There are tests to find out if PCDFs are in blood, body fat, and breast milk; however, these are not routinely done. High levels of PCDFs in these body fluids and in fat will show that one have been exposed to high levels of PCDFs. Blood tests can detect recent exposures to PCDFs, but are not always the easiest, safest, or best method.
Fat biopsies may be less traumatic to a small child or very sick person and more diagnostic than blood tests. Nearly everyone in industrial countries has been exposed to PCDFs because they are found throughout the environment, and nearly all people are likely to have some PCDFs in their blood, fat, and breast milk.