You can't stand on something because it is gas
what
the person will sufocate and die
cheese
the person will sufocate and die
They might barn and die.
zero gravity
If by humans visiting you mean , Which planet's have had humans land on that planet the answer is none. The only other place in space that humans have visited is the moon.
Nice Neptune, Neat Neptune. Sorry, that's all I have!
There are thousands of bacteria that effect humans. Some cause problems or illness and others actually help the body function.
The question is meaningless, Neptune is a planet!
Many types of spiders have venom that can cause serious health problems in humans. The venom of some species can kill if not treated.
Some of the Gasses that are on Neptune are Hydrogen and Ammonia.