While thinking of ways to harden rental for a long term hold, I thought if possibly replacing an existing bathroom vanity made of particle board with a vanity made of genuine wood.

Whomever told you that you can only do it once or twice was probably referring to an engineered hardwood product (they have a thin layer of real wood over a thicker layer of particle board).If the floors are real hardwood all the way through then you can sand and refinish them many many times.If you're good about it, you can usually get away with a light screen/buff and re-coat instead of a full deep sanding.

I usually get the unfinished cabinets because they cost less and seems like they would hold up better than the white ones that are made from particle board but I could be wrong.  

I would guess a lot of dust particles from drywall dust and construction materials would affect the air quality for the new homeowners.

The question is whether or not I should clean it or just replace the particle board.

I don't like that they use particle board for the main cabinet.

I would and have gone with the particle board prefab cabinets with the oak fronts from menards.

@Yerry Balenzuela - while cabinet doors may be made from solid wood, seldom are the cabinet boxes though... they are usually a veneer over particle board, MDF or plywood.  

The law is based upon lead particles being released as being harmful to those in the area and those working on the area.If there are no lead particles disturbed by the job then there can be no contamination and you are in compliance no matter who you use.Anyone can question what was done.

However, dust can have an adverse effect on smoke detectors because they typically use a photo-electric sensor that cannot always distinguish between smoke or dust particles, so I wonder if maybe that is what the fire department was thinking.This wasn't a combination smoke/CO alarm, was it?