Secondary exposure to topical finasteride

Companies selling topical finasteride formulations are proliferating, so I was wondering, are there any studies of the effects of secondary exposure to topical finasteride? With finasteride in pill form damage was, in large part, confined to the person ingesting the pill - but with topical finasteride, others could unwittingly be adversely affected by non-negligible levels of the medication transferred to them by contact with someone using finasteride or with something to which the medication has been transferred (like, say, a door handle). If there are no such studies, I’m surprised that a medication that can be absorbed through the skin (and poses a significant danger in pregnant women) can be sold as a topical formulation without further study and regulatory approval for that specific formulation.

I also thought about this
My guess is that we would need at least +0.02mg of finasteride to have a significant secondary exposure.
I also don’t know how quickly Finasteride is degradated and if they apply at night or day