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Assessing Health Risks from
Pesticides
January 1999
735-F-99-002
The Federal Government, in cooperation with
the States, carefully regulates pesticides to ensure that they do not pose
unreasonable risks to human health or the environment. As part of that
effort, the Environmental Protection Agency (EPA) requires extensive test
data from pesticide producers that demonstrate pesticide products can be
used without posing harm to human health and the environment. EPA scientists
and analysts carefully review these data to determine whether to register
(license) a pesticide product or a use and whether specific restrictions are
necessary. This fact sheet is a brief overview of EPA’s process for
assessing potential risks to human health when evaluating pesticide
products.
Background
There are more than 865 active ingredients
registered as pesticides, which are formulated into thousands of pesticide
products that are available in the marketplace. About 350 pesticides are
used on the foods we eat, and to protect our homes and pets.
EPA plays a critical role in evaluating these
chemicals prior to registration, and in reevaluating older pesticides
already on the market, to ensure that they can be used with a reasonable
certainty of no harm. The process EPA uses for evaluating the health impacts
of a pesticide is called risk assessment.
EPA uses the National Research Council’s
four-step process for human health risk assessment:
Step One: Hazard Identification
Step Two: Dose-Response Assessment
Step Three: Exposure Assessment
Step Four: Risk Characterization
The first step in the risk assessment process
is to identify potential health effects that may occur from different types
of pesticide exposure. EPA considers the full spectrum of a pesticide’s
potential health effects.
Generally, for human health risk assessments,
many toxicity studies are conducted on animals by pesticide companies in
independent laboratories and evaluated for acceptability by EPA scientists.
EPA evaluates pesticides for a wide range of adverse effects, from eye and
skin irritation to cancer and birth defects in laboratory animals. EPA may
also consult the public literature or other sources of supporting
information on any aspect of the chemical.
Paracelsus, the Swiss physician and
alchemist, the “father” of modern toxicology (1493-1541) said,
"The dose makes the poison."
In other words, the amount of a
substance a person is exposed to is as important as how
toxic the chemical might be. For example, small doses of aspirin
can be beneficial to people, but at very high doses, this common medicine
can be deadly. In some individuals, even at very low doses, aspirin may be
deadly.
Dose-response assessment involves considering
the dose levels at which adverse effects were observed in test animals, and
using these dose levels to calculate an equal dose in humans.
People can be exposed to
pesticides in three ways:
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Inhaling pesticides (inhalation exposure),
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Absorbing pesticides through the skin
(dermal exposure), and
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Getting pesticides in their mouth or
digestive tract (oral exposure).
Depending on the situation, pesticides could
enter the body by any one or all of these routes. Typical sources of
pesticide exposure include:
-
Food
Most of the foods we eat have been grown with the use of pesticides.
Therefore, pesticide residues may be present inside or on the surfaces of
these foods.
-
Home and Personal Use Pesticides
You might use pesticides in and around your home to control
insects, weeds, mold, mildew, bacteria, lawn and garden pests and to
protect your pets from pests such as fleas. Pesticides may also be used as
insect repellants which are directly applied to the skin or clothing.
-
Pesticides in Drinking Water
Some pesticides that are applied to farmland or other land
structures can make their way in small amounts to the ground water or
surface water systems that feed drinking water supplies.
-
Worker Exposure to Pesticides
Pesticide applicators, vegetable and fruit pickers and others who
work around pesticides can be exposed due to the nature of their jobs. To
address the unique risks workers face from occupational exposure, EPA
evaluates occupational exposure through a separate program. All pesticides
registered by EPA have been shown to be safe when used properly.
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Risk characterization is the final step in
assessing human health risks from pesticides. It is the process of combining
the hazard, dose-response and exposure assessments to describe the overall
risk from a pesticide. It explains the assumptions used in assessing
exposure as well as the uncertainties that are built into the dose-response
assessment. The strength of the overall database is considered, and broad
conclusions are made. EPA’s role is to evaluate both toxicity and exposure
and to determine the risk associated with use of the pesticide.
Simply put,
RISK = TOXICITY x EXPOSURE.
