Toxicants and Pesticide Safety

Toxicants and Pesticide Safety

In this Module

Learning Objectives
Terms to Know
Introduction
The Pesticide Label
Protecting People
Personal Protective Equipment
Protecting the Environment
Types of Pesticides
Rodenticides
Safe Handling Checklist
Additional Resources
Study Questions for Toxicants
Summary of Questions and Answers for Toxicants


Learning Objectives

  1. Explain the difference between anticoagulants and acute toxicants.
  2. Describe general application techniques for rodenticides and avicides.
  3. Explain the dangers of toxicants to non-target species.
  4. Explain why there are few toxicants listed for mammals.
  5. Know your state laws regarding the licensing for the applications of toxicants.

Terms to Know

Acute toxicant   A chemical that can cause severe illness or death with one feeding.

Chronic toxicant   A chemical that requires multiple feedings before causing severe illness or death.

Fumigant   A toxicant that is inhaled by a target species, causing illness or death.

Secondary poisoning   When a predator or scavenger ingests a toxicant by eating an animal killed by that toxicant. Secondary poisoning causes sickness or death.

Introduction

This module focuses on toxicants, which include poisons, fumigants, and some repellents. Before using any chemicals or toxicants check to be sure it is legal in your state. In most states, in addition to a WCO license, a Pesticide Applicator License is required to use or recommend the use of toxicants to control wildlife. The information in this module is included to help you better understand the limited role that toxicants play in solving wildlife damage conflicts.

Toxicants are chemical compounds used to intentionally kill or impair target species. 
“Target species” refers to animals that are the target of management. “Non-target species” or “non-targets” refer to wildlife, livestock, pets, and people that are not the target of management and could be harmed by toxicants.

Toxicants can impact non-targets through primary exposure (direct ingestion), or secondary exposure (consumption of an animal that has eaten the chemical). When misused, misapplied, or sometimes due to unfortunate circumstances, toxicants can pose a threat non-target species. Safeguards may be in place to minimize these risks, but in many situations, it is best to use reduced-risk alternatives to toxicants.

Toxicants can be beneficial and effective tools for controlling vertebrates such as house mice (Figure 1), Norway rats, pigeons, starlings, and house sparrows. Vertebrate toxicants can be applied in many forms and delivery methods to protect structures, turf, landscapes, cropland, rangeland, and other sites.

Figure 1. Toxicants in the form of bait blocks with bait stations are used to control house mice and Norway rats. Photo by unknown.

Public attitudes toward toxicants vary greatly. Some pest management professionals rely too heavily on pesticides when alternative, reduced-risk approaches may be just as, or more, effective. Excluding rodents from buildings is more effective in the long term than setting up toxicant bait stations. Alternatively, some people are so opposed to the application of chemicals in the environment that they oppose all use of toxicants. Opposition of this sort can be short-sighted in situations where damage is severe, human health concerns are high, and pesticides can be applied safely with minimal risk to the environment.

There are few toxicants other than rodenticides and some bird control products that are registered for use on mammals and even then, specialty toxicants may only be administered by federal agencies or with special permits.

If you follow an Integrated Wildlife Damage Management plan, you probably will use other methods before resorting to using a pesticide. When applying a pesticide is your best management option, the responsibility for safe use falls on you. This safety covers safety practices when using pesticides and issues such as the importance of the pesticide label, identifying sensitive areas, protecting non-target organisms and sensitive areas, and following safety precautions when using pesticides.

In most states, persons who must be certified to apply or recommend the use of pesticides to control vertebrate pests (Category 7D Vertebrate Pest Control certification) include 3 types of commercial applicators:

  • applicators for hire,
  • applicators not for hire, and
  • government employees.

An example of a commercial applicator for hire who needs certification in Vertebrate Pest Control is an employee of a wildlife management firm that uses pesticides to control vertebrate pests for the public. An example of a commercial applicator not for hire who needs Category 7D certification is a public golf course superintendent who uses any chemical to control or repel geese. A state park employee who uses a chemical to repel deer is an example of a government employee who needs certification in Vertebrate Pest Control.

Your state Cooperative Extension agent is also a good source of information about specific pesticides or pesticide safety. Any pesticide can be hazardous if misused. Make sure that the pesticides you use affect only the target pest(s). The main safety concerns are to protect people and the environment, which includes plants, animals, land, water, and air.

The Pesticide Label

  • Explain types of information on the pesticide label.
  • List when to read the pesticide label.
  • List the 3 signal words found on the label, from most to least hazardous.
  • Explain 4 types of exposure to pesticides.
  • Explain the importance of PPE and good personal hygiene to reduce exposure.
  • Describe why some sites are considered sensitive areas.

