The influence of interindividual variability is not typically assessed in traditional toxicological studies. Given that chemical exposures occur in heterogeneous populations, this knowledge gap has the potential to cause undue harm within the realms of public health and industrial and municipal finances. A recent report from the National Research Council (NRC) suggests that when accounting for interindividual variation in responses, traditionally assumed nonlinear dose-response relationships (DRRs) for noncancer-causing endpoints would better be explained with a linear relationship within the lowdose region. To address this knowledge gap and directly test the NRC's assumption, this study focused on assessing the DRR between 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD) exposure and immune suppression in a cohort of unique human donors. Human B cells were isolated from 51 individual donors and treated with logarithmically increasing concentrations of TCDD (0-30 nM TCDD). Two endpoints sensitive to TCDD were assessed: (1) number of IgM-secreting B cells and (2) quantity of IgM secreted. The results show that TCDD significantly suppressed both the number of IgM-secreting B cells and the quantity of IgM secreted (P < .05). Statistical model comparisons indicate that the low-dose region of the two DRRs is best explained with a nonlinear relationship. Rather than assuming low-dose linearity for all noncancer-causing DRRs, our study suggests the need to consider the specific mode of action of toxicants and pharmaceuticals during risk-management decision making.Key words: TCDD; AHR; human B cells; dose response; risk assessment; genetic variability.Understanding of the dose-response relationship (DRR) for any given chemical lies at the heart of risk assessment. Traditionally, data derived from lab-based toxicology studies are extrapolated in assessing the potential adverse health effects of chemicals in the human population. As traditional laboratory-based toxicology studies are performed on a small number of individuals or inbred mouse strains and as chemical exposures occur in a heterogeneous population of individuals, there lies a disconnect between lab-based toxicology and population-level risk assessment. Little is known regarding the degree of variability in a DRR within a heterogeneous population (Rhomberg, 2011).A recent report published by the National Research Council (NRC) suggested that interindividual variability within the human population would effectively linearize the low-dose region of DRRs for all noncancer-causing chemicals (NRC, 2009).