Before removing the knee bolster, be sure you have a black light or you might not see the leaking oil dye.

There's 3 nuts that hold the knee bolster and they're very tight from the factory so apparently someone's previously removed yours and failed to tighten it as they're never loose otherwise.

It comes out easier if you first remove the torques head screw that holds the right lower side of the dash to the body. Pull back the plastic cover (snaps off) and you'll see it. Then the lower corner of the dash can be pulled out enough to help remove that knee bolster. You'll still have to wrestle with it a little as they don't just fall out easily and re-installing it is also a bit tricky but not impossible.

You'll then need to remove the blower motor resistor to directly see your evap and using a small mirror with the black light helps too. What we use is a small 12V directional, beam type black light lamp that's made just for seeing AC dye (not cheap) but any black light will work too (no special glasses needed either).

I read before where someone said to look inside the AC drain tube for visable dye but in my experience, it's very rare where you'ld have that much dye making it that far as it'd take alot of dye leaking fast to make it that far. Most leaking evaps just leave residual spots on the lower part of the evap and sometimes can't be easily seen until the evap is removed.

As for your health, I've so far not read "officially" that the slight amount of 134a slowly leaking to your interior can cause any "known" health problems (Disclaimer: no, doesn't mean that I think it's OK either). Realize that evap leaks are typically VERY slow and it'll lose 134a slowly. During that time lots of fresh air enters your cabin so it's not like you'ld be breathing an interior full of freon.

I'm not a doctor or chemist, but I cant image in would be healthy if it's leaking inside of the passenger cabin.