■ The mode of uptake (along with food, gills, contact with skin, etc.)
■ The degree of fat solubility of the pollutant
■ The rate that the substance is eliminated from the organism
■ The transformation of the substance by metabolic processes
■ The lipid (fat) content of the organismBiomagnification
Biomagnification is the increasing concentration of a substance in the tissues of
organisms at successively higher trophic levels within a food chain. As a result
of biomagnification, organisms at the top of the food chain generally suffer
greater harm from a persistent toxin or pollutant than those at lower levels. For
biomagnification to occur:
■ The pollutant must be long-lived. If it is short-lived, it will be broken
down before it can become dangerous.
■ The pollutant must be mobile. If it is not mobile, it will stay in one place
and be less likely to be taken up by many organisms.
■ The pollutant must be soluble in fats. If the pollutant is soluble in water, it
will be excreted. In mammals, milk that is produced by females is often
tested since the milk is high in fat and because the young are often more
susceptible to damage from toxins.
■ The pollutant must be biologically active (chemicals that have adverse
effects in small amounts).