Pesticides are designed to be toxic and must be used with special care. Because of varying toxicity among pesticide products, it is important to consider the possible harm to humans and nontarget organisms when controlling pests. Always refer to the label and the Safety Data Sheet (SDS) for information on toxicity and precautions.
Toxicity, Exposure and Hazard
Toxicity is a combination of a pesticide product’s chemical properties and concentration and is a measure of the product’s acute (short-term) or chronic (long-term) effects. Exposure occurs when pesticides get onto or into the body through inhalation, dermal contact, oral contact or ocular contact. Toxicity and exposure risks vary greatly among pesticide products. Exposure may occur when handling opened containers, mixing and loading, applying products, cleaning up a spill and re-entering a treated area before it is safe to do so.
A hazard is defined as the potential or probability for injuries, illnesses or allergies to occur due to the combination of a product’s toxicity and the likelihood of the pesticide handlers exposure. Applicators may be able to reduce hazards by choosing less toxic products and/or reducing chance for exposure.
An everyday example of this equation is something most people can relate to – handling gasoline. Gas is very toxic to humans, especially orally or if inhaled, but we all use gas to fuel our cars without thinking twice about it. This is because safety measures have been put in place to reduce our risk of exposure (e.g., locking gas caps, automatic pump stops, long nozzle that dispenses gas). However, when you take the same substance with the same toxicity (gasoline) and siphon it without those safety measures, the hazard is greater because the exposure is greater.
Reading the label carefully and following all instructions will help pesticide users to understand what they are using and how to use it in a way that minimizes exposure. When pesticide users assume that they know exactly how to use a pesticide and do not to read the product label or take the proper precautions indicated by the label or SDS, they are more likely to experience exposure and thus, hazards.
Potential Harmful Effects of Pesticides
Effects from chemicals are classified into two categories: contact (or local) and systemic.
Contact effects are localized to the area that the pesticide actually touches, which is why it is also referred to a contact symptom. Examples of contact symptoms are skin irritation (itching, rashes and burns), eye irritation (swelling and burning) and nose, mouth or throat irritation (swelling, burning and respiratory damage).
Systemic effects may occur after a pesticide has been absorbed into the body. This type of reaction depends on the toxicological profile of the chemical, the amount absorbed and the affected individual’s ability to detoxify the chemical. Examples of systemic effects include: damage to nerves, impairment of the blood’s clotting ability, cancer, reproductive/hormonal problems, impaired metabolism and organ damage.
Exposure
Skin or Dermal Route of Entry
With up to 97% of all body related exposures to pesticides during a spraying operation occuring dermally, skin is the main route of pesticide entry into or onto the body. The chart above shows the most common ways that pesticide is absorbed dermally. When it comes to dermal absorption, all parts are not the same. The groin, armpits, head, neck, back of the hands and tops of the feet tend to be warm and moist, causing them to absorb faster than other areas. Cuts, abrasions and skin rashes may also accelerate the rate of absorption. Compared to water-soluble liquids or powders, wettable powders, dusts and granules and oil-based liquid formulations (e.g., emulsifiable concentrates) are quickly and easily absorbed.
Eye or Ocular Route of Entry
Because the blood vessels are very close to the surface of the eye, eye tissues are extremely absorbent. Even with their small size, eyes can quickly and easily absorb large amounts of chemical. Absorption through the eyes can be particularly hazardous because in addition to systemic concerns, the corrosive nature of some products may cause severe eye damage and even blindness.
Breathing or Inhalation Route of Entry
Mixing, loading and applying pesticides create the risk of inhalation. Aside from the contact damage that may occur to the pesticide user’s nose, throat and lung tissue, the pesticide may enter the bloodstream through the lung tissue and cause systemic issues.
Swallowing or Oral Route of Entry
Mixing, loading and cleaning liquid pesticide equipment can promote the risk of oral exposure through splashing. Your common sense should tell you to never use your mouth to clear a spray line or attempt to begin siphoning a pesticide! It is very important to mark all pesticide containers and measuring devices AND store them properly to avoid the risk of mistaking a pesticide container or it’s accessories as a household item. Pastes, gels and other baits also pose a threat if not properly placed. To a child or a pet, these baits can look like a fun treat.
