Polychlorinated Dibenzofurans and Dibenzo-p-Dioxin in Tree Bark from an Industrialized Area: What the 2,3,7,8-Cl Substituted Congeners Tell Us, and What Is Missing

Abstract

We analyzed polychlorinated dibenzofurans (PCDF) and dibenzo-p-dioxins (PCDD) in 27 tree bark samples from the industrialized area near Sauget, Illinois, USA. The trees were located within 4 km of the W. G. Krummrich (WGK) plant, the oldest and largest chemical plant in Sauget, with 24 of 27 samples collected from residential areas. The percent of total PCDF or PCDD profiles of ten 2,3,7,8-Cl substituted PCDF and seven PCDD congeners is homogeneous: 90% of the variance among the samples is explained by 3 eigenvalues in a principal components analysis. The homogeneity of the data suggests that samples were affected by similar types of sources which may have been influenced by electric power generation, chemical waste incineration, and large-scale thermal production of chlorinated chemicals. Quantitatively, the 2,3,7,8-Cl substituted congener analysis does not account for 90% of the concentration of tetra-and penta-Cl homologues and 80% of hexa-Cl and 50% of hepta-Cl homologues. The World Health Organization stated during establishment of toxic equivalence factors (TEF, 2005 version) that calculation of toxic equivalents (TEQs) is not suitable for abiotic matrices, such as tree bark, which are not involved in human exposures. Our results show that the non-2,3,7,8-Cl substituted congeners have high concentrations and should be included in analysis.

Tree Bark, a valuable source of information on air quality

“…Studies of Wang et al (2015) carried out over four seasons of the year confirm that tree bark can be an indicator of short-chain chlorinated paraffins, another group of POPs (SCCPs) [58]. The exact qualitative and quantitative analysis of PCBs, carried out on samples of bark from the area of the former production site in Sauget, Illinois (USA), confirmed the high correlation between proximity to the place of PCB emissions and the content in the bark of trees persisting even after several years of cessation of emissions [79,82]. Thus, tree bark is able to reveal the actual state of air pollution and topsoil by organic substances.…”

“…It is still not fully known how they interact in mixtures with other types of pollutants. Therefore, monitoring POPs emitted into the environment seems to be extremely important [12,25,50,[71][72][73][74][75][76][77][78][79][80][81].…”