The most important thing you can do to ensure personal and public safety when applying a pesticide is to read the product label before each use and follow all label directions. The label lists the legal uses for the product. Follow all label directions exactly. The label is the law. The following website is a good source for obtaining pesticide information.  http://www.kellysolutions.com/va/pesticideindex.htm

The label will answer the following questions:

  • Can you control the target pest with the product? The label lists the pests that the product controls.
  • Is the product labeled for the site? It identifies specific sites that may be treated. For example, a product that is labeled for use in an agronomic crop setting is illegal to use on a residential lawn.
  • Are there any weather-related restrictions? Some products cannot be applied under certain wind conditions or if rain is predicted.
  • How much product do you need? Will a repeat application be necessary? The label gives detailed application instructions, including the type of equipment to use and the correct application rate. The label gives directions on how to mix and use the product.
  • How dangerous is the chemical to humans and non-target organisms? The label will have a signal word, covered later in this chapter, to tell the hazard level of the product.
  • Is the product a restricted use pesticide? The label will tell if the product is a restricted use pesticide, which only a certified pesticide applicator may purchase and apply.
  • Does it pose any specific hazards to the applicator or the environment? Are there any special precautions for its use? The label will tell if there are specific risks to groundwater or surface water and, if so, special precautions to take.
  • What personal protective equipment (PPE) is required? The label will tell if specific gloves, eye protection, a respirator, or other PPE is required.
  • How much time must pass after an application before the treatment area is safe to enter? The pesticide will have a restricted entry interval (REI), during which people should not enter. If none is listed, a general rule is to wait until a liquid has dried or dust has settled.
  • Are there specific storage requirements? The label has information on how to store the chemical properly. Some pesticides will lose effectiveness if exposed to extreme temperatures. Others may be a fire or explosion hazard under certain conditions.
  • How do I handle excess pesticide or empty containers? The pesticide label will list legal options for handling excess pesticides and disposing of empty containers. You will have to check local regulations for options in your area.

The label is the most important resource in making pesticide-use decisions. Pesticide label directions, such as application rates and special precautions, may change over time. Do not assume that just because you have used a product before, you will remember all the label directions. The best time to read the label is:

  • Before you purchase a pesticide. Compare products so you know which is legal for the pest and the site, and that you have the proper application equipment and personal protective equipment (PPE), such as gloves and eye protection.
  • Before you mix the pesticide. Find out the required PPE for mixing, and how to properly dilute, if necessary.
  • Before you apply the pesticide. Make sure you have the correct application equipment, PPE, and are using the correct rates. In some cases, weather may play a role. Wind or rain may alter application plans. Also, refresh your memory on what to do if there is a spill or accidental exposure to the product.
  • After the application. Find out how to properly clean equipment and PPE, and store the product after use.

Another good resource is the Safety Data Sheet (SDS). Manufacturers and distributors of pesticides must provide an SDS for each product that they sell. The SDS includes information about the product’s toxicity, how readily it dissolves in water, and if it is flammable, explosive, etc. Consult a product’s SDS for additional information about:

  • first aid,
  • LD50 (a measure pf toxicity),
  • storage and handling precautions,
  • disposal procedures, and
  • safe storage and transport.

Protecting People

Many people can be affected by use of a pesticide – the applicator, the customer, and the general public. Most chemicals that kill mammals and birds also affect humans. Always consider your own safety as well as that of coworkers, clients, and the people who will use the treated areas. The best way to reduce risk to people when using pesticides is to use the least toxic product that is effective, and to limit exposure as much as possible. The label has the best information for doing so.

Toxicity and Exposure

Risks to pesticide handlers and applicators depend on 2 factors: the toxicity of the product and the exposure to it. You can reduce your risk when using pesticides by choosing products with low toxicity and by minimizing your exposure to them. Be sure to use the appropriate PPE for EVERY pesticide, regardless of its toxicity.

LD50 (Toxicity)

The term “LD50” tells the level of toxicity of chemicals. “LD” means lethal dose. LD50 is the dose, based on weight, which will kill 50% of a population of test animals. This value is usually expressed as milligrams of a chemical per kilogram of body weight, written as mg/kg. A chemical with an LD50 of 5,000 mg/kg requires about 0.1 ounce of the chemical per pound of body weight to reach the LD50 value. For a 150-pound person, this would be about 15 ounces.

The lower the LD50 value, the more toxic the chemical, because it takes less to kill 50% of the test animals. A pesticide with an LD50 of 100 is more toxic than a pesticide with an LD50 of 1,000. The SDS will cite the LD50 for a pesticide product formulation: active ingredient (the chemical that controls the pest) plus inert ingredients (other materials added when the product is made) and adjuvants (a product added to make the active ingredient more effective).

Pesticides differ in their toxicity to humans. Some are highly toxic. Others are relatively nontoxic. The label is the best guide for all products. It has a signal word that gives the toxicity of the pesticide:

  • CAUTION: Slightly toxic. The oral lethal dose for a 150-pound person is 1 tablespoon to more than a pint.
  • WARNING: Moderately toxic. The oral lethal dose for a 150-pound person is 1 teaspoon to 1 tablespoon.
  • DANGER: Highly toxic. These pesticide labels may have the skull and crossbones symbol. The oral lethal dose for a 150-pound person is a few drops to 1 teaspoon.

