Bioconcentration factors (BCFs) express contaminant concentration in edible plants as a function of the concentration in soil. Routine risk assessments rarely include site-specific analyses of contaminants in vegetables. Instead a common procedure is to use generic BCFs which are uncertain for several reasons. There is a natural variability in metal uptake in plants. The uptake varies between crops, and depends largely on both geochemical and hydrological conditions of the soil. Despite this many risk assessments in practice use BCFs, without taking into account the influence of geochemical factors.

A study at the Linnaeus University aimed to quantify the variability in BCFs and to evaluate the implication of this variability for human exposure assessments. Potatoes and lettuce with corresponding soil samples were collected from contaminated glasswork sites and analyzed for cadmium and lead.

The results indicated that the variability in BCF values was greater than indicated by previous studies (having a larger possible min–max span). The importance of this variability in exposure assessments was, however, most evident at low soil metal concentrations. At high concentrations, BCFs were lower and the variability in calculated exposure was mainly dependent on the soil contamination level. Although the conclusion is that the BCFs is of relatively little importance compared to the concentration in soil, the BCFs is still of equal or greater importance than the other exposure factors included in the calculation of exposure via vegetable consumption. The lower BCFs at high contamination levels also highlight the importance of selecting BCFs that are characterized for relevant contamination levels.

Much of the variability described in this study may, however, reflect the results of a BCF characterization approach that is uncertain. Thus, BCF characterizations using more precise methods should be prioritized in future studies.