How Reliable are Saliva Tests for Blood Toxins?

I've heard of a test that requires you to take a saliva sample and that will evaluate the various toxins in your body. My question is this. How accurate is this test and how far back is the time frame that the test evaluates?

Saliva tests are used effectively to evaluate various chemicals in the body, including hormones and toxins. I do not use saliva tests, and cannot answer your questions.