Exposure

People can be exposed to pesticides in 2 major ways: acute exposure and chronic exposure.

Acute exposure is a single incident, such as splashing concentrate into your mouth during mixing. It can include spilling or spraying a pesticide onto your clothing, face, or body. For acute toxicity, symptoms usually begin quickly, within 24 hours.

Acute oral exposure refers to a single dose taken by mouth (ingested). Acute dermal exposure means a single dose touching the skin or eyes (skin absorption). Acute inhalation exposure is inhaling a breath of pesticide-contaminated air.

Chronic exposure is repeated contact with low levels of pesticides over a long period, usually several years. Delayed health problems may follow. Chronic toxicity means that the effects will be seen after long-term or repeated low-level exposures. Effects can include cancer, birth defects, liver damage, reproductive disorders, nerve damage, and sensitivity or allergic reactions. An example of a pesticide with chronic toxicity is a rodenticide that is an anticoagulant (prevents blood from clotting). The rodent dies after a number of feedings.

Exposure of any kind usually results from inadequate PPE. Causes include failure to wear gloves, re-wearing contaminated clothes, not bathing after contamination, or working in a contaminated area.

Routes of Exposure

There are 4 main ways a person can be exposed to a pesticide: oral, inhalation, dermal, and ocular.

Oral exposure can result if a pesticide is accidentally swallowed. This may occur if pesticides are transferred to beverage containers, unlabeled containers, or are stored near food or drink. Do not repackage pesticides into anything other than their original containers. Children have died from drinking pesticides stored in old beverage containers. Most pesticide poisonings of children are due to oral exposure. Always keep pesticides in labeled and suitable containers in a secure area. Wear clean gloves, and after handling a pesticide, wash gloves before removing them. Then, wash your hands before smoking, eating, or drinking. Never siphon a pesticide by mouth or blow through a nozzle to clean it.

Inhalation exposure occurs you breathe the dust, spray, or vapors of a pesticide. In vertebrate pest control, dust from baits and gas from some fumigants pose the biggest risk of inhalation exposure. To avoid inhaling pesticides, always wear proper PPE. Some pesticide labels require the use of a respirator to reduce the risk of inhalation. Work in a well-ventilated area.

Dermal exposure occurs when a pesticide touches the skin. For most applications, the skin is most likely to be exposed. Most pesticide poisonings of applicators are due to dermal exposure. If you accidentally spill or spray pesticides on your skin, drench the affected area (skin and clothing) with water immediately. If a shower is available, use it. This is the best way to wash and rinse the entire body surface. After using a pesticide, wash your hands thoroughly before using the toilet. Remove contaminated clothing. Properly clean all clothing soiled with a pesticide, or discard it.

Ocular exposure occurs when a pesticide gets into the eye. This can happen when fine droplets or dust drifts into the eye. It also can happen if you touch your eye after handling pesticides. Wear protective eyewear when mixing pesticides and using liquid or aerosol products. If you do get a pesticide in your eyes, flush them immediately with water.

A pesticide accident may require medical attention. If you suspect poisoning is due to a pesticide, get immediate help from a local hospital, physician, or the nearest Poison Control Center (800-222-1222). Have the pesticide label handy as it has important information about the product, as well as first aid measures.

Personal Protective Equipment

Personal protective equipment (PPE) is clothing and devices that protect the body from contact with pesticides. Each pesticide product label lists the minimum PPE required for using that pesticide. Different handling activities (mixing and loading, applying, and cleaning application equipment) may call for different PPE. Federal and state laws require those who use pesticides to follow all instructions on the product label, including wearing PPE. Some labels do not list PPE. In that case, a wise option is to wear a long-sleeved shirt, gloves, long pants, shoes, and socks.

Before opening a pesticide container, put on all of the required PPE, at a minimum. You may decide to use extra PPE, depending on:

  • the signal word on the label,
  • the application situation and site, and
  • common sense.

Good Personal Hygiene

Practicing good hygiene is important when working with pesticides. Follow these guidelines:

  • When you work with pesticides, wash hands often (Figure 2). This is especially important before using the restroom, smoking, or eating.
  • Do not eat, drink, or smoke where pesticides are mixed, used, or stored. Those actions will increase the risk of accidental exposure.
  • Remove your work gloves before driving, handling paperwork, phones, or equipment that you or others may handle with unprotected hands.

Figure 2. Always wash after handling pesticides.

Always wash hands after handling pesticides.
  • Wash protective clothing at the work site. If you must wash your work clothes at home, wash them separately from other laundry, with hot water and a detergent. Line dry rather than use a clothes dryer, if possible. Run an empty, hot-water wash cycle (using detergent) afterward to clean the washing machine.

