I used to sprinkle it in the bottom before I added pine shavings. I never noticed any health issues, but there was a good layer of shavings between the rats and the litter. I have since switched to a combination of softwood shavings and the compressed wood pellets for horse stalls. The wood pellets are easily as absorbent as the cat litter and they are affordable. The downside is the dust and weight (also a downside to cat litter), but combining the pellets with shavings moderates those negative aspects.
- Paul