is clumping litter really dangerous

[sandyrivers]

I have 7 cats in my appartment, 3 adults and 4 kittens.
I have 3 litter pans scattered here and there, using regular Saular brand clay litter.
I have to change all 3 pans every 3 days in order to keep my place smellfree. I take out the poop as soon as it gets there, but the problem about the smell is the urine...after 3 days it starts to smell...
I heard that clumping litter avoids this problem by allowing the removal of urine. Thing is, i also heard horror stories that the clumping litter can be ingested by the cats when they wash and cause grave or mortal problems by making hard clumps in the stomach and intestines.
Can anyone tell me the truth about the clumping litter.
Is it really a risk for my cats... in which case i will continue using the clay and changing it every 3 days, otherwise, i would seriously consider switching to clumping litter.
Any input would be greatly appreciated

Thanks
Sandyrivers