You can even put them in the walls in the existing wall system.Chances are the old pipes in the flooring are copper or steel and the chemicals in the cement  use to work on corroding the pipes over time. 

where there any issues as to the chemicals they use?

Building inspectors are MUCH harsher on commercial buildings than a homeowner doing a little work on their own house.

@Aidan Mulligan I’m working with ShawnHuss.com at Chemical Bank.

Phase I: An assessment and report prepared by a professional environmental consultant who reviews the property, both land and improvements, to ascertain the presence or potential presence of environmental hazards at the property, such as underground water contamination, PCB's, abandoned disposal of paints and other chemicals, asbestos, and a wide range of other potentially damaging materials.

If you're property is over 50 years old there is a greater chance of lead based paint and/or other environmentally hazard based chemicals in the house.

(The standards of practice also further cause these things to in a a sense become more illegal, and create harsher enforcement since.)

I would get a professional to do it.I have seen tenants get paint all over the carpet,hardwoods floors,counters,etc.I have seen them ruin vents,not tape over electrical outlets and plugs etc.Ruined some of the switches and had to be replaced.The can improperly dispose of the paint and chemicals as well causing a liability.The fact that they have been there 3 years is worth something.Maybe you could have them extend the lease more in exchange for painting the unit or slightly up the monthly rent or you could ask for a paint deposit to be held and if upon move out it's not changed back to white walls you keep the deposit.

Companies that use Termidor, will drill holes along the foundation in your basement about every 12" and pump the chemical down into the ground, they sometimes also do the block.

One month later, the bayou was dead, turns out the ground water was contaminated with PERK (dry cleaning chemical) that had been leaking for decades from a dry cleaner in the retail center.