Not that I'd recommend eating house paint, and remember I'm not a
toxicologist (and definatley not a *cat* toxicologist), merely someone who
mucks about with paint for a living, I'd say most housepaints are
*relatively* safe for if accidently digested, once dried. The reason being
that even with relatively toxic componants, the binder surrounds them and
effectively seals them off to any sort of biological activity. It would be
approximatley equivalent to a pet eating the equivalent weight (and shape)
in plastic, in that in most lieklyhood it will just pass through with no
harm done.

Paints for outside would most likely be more dangerous as they'd have the
"ceramic" pigments (metal oxides) as "ceramic" pigments don't fade in the
sun. But these are still surrounded by the binder, and arne't likely to be
highly available to biological process (the pigments used tend to be
non-soluble, so can't be biologically active).

Paints for internal decoration would generally contain almost exclusively
titanium dioxide, which is pretty much biologically inert, plus a *tiny*
amount of organic dye to give it the colour. Most coloured dyes, whilst
being (mildly) toxic in their pure form, won't be able to work their way out
of the surrounding binder in suffecient quantaties to do too much damage,
and aren't generally all that toxic in the amounts that would get out.

Even lead-based paints (which I gather are no longer available anyway)
became far more dangerous when they started to get old, and the binder
started to degrade (ie, the paint lost its gloss and started to go
"powdery") because then the pigment was directly exposed without a coating
of polymer to protect it.

The toxicity of paint is dependant on how much of the bad stuff can actually
get out of the paint within the time it is going through the system. A big
chip of paint is less toxic than the same weight in little chips, becaue of
the icrease in surface area, a less toxic pigment could cause more problems
than a more toxic one if the binder used on the less toxic one is more
permeable to digestive juices than the one used with the more toxic pigment
etc etc. As decorative housepaints are not designed to have any component to
be chemically active after it dries (in fact, its designed to be *inert* as
possible) getting seriously poisoned by just a "nibble" would, IMHO, be
quite difficult. (Primers and anti-corrosives[1] are different, because they
are designed to be chemically active)

The general upshot being that dried, modern, decorative housepaint shouldn't
be fatal to a cat thats just had a small nibble, but you'd be darn stupid
*not* to take your cat to a vet immediatly if you suspected that they had
eaten *any* type of paint.

Hope that helps someone,

Yowie
[1] My main work is with anti-corrosive primers for metals. Its a fine
balance with a primer to allow the active ingredient to be available enough
to stop the metal form corroding but not be so available that it washes out
before it does its job and/or comes out in such quantiaties as to be toxic
to humans and other lifeforms. Ideally, you need a pigment that is only
*just* soluble in water *and* stops corrosion, *and* isn't toxic in the
quantaties needed to be effective, *and* that does't cost the earth. So far,
one hasn't been found that meets all four requirements. Which is why I have
a job :-)