These actions can greatly reduce the risk of long-term exposure to pesticides.

Protecting the Environment

The environment consists of non-target animals, water, plants, and other natural resources. To protect the environment, you must protect all of these elements. If you harm the environment, you risk public disapproval and legal penalty. This is true even when your pest control operations are legal.

When developing a pest management plan, try to choose the control method that is the least harmful. Usually, non-chemical control methods such as sanitation, exclusion, harassment, or trapping are preferred to the use of pesticides.

When a pesticide is to be used, consider all labeled products. Choose one that is best suited for the site, situation, and pest. Handle and apply it properly. Store and dispose of pesticide containers properly to prevent contamination of the environment. Dispose of dead animals quickly and correctly. Plan every pesticide application with care.

Pesticides that are accidentally released into the environment pose a threat to people, animals, endangered species, plants, surface water, and groundwater. This can happen during pesticide:

  • application,
  • equipment cleaning,
  • storage,
  • transportation, or

Sensitive Areas

Pesticide applicators must be careful when using pesticides, and even more so when working on or near sensitive areas. These are areas that are more susceptible to negative side-effects of pesticides. An area may be considered sensitive because of the way it is used, the organisms that normally live there, or the potential for chemicals to affect certain natural features. The use of chemicals in and around such sites requires even more planning and care than usual.

The following are sensitive areas that you may encounter in the course of your work.

Habitats of threatened and endangered species  Critical nesting, denning, shelter, food resources, and water supplies used by federal or state-threatened or endangered species are sensitive areas. Applying pesticides in and around these sites could cause direct or secondary poisoning of these species.

Under the Endangered Species Act, it is a federal offense to use any pesticide in a manner that kills an endangered wildlife species. Before making an application, you must determine if endangered species are located in or next to the site to be treated. If you do not know whether endangered species may be affected, contact an endangered species specialist from the regional US Fish and Wildlife Service office or personnel from the Virginia Department of Game and Inland Fisheries.

Under EPA’s Endangered Species Protection Program, some pesticide labels may include a statement that directs the user to check a specific website (https://www.epa.gov/endangered-species/bulletins-live-two-view-bulletins) or call the Endangered Species Hotline at 1-800-447-3813. These EPA sources will tell you of any restrictions based on the pesticide, the geographic area, and the date of the application. A pesticide applicator can check for information up to 6 months before applying a pesticide. You must abide by any restrictions.

Areas with organic crops or livestock, bee hives (apiaries), or plants that are extremely sensitive – An organic operation could lose its certification if a pesticide not approved for use is applied or drifts onto the property. Typically, land that produces certified organic products must be free of most human-made pesticides for at least 3 years. As for apiaries, bees are extremely susceptible to some pesticides.

Areas with sensitive populations – Children, the elderly, and those with health problems are more susceptible than the general public. Schools, daycares, hospitals, and nursing homes are examples of areas with sensitive populations.

Public lands — Parks and recreation areas; wildlife refuges; and federal, state, and county forests are sensitive areas because of high public use, certain natural features, and public opinion.

Urban and suburban areas — Office parks, neighborhoods, shopping centers, colleges, and universities are areas of concern because of high public use. In these areas, wildlife damage programs often attract public and media attention. They may generate controversy, as well.

Areas with surface water — Lakes, ponds, marshes, swamps, streams, and other wet areas are sensitive areas (Figure 3). Pesticide runoff can harm organisms directly and taint the water that humans and wildlife depend on.

Figure 3. Water bodies are sensitive areas. Photo by Jan Hygnstrom.

Sources of drinking water — Municipal water well fields, wellhead protection areas, and private wells must be protected from contamination, as people rely on them for drinking water.

When you plan to make an application, check to see if it is in or near a sensitive area. Because water is so important, we’ll look closely at groundwater and surface water, and how pesticides can impact them.

Groundwater

Water that is stored in the spaces and cracks between particles of soil, sand, gravel, rock, or other material in the earth is called groundwater. It is always moving, at rates between 0.1 and 3 feet per day, depending on the area. Groundwater may connect with and supply water to streams, rivers, or lakes, or draw water from those sources.

Many Virginians get their drinking water from groundwater. In some communities, groundwater is the only source of drinking water. Many farmers and producers depend on groundwater for day-to-day activities. It is easy to see why you should be concerned about keeping pesticides out of groundwater. Pesticides may reach groundwater easily by leaching through sandy soil or cracks in dry clay soil or limestone rock. They may travel through interconnections between groundwater and surface water.

Surface Water

Surface water consists of bodies of water that we can see, such as ponds, lakes, rivers, and oceans. Surface water is especially likely to suffer contamination from many sources. Fertilizer and animal feces are often to blame. Pesticides and other chemicals can cause contamination as well. Take care not to contaminate water while diluting your pesticide or mixing it with bait.

