Which piece of protective equipment must always be worn when handling highly toxic pesticides?

When handling highly toxic pesticides, wearing a chemical-resistant suit is essential because it provides a robust barrier against pesticide exposure, minimizing the risk of absorption through the skin or potential contamination of clothing. Highly toxic pesticides are especially dangerous and can pose severe health risks with even minimal exposure. A chemical-resistant suit is specifically designed to withstand the corrosive properties of these substances, ensuring maximum protection for the applicator.

In contrast, while cotton overalls, standard work gloves, and safety goggles offer some level of protection, they may not provide the necessary level of safety against highly toxic materials. Cotton overalls can absorb chemicals and may not be impermeable, while standard work gloves might not be designed to protect against all types of chemicals. Safety goggles protect the eyes from splashes but do not offer coverage for the body or skin. Thus, the chemical-resistant suit is the most appropriate and necessary gear for ensuring safety when dealing with highly toxic pesticides.