I was told by my midwife/doctor while I was pregnant that most likely if you come into contact with cat feces that you already have built up immunity to Toxo, so that if you do get pregnant you can clean the catbox etc. I cleaned the boxes when I was pregnant and I didn't have a problem. I used to wear masks when we used clay litter but after we switched to clumping litter it's not as dusty, so it's not really needed. Interesting topic though!