Offsite Movement

In general, pesticides can move offsite in 2 ways: in air currents or in water. Offsite movement is the most troublesome and costly problem that many pesticide applicators face. If you apply a pesticide that moves offsite, you may face a lawsuit. Pesticide management is the responsibility of you and your crew. In vertebrate pest control, because offsite movement with water is a major concern, we’ll look at this more closely.

Movement with Water

Some pesticides can easily move offsite in water. After a heavy rain or irrigation, runoff water can carry contaminants to surface water in 1 of 2 ways.

  1. Chemicals can dissolve or be suspended in the runoff water, or
  2. Chemicals might be adsorbed by (stick to) soil particles carried by runoff.

Either way, the chemicals could end up in a lake, river, or other surface water.

Pesticides can move to groundwater, as well. A pesticide can leach, or be carried with water downward through soil. Leaching is more common in sandy soils and in places where the water table is near the surface.

Both runoff and leaching are concerns near water sources such as wells, ponds, rivers, and drainage pipes. Some general ways to prevent pesticides from moving offsite in water include:

  • Read the label. Follow any special precautions for protecting water sources.
  • Avoid or work carefully in and around sensitive areas such as surface water, wells, drains, wetlands, etc.
A predator such as a red-tailed hawk could suffer from secondary poisoning if it eats a mouse or bird that had been poisoned. Photo by Jan Hygnstrom.

Protecting Non-target Animals

As a WCO, you must be aware of non-target animals – animals you do not intend to harm – when carrying out all pest control activities. One of the greatest risks in vertebrate pest control is harming non-target animals. These may be pets, livestock, and wildlife such as migratory birds, endangered or threatened species, or other animals not causing damage.

Pest control activities can injure or kill a non-target animal in many ways. Sometimes misplaced traps and poorly installed barriers will hurt non-target animals. Other times, chemical exposure may threaten their health. This chapter covers safety risks specific to pesticide use. These include improperly applied chemicals and secondary poisoning.

Secondary poisoning can occur when a predator or scavenger eats the organs or muscles of a pesticide victim. If the pesticide has accumulated in the flesh of the target animal, the scavenger or predator (Figure 6) may be poisoned.

Unfortunately, some applicators have intentionally misused chemicals. For example, insecticides have been applied to meat or to dead animals to kill scavengers or predators. This illegal behavior is a threat to non-target animals and even to people.

Improper application, whether intentional or not, can directly harm or kill non-target animals. The best way to avoid misapplication of a pesticide is to follow all label instructions. Check the pesticide label for application restrictions near wildlife habitats.

Types of Pesticides

The types of pesticides most often used in vertebrate pest control include chemical repellents, toxicants, chemical frightening agents, and certain fumigants. Each one has unique risks. Special application techniques limit these risks and help protect the environment, non-target animals, and you.

Chemical Repellents

The most common chemical repellents used to control vertebrates are tactile repellents. These rely on touch. They work best to repel birds from ledges and other roosting spots. Use tactile repellents for birds with care and according to the label. More is not always better. Improper or excessive application of the sticky material may foul the feathers of non-target birds. Also, it can trap birds on ledges or other sites. Dead birds that stick to ledges will decay and are hard to remove. This not only violates label laws, it can create a sanitation problem as well.

Taste repellents can affect non-target animals and disperse them from the treated area. Some taste repellents are formulated as fogs or are placed in surface drinking water. These pesticides may disperse all target and non-target animals from an area. Evaluate the potential effects on non-target wildlife before using repellents. Just because a pesticide is not lethal does not justify harming non-target wildlife.

Toxicants (Baits)

Wildlife control may require using toxic baits. Baiting with toxicants is a complex process that requires careful attention to detail. The easiest way to harm non-targets is to take shortcuts. Read and follow all label directions carefully.

Figure 5. Bait stations and bait for rodent control. Photo by University of Nebraska – Lincoln.

Toxic baits are a hazard to non-target wildlife and domestic animals. Good bait placement and site cleanup can reduce or eliminate these hazards. Try to bait in areas not frequented by non-target animals. Pick up and dispose of any uneaten treated bait according to label instructions. Remove dead animal carcasses promptly. By using safe baiting techniques, you can greatly reduce hazards to non-target animals.

Some baits must be placed in bait stations (Figure 5) to reduce the risk that children or other non-targets will be exposed to the pesticide. Be careful to follow all label requirements. More information is available in Module 8 Chemical Control.

Rodenticides

Rodenticides are classified by their modes of action. Most registered rodenticides are anticoagulants. When ingested, anticoagulants inhibit clotting of the blood. Animals die from stress-related internal bleeding or bleeding from external wounds. Rodenticides include first-generation products (e.g., warfarin), and more recently developed second-generation toxicants (e.g., brodifacoum, chlorophacinone, difethailone, and diphacinone). While the effects of all anticoagulants are cumulative, causing chronic toxicity, some may be effective with a single dose. Keep fresh bait available continuously for at least 2 weeks, or until all feeding ceases.

