Names, Classification, and Toxicity of Pesticides
Pesticide labels contain the brand or trade name of the pesticide product, the common name, and the chemical name of the active ingredient in the pesticide formulation. The active ingredient of a pesticide is the portion of the product that affects the target pest. Pesticide manufacturers may use many different copyrighted brand names for pesticide formulations that contain the same active ingredient. The common name of a pesticide active ingredient is commonly used and has usually been approved by an appropriate scientific group. The chemical names of pesticide active ingredients are usually complex and are generally used only in the active ingredient statement on the pesticide label and in scientific or technical publications. A pesticide active ingredient will usually have only one common name, but it may have several trade names. For example, glyphosphate is the common name for the chemical name isopropylamine salt of N-(phosphonomethyl) glycine, the active ingredient in the Roundup® brand of glyphosate.
Insecticides, herbicides, fungicides, and other pesticides are primarily classified on the basis of their chemical structure or origin. The inorganic pesticides are those that contain no carbon in their chemical structure. The organic pesticides, those that contain carbon, are usually synthetic, but some are obtained from natural sources such as plants or microorganisms. Some synthetic organic pesticides such as the pyrethroids, or synthetic pyrethrins, are based on naturally occurring chemicals.
The Environmental Protection Agency (EPA) uses the results of acute (short term) toxicity studies on test animals, usually rats and rabbits, to place pesticides in toxicity categories (I-IV) (one-four) that determine what signal word must appear on the label. Although inhalation toxicity, eye corrosiveness, and skin corrosiveness studies are also used, results of acute dermal and acute oral toxicity studies are more publicized and usually more important.
The table at the end of this document shows the signal words that must appear on the pesticide label for each toxicity category and the range of the oral and dermal median lethal doses (LD50) for each category. A pesticide that falls into category I only because of eye or skin corrosiveness must bear "Danger" but not "Poison" nor the skull and crossbones symbol on its label.
The LD50 (Lethal Dose) is the amount of a substance at which one-half of the exposed test animals are killed. It is based on the body weight of the animal and is expressed in milligrams of the substance per kilogram of animal weight (mg/kg). One mg/kg is equivalent to 1 ppm. The lower the LD50 value, the greater the toxicity of the substance. Although most LD50 values that are readily available in publications are for the pesticide active ingredient or actual toxicant, the signal word on each pesticide product is determined by the toxicity of that particular formulation. Formulated pesticides are usually, but not necessarily, less toxic than the concentrated active ingredient. The toxicity categories given in the following tables are based solely on the accompanying LD50 values which, unless stated otherwise, are for the active ingredient. The EPA would not necessarily assign the same category shown in the tables. Refer to the Table at the end of this document.
What Is Exposure?
Accidental exposure or chronic overexposure to pesticides can create serious health problems. While most pesticides pose minimal risks (as long as label directions are followed), others can be extremely toxic and require special precautions. In general, the vast majority of pesticide exposure injuries result in only eye/skin irritations.
Pesticide exposures can lead to symptoms of great concern including:
- shortness of breath
Wearing the proper protective clothing and equipment while handling or applying pesticides significantly reduces the risk of pesticide poisoning through accidental exposure.
Treat all pesticides as toxic. Differing degrees of toxicity are potentially dangerous to all people if exposure is excessive. For this reason, it is important to know how toxic each product is and how you can manage and lower the risk for personal exposure.
A pesticide product label will contain one of three signal words: Danger, Warning, or Caution. These signal words clearly indicate the degree of toxicity associated with the product. Acute or short-term toxicities are the basis for assigning pesticides to a toxicity category and selecting the appropriate signal word for the product label. Pesticides that are classified as "highly toxic," on the basis of either oral, dermal, or inhalation toxicity, must have the signal words DANGER and POISON (in red letters) and a graphic of a skull and crossbones prominently displayed on the package label. PELIGRO, the Spanish word for danger, must also appear on the label of highly toxic chemicals. An exposure of a few drops of a highly toxic material taken orally could be fatal to a 150-pound person.
Some pesticide products are labeled with the signal word DANGER without the skull and crossbones symbol. This signal word alerts the user of potentially more severe skin or eye effects from the product (caused by its irritant or corrosive properties).
Pesticide products considered "moderately toxic" must have the signal words WARNING and AVISO (Spanish) displayed on the label. An exposure of 1 teaspoon to 1 ounce could be fatal to a 150-pound person.
