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Item No.: 6030

Framework for Assessing Non-
occupational, Non-dietary (Residential)
Exposure to Pesticides
(Draft 12/22/98)

Pesticide - a

compound used to
control a pest. A
pest can be an
insect, plant or any
organism such as a
mold or bacteria.

Executive Summary

Non-occupational, non-dietary exposure assessment is an
important component in establishing an individual's overall risk
from pesticides. This type of assessment focuses primarily on
those exposures that occur in and around the home (otherwise
known as residential exposure assessment). It is important to
note that exposures that occur as a result of pesticide
applications in schools, parks and day care centers are
included under the term "residential." Residential exposures
are "non-dietary" in nature (i.e., through the skin or inhaled).

The importance of non-dietary residential exposure assessment
has only increased with the passage of the Food Quality
Protection Act of 1996 and the statute's increased emphasis on
the protection of children. EPA is currently refining its
assessments in order to improve overall quality and achieve
more realistic exposure estimates. This paper discusses:

~	exposure basics;

~	how EPA currently conducts non-dietary residential
exposure assessment;

~	the generally conservative nature of the Agency's non-
dietary residential exposure assessment; and

~	how EPA is refining non-dietary residential exposure
assessments.

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Exposure Basics

Why Does EPA Regulate Pesticide Exposure?

The Agency's basic mandate is to protect the environment and
to protect the general public from unsafe exposure to
pesticides. Assessing the exposure a person might receive to a
pesticide is a key component of making sure the person is
protected.

Congress has passed three main statutes that require us to
make sure that pesticides are used safely:

~	The Federal Insecticide, Fungicide, Rodenticide Act
(FIFRA) as amended in 1988;

~	The Federal Food, Drug, and Cosmetic Act (FFDCA);
and

Pesticide Residue

- can be the original
(known as the
parent) chemical or
can be a break-
down product (such
as a metabolite)

~	The Food Quality Protection Act (FQPA) of 1996 (which
updates both FIFRA and FFDCA)

How are We Exposed to Pesticides?

Basically, we are exposed to pesticide residues through four

ways:

~	using a pesticide (including mixing it up and spraying it);

~	eating food that contains pesticide residues;

~	using drinking water that contains pesticide residues; or

~	coming into (or near) an area where a pesticide has
been used or deposited, and touching surfaces,
breathing vapors in the air or by putting contaminated
hands or objects in ones mouth.

What Exposures to People Does EPA Regulate?

The agency has developed a series of tools including models,

databases, and guidance/reference documents that are used in

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conjunction with chemical-specific information to conduct
pesticide exposure assessments. The four basic kinds of
exposures we currently look at include:

~	Dietary Exposure from Food - how much pesticide
residues we may receive through our daily diet;

~	Drinking Water Exposure - how much pesticide residues
we may receive through our drinking water. (It should be
noted that not all pesticides are found in drinking water
and this exposure analysis is conducted on a proportion
of chemicals.);

~ Occupational Exposure - how much pesticide residue we
may receive directly from use at our places of work.

(This is especially important for professional pesticide
applicators in residential/agricultural settings and
farmers.); and

~ Residential Exposure - how much pesticide residues we
may come in contact with beyond our diet and outside
occupational settings, primarily in our homes and our
lawns and gardens. Also included in this category are
other general population exposures such as in schools,
parks and daycare centers.

EPA uses the term
"residential
exposure" to refer
to any exposure to
any person who
lives in a home.
This means
children, as well as
adults, are taken
into consideration.

Residential Exposure

What is Residential Exposure?

EPA looks at residential exposure by assessing how a person

could come in contact with the pesticide by:

1)	using the pesticide in and around the home (home
applicator) and

2)	touching, breathing or ingesting (non-dietary) any
residues that remain in and around the home after the
pesticide is used (post-application).

The "home" is not limited to the inside of the actual building.

Use of a pesticide on the property outside a home (such as use

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The term "home"
means any domicile
(apartment, house
trailer, etc.), not just
a single family
dwelling.

Exposure
Scenario - a

description of a
location and activity
that leads to
pesticide exposure.

Toxicity Endpoint

-A dose where no
adverse effects are
measured.

of a lawn pesticide product) is also considered a residential
use; examples would be products that are used on pets, lawns
or gardens.

How is a Residential Risk Assessment Conducted?

Addressing exposures to the general population, and
particularly to children, is a complex task. Because of the many
ways in which non-dietary residential exposures can occur, the
agency has developed "Standard Operating Procedures (SOPs)
for Residential Exposure Assessment" in order to add
consistency and transparency to the risk assessment and
regulatory process.

