Environmental physiology history

Elimination can be accomplished by passive diffusion when external concentrations are lower than internal concentrations favoring outward flux and by enzymatic pathways that convert hydrophobic parent compounds to more polar metabolites that can be more readily excreted by those taxa that possess a kidney or kidney-like organ (vertebrates and invertebrates such as annelids, molluscs, and arthropods). Conversion of the hydrophobic PAH to a more polar metabolite will decrease its ability to diffuse through the gill membrane, thus favoring the excretory route. The rate of elimination may be affected by environmental factors such as temperature and salinity, and by physiological factors, including reproductive state, age, sex, stress, and enzyme induction, in addition to such factors as route of uptake, chemical hydrophobicity, and exposure history. 

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