Acute vs. Chronic Toxicity
Acute toxicity is when illness or injury occurs from one single exposure to a pesticide. This exposure can come from inhalation, eye or skin exposure and may have a systematic effect, contact effect or both. Acute effects usually occur within 24 hours of exposure, unless systemic.
Acute toxicity is measured by a pesticide’s lethal dose 50%, or LD50, which is the dose that it would take to kill 50% of the population of test animals under standard conditions. Results are given for oral contact (oral LD50) as well as dermal contact (dermal LD50). Inhalation toxicity is measured by the concentration it would take to kill 50% of a test population through air or water. The lethal concentration 50%, or LC50, is often used to evaluate the lethal effects of chemicals on fish or other aquatic organisms, but is also very applicable to human health as it measures the LC of the air we breathe when around a pesticide.
LC50 and LD50 are limited in their toxicity reports because they only measure death that may occur after a single exposure. They do not address any less serious contact effects or delayed systemic effects. All toxicity concerns, including contact and systemic, are indicated by the signal word on the label and are further explained in the “Hazards to Humans and Domestic Animals” section of the label.
Chronic toxicity is a measure of illnesses or injuries that occur due to long-term exposure to small doses of a pesticide. General effects from chronic exposure include, but are not limited to: tumors, cancer, blood and/or nerve disorders and birth defects. Because the chronic toxicity of a pesticide is harder to measure due to changes in timing, doses, conditions and modes of exposure, there is not an equivalent to LD50 or LC50.
The graph below shows the lethal doses and concentrations associated with the correct signal word.
| Signal Word | Toxicity Level & Class | LD50Oralmg/kg | LD50Dermalmg/kg | LC50Inhalationmg/l | Contact Injury Concern | Toxicity Concern |
| DANGER – POISON/PELIGRO | Highly toxic, Hazard Class I | Trace to 50 | Trace to 200 | Trace to 0.2 | Severe oral, dermal or inhalation toxicity | Very low dose could kill a person (a few drops to 1 teaspoon) |
| DANGER/PELIGRO | Highly toxic, Hazard Class II | Trace to 50 | Trace to 200 | Trace to 0.2 | Corrosive – permanent or severe eye, skin or respiratory damage | Corrosive or irritant properties make this product dangerous |
| WARNING/ AVISO | Moderately toxic, Hazard Class II | 50 to 500 | 200 to 2,000 | 0.2 to 2 | Moderate skin, eye or respiratory damage | 1 teaspoon to 1 ounce doses could cause death or contact damage |
| CAUTION | Slightly toxic, Hazard Class III | 500 to 5,000 | 2,000 to 20,000 | 2 to 20 | Mid skin, eye or respiratory irritation | 1 ounce to 1 pound doses could cause death or contact damage. |
| CAUTION or no signal word | Hazard Class IV | Greater than 5,000 | Greater than 20,000 | Greater than 20 | Slight concern for skin, eye or respiratory injury | Slight to no risk for death or injury. |
First Aid
When it comes to seeking medical advice for unexplained symptoms that may occur after a pesticide exposure, it is always better to be safe than sorry. Many common illnesses such as the flu, heat stroke, asthma and hangovers have similar side effects to pesticide exposure. Additionally, contact with plants like poison ivy or poison oak may produce rashes, bumps and irritation that may be similar to pesticide contact. Though your symptoms may seem like no big deal, if you experience them within 24 hours of pesticide exposure, please call your physician or go to the hospital. Having the pesticide label and its SDS sheet (or copies of these documents) will help guide medical professionals on how to treat you quickly and appropriately.
In the initial effort to help someone in the event of pesticide poisoning, you should be able to administer general first aid. First, be sure that you are protected from pesticide exposure by wearing appropriate PPE, including a respirator if necessary, before helping others. Next, make sure the victim is breathing and is no longer exposed to the pesticide, then call 911 or the American Association of Poison Control Centers (AAPCC). You should always follow the label’s first aid instructions as well as instructions given by the AAPCC or 911, but it is good to have an understanding on what to do should you need to administer first aid during a pesticide emergency.
Pesticide On Skin
In the event that pesticide is spilled or splashed onto the skin, it is important to follow these steps:
- If any clothing is contaminated, remove immediately. In mild cases, contaminated clothes should be washed separately, but in more extreme cases, it is best to throw them out.