Anticoagulant rodenticides seldom pose a hazard when they are consumed in a single feeding because the concentration of active ingredient typically is below 0.01%. A non-target animal usually must consume toxic bait several times to experience negative effects. In addition, Vitamin K1 can be used as an antidote to counteract the effects of anticoagulants. However, remember that any chemical, even one not used as a pesticide (table salt), may cause harm if enough is consumed. 


An opossum showing the effects of poisoning by anticoagulants.
Photo taken by a concerned WCO.

The greatest risk when using toxic baits is poisoning non-target animals. The best way to reduce poisoning non-targets with rodenticide baits is to avoid using them where pets, livestock, children, and other non-targets are present. Apply baits only in tamper-resistant, locking bait boxes that prevent access by non-target species.

Anticoagulants do pose hazards for non-targets through secondary exposure.

A rodent that has consumed an anticoagulant has concentrated levels of that compound in its body, especially in the liver, for several days. A predator or scavenger that eats poisoned rodents may receive a high dose of the toxicant. This can lead to impaired clotting of the blood and death. Brodifacoum and diphacinone are toxic, particularly to dogs, and have relatively long biological half-lives.

Bait stations (Figure 6) have become the standard tool for applying rodenticides. Bait stations come in a variety of shapes and sizes, all of which are used to protect the bait, increase consumption of the bait by rodents, and minimize access to the bait by non-target animals. The rodenticide label may require the use of a bait station.

The following list outlines tactics to reduce hazards from anticoagulant rodenticide baits:

  • avoid using where children, pets, livestock, and other non-targets are present;
  • use the lowest hazard toxicant that will be effective (i.e., a high LD50), and apply toxicants in tamper-resistant bait boxes to minimize direct contact by non-targets;
  • remove dead and impaired rodents found during daily inspections and follow proper sanitation practices; and
  • use toxicants as part of an IWDM program, when other less hazardous methods have failed or will not meet management goals.

Some bait stations are large enough that bait and water can be placed inside. Place bait stations where rodents are active, especially where rodent signs (e.g., droppings, gnaw marks) occur along walls, under pallets, and behind equipment. Secure bait stations with screws, anchor bolts, or other fasteners. Use locks, seals, and concealed latches to make bait boxes tamper-resistant.

Check bait stations regularly to find out whether the target pests are using a station and to spot signs of trouble. If the pest does not take the bait, switch to another brand of bait or remove competing food sources. If some bait stations are working and others are not, relocate the ones that are not attracting pests.

Check bait stations daily if possible during the first week, and at least once per week thereafter, gradually reducing to monthly inspections. Refresh or replace bait as need.

In June 2011, the EPA implemented a Rodenticide Risk Mitigation Plan that is designed to reduce the risk of rodenticide exposure to children and non-target animals. The Plan restricts the use of second-generation anticoagulant rodenticides by the public and requires that all rodenticides be applied in bait stations. Certified pesticide applicators still can use second-generation anticoagulants, but amounts are restricted and some products have been removed from the market. For additional information, visit the website of the EPA at https://www.epa.gov/rodenticides   

Besides anticoagulant (chronic toxicant) rodenticides, some are acute toxicants and have other modes of action. The concentration (%) of active ingredient in most formulations typically is much higher than in anticoagulant rodenticides. No antidotes exist for acute toxicants, so even greater care must be used during application. Acute toxicants, such as bromethalin, cholecalcoferol, and zinc phosphide, can cause a quick reduction of a rodent population (often within a day), while anticoagulants typically reduce a population within 1 to 3 weeks. Quick-acting toxicants are useful when the risk of disease is high or when a very large population must be reduced in a short period of time.

Acute toxicants only should be used once or twice a year in the same locality to avoid the development of bait shyness in rodents. Bait shyness, when an animal avoids a bait, can occur when an animal eats a partial dose of a pesticide. This dose does not kill the animal but may produce side effects that could make the pest refuse the bait in the future.

Slow-Acting Toxicants – Avicides

Any pesticide used to control pest birds is called an avicide. Avicides that are slow-acting toxicants will control starlings around livestock and poultry operations. They are toxic to chickens, turkeys, ducks, and some other birds in differing amounts. However, they will not kill house sparrows. Mammals, including humans, are generally unaffected by these toxicants. Never place these baits in areas accessible to poultry, livestock, or non-target wildlife.

Affected birds experience a slow, nonviolent death. They usually die from 1 to 3 days after feeding. Often they die at their roost or along flight lines. You will find few dead starlings at the baiting site. To provide good sanitation and to prevent the spread of disease, pick up any dead starlings that you find. Properly dispose of them by deep burial or burning.

Do not leave toxic baits exposed for a long time. This may cause bait rejection due to discoloration. It could endanger protected bird species and other non-targets.

