What type of pesticide formulation is considered the most severe in terms of dermal toxicity?

Oil-based formulations are considered the most severe in terms of dermal toxicity primarily due to their composition and how they interact with the skin. These formulations are designed to enhance the penetration of active ingredients through the skin barrier, which can result in more significant exposure and absorption of toxic substances. The oil base can solubilize many active ingredients, making them more readily absorbable by the skin, leading to heightened risks of toxicity.

In contrast, liquid formulations can vary widely in toxicity depending on their specific chemical makeup and concentration but do not inherently possess the same level of dermal absorption capability as oil-based formulations. Wettable powders, while they can pose risks, typically need to be mixed with water and can create a less immediate risk of dermal exposure compared to oils. Granular formulations, on the other hand, are usually less likely to be absorbed through the skin because of their larger particle size and lower surface area for immediate contact.

Ultimately, the enhanced permeability and potential for absorption make oil-based formulations the most concerning type regarding dermal toxicity.