Non-invasive Investigations into the Biomagnification of Organic Contaminants

Biomagnification is the process which causes the chemical concentration in an organism to exceed that in the organism’s diet, i.e., C_organism/C_diet > 1. This ratio is called the Biomagnification Factor (BMF) and traditionally determined by chemical analysis of tissues from carcasses or biopsies. To overcome ethical concerns, a non-invasive method to determine the thermodynamic limit to biomagnification (BMF_lim) and the feces-based biomagnification factor (BMF_F) was developed by utilizing equilibrium sampling and chemical analysis of paired food and feces. This method was applied to a domestic dog, zoo-housed Arctic wolves and polar bears and human volunteers, thereby proving this method capable of 1) measuring the fugacity (f) and fugacity capacity (Z) of even small biological samples since the Z-value of samples can be determined using isotopically labeled contaminants spiked into the samples; 2) determining the BMF_lim and BMF_F in different individuals repeatedly over time in order to study their intraindividual and interindividual differences and 3) exploring the possibility of estimating the blood-based biomagnification factor, BMFB in humans using the fugacity in feces, f_F and BMF_F. Among the three BMFs, the BMF_lim is easiest to determine, because knowledge of the native contaminant levels in samples, C_native, is not required. The BMFlim is also strongly related to, and can be estimated from, an organisms’ lipid assimilation efficiency, AE_lipids. Cnative is necessary for the determination of f_F and BMF_F, and the estimation of BMF_B. Factors facilitating biomagnification include a lipid-rich diet, a high digestion efficiency (especially a high AE_lipids), and a high abundance of gut microbes that promote lipid assimilation. Those factors lead to large intraindividual and interindividual differences (up to a factor of 5.5) in the BMF_lim and BMF_F in the same species, which are comparable to interspecies difference (up to a factor of 4). The non-invasive approach to determining the biomagnification potential of contaminants developed here can be applied to any organisms at any time as long as paired food and feces samples are available. Potential future applications include the study of the impact of ingested microplastics on biomagnification and determination of the biomagnification potential of emerging contaminants in humans and endangered species.