Understanding Pesticide Exposure and Toxicity

A newer technician recently reached out with concerns about the long-term effects of working in our industry. He was nervous about his exposure to pesticides, especially during exterior sprays.

Pesticides play a crucial role in our industry. Therefore, how do so many enjoy long careers as pest management professionals? The key is understanding the formula: Hazard = Toxicity x Exposure.

As new applicators, we are taught that Hazard = Toxicity x Exposure. This means that hazard, or risk, depends on both toxicity and exposure. Hazard is the potential or probability for harm to occur because of the combination of the product’s innate toxicity and the level of human exposure.

WHAT IS TOXICITY? Toxicity refers to a substance’s ability to cause harm to living organisms. In the context of pesticides, toxicity is a measure of a pesticide’s capacity to cause injury or illness. This measure is determined by the chemical properties and concentration of the pesticide.

Pesticide toxicity is evaluated based on two primary types, acute and chronic.

Acute toxicity refers to the immediate effects of a single or short-term exposure. It is often measured using the LD50 value, which indicates the lethal dose required to kill 50 percent of a test animal population. The LD50 is expressed in milligrams of pesticide per kilogram of body weight (mg/kg). A lower LD50 value means a higher level of toxicity.

Acute toxicity is assessed in two ways: Oral LD₅₀ (exposure through ingestion) and Dermal LD₅₀ (exposure through skin contact).

Chronic toxicity relates to the effects of long-term or repeated exposure to a pesticide. Chronic toxicity includes potential outcomes like cancer, reproductive harm or other long-term health effects.

To give applicators a snapshot of the toxicity of a product, the toxicity level is indicated by signal words on the label:

• Danger-Poison: Extremely toxic.
• Danger: Highly toxic.
• Warning: Moderately toxic.
• Caution: Low toxicity.

For example, a product labeled with “Caution” requires a relatively larger dose to cause harm compared to those labeled with “Danger-Poison.”

Additional toxicity information can be found on a product’s Safety Data Sheet (SDS).

As pest control operators, we usually focus on the product label because that contains important information like application rates, required personal protective equipment, environmental hazards, etc. However, the SDS includes additional important information such as the product’s hazards, accidental release information and toxicology.

REDUCING HAZARD AND RISK. The toxicity of a product cannot change. However, you can minimize its hazard by reducing your exposure. This means wearing all label-required PPE. You can also go beyond label requirements and wear additional PPE as appropriate. Furthermore, there are tricks for providing additional protection while treating. For example: cuffing your chemical-resistant gloves up while spraying overhead to collect any liquid that may run down your gloves.

Reducing hazard also means being aware of the situations during which products might pose the most exposure risk. For example, the period of mixing and loading liquid concentrates carries the highest exposure risk. That is why, on some labels, additional PPE is required during the mixing and loading process.

You can further decrease your risk by selecting a formulation that lowers your exposure. For example, emulsifiable concentrates pose a higher risk of dermal exposure than wettable powders, but wettable powders pose a higher inhalation risk than emulsifiable concentrates. Water dispersible granules pose low dermal and low inhalation hazards, but all liquid formulations pose a higher dermal exposure risk than dry formulations. Becoming familiar with the hazards of each of the formulations will help you select the appropriate product.

Finally, reducing your exposure doesn’t stop once your last stop is completed. Upon returning home, wash your hands with soap and water, and change out of your work clothing and boots. This prevents residues from your clothing and footwear from transferring onto furniture or carpeting within the home. You must also wash your uniform separately from family clothing so that family member clothing does not become contaminated.

CONCLUSION. No pesticide can be sold in the U.S. without EPA approval, ensuring it does not pose unreasonable risks to humans, wildlife or the environment. However, understanding how toxicity, exposure and hazard are related is crucial in safely managing pesticides.

Always follow label instructions and refer to SDS for comprehensive safety information. Reducing exposure is key to minimizing risk while effectively controlling pest populations.

Caroline Kohnert is the technical director and staff entomologist at Plunkett’s Pest Control. She is an Associate Certified Entomologist and past president of the Urban Pest Management Technical Committee (upmtc.org).