Health and Nontarget Concerns with Pestici

Health and Nontarget Concerns with Pestici

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Pesticide applications can pose potential
hazards for people and nontarget organisms. When selecting a pesticide, it is important
to consider how people could be exposed to it and the various methods available to reduce
that exposure. Likewise, direct and indirect impacts on wildlife
and beneficial organisms and the means to reduce these impacts must be adequately considered. Toxicology is the science that deals with
poisons and their effect on living organisms. All pesticides are toxic at some level. Some pesticides are more toxic than others
and therefore present higher risks to users, nontarget organisms, and the environment. Toxicology is based on the premise that a
relationship exists between the dose (the amount of a pesticide applied) and the response
(the toxic reaction) and that there is almost always a dose below which no response occurs
or is measurable. I’m Dr. DeBusk and in this video, I’m
going to discuss health and nontarget concerns with pesticide use. Toxicity is the general term used to describe
the potential for a chemical to cause harm. Toxicity is commonly measured by the lethal
dose (LD) that kills 50% of the animals tested (LD50). LD50 is expressed as milligrams of active
ingredient of pesticide per kilogram of body weight of the test animal (mg/kg). A pesticide with a low LD50 (e.g. 5 mg/kg)
is very toxic, whereas a pesticide with a high LD50 (e.g., 1,000 to 2,000 mg/kg) is
less toxic to the tested animal. Toxicity measurements are used to compare
the lethal potential of one dose of one pesticide with another. The LD50 does not provide information on long-term
toxic effects. While a pesticide with a low LD50 may pose
a higher risk than one with a large LD50, it can often be used safely provided precautions
are taken to protect nontarget organisms. Another measurement of toxicity is the lethal
concentration of a pesticide in the air or water that will kill 50% of a test animal
population (LC50). The table shows the toxicity and potential
for causing injury to people for the three toxicity categories (Danger, Warning, and
Caution). Hazard, the inherent ability of a pesticide
to produce an adverse affect, is a constant for a particular pesticide product. Risk, in toxicology, is the probability that
a chemical will cause harm. In the case of pesticides, risk is a function
of hazard and dose. The degree of risk can depend on the concentration
of the pesticide, the way it is handled, and the duration of exposure. Many factors impact risks associated with
the use of a pesticide product. Different pesticide formulations can substantially
influence the potential for hazard of a given pesticide. Formulation may affect its percentage of active
ingredient, propensity to drift, phytotoxicity, or persistence in the environment. It may also affect a pesticide’s potential
for dermal uptake, inhalation, or ability to pass through the skin (oil versus water). Environmental conditions can increase the
potential for injuring living organisms.. Heat, light, and precipitation can speed up
or slow down the breakdown of toxic residues. Weather conditions, for example, that are
favorable to drift or inversion layers can cause pesticides to move beyond the target
site, increasing the risk of exposure or environmental contamination. The closer a person or organism gets to an
application or mixing activity, the greater the chance that they will receive an exposure
(dose) that will cause harm. For example, the risk of exposure to the applicator
is highest during mixing, loading, and application of the material. The risk of exposure to the fieldworker from
residues on the crop increases if fieldworkers are in the field during or following an application. Many steps can be taken to reduce the potential
risk of pesticides to people. For example, closed mixing system allow for
the safe handling of toxic liquid pesticides because applicators do not have to handle
opened pesticide containers, thereby eliminating accidental contact. The use of water-soluble packaging also reduces
the risks of exposure during mixing and loading because direct contact is eliminated. Wearing protective clothing and equipment
reduces the risk of exposure when handling pesticides or entering an application site
before the expiration of the restricted-entry interval (REI). Personal protective equipment (PPE) includes
all or some of the following: waterproof apron, chemical-resistant boots, gloves, head protection,
clean coveralls or outer clothing, goggles, face shield, and dust- or mist-filtering respirator
or an organic/vapor-removing respirator. Personal protective equipment prevents pesticides
from contacting the body and eyes and can also protect against inhaling pesticide dusts,
droplets, and vapors. PPE requirements are listed on the pesticide
label. Entering or working in a treated area soon
after an application increases the risk of exposure to harmful levels of pesticide residues. Observing the established restricted-entry
interval is an important requirement to reduce this type of exposure. The pesticide label provides guidelines for
restricted-entry intervals. A pesticide-related illness or injury may
have a sudden onset and last for a short duration before the person recovers. This is acute illness. Usually, the exposed person recovers as a
result of medical treatment, but with a severe exposure, the person may die. The most common symptoms include headache,
