How does the exposure pathway differ between insulation use and potting soil use of vermiculite?

Soil exposure occurs via intentional handling/mixing, while insulation exposure occurs via physical disruption of settled material.

The risk assessment differs significantly based on how the material is typically used. In the case of attic insulation, the material sits undisturbed, posing a low risk until a human action—such as renovation or storage—physically agitates the settled mass, releasing large quantities of fibers acutely. Conversely, gardening soil amendments containing contaminated vermiculite are intentionally handled, mixed, and spread by the gardener. This results in repeated, direct creation of airborne dust pathways during typical use activities like repotting or blending, establishing a different pattern of potential exposure even though the overall volume handled might be smaller than an attic space.