I came across this “Being in the path of the mercury arc light would have exposed this glass to intense UV rays which would sterilize any microbes.”
Can you imagine where this came from? Of all things a photography article on lenses. They get “infected with fungus” and other microbes. This can cause an etching on the surface of the glass.
Know your fungus!
Fungus are parasites. Viruses are parasites.
HIP – Human I Parasite
Fungus spores travel through the air – The structures send forth runners (mycelium fibrils) to locate and tap more energy sources, in hopes of finding a food bonanza that will supply enough energy and material to launch baby funguses (spores) into the air, where they can travel to new, distant food sources.