Remember, avicides (used for bird control) are pesticides. Follow all safety precautions for pesticide use. Thoroughly understand your target bird’s biology and habits as well as those of non-target birds in the area. Keep in mind your desired results, and use the minimum dosage (according to the label) to get those results. Know the avicide’s mode of action – how it works. Do what is necessary to protect non-target animals and to lessen the possibility of secondary poisoning.

You can minimize the impact to non-target animals when using avicides through the following:

  1. Prebait, with an ample supply. You are training the birds to come to the site. You cannot accomplish this if they can’t get enough to eat; they will go elsewhere to feed.
  2. Place toxic bait in a knowledgeable and timely fashion. For example, set out toxic bait before daybreak, otherwise birds may feed elsewhere before arriving at the bait site. Bait acceptance will be poorer, increasing the length of your control program.
  3. Remove and dispose of any dead birds and uneaten bait.
  4. Monitor animals feeding on the bait.

Chemical Frightening Agents

Chemical frightening agents for birds, another type of avicide, often are single-dose pesticides that act on the central nervous system. The few birds that eat the toxic bait react violently with convulsions and erratic behavior before they die. This frightens other birds from the site.

Frightening agents may be toxic to many species of birds and mammals, including humans. If ingested by a person, some of these pesticides cause excited behavior, salivation, tremors, lack of coordination, convulsions, and cardiac or respiratory arrest. Symptoms begin within 15 minutes of ingestion. Death can occur within 15 minutes to 4 hours. If someone swallows a frightening agent, call for medical help. Induce vomiting only if the label instructs you to do so. In the case of skin contact, wash the area with soap and water.

Toxicants (fumigants)

Gas cartridges and moisture-activated fumigants are the 2 most common fumigants used in vertebrate control programs. Many of these toxicants are restricted use and additional permits or legal jurisdiction may be required. Here are some safety guidelines when using these fumigants.

Precautions for Using Gas Cartridges

Read the label carefully. Follow the directions exactly. Take these precautions:

Gas cartridges are a fire hazard. Never use gas cartridges in burrows under sheds or buildings, or near other combustible materials.

Avoid prolonged breathing of the fumes.

gas cartridge

Gas cartridges pose a fire hazard. Photo by University of Nebraska-Lincoln.

Risks When Using Moisture-activated Fumigants

Moisture-activated fumigants are effective but very dangerous. The gas they release is extremely toxic to all mammals, including humans. Use extreme caution when applying these fumigants. Take these precautions:

  • Open the container only in fresh air or near a fan or other ventilation system.
  • When opening, point the container away from your face and body. Loosen the lid slowly.
  • As with all pesticides, follow the label directions carefully and exactly. Wear all required PPE.

Many moisture-activated fumigants are restricted use pesticides. Check your state for certification requirements regarding the purchase and use of fumigants, as well as any other pesticides.

Safe Handling Checklist

Make safety your first concern every time you handle pesticides or supervise someone who does. Use gloves and personal protection equipment.

Before applying any chemical, ask these questions:

  • Have I read the labeling?
  • How can I avoid exposure to pesticides?
  • What PPE do I need? Is it in good condition?
  • Is the PPE and/or application equipment safe and ready to use?
  • How can I keep pesticides out of sensitive areas?
  • Am I prepared for emergencies?
  • Are people and non-target wildlife out of the area?

By addressing these basic questions, you can prevent many pesticide accidents or reduce their severity.

More Terms to know

Adsorption – The process of binding and holding something to a surface.

Dermal – Refers to the skin.

Exposure – Having contact with a pesticide. This may be through the eyes (ocular), the mouth (oral), the lungs (inhalation), or the skin (dermal).

Repellent – An object, sound, action, or chemical used to deter pests.

Secondary Poisoning – When a predator or scavenger ingests pesticide by eating an animal killed by a pesticide. Secondary poisoning causes sickness or death.

Tactile – Refers to the sense of touch.

Additional Resources

  • US Environmental Protection Agency (http://www.epa.gov/pesticides),
  • US Fish and Wildlife Service (http://www.fws.gov),
  • University Extension Pesticide Safety Education Program

Study Questions for Toxicants

Questions for Reflection

  1. A client is concerned about the risk of using an anticoagulant rodenticide to control mice with a dog on the property. How would you respond?
  2. What are some ways you can reduce the risk of toxicants to non-targets?
  3. Why is it important to wash your hands after every rodenticide or avicide application?
  4. Someone may be tempted to apply a toxicant without following information on the label. What are some outcomes of the misapplication of a toxicant?

Objective Questions

  1. True or False – “Target species” refers to those animals that are the intended subjects of control.
  1. What can toxicants potentially harm?
    1. the applicator
    2. animals
    3. the customer
    4. all of the above
  1. How do anticoagulant rodenticides kill an animal?
    1. interfering with clotting of the blood
    2. interfering with heart muscle activity
    3. interfering with the nervous system
    4. interfering with the respiratory system
  1. First-generation anticoagulants
    1. require 1 feeding to kill
    2. require multiple feedings to kill
    3. are older than second-generation anticoagulants
    4. a and c only
    5. b and c only

True or False – Dozens of active ingredients are registered for the lethal control of wildlife in the US.

