Applying the maximum cumulative ratio methodology to biomonitoring data on dioxin-like compounds in the general public and two occupationally exposed populations

Maximum cumulative ratio (MCR) is a person's cumulative exposure to multiple chemicals divided by the maximum chemical-specific exposure where exposure is expressed on a toxicologically equivalent basis. It is a tool for assessing the need for performing cumulative exposure assessments. In this paper, MCR values were calculated for the three groups of individuals with biomonitoring data of 26 dioxin-like compounds (DLCs) based on the World Health Organization toxic equivalent factors (TEFs). Although the two occupational groups have higher total toxicity equivalence (TEQ) levels than the NHANES group, average MCR values of the three groups are similar (3.5, 3.6, and 3.2). These MCR values are higher than those seen in our earlier studies, supporting the practice of performing cumulative assessments for DLCs. The MCR values also indicate that only 2-5 of the 26 chemicals make significant contributions to total TEQ values. Interestingly, MCR is negatively correlated with total TEQ (in all the three groups) and age (in the NHANES group). Additionally, MCR is lower in workers where occupational exposures are larger than background exposures. Although overall exposure is the first factor to consider in any mixtures assessment, this paper confirms the usefulness of MCR as a tool for analyzing the pattern of chemical-specific contributions to the total exposure levels of mixtures based on biomonitoring data when TEFs or similar approaches are available.