Couple ideas.

I had the exact same thought when I was becoming sick from my amalgams. I was searching for answers and considered that the pet cat may be the cause somehow.

Of course, I later realized that the amalgams were causing all my problems.

I will say this. We tested fish-based cat food last year and found that mercury coming off the cans once opened was very high. In fact, the entire kitchen—where we took the measurements—became inundated with mercury vapor within minutes of opening the can. I have this on video and will post it here soon.

As a natural consequence, the litter box also become a high-mercury area. We have since eliminated all fish-based cat food from the cat's diet.

Did you ever wonder why cats seems so lazy and sleep all the time?

Just a thought.