Grossness warning :) Researchers have found that toilets produce an aerosol of the water in the toilet bowl, when they're flushed - review of research.  These tiny droplets can dry out, then the germs remain airborne for awhile, and settle in various places in the bathroom, such as on one's toothbrush or on a roll of toilet paper. So shutting the lid before flushing could be important.  Toilets i…