rash, or eye irritation. Exposure to some pesticides produces chronic
health effects. These are long-lasting and often permanent
disorders such as cancer, permanent nerve damage, sterility, and blindness. One good source of information to assess the
potential health hazard from a pesticide is the Safety Data Sheet (SDS). Some pesticide labels also have important
information on health hazards. All labels have one of three signal words
(Caution, Warning, or Danger) that indicate the level of acute toxicity (based on animal
studies) or other hazard posed by the pesticide product. The signal word indicates the degree of risk
to the user and is usually measured in terms of oral or dermal toxicity. Along with signal words, labels include precautionary
statements about the most common route of entry (usually dermal or oral) and specific
actions that must be taken to avoid exposure. Even after a pesticide is applied, the risk
of exposure may remain because residues may stay on the treated surface for a period of
time. Residues are important and necessary in some
types of pest control because they provide continuous exposure to the pest, improving
the chances of control. They are undesirable, however, when they expose
people and other nontarget organisms to unsafe levels of pesticides. Pesticides can remain as residues on or in
the plant material and in soil, water, or on surfaces in nontarget areas. To protect the public from harmful residues
on harvested produce, federal law establishes pesticide residue tolerances for all materials
registered for use on agricultural products. These tolerances are based on laboratory and
animal testing with a margin of safety to allow for differences in people and to protect
children. These tolerances, also know as maximum residue
limits (MLRs), are established for each commodity the pesticide is used on. Preharvest intervals prohibit application
of some pesticides during a specified time before harvesting a commodity. These are established to allow residues to
break down before reaching consumers. Pesticides can enter the body through four
major routes; dermal (absorption by the skin), ocular (through the eyes), oral (ingestion
through the mouth), and inhalation (breathing into the lungs). Dermal exposure is the most frequent type
of pesticide exposure by those using pesticides. Certain pesticides injure the skin, while
others may pass through the skin and affect internal organs. Absorption into the body starts as soon as
the pesticide touches the skin and continues as long as there is contact. Wear the proper PPE and avoid contact with
treated surfaces. Ocular exposure is the second most frequent
type of pesticide injury. Wearing protective eyewear can protect the
eyes. Oral exposure usually occurs accidentally,
for example, by drinking out of a container that has had a pesticide stored in it. It also occurs through splashing of spray
materials or pesticide dust into the mouth, by eating or drinking contaminated foods or
liquids, or by smoking while handling pesticides. Inhalation exposure occurs if dusts, mists,
or vapors are inhaled during mixing or application. Inhalation or respiratory exposure is particularly
hazardous because pesticides are quickly absorbed by the lungs and transported in the bloodstream
to other areas of the body. Many state and federal regulations are in
place to protect employees working in urban landscapes, farms, forests, nurseries, and
greenhouses from occupational exposure to pesticides. The federal regulation that governs all aspects
of agricultural pesticide use is the Federal Insecticide, Fungicide, and Rodenticide Act
(FIFRA) The Worker Protection Standard (WPS) is an amendment to FIFRA designed to set standards
for basic workplace protections. The WPS is intended to reduce the risk of
illness and injury from occupational exposures for agricultural workers and pesticide handlers. Its requirements include protection during
applications, restricted-entry intervals, personal protective equipment, notification
of workers, decontamination supplies, emergency assistance, pesticide safety training, and
access to labeling and site-specific information. If the workers speak another language, training
and signage must also be in the language of the workers. Safety Data Sheets (SDSs) are another tool
that provides information about the potential hazards from using a particular pesticide. An SDS, prepared by the manufacturer, is available
for every labeled pesticide. It describes the chemical characteristics
of active and other hazardous ingredients and lists fire and explosion hazards, health
hazards, reactivity and incompatibility characteristics, along with types of protective equipment required
for handling. Storage information and emergency spill or
leak cleanup procedures are described. LD50 and LC50 ratings are given for various
test animals. Emergency telephone numbers of the manufacturer
are also listed. Workers who handle pesticides or work in the
field where pesticides are applied must be told about the potential hazards in the workplace
and must be provided with information on how to avoid these hazards. They must also be trained on what to do in
case they are exposed to pesticide sprays or residues. The SDS for each material that they may be
exposed to must be available and accessible to workers at their request. Nontarget organisms include all plants, vertebrates,
invertebrates, and microorganisms in or near a treated area that are not the intended target
