) defining how much can be
removed  by touching the animal (i.e., transferability to the skin); 3)
defining how long it takes residues to dissipate from the animal; 4)
defining how much contact toddlers may have with treated animals; and 5)
defining human dose related to contact with treated animals.  The
approaches for each step in the calculations are presented below as well
as the recommended input values.

Step 1: Defining Residue Deposition On Treated Animal

The first step required for defining how much residues are deposited on
the surface (fur/coat) of the animal is to identify the label
application rate on a per animal basis if possible for dusts and
liquids.  For collars, the active lifetime of the collar is usually
included on labels.  This is needed to define daily emission rates from
the collar.  If these values are not available, the value from Exposure
SAC Policy 12 (( container of end-use product per animal) is to be used
to define how much material is deposited on the animal for each
treatment.  Labels which have specific directions on the amount to be
used should also be considered in the assessment.  For example, a label
might say a can of material is good for five treatments.

Dusts and Liquids:  The next step in the process is to equally spread
the residues over the surfaces of the treated animals.  Dusts and liquid
treatments are handled differently than the use of collars.  This is
done by dividing the amount of active ingredient used to treat the
animal by the surface area of a dog which has been selected by the
Agency to represent companion animal uses.  Cat only treatments will
have to be defined separately on a case-by-case basis.  The surface area
for a dog is based on a 30 pound animal and an algorithm described in
the 1999 presentation to the SAP ((12.3*((BW (lb)*454)^0.65)) resulting
in a surface area for the standard treated dog of 5986 cm2. 

For illustrative purposes, if an animal was treated with 1 gram of
active ingredient the deposited total residues would be 167 (g/cm2
(i.e., [1 g * 1000 mg/g * 1000 (g/mg]/5986 cm2).

Collars:  The intent of a collar is significantly different from the use
of dusts or liquid treatments where the entire dog is to be coated as a
course of treatment.  For collars, residues are not spread evenly over
an entire animal because residues from collars are expected to be
localized.  This position is supported by ongoing research at
Mississippi State University where transferable residues from collar use
have been measured and they appear to be localized around the collar
region with residues diminishing as distance from the collar increases. 
The Agency has used these data to define a region covered by a single
dermal hug around the collar for risk assessment purposes (see Step 2
below for further information).

Step 2: Defining residue removal while touching the animal (i.e.,
transferability to the skin)

The next step in the process is to define how much can rub from the
treated animal(s skin and fur when toddlers contact the animal.  Dusts
and liquid treatments such as shampoos are again considered differently
from collars in this step of the process.

Dusts and Liquids:  The Agency proposed at the 1999 FIFRA SAP that a
value of 20 percent transferability be used for liquids and dusts.  This
value should be used by exposure assessors unless  another value can be
justified such as through the use of chemical-specific data.

Collars: As indicated above, the intent of a collar is significantly
different from the use of dusts or liquid treatments where the entire
dog is to be coated as a course of treatment.  For collars, residues are
not spread evenly over an entire animal because residues from collars
are expected to be localized.  In the recent monitoring efforts (Boone
et al at ISEA, 2001) at Mississippi State University, residues were
collected on the neck with the collar on, on the neck with the collar
off, and on the back of the dog.  The Agency took the average of these
three areas to define the transferable residues from a collar.  The
Agency also normalized the results to calculate a factor on a per gram
active ingredient in the collar basis.  The factor that should be used
by assessors when considering the use of collars is 0.00027 mg/cm2/gram
ai in collar.  The specific data and approach used to define this factor
was discussed at several SAC meetings.  The notes and discussions are
summarized in SAC meeting minutes. [Question to SAC - should we use
different factors for short- and inter-term??]

Step 3: Defining how long it takes residues to dissipate from the animal

The next step in the process is to define how long residues are present
on the animal.  Dusts and liquid treatments are handled differently than
the use of collars.  

Dusts and Liquids: Dusts and liquid treatments are expected to dissipate
from the animal after treatment.  As such the Agency treats this like
any other residue dissipation situation in a risk assessment (e.g., DFRs
or TTRs).  In cases, where no chemical-specific dissipation data are
available, the Agency uses a generic factor of 5 percent of the total
dissipates per day.  This is half that used for DFRs and TTRs because
the limited pet fur data indicate lower dissipation rates (based on
unpublished phosmet data conducted concurrently with Boone, 2001).

Collars:  The intent of a collar is significantly different from the use
of dusts or liquid treatments where a collar is intended to provide
constant control over a long period of time.  This means that a collar
should have a slow, constant emission of residues over its useful
lifetime (i.e., there is no real dissipation).  As such, the Agency
calculates a daily constant emission rate over the life of the collar
that is used (i.e., how much emits per day from the collar over the life
of the collar).  The emission term described in Step 2 above is based on
longitudinal sampling so the Agency is confident that this value
represents an appropriate factor for calculating long-term emissions
from collars.

