I've had some concerns about the clay litter and posted a thread a few months ago about it. Since then I switched my cats to a kitty litter called Swheat Scoop but recently I switched back to clay because the Swheat Scoop tracks everywhere. But it's a pretty good litter and has kind of a 'country' smell to it, like a hayfield. It doesn't control odours as well as clay though but in the end, it is healthier for cats and people who scoop it!
Here is the thread about this topic from a few months ago with a link to another article about it.
http://petoftheday.com/talk/showthre...ghlight=litter