Fluid dynamics are notoriously complicated. And AFAIK we also lack good models for how long any particular aerosol cloud remains dangerous over time / travel-di

Fluid dynamics are notoriously complicated. And AFAIK we also lack good models for how long any particular aerosol cloud remains dangerous over time / travel-distance. That makes it really hard for (most?) anyone to quantify the risk level of a particular environment, or to design a mitigation with well-understood risk/cost tradeoffs. Compare that to a simple ballistic model, where: - most adults can intuitively grasp and apply such a model, and - it's somewhat easier to calculate a risk/cost tradeoff for mitigations.