As an effort to prevent the severe health consequences from exposure to POCs, some health regulatory authorities have established health advisories or legal tolerances for certain POCs in fish. Because these residue levels are intended more for health risk prevention purposes, they are each set equal to or lower than their mostly out-dated international legal limits compiled by FAO (Nauen, 1983), which were primarily or initially for trade purposes. These tolerance limits are largely expressed as mg of contaminant per kg of fish tissue on wet weight basis (i.e., parts per million = ppm). Different countries or regions have interpreted or used these tolerance limits differently, however, whether for legal action or for health advisory purposes.