Pesticide products classified as either "slightly toxic" or "relatively nontoxic" are required to have the signal word CAUTION on the pesticide label. All pesticides, regardless of the signal word, should be handled with extreme care.
Routes of Entry
After the signal words, pesticide labels will also include statements concerning routes of entry and specific actions to be taken against exposure.
Route of entry statements indicate the outcome expected from accidental exposure. Some examples from a pesticide label might read: 1) "Poisonous if swallowed, inhaled or absorbed through the skin" or 2) "Rapidly absorbed through the skin and eyes."
Pesticides can enter the human body four ways:
- Absorption through the skin (dermal)
- Intake through the mouth (oral)
- Intake and passage into the lungs (inhalation)
- Absorption through the eyes (ocular)
Dermal exposure results from immediate absorption when a pesticide contacts the skin or eyes. Absorption can continue as long as the pesticide remains in contact with the skin. The rate at which this occurs is different for each part of the body. Some parts of the body absorb pesticides rapidly and need extra protection. Examples of rapid absorption areas are the head and groin area.
Oral exposure to pesticides can cause severe injury. This type of exposure can result in serious illness or even death. The most common accidental oral exposures occur when pesticides have been removed from their original containers and placed into an unlabeled bottle, jar, or food container.
Children under 10 are victims of at least 1/2 of the accidental pesticide deaths in the United States. To prevent oral exposure, follow these guidelines:
- Always store pesticides in their original labeled containers.
- Do not bring pesticides home from the workplace.
- Never use the mouth to clear a spray hose or nozzle, or to begin siphoning a pesticide.
- Never eat, drink, or use tobacco until after leaving the work area and washing thoroughly.
Inhalation exposure is particularly hazardous because pesticide particles such as powders, airborne droplets, or vapors can be rapidly absorbed by the lungs into the bloodstream. Pesticides can cause serious damage to nose, throat, and lung tissue if inhaled in sufficient amounts and concentration. Vapors and very small particles pose the most serious risks.
Handling concentrated wettable powders can pose a hazard if inhaled during mixing. The hazard from inhaling pesticide spray droplets is fairly low when dilute sprays are applied with low pressure application equipment. This is because most droplets are too large to remain airborne long enough to be inhaled.
However, when using high pressure, ultra low volume (ULV), or fogging equipment, the potential for respiratory exposure is increased. The droplets produced during these operations are in the mist or fog size range and can be carried on air currents for a considerable distance into the working area of other workers.
Ocular exposure can result when pesticides contact the eyes, which can quickly absorb the pesticide material. Illness, serious eye injuries, or irritation can be avoided by wearing protective glasses, goggles, or shields when mixing, loading, or applying pesticides.
Multiple Choice Questions
- ______ Pesticide absorption through the eyes is known as what kind of exposure?
2.______ Pesticide absorption through the skin is known as what kind of exposure?
3.______ Pesticide absorption through the mouth is known as what kind of exposure?
4.______ Pesticide absorption through the lungs is known as what kind of exposure?
5. Pesticide exposures can result in which of the following symptoms?
d) All of the Above
6. Which area of the body absorbs chemicals most rapidly?
a) Palm of the hand
b) Scrotal area
c) Any exposed skin
d) Ear canal
7. What is the best way to prevent pesticides from entering the body?
a) Not using pesticides
b) Using personal protective equipment
c) Understanding the label
d) b and c
Personal Protective Equipment
Most of the pesticide spilled on the skin is absorbed in the first few minutes, so immediately washing the affected area with soap and clean water is recommended. The best method to avoid direct contact with pesticides is to wear personal protective clothing. The pesticide label will indicate the PPE required for mix/loaders and applicators. When tank-mixing pesticides, the pesticide requiring the most PPE takes precedence. It is the user's responsibility to follow the directions on the label. The label is the law!
Always wear unlined, elbow-length chemical-resistant gloves when handling all pesticides, except those that are relatively nontoxic. Elbow-length gloves protect the wrists and prevent pesticides from running down the sleeves into the gloves. Refer to the table at the end of this document for gloves made of various materials and the level of protection they offer.
Wear a chemical-resistant apron while repairing or cleaning spray equipment and while mixing or loading chemicals. This should be practiced for all pesticide handling but is mandatory for pesticides of category I and II toxicity. Aprons offer excellent protection and barriers against spills and splashes of liquid formulations and dry pesticide formulations.
