Comprehensive compilation of congener profiles to support health assessment of environmental exposures to polychlorinated biphenyl mixtures

Abstract

Exposure to polychlorinated biphenyls (PCBs) remains a potential human health risk due to their persistence in the environment, despite a global ban on their production. Understanding the composition of PCB mixtures is essential for the application of a mixtures-based approach to assessing health risks of PCB exposure. This work represents the most extensive effort to date to compile and make publicly available the PCB congener profiles for mixtures with toxicological data, providing a foundation for understanding toxicological potency of PCB mixtures in the environment. We searched for published congener profiles across 29 commercial and simulated environmental PCB mixtures, including various Aroclors, Phenoclors, Clophens, and Kanechlors, among others. A total of 117 references containing 401 distinct complete or partial tabularized profiles were found. Aroclor 1254 had the most published profiles, with 79 unique datasets characterizing multiple mixture lots. In contrast, no congener-specific composition data were identified for Fenclors, Clophen C, or Pyralenes. Eighty-seven of the most complete and clearly reported profiles underwent a detailed extraction of the congener data, PCB mixture source, and analytical methods. Challenges encountered during data extraction included congener coelutions, incomplete methods reporting, and inconsistencies in PCB nomenclature. These factors complicate data visualization, comparisons across datasets, and use of the data in subsequent analyses. Where possible, we have converted profiles to the same units and congener numbering convention to allow for easier comparison. The extracted data are publicly available online as interactive visuals and as a downloadable Microsoft Excel® workbook. This dataset provides researchers with an overview of the current PCB mixture profile landscape that can serve as a tool to support efforts to minimize the health impacts of environmental PCB exposure, including the exploration of links between mixture composition and toxicity and the identification of the most efficient and effective remediation strategies at contaminated sites.

Keywords: Aroclor; Congener profile; Congener-specific analysis; Homolog; PCB mixture; Polychlorinated biphenyl.

Figure 1.. Heatmap of congener-specific profiles for commercial PCB mixtures. References are available by filtering and clicking within the interactive web-based version.

Figure 2.. A screenshot of the PCB Mixtures Table dashboard, filtered to display Aroclor 1242 profiles with coelutions resolved (see web-based version).

The dashboard can be filtered by PCB mixture (listed at the upper right), completeness of congener reporting (options listed at the middle right), and resolution of congener coelutions (options listed at the bottom right), or by publication or specific congener profile (shown in the table header – see more options by scrolling to the right), or by PCB congener (listed in the second column from the left – see more options by scrolling down).

Figure 3.. Count of extracted mixture profiles by PCB numbering system (see interactive version in PCB Mixtures Details dashboard).

Figure 4.. A screenshot of the Tableau dashboard depicting Kanechlor homolog distributions based on data from Boonyathumanondh et al. (see web-based version).

All coelutions in this dataset occurred among congeners within the same homolog group.

Figure 5.. A screenshot of the PCB Mixtures Details dashboard, filtered to display information on profiles with reporting limits specified (see web-based version).

(A) The panel labeled “Profile Details Table” contains the following information for each publication, listed from left to right: publication; column type; detection method; reporting of LOD or LOQ; reported units for congener measurements; other mixture components quantified; manufacturer or source; PCB mixture name; and lot number. The full content of the “Profile Details Table” can be accessed by scrolling down and to the right. The dashboard can be filtered by PCB mixture (listed at the upper left), publication (listed at the upper right), resolution of congener coelutions (options listed at the bottom left), congener numbering system used (options listed to the right of the congener coelution options), detection method (options listed at the bottom right), knowledge of reporting limits (options listed to the left of the detection method options), and standardization of congener data to facilitate comparisons in the PCB Mixtures Table (options listed at the middle right). (B) At the far right of the “Profile Details Table”, after the lot number, a blue square indicates the presence of a “tooltip”. Users can hover over each tooltip for more detailed methodological information.

Figure 6.. Comparison of Phenochlor DP5 and DP6 profiles using different analytical methods.

Gray shading is used to highlight congeners detected and quantifiable using mass spectrometry (MS) but not flame ionization detection (FID). For Phenochlor DP5, this is true for congeners 170 and 187; for Phenochlor DP6, it is true for PCBs 129, 130, 137, 194, 195, and 196. Data source: Sabbah and Bouguerra (1991).

Figure 7.. Comparison of Aroclor 1254 profiles from various sources.

Gray shading is used to highlight regions of the profiles that could be especially useful for distinguishing “typical” Aroclor 1254 from “late” Aroclor 1254. For example, based on a comparison of congener profiles reported by Frame et al. (1996), PCBs 44, 49, and 52 are present in notably greater amounts in “typical” Aroclor 1254, and PCB 118 is more abundant in “late” Aroclor 1254. Congeners reported as coelutions are not included in the profiles.