After confirming that a toilet flush does emit an aerosol spray, Adam builds a rack to hold 44 toothbrushes at various distances from the toilet in the shop, as

After confirming that a toilet flush does emit an aerosol spray, Adam builds a rack to hold 44 toothbrushes at various distances from the toilet in the shop, as well as two controls kept in the office. Each day, Adam and Jamie exposed the brushes to toothpaste and rinsed with distilled water, with brushing with a pair kept right above the toilet bowl. Fecal coliforms were indeed found on all the test brushes, including the control ones, but none at a level high enough to be dangerous. A microbiologist from UCSF confirmed that such coliforms were impossible to completely avoid, and that there was no significant difference in the number of bacteria based on where the toothbrushes were placed in respect to the toilet bowl. This surprising result prompts the narrator to proclaim "Some myths are best left unanswered!" Since the controls were kept in his office... it does seem like it's impossible to avoid fecal coliform bacteria.