I keep losing my reply this morning - how high is your chromium level? Is your cobalt level also elevated?
NAC is N-acetyl cysteine, a precursor of glutathione, which is helps remove some excess metal ions from the body. It works on chromium, but not cobalt. The study cited above reported reduced chromium in people whose level was 2-3 times normal (normal is less than 1 part per billion.)

I went through revision for failed metal-on-metal implants 12 years ago, and my levels of both chromium and cobalt were in the toxic range - recovery to normal levels took about a year and left me with a few long-term health issues. I urge you to get the problem removed as soon as you can. Your body will thank you.

PS When you request testing, ask for both chromium and SERUM cobalt to be screened.
Here are the normal and elevated levels;
Cobalt Normal .8 micrograms/liter
Elevated 2 micrograms/liter
Toxic 5 micrograms/liter
Chromiun Normal < 1 parts per billion (ppb)
Elevated > 7 ppb
Concern > 50 ppb