Memory Alpha defines baryons as subatomic particles that "accumulated aboard starships as a result of warp travel", and had to be removed by baryon sweeps- "a procedure lethal to organic material."
However, the site does not explain exactly what it is about these particles that they had to be cleansed from the ship in such a drastic manner- is there any material that does?
The script mentions that the array will use "high-frequency plasma field" remove the baryon particles in order to "get rid of all the radiation".
LAFORGE: Yes, sir. We've logged in five years more warp hours than most ships do in ten, so our baryon particle levels are high. I'm a little concerned that when the Remmler Array starts to sweep the ship it'll have to use a stronger beam than normal in order to get rid of all the radiation.
Since we know from DS9: For the Cause and TNG: Suspicions that this kind of radiation is deadly to lifeforms, presumably the goal of the sweep is ultimately to prevent the buildup of harmful radiation throughout the ship.
ODO: Temecklian virus. There've been some reports of an outbreak on Bajor, so we're scanning all ships and cargo before they leave the system.
...
KASIDY: Ben, please. I promise to flood the entire cargo hold with baryon radiation as a precaution, but I need to go now or I'll lose the entire consignment.
I would not really call it a drastic measure intense UV light will sterilize an object but if the light is intense enough could easily kill a person.
As for the question I do not believe there is anything in canon (IIRC canon is the shows and movies) that being said the way I interpret it is baryons on a warp ship are akin to barnacles on a water going vessel enough barnacles can compromise a hull I assume enough baryon particles somehow interfere with warp fields.
Memory Alpha says "to keep harmful radiation from building up" which could also mean enough baryon particles could harm people
There is actually a very similar thing that occurs with real world nuclear reactors called the "Wigner Effect" and led to the devastating windscale fire before it was fully understood.
What happens is over time stray neutron radiation knocks atoms out of alignment so they are not quite in the exact spot that is perfect for them in their crystal lattice. It was known the neutrons were not strong enough to cause neutron activation to make things radioactive, they were not even strong enough to break atomic bonds so were considered relatively harmless as far as nuclear reactor dangers go. A crystal is very orderly because everything is in its lowest energy state, knocking things out of place adds energy to the system that can build up and up over time until something triggers its release which is what caused the fire when inert non radioactive chunks of graphite suddenly started to self heat. It is a pure physical effect of slight atom misalignment in an otherwise perfectly stable substance and mostly undetectable.
So how do we get rid of it? We anneal things at 250°C for a bit and the energy harmlessly dissipates. The slow build up of Wigner energy is harmless as long as it doesn't go on too long, but the heating to 250° would most certainly be deadly to any life forms that decided to stick around while it is annealed.
The baryon sweep seemed to pretty much mirror this sort of maintenance that needs to happen to anything that sits around a nuclear reactor too long.
