In addition to amalgam fillings, common sources of mercury include pesticides, laxatives, batteries, paper and pulp products manufacturing, drinking water, and paint products. The diagnosis of heavy metal toxicity must take into account the exposure history, clinical signs and symptoms, and laboratory tests. Blood levels may not accurately reflect the total body burden of toxic metals. High blood levels are usually only found in acute toxic metal exposure, or in people exposed to high levels of toxins over a long period of time. In chronic low level exposure, however, the blood levels may actually be low due to redistribution of the toxins throughout the body, while bone and other tissue levels remain high.
Hair analysis is another method of determining toxin exposure that is popular with many clinicians.
Hair can be a good indicator of exposure because it grows slowly and incorporates toxic metals into its structure over a long period of time, and therefore may be a better measure of actual tissue levels. There are arguments over the accuracy of hair analysis due to the possibility of contamination from hair dyes, shampoo, and other factors. Nevertheless, hair analysis can be a valuable screening tool if the proper questions are asked and the proper steps are taken prior to its use. A more accurate method for evaluating toxic metal burden is to do a urine challenge test with a chelating agent. Chelating agents bind to heavy metals throughout the body, and then are excreted in the urine, taking the heavy metals with them.