Microbiologist Dr. Charles Gerba says, it’s pretty gross! You can’t see it with the naked eye, but every flush sprays germs out like a Fourth of July firework. It’s the “aerosol effect,” which showers everything within a 5-foot radius with germs and viruses. And yes, Dr. Gerba says you could get physically ill from leaving the lid up while flushing.
Because even with a low-flow toilet, the aerosol effect spews thousands of little droplets into the air. So no matter what type of toilet you’re using, flush with the lid down.