The SOPs were developed very shortly after the passage of
FQPA and address over 40 different exposure scenarios. The
SOPs provide guidance for our scientists to ensure consistency
in the risk assessment process. The SOPs were developed
using the most current data available and provide a "handbook"
approach by presenting a description of each scenario with
recommended algorithms, example calculations, a discussion of
uncertainties and available references.

The first step in the risk assessment process identifies the uses
of a pesticide from its registered label (such as use on lawns,
use on carpets, crack and crevice, etc.) and how it's applied
(powder, spray, fogger, etc.).

Secondly, the pesticide's toxicity is studied. EPA determines
the most sensitive effect for each exposure route. A toxicity
endpoint is ascertained for several exposure durations (such as
acute , chronic, etc.).

Next, all appropriate exposure scenarios are determined.
Examples of scenarios include:

~	A toddler crawling on a treated lawn

~	A person spraying a liquid pesticide

~	A person working in a home garden

~	A person living in a house treated for insects

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Pesticide Handlers
Exposure
Database (PHED) -

A large database of
actual pesticide
exposure studies
that EPA uses to
estimate exposure
when data are not
available for a
specific chemical
exposure scenario.

A company may be required to conduct exposure studies that
address specific exposure scenarios for an individual specific
chemical. If an exposure study that addresses a specific
exposure scenario has not been conducted, EPA scientists will
use a model to evaluate available data, published literature, or
some other source of information to develop a risk assessment
for that scenario.

How Does EPA Assess a Residential Exposure for an
Applicator?

EPA uses a model that focuses on those who directly handle or
apply pesticide-containing products. The premise of this model
is that exposure levels are related to the kind of equipment
used during application (such as spray can, tractor-drawn
sprayer, handheld garden sprayer); the physical form of the
product (for example, liquid, powder, granules); and the kinds of
clothing and equipment worn by the exposed individuals. EPA
formally accepted this premise by including it in monitoring
guidelines and initiating the development of a tool known as the
Pesticide Handlers Exposure Database (PHED) in the mid
1980s.

From the beginning, PHED has been a collaborative task force
effort on the part of EPA, the Canadian Pest Management
Regulatory Agency, the California Department of Pesticide
Regulation, and the pesticide industry. PHED contains the
results of over 100 exposure studies completed using
pesticides under actual use conditions. PHED was designed
after intensive discussions involving exposure assessment
experts, computer scientists, and statisticians. It was initially
released in 1992. It is currently in use in many foreign
countries (such as England, France, Australia, Japan) and
throughout the industry. The program itself has been
thoroughly evaluated as have all of the data in the system. The
actual system and the monitoring techniques upon which the
system is based have been "peer reviewed" (evaluated) by
several scientific advisory committees over the years. This
system is used to calculate exposures that are then coupled
with pesticide use and cultural practice information to calculate
exposures. Exposure is calculated by following formula:

Exposure = PHED Unit X Application X Area

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Exposure	Rate Treated

A dose can then be calculated from the exposure. When
calculating a dose we adjust for body weight and the amount
absorbed for both dermal and inhalation exposures.

How Does EPA Assess Residential Exposure for Post-
Application Using a Model?

A second model focuses on those who are exposed to
pesticides but who have not directly used them (i.e., post-
application exposures). This exposure scenario would include
a person harvesting in a home garden or a child playing on a
pesticide-treated lawn. The premise of this model is that
exposure levels are related to one's activity while in a
previously treated area and the amount of pesticide available in
that environment to the individual.

Exposure = Transfer X Amount X Duration
Coefficient of Pesticide

The agency formally adopted this premise by publishing it in
exposure monitoring guidelines as early as 1984. These kinds
of exposure data are coupled with behavioral and
environmental data (specific to individual chemicals) to
calculate risks.

What is the Transfer Coefficient?

The transfer coefficient is similar to the PHED unit exposure
used in applicator exposure assessments as described above.
The transfer coefficient is calculated by the following formula:

TC = 	Dermal Exposure

Available Residue Concentration

Dermal exposure is determined by the exposure scenario. A
monitoring study is conducted in order determine how much
exposure would occur over a given time.

For example, when calculating the transfer coefficient for
exposure to children when they are playing on a pesticide
treated lawn or carpet, we use the dermal exposure calculated

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Dosimeter -

material used to
trap or collect
pesticide residues.

in the "Jazzercisetm" monitoring study. Jazzercisetm is a type of
aerobic dance exercise choreographed to music and is
especially good as an exposure monitoring tool because it was
designed to achieve maximum contact of the entire body with
the ground. In the monitoring study participants wore special
outfits containing dosimeters and performed the exercise
routine for twenty minutes in an area treated with a known
amount of pesticide. The dosimeters were then analyzed for
the amount of pesticide that was transferred to them. An
dermal exposure was then calculated. The Jazzercisetm
monitoring study is useful because it is highly choreographed
and its results can be reproduced. Reproducibility is very
important in validating a scientific study because the study can
be used with confidence by a variety of investigators. A study
is said to be reproducible when can be repeated and the same
results obtained.