Aprons can be easily worn over other protective clothing and are comfortable enough for use on hot days. Choose an apron that extends from the neck to the knees. Some aprons have other attachments such as sleeves. Nitrile, butyl, and neoprene aprons offer the best protection. PVC and natural rubber are also available.
Always wear unlined chemical-resistant boots that cover the ankles while handling or applying moderately to highly toxic pesticides. Nitrile, butyl or rubber boots will give the best protection. Do not use leather boots; they are difficult, if not impossible, to decontaminate. If chemical-resistant boots are too hot or cumbersome to wear, try wearing chemical-resistant overboots, which should be worn with washable shoes such as canvas sneakers.
Always remember to put your pant legs outside the boots, otherwise the pesticide can drain into the boot. Wash boots after each pesticide application and dry thoroughly inside and out to remove all pesticide residue. It is wise to keep two pair of boots on hand in case of accidental contamination.
Protective masks cover the nose and mouth to filter out dust, mists, powders, and small particles in the air. Dust masks should never be worn in place of a respirator, if so required. In citrus operations, all respirators must have MISH/NIOSH approval number prefix RC-21C.
Different types of respirators are required for different pesticide formulations. The pesticide label will describe what kind of filter, cartridge, or canister type to use.
Respirators protect you from breathing pesticide-laden air and inhaling toxic chemicals. The pesticide label will tell you if a respirator is required. However, consider wearing one during any lengthy exposure with a high risk of pesticide inhalation. Always wear a respirator while mixing or loading highly toxic pesticides. Applicators who will be constantly exposed, like those mixing, loading, or applying pesticides, to small amounts of moderately toxic pesticides for a day or several days, should also wear respirators.
Before a respirator is worn, a qualified person should fit test each person that will be using this safety device. Fit tests are mandatory and are an important step in ensuring that exposure is prevented.
Respirators come in different sizes and should be worn tightly enough to form a seal all around your face. Remember that there is no substitute for a respirator. If the label requires its use, it is against the law to proceed without one.
Goggles or Face Shields
Wear shielded safety glasses, full-face respirators, snug-fitting, non-fogging goggles, or full-face shields whenever any chemical can possibly come into contact with the eyes. Safety glasses with brow and side shields are acceptable for low exposure situations. Always wear goggles or full-face respirators while pouring or mixing concentrates or while working with toxic sprays or dusts. In high exposure situations when both face and eye protection are needed, a face shield can be worn over goggles.
Clean face shields and goggles after each use with soap and water. Headbands are often made of materials that readily absorb and hold chemicals. For this reason have several spares and change them often. The best option is to use a chemical-resistant strap. Always wear the strap under your head covering.
Noise of all levels is found in many workplaces. Research has shown that high levels of noise can damage your hearing. Losing your hearing is a gradual process and is less noticeable than other types of workplace injuries. It is, however, a permanent handicap for those who are affected.
Hearing loss has been a common problem among farmers and farm workers for years. Since most farm equipment cannot be operated in a sound-proof enclosure, workers should use hearing protection when operating or working in the vicinity of noisy machinery. Earmuffs and plugs are available to provide hearing protection for most situations. Modern tractor cabs with noise reduction ratings will also provide adequate hearing protection for most situations.
Regular work attire such as long pants and a long-sleeved shirt, shoes, and socks are acceptable for slightly toxic (Category III) and relatively non-toxic (Category IV) pesticides. However, many applicators prefer work uniforms and cotton coveralls that fit the regular-work-attire description and provide equal protection. Disposable coveralls made of a non-woven, water resistant fabric such as Tyvek® can be worn over other clothing to add increased protection. Applicators should reserve one set of clothing for pesticide use only. Always launder and store the pesticide set separately from all other clothing.
Personal protective equipment (PPE) is given a rating scale by the EPA according to a resistance factor against pesticides.
A high PPE rating means that the material is highly resistant to pesticides in that category. PPE made of this type of material can be expected to protect you for an 8-hour work period. The remaining pieces of the PPE, especially gloves, should be washed at rest breaks or every four hours. Highly resistant PPE is a good choice when handling pesticides, especially emulsifiable concentrates, for long periods of time.
