I think it's the ammonia in the product. In the UK recently there have been a handful of cases where cats have died from drinking anti-freeze (the type used in cars) There is now a website about the dangers of Anti-freeze and to not leave it lying around or let them near it.
There was also a list of cleaning products in my magazine to look out for one including Dettol ( I don't know if you have that in the US?) which is a disinfectant that can be used for cleaning, cuts and grazes, on anything, and one cat dyed after licking it's owners laminate wooden floor after she mopped it.
So I would be careful and definately don't let them near the bleach or lick anything that has been cleaned with it. Silly cats!