Biomagnification Subject

As early as 1961 scientists looked for and found measurable levels of POCs, indeed POCs that would become classified as POPs, in human fat and by 1965 in human breast milk [77]. While something of a surprise at the time, the current understanding of bioaccumulation and biomagnification explain this, as humans tend to eat high in the food web. For people reliant on alpine sources for food then, it is possible that they are exposed to higher levels of certain POCs, i.e. those that are subject to efficient mountain cold-trapping, than are people nearer to the POC sources. 

Nendza (1998) has defined bioaccumulation as uptake by an organism of a chemical from the environment via any possible pathway, and this can be subdivided into biomagnification (uptake via the food chain) and bioconcentration (uptake from the surrounding milieu). As we shall see, it is the latter that has been the subject of by far the greater number of quantitative structure-activity relationship (QSAR) studies of bioaccumulation. The bioconcentration factor (BCF) is defined as ... 

Regardless of one s position in this debate, it is apparent that the use of compounds that show persistence in the environment must be carefully examined and monitored. Any compound that is persistent and hydrophobic (lipophilic or fat soluble) will be subject to the process of biomagnification and may present special problems. In addition to DDT and other chlorinated pesticides, another example is provided by the polychlorinated biphenyls (PCBs). These compounds have two benzene rings bonded together, with varying numbers of chlorines substituted on the rings. One example is provided by the following structure ... 

The PCBs as environmental contaminants were first detected in Baltic Sea seals and herring in the 1960s (Jensen, 1966). Heavy bioaccumulation and biomagnification can result in very high concentrations in the fatty tissues of top predators, especially in aquatic food webs. The PCBs are also subject to long-distance air distribution and today they have contaminated the biosphere worldwide (Skaare et al., 2002). 

B. Chlorinated Hydrocarbons These agents are persistent—very poorly metabolized— lipophilic chemicals that accumulate in body fat and thus are subject to both bioaccumulation and biomagnification (see Table 57-1). 

Health risks associated with PFASs are not yet well established however the assessment of potential risks is the subject of numerous studies [151—153]. Knovm or suspected risks include chronic toxicity, carcinogenic activity, endocrine effects, and bioaccumulation—biomagnification. PFASs are included in the National Health and Nutrition Examination Survey (NHANES) conducted by the Centers for Disease Control and Prevention (CDC) [154], and the National Toxicology Program has included various PFASs in their assessment of toxicity, carcinogenicity, and persistence in human blood [155]. 

TBBPA is not subject to the process of biomagnification and the main source of exposure is considered to be inhalation. It is assumed... 

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