40. Recycle, Reuse

This fun fact is in the running to be the grossest one on this list. Ancient Romans used urine in their everyday lives. No, we don’t just mean in the bathroom. Urine was used to wash clothes, tan leather, and even clean their teeth! This sounds absolutely abhorrent, but there is actual science behind its use. 

Urine was valued for its ammonia content. The ammonia would brighten togas, fertilize fruit trees, and leave Romans’ teeth sparkling white. The ancient Romans valued urine so much, in fact, that it was an equitable trade. It would be collected from public restrooms, and the government even charged tax on its trade and sale.