Step 4: Defining how much contact toddlers may have with treated animal

At the September 1999 FIFRA SAP meeting, the Agency proposed a number of
new or revised methods for calculating residential exposures including
from dermal contact with treated pets and for hand-to-mouth behaviors. 
The newly proposed approach for dermal contact with treated pets used a
single hug technique for a child wearing short pants and a short-sleeved
shirt.  Using a clothing penetration factor of 50 percent and accounting
for bareskin, the total surface area of a child  that contacts a treated
pet is 1875 cm2/hug.  In this approach, once a hug has occurred, a
residue equilibrium is thought to be established on the child. 
Therefore, a single hug/loading of the skin is the basis for this
approach.

Revisions to the inputs used to calculate hand-to-mouth exposures were
also presented at the 1999 FIFRA SAP.  The basic methodology remains the
same.  There were three major input changes including: 1) hand surface
area per contact was changed to 20 cm2 per event to represent the palmar
surfaces of the three middle fingers; 2) the frequency of events was
increased from 1.56 events/hour to 20 events/hour; and 3) a saliva
extraction factor of 50 percent was added to account for the likelihood
that residues are not quantitatively removed every time the hand goes in
the mouth.

Step 5: Defining human dose related to contact with treated animal

The algorithms which can be used to calculate dermal and hand-to-mouth
exposures are presented below.  They incorporate each of the steps
described above.

Dermal Dose:

 

where:

D		=	dose from dermal pet contact (mg/day);

AR		=	application rate or amount applied to animal in a single treatment
(mg ai/animal);

FAR		=	fraction of the application rate available for dermal contact as
transferable residue (20%/100); 

SApet		=	surface area of a treated dog (5986cm2/animal);

t		=	time after application (days);

DR		=	fractional dissipation rate per day (5% per day/100); and

SA hug		=	surface area of a child hug (1875cm2 contact/hug).

[Note: For collars, the ((AR*FAR)/SAPet) term is replaced by the generic
factor for determining transferable residue levels described above in
Step 2 (0.00027 mg/cm2/gram ai in collar).  An adjustment to the proper
amount of active ingredient is also required.]

Hand-to-mouth dose:

 

where:

D		=	nondietary ingestion dose from with treated pets (mg/day);

AR		=	application rate or amount applied to animal in a single treatment
(mg ai/animal);

FAR		=	fraction of the application rate available as transferable
residue (20%/100);

SApet		=	surface area of a treated dog (5986cm2/animal);

t		=	time after application (days);

DR		=	fractional dissipation rate per day (5% per day/100); 

SAL		=	saliva extraction factor (50% extractability);

SAhands		=	surface area of the hands (20cm2);

Freq		=	frequency of hand-to-mouth events (20events/hour); and

Hr		=	exposure duration (2 hours).

[Note: For collars, the ((AR*FAR)/SAPet) term is replaced by the
generic factor for determining transferable residue levels described
above in Step 2 (0.00027 mg/cm2/gram ai in collar).  An adjustment to
the proper amount of active ingredient is also required.]

ISSUES FOR CONSIDERATION:

There are several other issues that should be generically considered in
the calculation of postapplication residential risk values such as
whether or not to average transferable residue levels over specific
timeframes.  Please refer to other appropriate Agency policy documents
for guidance on these issues such as the SOPs For Residential Exposure
Assessment, Health Effects Division Hotsheets, or policies developed by
the Exposure Science Advisory Council.

The pet collar study (Boone et al at ISEA, 2001) also included a
biological monitoring component.  Although the pet collar study is a
good start into researching the potential exposures children may receive
from treated pet collars, the design of the biological monitoring
portion of the study was insufficient for regulatory purposes.  The
study design did not include a (play routine( to determine exposure to
children that have intensive contact with the dog.  The monitoring of
children without a specific activity to mimic those who play with their
dogs (i.e., study did not record contact of children with the dog) would
require a larger sample size than 24 to be able to draw regulatory
conclusions from the biological monitoring portion of the study. 

The scope of this policy should also be carefully considered.  This
policy is not intended to address issues of aggregation.  This policy is
only intended to focus on children(s postapplication exposures from
treated animals.

REFERENCES:

Boone, J.S.; Chambers  J.E.; and Tyler, J.W., (2001), Exposure to
Children and Adults to Transferable Residues Chlorpyrifos from Dogs
Treated with Flea Control Collars, Presented at International Society of
Exposure Analysis Meeting, 2001.

Boone, J.S.; Tyler, J.W.; and Chambers, J.E. (2001), Transferable
Residues From Dog Fur and Plasma Cholinesterase Inhibition in Dogs
Treated With A Flea Control Dip Containing Chlorpyrifos, Environmental
Health Perspectives, Volume 109, Number 11, November 2001.

U.S. EPA (1997) Standard Operating Procedures For Residential Exposure
Assessment, Health Effects Division of the Office of Pesticide Programs.

U.S. EPA (1999) Overview of Issues Related To The Standard Operating
Procedures For Residential Exposure Assessment, Health Effects Division
of the Office of Pesticide Programs. [Presented to the FIFRA SAP in
September, 1999.]

DRAFT, DELIBERATIVE, INTERNAL TO HED