Q. Should I be concerned about flushing my cats waste?
A. The US Environmental Protection Agency recommends that pet waste be flushed down the toilet allowing waste to be properly treated by sewage treatment plants and septic systems. Not properly disposing of pet waste increases public health risks by allowing harmful bacteria and nutrients to wash into storm drains and eventually into local waterbodies.
What I believe - this is a bit misleading. The EPA are probably talking about dog poo (how else could cat waste that's thrown in the trash migrate to the storm drains) What is harmful is the possibility of toxoplasma (only found in cat poo not dog poo) getting into the drinking supply of humans.
Good on you GCG for training your cat, that is a remarkable task (not being sarcastic). I admit myself I have not seen hard evidence or peer-reviewed studies or papers on the release of toxoplasmosa into the drinking water supply of cities. I will be the first to admit I am wrong if shown otherwise. I guess it also depends on how your city handles its water treatment. I wish I could train my dog to use the toilet but it is just not possible.
Thanks for your response.