A moderate rating means that the material is moderately resistant to pesticides in that category. PPE made of this type of material can be expected to protect you for one to two hours. Replace this type of PPE after the allotted time with new items or thoroughly wash the outside with soap and water. PPE with a moderate rating may be a good choice for pesticide handling tasks that last only a couple of hours.
A low resistance rating means the material is only slightly resistant to pesticides in that category. PPE constructed with this type of material can be expected to protect you for only a few minutes after exposure to the pesticide product. Replace this type of PPE after the allotted time with new items or thoroughly wash the outside with soap and water. Slightly resistant PPE may be a good choice for pesticide handling tasks that last only a few minutes.
Cleaning and Disposal
Any respirator that has been contaminated with organophosphate pesticides needs to be washed with alkaline soap and rinsed with 50% alcohol (ethanol or isopropanol) before normal cleaning procedures.
- Remove any filters or cartridges from the respirator.
- Wash the facepiece in cleaner/disinfectant solution.
- Add suitable cleaner/sanitizer to a gallon of warm water (about 120ºF).
Immerse contaminated equipment in the solution and gently scrub with a soft brush until clean. Care should be taken to clean the exhalation valve in the facepiece and all other parts that the exhaled air contacts.
- Rinse completely in clean, warm water.
- Air dry in a clean area (preferably overnight).
- Place in a plastic bag for storage and label it with the date cleaned.
Any replacement of parts or repairs to the respirator shall be done only with parts designed for that respirator by the manufacturer. There should not be any attempts made to replace components or to make adjustments or repairs beyond the manufacturer's recommendations.
After inspection, cleaning, and necessary repairs, respirators should be stored to protect against dust, sunlight, heat, extreme cold, excessive moisture, or damaging chemicals. Pesticide approved respirators as well as other PPE should always be stored in a clean, pesticide-free area.
Regular cleaning and inspection prolongs the useful life of all PPE, and assures the wearer that the PPE will perform as efficiently as possible. For personal hygiene and communicable disease considerations, do not pass respirators from one individual to another without cleaning and sanitizing.
Plastic containers with lids provide adequate storage for respirators. During a respirator inspection, check for cleanliness and ensure the components are present and operable.
True or False
- _____ To determine the toxicity of the pesticide, it is important to read the pesticide label.
- _____ Pesticide-soiled clothing should be removed outdoors.
- _____ All pesticide-soiled clothing can be safely laundered.
- _____ Never pre-rinse pesticide soiled clothing.
5. Which glove material below would be the best choice to protect against chemicals?
6. When are chemically resistant aprons most useful?
a) During an application
b) Equipment clean-up
c) During mixing and loading
7. If a respirator is not available which piece of PPE can be used as a substitute?
a) Dust mask
c) A & B
8. How frequently must respirator cartridges be replaced?
a) At least every 8 hours of use
b) At least every 12 hours of use
c) At least every 48 hours of use
9. What is the best material for work boots while applying pesticides?
c) Chemical-resistant material
d) none of these
United States Department of Labor, Personal Protective Equipment (PPE), http://www.osha.gov
Centers for Disease Control and Prevention, Personal Protective Equipment Program, http://www.cdc.gov/niosh/programs/ppt/
National Agriculture Safety Database, Personal Protective Equipment, http://nasdonline.org/browse/14/personal-protective-equipment-ppe.html
Personal Protective Equipment and Clothing, Pesticide Information Program, Clemson University, http://www.clemson.edu/extension/pest_ed/safety_ed_prog/ppe/index.html
Protective Clothing for Pesticide Users, Bulletin 750, http://ohioline.osu.edu/b750/b750_2.html
The following publications that provide information for citrus grove workers are available through EDIS, the UF/IFAS on-line document system.
- Understanding the Pesticide Label for Citrus Grove Workers, https://edis.ifas.ufl.edu/ae243
- Pesticide Safety and Personal Protective Equipment for Citrus Grove Workers, https://edis.ifas.ufl.edu/ae244
- Herbicide Application BMPs for Citrus Grove Workers, https://edis.ifas.ufl.edu/ae246
- Pesticide Application BMPs for Citrus Grove Workers, https://edis.ifas.ufl.edu/ae247
- Fertilizer Application BMPs for Citrus Grove Workers, https://edis.ifas.ufl.edu/ae248
Use this table to guide the proper selection of gloves with different material composition and physical and chemical protection.
This table shows the signal words that must appear on the pesticide label for each toxicity category and the range of the oral and dermal median lethal doses (LD50) for each category.