of a pesticide application. Pesticides can injure nontarget organisms
directly or indirectly. Direct poisoning harms nontarget organisms
that encounter pesticides during application or directly afterward by coming into contact
with harmful residues. For example, pesticides applied while bees
are foraging in the treated area can harm them and other pollinators near the application
site. The table on the slide lists examples of insecticides
that are highly toxic to bees and those with low or no toxicity. Migrating birds and other vertebrates can
be harmed by improper applications of granular pesticides. Drift from an application site can harm nearby
wildlife, livestock, pests, and sensitive plants. Residues remaining on crop plants may kill
natural enemies, pollinators, birds, or other wildlife immigrating into the site after the
application. It may be several years after a problem arises
before a cause and solution can be identified. For example, dormant sprays of the organophosphate
parathion were commonly applied in California orchards in the 1980s. Early reports from the Department of Fish
and Game suggested these sprays might have adverse effects on raptors. After several years of research, these suspicions
were confirmed, and mortality of hawks was directly related to dormant applications of
parathion in 1989. Hawks absorbed the pesticide through their
feet when landing on treated trees. These findings led to regulatory changes and
changes in pest management practices. Use of reduced rates and alternate materials
in the 1990s eliminated the problem. Runoff from pesticide applications into nearby
ponds, streams, and lakes can harm aquatic animals and plants. For example, dormant sprays of certain organophosphate
or pyrethroid insecticides are typically made to stone fruit orchards during January and
February, often the wettest time of the year. When it rains soon after an application, elevated
concentrations of organophosphate insecticides have been detected in storm drains, rivers,
and other waterways. The concentration of these insecticides in
waterways is of particular concern because of potential toxicity to some aquatic organisms
at relatively low concentrations. From 1992 to 1995, the U.S. Geological Survey
found that concentrations of diazinon in several rivers exceeded levels that are toxic to aquatic
life after winter storms. Pesticide runoff in orchards was reduced in
the 2000s by treating later in the year and/or switching to sprays of reduced-risk materials
(Bacillus thuringiensis or spinosad) that do not run off into water or pose threats
to aquatic invertebrates. Pesticide runoff continues to be a threat
to aquatic wildlife, however, especially with the use of pesticides applied to control ants
and other pests in urban areas. Applications of persistent pesticides can
also lead to secondary poisoning of nontarget organisms. This phenomenon, called biomagnification,
occurs when certain pesticides gradually build up within the tissues of living organisms
after feeding on other organisms (pest or nontarget) containing smaller amounts of these
pesticides. Animals higher up on the food chain accumulate
greater amounts of these pesticides in their tissues as time passes. Although this phenomenon is mostly associated
with long-banned organochlorine insecticides, recent studies show that DDT, toxaphene, and
chlordane continue to accumulate and build up in tissues of clams, fish, and other aquatic
organisms relative to values in the 1970s and 1980s. These sediment-bound organochlorine insecticides
continue to arrive in rivers through soil erosion. Secondary kill may also occur when carnivores
feed on dead or dying rodents that have consumed rodenticide baits. The impact of pesticides on nontarget organisms
can be reduced by choosing pesticides that are less toxic to nontarget organisms, applying
at times when nontarget organisms are least likely to be harmed, using lower rates (when
possible), and using spot treatments or other methods to selectively place pesticides. For example, pesticide applications made in
early morning, late afternoon, or at night are less harmful to bees because they are
not foraging at these times. There are regulatory restrictions for applying
certain pesticides while bees are foraging. The pesticide label will have a “bee advisory
box” to inform the user of precautions for bees. Warning statements on labels provide information
about problems that could occur if the material drifts onto blooming crops or if bees are
visiting the treatment site. Likewise, statements such as “This product
is toxic to fish” or “Keep out of lakes, streams, rivers” helps you evaluate the
potential impact of a material on nontarget organisms. Federal and state laws are in place to protect
endangered species from extinction. An endangered species is any rare or vulnerable
animal or plant species that is in danger of becoming extinct. To ensure that endangered species are protected,
the use of certain pesticides in areas where endangered species are known to exist may
be highly restricted. Before using a pesticide, read the pesticide
label carefully for precautions to protect endangered species and for the location of
restricted areas. In conclusion, pesticides are important and
necessary pest management tools for agriculture, urban landscapes, forestry, and public health,
but they must be handled with appropriate caution to minimize exposure and avoid risks
to human health and nontarget organisms.

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