Estimating and testing bioconcentration factors

Bioconcentration factors (BCFs) are commonly calculated to represent the equilibrium concentration of a substance in an organism relative to environmental concentrations of the same substance. The BCF is derived from parameters estimated in uptake and elimination experiments and is presented as a single value without error estimates or confidence intervals. However, it is desirable to know the variability/precision of the BCF estimate and to statistically compare BCFs among experimental conditions. In this study, the calculation of standard errors and confidence intervals for BCFs is presented. In addition, a statistical method for formally comparing the BCFs derived under two or more experimental conditions is discussed. These methods are illustrated using data from a study of DDT-exposed Hyalella azteca and Diporeia spp.