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6701604 
Journal Article 
Factors Affecting the Bioavailability of Chemicals 
Nikinmaa, M; , 
2014 
ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD 
LONDON 
INTRODUCTION TO AQUATIC TOXICOLOGY 
65-72 
WOS:000341814100007 
Bioavailability, uptake, metabolism, storage, and excretion of chemicals constitute toxicokinetics. Bioavailability is the potential for uptake of a substance by a living organism. It is usually expressed as the fraction that can be taken up by the organism in relation to the total amount of the substance available. In pharmacology, the bioavailability is the ratio of the amount of a compound in circulation after its extravenous application and its intravenous injection. In aquatic toxicology, environmental bioavailability is usually relevant. Factors affecting the bioavailability of a chemical depend on the route of uptake, and whether the chemical is in the bottom sediment, dissolved in water, or is a constituent of the organisms. In the case of water-soluble substances, the primary source of toxicant is water, and the bioavailability depends on complex formation, especially with humic substances. Even when water-soluble substances are sediment bound, they reside mainly in pore water. Lipid-soluble substances are taken up especially from sediment or from other organisms. The bioavailability from water decreases with increasing lipophilicity and with increasing amount of dissolved organic carbon or colloids in the aquatic phase. With regard to sediment, both the sediment properties ( e. g. grain size) and the amount of organic material in the sediment affect bioavailability. The main abiotic factors affecting bioavailability are oxygenation and pH. As an example, metal speciation, affecting bioavailability, depends very much on the pH. 
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