Understanding Human Hazard, Toxicity, Exposure, and Risk Management In the Context of Following the Pesticide Label

Most of us do not have an in-depth understanding of terms like hazard, toxicity, exposure, and risk management, as they relate to the pesticide label. Here is an overview.

Directions, precautions, and restrictions on pesticide labels are based on extensive research studies with built-in safety factors. As with many other products (medications, electrical appliances, gasoline, etc.), following the label is the best way you can prevent harm to yourself, to others, and to the environment.


Many things in your everyday life are hazardous if not used properly. The hazard of using a pesticide is based on its ability to cause harm (due to its toxicity, corrosiveness, difficulty of the application, etc.) and the amount of your exposure. When the label is followed, even a highly toxic pesticide can be applied with relatively low hazard. Alternately, if you don’t follow the label, a low toxicity pesticide can pose a significant hazard to you, your family, others, and the environment.*

Pesticide labels warn of potential hazards of the product, explain how to reduce potential exposure to humans and the environment, and provide first aid instructions in case of accidents. Examples from the label include Hazards to Humans and Domestic Animals, Personal Protective Equipment, and First Aid statements, and the Signal Word (Caution, Warning, or Danger). All of this information is based on the results of acute toxicity studies performed during product development. The signal word is based on the route of exposure with the highest level of toxicity; for example, if a product is slightly toxic by most routes of exposure but highly toxic by inhalation, the label will have a signal word indicating high toxicity.

Toxicity and Exposure

The toxicity of a pesticide is its potential to cause damage to any living organism or its components, when exposure occurs. Both amount (dose) and time (length and/or frequency) of exposure are important in understanding the toxicity of a pesticide.

There are two types of toxicity effects – acute and chronic. Both can be predicted under experimental conditions.

Acute toxicity effects are those toxic effects that appear immediately or within 24 hours of exposure. These types of effects are measured under experimental conditions for 24 hours or less, using one or more high doses (exposures). A pesticide with a high acute toxicity can be deadly or destructive even when a very small amount is absorbed through the skin (acute dermal toxicity), inhaled (acute inhalation toxicity), ingested (acute oral toxicity), or spilled in the eyes (acute eye irritation).

Sub-chronic and chronic toxicity effects are toxic effects from longer-term exposures. These types of effects are measured under experimental conditions for 21 days to 2 years or even longer, using continuous or repeated exposures. For many pesticides, the toxic effects following chronic exposure are quite different from those produced by acute exposure.

Risk Management

The EPA determines the level of risk by considering toxicity and exposure (as well as other factors). Based on the level of risk, specific directions, precautions, and restrictions are included on the label – this is risk management. Following the label keeps your exposure below potentially harmful levels.

Examples of risk management measures, used in various combinations, include:

  • Restricting purchase and use of some products to certified applicators or those under their direct supervision
  • Personal protective equipment such as chemical-resistant gloves, goggles, and respirators
  • Required intervals between application and harvest of crops (pre-harvest intervals)
  • Required intervals between application and reentering the treated area (restricted entry intervals)
  • Special certifications and safety training
  • Reduced rates or frequency of application
  • Fewer types of application sites allowed on the label
  • Buffer zones (untreated areas) between the application site and other areas (for example, schools, sensitive crops, waterways)
  • Application restrictions (for example, a maximum wind speed)
  • Special packaging requirements

Risk management measures on the label will depend on various factors, so:

  • Never use a product that is not registered for that use
  • Never use a product in a different way than specified on the label
  • Never use a product that you are not allowed to use (‘restricted use’ category)
  • Never change formulations without reading the entire label of the new product

 Not following the label is not only illegal – it is also dangerous because it ignores practices put in place to prevent hazard, exposure, and risk.

*Detailed research studies are also conducted to determine acute and chronic toxicity to birds, fish, invertebrates, honeybees and mammals, and impacts on water, soil and air. The resulting use of these studies is the same – directions, precautions, restrictions, etc. on the label, to guide pesticide users.