Whilst it has a variety of properties, when exposed to near infrared light (red light) because it penetrates the tissue more deeply, MB's activity greatly increases its anti bacterial, anti viral, anti cytokine, anti-fungal, anti depressant (MAOI), and more activity. Its a rapid electro donor, some 30times faster than auto oxidation in the mitochondria, and unlike vit C, another electron donor, it increases the conversion of ferric iron (state3) into ferrous (state2) iron helping to improve physical performance which is why its an effective treatment for methemoglobinemia.
The main reason it fell out of medical fashion? The blue stain gets everywhere! Used extensively by the US Navy, it even helped coin its own saying "Even at the loo, we see, we pee, navy blue".
But this is how denim was self cleaning, leave the clothing out in the sun and the dye got to work on the bacteria you'd find in your clothes, and whilst copper rivets in jeans were used to hold the clothes together in a rugged fashion, the copper also helped play its part in being an antibacterial implement.
Whilst the medical profession are revisiting it, its cited as cancerous, but this was based on a lifelong study on F344 rats which are a 1920's breed of rat, that were inbred and predisposed to various cancers and thus became one of the cancer model rats. This appears to be a form of vested interest manipulation by some sectors of the scientific community in order to manipulate decision makers so much so its enough for Canada and the UK to ban it!
But that is how Denim self cleans.