Dioxins are known to cause the breakdown of the heme production process, resulting in the buildup of heme precursors called porphyrins. Hepatic porphyria is a condition in which there is disruption ofthe process by which the liver produces heme, the active component of the blood pigment hemoglobin. The buildup of porphyrins in blood, tissues, and feces is used as a biomarker of dioxin exposure. In the Great Lakes, USA, porphyrin levels in Herring gull blood serum and tissue have been correlated with environmental exposure to PCDDs, PCDFs, and dichlorodiphenyldichloroethylene (DDE); it is not clear, at present, which compounds have been more responsible for declines in the population.
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