- Wash the affected area with soap and water, but do not scrub! Scrubbing may cause abrasions in the skin allowing for faster pesticide absorption.
- If the skin has chemical burns, consult your doctor. Do not apply any medicine to the affected area as they could cause a chemical reaction with the pesticide – ouch, double whammy!
Pesticide In The Eyes
Because of the blood vessels that sit so close to the surface, eyes absorb materials (including pesticides) very quickly. If pesticides come in contact with the eye the top priority is washing the eye out with drops of clean water. Do not use saline or medicated eye drops unless instructed by a doctor. Do not drop directly into the eye, instead let the water drip across. You should continue to clean out the eye for a minimum of 15 minutes, being sure to get under the eyelid as well. Once the eye has been thoroughly rinsed, seek medical attention!
Pesticide Inhalation
Inhalation of pesticides can be very dangerous to the person poisoned as well as the people around them. When dealing with pesticide inhalation, remember to follow these steps:
- If the victim is in an enclosed contaminated area, you must wear the proper PPE, including a respirator, when helping them.
- Get the victim to fresh air as fast as possible. Have them lie down and instruct them not to speak and to remain calm.
- If other people are in the area, warn them of the danger.
- If victim is seizing, protect their head and try to keep their chin up to ensure their air passages are open.
- If breathing stops or is irregular, give artificial respiration.
Pesticide In The Mouth or Swallowed
If someone has pesticide in their mouth or accidentally swallows pesticide, your first instinct might be to induce vomiting. However, that may NOT be the best decision. If the pesticide was just in the mouth, and not swallowed, rinse the mouth out with water and make the victim drink up to one quart of milk or water. If the pesticide is swallowed, check the label to see if it specifies that you induce vomiting. Some pesticides do more harm when vomited!
NEVER induce vomiting if the victim is unconscious of having convulsions or has swallowed a corrosive poison or an emulsifiable concentrate.
Summary
- Exposure occurs when pesticides get onto or into the body through inhalation, dermal contact, oral contact or ocular contact. Toxicity and exposure risks vary greatly among pesticide products. Exposure may occur when handling opened containers, mixing and loading, applying products, cleaning up a spill and re-entering a treated area before it is safe to do so.
- Contact effects are localized to the area that the pesticide actually touches, which is why it’s also referred to a contact symptom. Systemic effects may occur after a pesticide has been absorbed into the body. This type of reaction depends on the toxicological profile of the chemical, the amount absorbed and the affected individual’s ability to detoxify the chemical.
- With up to 97% of all body related exposures to pesticides during a spraying operation occuring dermally, skin is the main route of pesticide entry into or onto the body.
- Mixing, loading and cleaning liquid pesticide equipment can promote the risk of oral and inhalation exposure through splashing.
- Acute toxicity is measured by a pesticide’s lethal dose 50%, or LD50, which is the dose that it would take to kill 50% of the population of test animals under standard conditions. Results are given for oral contact (oral LD50) as well as dermal contact (dermal LD50). Inhalation toxicity is measured by the concentration it would take to kill 50% of a test population through air or water. The lethal concentration 50%, or LC50, is often used to evaluate the lethal effects of chemicals on fish or other aquatic organisms, but is also very applicable to human health as it measures the LC of the air we breathe when around a pesticide. LC50 and LD50 are limited in their toxicity reports because they only measure death that may occur after a single exposure.
- Having the pesticide label and its SDS sheet (or copies of these documents) will help guide medical professionals on how to treat you quickly and appropriately. In the initial effort to help someone in the event of pesticide poisoning, you should be able to administer general first aid. First, be sure that you are protected from pesticide exposure by wearing appropriate PPE, including a respirator if necessary, before helping others.
- If the pesticide is swallowed, check the label to see if it specifies that you induce vomiting. Some pesticides do more harm when vomited!
- When pesticide users assume that they know exactly how to use a pesticide and do not to read the product label or take the proper precautions indicated by the label or SDS, they are more likely to experience exposure and thus, hazards.
- Chronic toxicity is a measure of illnesses or injuries that occur due to long-term exposure to small doses of a pesticide. General effects from chronic exposure include, but are not limited to tumors, cancer, blood and/or nerve disorders and birth defects