Most toothpastes contain fluoride.

We heard about the atmosphere as a thin layer of varnish.

There is a lot of varnish still sitting there, several retouches, and some over cleaning. It becomes very visible.

At the same time, aquifers tapped for domestic use increasingly have unsafe levels of naturally occurring contaminants, including arsenic and fluoride.

Microbiological contamination of water sources is a common problem in many countries and chemical contamination (notably arsenic and fluoride) is increasingly a concern.

The design of the round can include features to prevent these failure modes such as the application of some form or waterproofing coat such as varnish shellac around the primer, and the application of a suitable crimping pressure to ensure a tight fit of the projectile in the cartridge case.