Summary of Questions and Answers for Toxicants

Explain the difference between anticoagulant (chronic) rodenticides and other (acute) rodenticides.

Anticoagulant rodenticides cause internal bleeding. The affected animal will then bleed to death. Chronic rodenticides kill only after the animal consumes the treated bait several times. After a rodent eats the toxicant a number of times, a low dosage becomes lethal.

Other (acute) rodenticides are lethal when the target animal ingests a single dose with food and drink. Acute rodenticides cause death by heart paralysis, internal organ damage, or by attacking the central nervous system. The target animal must consume a lethal dose for symptoms to develop.

How does an animal become bait shy? How can you prevent this problem?

By eating a partial dose of a pesticide. This dose does not kill the animal but may produce side effects that could make the pest refuse the bait. Prebaiting is the best way to prevent bait shyness.

Why is it important to check bait stations regularly?

To find out whether the target pests are using a station and to spot signs of trouble. If the pest does not take the bait, switch to another brand of bait or remove competing food sources. If some bait stations are working and others are not, relocate the ones that are not attracting pests.

Which type of fumigant is more dangerous to use: gas cartridges or moisture-activated fumigants? Why?

Moisture-activated fumigants are more dangerous. The phosphine gas they release is extremely toxic to all mammals, including humans. Use extreme caution and pay close attention to label instructions when applying this pesticide. Always open phosphine canisters outside or near a fan.

List the steps to follow when placing and igniting a gas cartridge.

  1. Locate the main burrow opening and all secondary entrances.
  2. Cut a clump of sod slightly larger than each opening. Place a piece of sod over each entrance except the main entrance. Leave a precut sod clump next to the main entrance for later use.
  3. To prepare the gas cartridge for ignition and placement, follow the instructions on the label. Insert the fuse.
  4. Kneel at the burrow opening, light the fuse, and immediately place (do not throw) the cartridge as far down the hole as possible.
  5. Immediately close the main opening by placing the piece of precut sod, grass side down, over the opening. Make a tight seal with loose soil.
  6. Stand by for 3 to 4 minutes and watch nearby holes. Reseal any holes from which smoke is escaping.
  7. Repeat these steps until you have treated all burrow systems in the problem area.

What is the greatest risk when using toxic baits?

Poisoning non-target animals.

How can you minimize the threat to non-target animals when using avicides?

  1. Place toxic bait in a knowledgeable and timely fashion.
  2. Remove and dispose of any dead birds and uneaten bait.
  3. Monitor animals feeding on the bait.

Why is it important to furnish an ample supply of prebait for target birds?

You cannot train birds to feed at a site where they cannot get enough to eat. They will simply go elsewhere to feed, and the prebaiting program will fail.

At what time of day should you set out toxic bait? Why?

Before daybreak. Otherwise, birds may feed elsewhere before arriving at the bait site. Bait acceptance will be poorer, and time until death will increase.

What are fertility or reproductive controls? How can they help control pest birds?

Products used to reduce hatchability of pigeon eggs (e.g., OvocontrolTM, active ingredient nicarbazin). In some states, even food-grade corn oil is considered a pesticide when applied to eggs to reduce hatchability.

Name several ways that a wildlife manager might accidentally harm non-target animals.

By misplaced traps, poorly installed barriers, and chemical exposure.

How does secondary poisoning occur?

When a predator or scavenger eats the flesh of a pesticide victim. The scavenger or predator may become poisoned if the pesticide has accumulated in the flesh of the target animal.

True or False: When choosing personal protective equipment (PPE) to wear while applying pesticides, you should always use exactly what the label specifies: no more and no less.

False. Federal and state laws require you to wear at least what is specified on the product label. For certain higher risk situations (mixing and loading), you may be wise to use more protective clothing than the label requires.

How can you find out the toxicity of a pesticide such as a toxicant?

Refer to the label as a guide for toxicity and other product information. The label will include a signal word that gives the toxicity of the pesticide. The SDS will give the LD50 (toxicity measure) for the formulated product.

Why should you never use gas cartridges to fumigate burrows under sheds or buildings, or near other combustible materials?

Gas cartridges are a fire hazard. They are dangerous around combustible materials.

What precautions should you follow when using moisture-activated fumigants?

  1. Open the container only in fresh air or near a fan or other ventilation system.
  2. When opening, point the container away from your face and body. Loosen the lid slowly.
  3. As with all pesticides, follow the label directions carefully and exactly. Wear all required PPE.

Why should you avoid leaving toxic baits exposed for long periods?

The baits often become discolored, which may cause bait rejection. These baits may also endanger some protected bird species.