Lipophilic contamination

If areas identified as likely to receive significant atmospheric contaminant concentrations include areas supporting edible biota, the biouptake of contaminants must be considered as a possible environmental fate pathway. Direct biouptake from the atmosphere is a potential fate mechanism for lipophilic contaminants. Biouptake from soil or water following transfer of contaminants to these media must also be considered as part of the screening assessments of these media. 

Huckins, J.N., M.W. Tubergen, and G.K. Manuweera. 1990b. Semipermeable membrane devices containing model lipid a new approach to monitoring the bioavailability of lipophilic contaminants and estimating their bioconcentration potential. Chemosphere 20 533-552. 

Connel, D.W., Miller, G.J., Mortimer, M.R., Shaw, G.R., Anderson, S.M., 1999. Persistent lipophilic contaminants and other chemical residues in the southern hemisphere. Crit. Rev. Environ. Sci. Technol. 29(1), 47-82. 

The study by Hites et al. (2004) of BDEs in farmed and wild salmon promoted discussions regarding the consumption of fatty fish. The health benefits of omega-3 fatty acids are clear, but the consumption of (especially) farmed fish exposes consumers to higher intakes of lipophilic contaminants (including BDEs) and so presumably to an additional health risk (Law et al, 2006a). The development of less contaminated feeds for use in salmon farms may be a way of reducing this risk. 

Humans are exposed to pollutants via inhalation, dermal uptake and dietary and nondietary ingestion. In fact, human exposure begins from the womb and continues until death. Since POPs are lipophilic contaminants, they tend to accumulate in large quantities in lipid rich tissues. Their accumulation in human milk has received considerable attention because of... 

Theory and modelling of chemical partitioning and uptake from water phase to the SPMD has been described in detail by Huckins et al. (1990). Briefly, dissolved, nonionic lipophilic contaminants from water column diffuse across various rate-limiting barriers which consist of the water boundary layer, the biofilm, and the hydrophobic LDPE membrane prior to concentrating in the triolein. 

In any study, it is important that researchers first establish whether or not their data demonstrate a relationship between POP tissue concentration and tissue lipid levels. This is seldom done, as it is typically assumed that such a relationship must exist for lipophilic contaminants. As is compellingly demonstrated by Hebert and Keenley-side47 in their paper To normalize or not to normalize Fat is the question , such assumptions can lead to lipid normalized POP concentrations that are completely at odds with measured wet weight POP values. Further, since factors other than total lipid (such as differences in lipid class, for example) can affect POP levels in organisms, simple ratios (e.g. ng POP/ng lipid) are often inadequate and may actually increase data variability. In many cases, analysis of covariance (ANCOVA) may prove to be a more appropriate method for lipid normalization of POP concentrations47. 

A range of passive sampling devices has also recently been developed. Such devices operate on the basis of diffusion of contaminants of interest across an appropriate membrane into a storage medium such as triolein or isooctane (in case of lipophilic contaminants). These latter devices are discussed more fully below. 

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