For example. I cannot provide any insight because I don’t with in that field, but it would not be necessarily surprising that e.g. inhaled powders could have different effects than ingested compounds diluted in something else. Quantity would matter a lot as well.

It’s not only if it enters the body but also how, for example inhaling aspartame can be very different to ingesting it.

It’s the dose that makes the poison maybe?

Sand is not a different physical form than that which causes cancer. (See: toxic silicosis) Often it's dosage that leads to concern. A typical walk on the beach will not result in cancer from sand exposure.

That's not the only option there. It also could be the amount of exposure.