I use Feline Pine. I've never had any issues with any of my cats with this litter. I tried the Feline Pine clumping litter and found the tracking awful. But that was when I had litterboxes. I now have 3 deep Rubbermaid bins and it seems to have done the trick. I tried the Crystals when they first came out and my cat Casey told me right away (by peeing in my lap as I read my book) that he didn't like them. So, back to the drawing board I went. I like FP because it absorbs the urine and it's odor. I remove solid waste whenever someone takes a dump. The only downside to FP is when it gets humid out, like it has been for the past couple of weeks, the litter doesn't last as long. One bag is supposed to last 10 weeks. I'm lucky if it lasts a week in this humidity.

I can't use clumping clay litters because my 16 year old cat, Mollie Rose has kitty asthma and it reeks havoc on her lungs.

That was a great article, Catty1. Thanks for sharing it. I've sent it to my daughter so she can read up on it.