This means that the risk to human health from
pesticide exposure depends on both the toxicity of the pesticide and the
likelihood of people coming into contact with it. At least some
exposure and some toxicity are required to result in a risk. For
example, if the pesticide is very poisonous, but no people are exposed,
there is no risk. Likewise, if there is ample exposure but the chemical is
non-toxic, there is no risk. However, usually when pesticides are used,
there is some toxicity and exposure, which results in a potential risk.
EPA recognizes that effects vary between
animals of different species and from person to person. To account for this
variability, uncertainty factors are built into the risk assessment.
These uncertainty factors create an additional margin of safety for
protecting people who may be exposed to the pesticides. FQPA requires EPA to
use an extra 10-fold safety factor, if necessary, to protect infants and
children from effects of the pesticide.
Types of Toxicity Tests EPA Requires for
Human Health Risk Assessments
EPA evaluates studies conducted over
different periods of time and that measure specific types of effects. These
tests are evaluated to screen for potential health effects in infants,
children and adults.
Acute Testing: Short-term
exposure; a single exposure (dose).
Sub-chronic Testing:
Intermediate exposure; repeated exposure over a longer period of time (i.e.,
30-90 days).
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Oral, dermal (skin), and inhalation
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Neurotoxicity (nerve system damage)
Chronic Toxicity Testing:
Long-term exposure; repeated exposure lasting for most of the test animal's
life span. Intended to determine the effects of a pesticide after prolonged
and repeated exposures.
Developmental and Reproductive Testing:
Identify effects in the fetus of an exposed pregnant female (birth defects)
and how pesticide exposure affects the ability of a test animal to
successfully reproduce.
Mutagenicity Testing: Assess a
pesticide's potential to affect the cell's genetic components.
Hormone Disruption: Measure effects for their
potential to disrupt the endocrine system. The endocrine system consists of
a set of glands and the hormones they produce that help guide the
development, growth, reproduction, and behavior of animals including humans.
Risk Management
Once EPA completes the risk assessment
process for a pesticide, we use this information to determine if (when used
according to label directions), there is a reasonable certainty that the
pesticide will not harm a person’s health.
Using the conclusions of a risk assessment,
EPA can then make a more informed decision regarding whether to approve a
pesticide chemical or use, as proposed, or whether additional protective
measures are necessary to limit occupational or non-occupational exposure to
a pesticide. For example, EPA may prohibit a pesticide from being used on
certain crops because consuming too much food treated with the pesticide may
result in an unacceptable risk to consumers. Another example of protective
measures is requiring workers to wear personal protective equipment (PPE)
such as a respirator or chemical resistant gloves, or not allowing workers
to enter treated crop fields until a specific period of time has passed.
If, after considering all appropriate risk
reduction measures, the pesticide still does not meet EPA’s safety standard,
the Agency will not allow the proposed chemical or use. Regardless of the
specific measures enforced, EPA’s primary goal is to ensure that legal uses
of the pesticide are protective of human health, especially the health of
children, and the environment.
Human Health Risk Assessment and the Law
Federal law requires detailed evaluation of
pesticides to protect human health and the environment. In 1996, Congress
made significant changes to strengthen pesticide laws through the Food
Quality Protection Act (FQPA). Many of these changes are key elements of the
current risk assessment process. FQPA required that EPA consider:
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A New Safety Standard: FQPA
strengthened the safety standard that pesticides must meet before being
approved for use. EPA must ensure with a reasonable certainty that no harm
will result from the legal uses of the pesticide.
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Exposure from All Sources: In
evaluating a pesticide, EPA must estimate the combined risk from that
pesticide from all non-occupational sources, such as:
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Food Sources
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Drinking Water Sources
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Residential Sources
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Cumulative Risk: EPA is required to
evaluate pesticides in light of similar toxic effects that different
pesticides may share, or “a common mechanism of toxicity.” At this time,
EPA is developing a methodology for this type of assessment.
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Special Sensitivity of Children to
Pesticides: EPA must ascertain whether there is an increased
susceptibility from exposure to the pesticide to infants and children. EPA
must build an additional 10-fold safety factor into risk assessments to
ensure the protection of infants and children, unless it is determined
that a lesser margin of safety will be safe for infants and children.
Reference: U.S. Environmental Protection
Agency
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