Nice way to conviently omit the next fucking bit of the article like Google does 🙄

However, use of the lid also increased the diameter and concentration of the bacteria in these droplets.

It was also found that airborne microdroplets were detected for 16 minutes after flushing the toilet with the lid down, 11 minutes longer than when the toilet was flushed with the lid up. The researchers suggest that this could be due to particles being re-aerosolised from surfaces rather than being created by the turbulence of the toilet flushing. Alternatively, the researchers suggest that airborne particles could stick together, or agglomerate, which would cause them to remain airborne for longer.

I.e droplets with more bacteria lingering around longer in the air and traveling further. The biggest risk with bacterial contamination is concentration, which this literally tells you is increased by putting down the lid as well as spreading further with a longer time airborne. But go on showing your lack of comprehension.