Composition of Dioxin-like PCBs in Fish:  An Application for Risk Assessment

Abstract

It is widely accepted that a congener-specific analysis of polychlorinated biphenyls (PCBs), rather than traditional Aroclor equivalent total PCB analysis, is required for risk assessment. This is based on the fact that environmental processes alter the original distribution of PCB congeners in Aroclors and that toxicity varies considerably among the congeners with dioxin-like PCBs (dl-PCBs) generally being among the most toxic. Using the largest known dl-PCB fish dataset, here we present a likely composition of dl-PCBs in fish. In contrast to common perception, we found that the dl-PCB composition is relatively constant (within approximately a factor of 2) regardless of fish species and total PCB level. The abundance of dl-PCBs expressed as a percentage of total PCB (25-75 quartile range) in fish is generally in the order of PCB-118 (3.0-6.2%) > PCB-105 (1.1-2.4%) > PCB-156 (0.39-0.75%) > PCB-167 (0.20-0.43%) > PCB-123 (0.11-0.26%) > PCB-157 (0.09-0.19%) = PCB-114 (0.08-0.18%) > PCB-189 (0.045-0.094%) > PCB-77 (0.018-0.093%) > PCB-126 (0.015-0.036%) > PCB-81 (0.002-0.007%) = PCB-169 (0.001-0.006%). The most toxic dl-PCB congeners PCB-126 and -169 contribute on average only 0.027 and 0.004% of total PCB, respectively. The statistically significant relationships presented between individual di-PCB and total-PCB concentrations can be used as a practical tool to estimate dl-PCBs for risk assessment purposes. A comparison of the dl-PCB pattern presented here with other studies suggests that this dl-PCB composition is applicable to fish from North America and perhaps from other geographical regions throughout the world.

Reproduction of European eel jeopardised by high levels of dioxins and dioxin-like PCBs?

“…Results from a study by Bhavsar et al (2007) about the distribution of the DL-PCB congeners (absolute concentrations) in different fish species from 1700 locations in Ontario's inland lakes/rivers and the Great Lakes (Canada) are similar as our results. They reported the two MO-PCBs 118 and 105 as the most abundant DL-PCB congeners while the most toxic DL-PCB congeners, PCBs 126 and 169 contributed on average only 0.027% and 0.004% of total-PCBs, respectively (Bhavsar et al, 2007). Bhavsar et al (2007) also reported that all NO-PCBs (i.e.…”

“…PCB 77, PCB 81, PCB 126, and PCB 169) are the lowest DL-PCB contributors to total-PCBs levels in fish. Also following Bhavsar et al (2007), the abundance of DL-PCBs in fish is generally in the order of In our study the 1,2,3,7,8-PentaCDD and the 2,3,4,7,8-PentaCDF congeners accounted for 35% and 38% respectively of the total PCDD/ Fs congeners (expressed as pg WHO 1998 TEQ g − 1 (lower bound) on fresh weight basis; Fig. 3A).…”

“…They reported the two MO-PCBs 118 and 105 as the most abundant DL-PCB congeners while the most toxic DL-PCB congeners, PCBs 126 and 169 contributed on average only 0.027% and 0.004% of total-PCBs, respectively (Bhavsar et al, 2007). Bhavsar et al (2007) also reported that all NO-PCBs (i.e. PCB 77, PCB 81, PCB 126, and PCB 169) are the lowest DL-PCB contributors to total-PCBs levels in fish.…”

“…PCDDs, PCDFs, and dioxin-like PCBs (DL-PCBs) have comparable chemical structures and toxicological characteristics. PCB mixtures have been used for a variety of applications largely based on their chemical stability and physical properties (Bhavsar et al, 2007). De Boer et al ( , 2010 demonstrated that elimination half-lives of PCBs are in the order of years.…”

Nationwide PCB congener pattern analysis in freshwater fish samples in France

“…set a threshold of 8 pg·g −1 wet weight (ww) for the toxic equivalent concentration (TEQ) standardised to the 2378 tetrachlorodibenzodioxin toxicity in all fish species, except eel, for which the threshold was set at 12 pg·g −1 ww. Most of the TEQ load in fish is due to dioxin-like PCBs (DL-PCBs), and is correlated with the total PCB load (Bhavsar et al, 2007a;Bhavsar et al, 2007b) or the sum of indicator congeners (ΣiPCB; Babut et al, 2009). Thus a ΣiPCB load of 154 ng.g −1 (ww, confidence interval 120−200 ng.g −1 ww) generally corresponds to an exceedance of the TEQ regulatory limit.…”