How Realistic Are EPA Residential Exposure
Assessments?

EPA's residential exposure assessments are designed to be as
realistic as possible. They are, however, generally
conservative and this adds an extra measure of safety when
regulating pesticides. When scientists have studied people in
the real world (including the children of farmworkers) they have
generally found a person's exposure to be less than that
predicted by our exposure assessments.

The conservative nature of our exposure assessments can be
ascribed to several assumptions:

~	We assume high amounts of pesticide residues will
transfer to a person. Generally we assume 20-50% of
the residues will transfer. Some techniques have shown
that in some situations, only 1-3% of the residues are
transferred. The highest reasonably possible transfer
rate must be assumed for safety.

~	We assume no residue dissipation. In other words, all
the residues available initially, are available throughout
the time a person is exposed. Dissipation rate is based
on many factors (heat, sunlight, rain, etc.) so we must

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include the conservative prospect that in a given case
there is no residue dissipation.

~	We assume that a person has no clothing on to protect
themselves from exposure because little or no clothing is
a possible realistic scenario in some circumstances.

~	We assume 2 to 8 hours of continuous contact.

Development of Residential Exposure
Assessment

the Agency has
always been
proactive in
addressing the
residential
exposure issue,
particularly to
children

How Has EPA Developed Residential Exposure Data?

Historically, the generation of post-application exposure data
has been limited in comparison to the data available for
handlers and generally has been intended to address farm
worker issues. Nevertheless, the Agency has always been
proactive in addressing the residential exposure issue,
particularly to children. Beginning in the late 1980s, the Agency
began to identify research needs in order to refine and better
understand children's exposure. This effort culminated in the
development of a research plan and several interactive
workshops with academia, industry and other regulatory
agencies in the 1990s. In 1995, realizing that additional data
were required, the Agency issued two FIFRA Data Call-In
Notices that specifically included requirements for the data
needed to address farm worker issues and to address issues
related to turf chemicals commonly illustrated by children
playing on treated lawns. The difficulty of these tasks prompted
the formation of two pesticide industry task forces each made
up of about 40 companies with a total budget that will probably
exceed $50 million. The membership of these task forces
represents a vast majority of the basic registrants in the
pesticide industry. From the onset, the technical evolution of
these task forces has been a collaborative effort between EPA,
Health Canada, the California Department of Pesticide
Regulation, and the pesticide industry members. In fact, a
technical oversight committee exists that routinely meets to
address research issues and progress. After the Food Quality
Protection Act (FQPA) was enacted, several other task forces
were also formed, or are in the process of forming, to address

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residential exposure issues. The focus of these groups is to
address indoor, residential issues and to develop a better
understanding of residential pesticide use patterns. Agency
representatives as well as representatives from academia and
other regulatory agencies are also working very closely with
these groups.

How Will EPA Further Improve Non-dietary Residential
Exposure Assessment?

Exposure science is evolving rapidly and we are working
diligently to make sure EPA's assessments are on the cutting
edge. We are improving and refining our residential exposure
assessments by:

~ Expanding our evaluation of residential exposures to
include playgrounds, schools, daycare centers,
farmworker children in and around agricultural sites, etc.

Toxic Release
Inventory (TRD

- An EPA database
containing
information about
releases and
transfers of more
than 650 toxic
chemicals and
compounds to the

~	Funding and conducting research into exposure science.
We are also reviewing available biomonitoring and
health surveillance data to calibrate our existing
assessments.

~	Revising our SOPs to increase realism (such as
determining a realistic transfer rate).

~	Identifying the range of exposure variables where
available. For example, the amount of time spent on a
lawn. Instead of using an average, we would look at the
range of time a person might spend on a lawn.

~	Identifying exposure scenarios which are not a direct
consequence of pesticide use (e.g. releases from
facilities as reported in the Toxic Release Inventory
(TRD).

How Will Task Force Data Be Used?

Data are being developed by several task forces to develop

better exposure assessments. These data are, however,

proprietary data and generally can only be used in exposure

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environment. TRI
stores

release-transfer
data hierarchically
by facility, by year
and chemical, and
by medium of
release (air, water,
underground
injection, land
disposal, and
offsite).

assessments to support chemicals that are manufactured by
companies that are a members of the task force or otherwise
entitled to use the data.

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