Dioxin-like PCBs

Ahlborg, U.G., Becking, G.C., and Birnbaum, L.S. et al. (1994). Toxic equivalency factors for dioxin-like PCBs. Chemosphere 28, 1049-1067. 

Further evidence to support the notion of a role for immunotoxic environmental contaminants in the 1988 outbreak came from two studies of laboratory rats carried out in tandem with the seal studies. PVG rats were fed the same two batches of herring used in the seal study, with a similar pattern of effects observed in the seals [63,64], However, there were additional indications of immunotoxicity that could not be evaluated in seals for ethical or technical reasons, including increased virus titers in a rat cytomegalovirus (RCMV) host resistance model, and reduced thymus cellularity in the rats fed Baltic Sea herring. A positive control group of rats in one of the studies was exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin, thereafter exhibiting an amplified pattern of the effects that had been observed in the Baltic group. The collective results from the captive seal studies and the laboratory animal studies were seen to implicate an AhR-mediated immunotoxicity, in which dioxin-like PCBs played a dominant role [64, 65],... 

Importantly, past and present human exposure to PCDD/PCDFs and PCBs results primarily from their transfer along the pathway atmospheric emissions air deposition -> terrestrial/aquatic food chains - human diet. Information from food surveys in industrialized countries indicates a daily intake of PCDD/PCDFs on the order of 50-200 pg I-TEQ/person per day for a 60 kg adult, or 1-3 pg I-TEQ/kg bw per day. If dioxin-like PCBs are also included, the daily total TEQ intake can be higher by a factor of 2-3. Recent studies from countries that started to implement measures to reduce dioxin emissions in the late 1980s clearly show decreasing PCDD/PCDF and PCB levels in food and, consequently, a lower dietary intake of these compounds by almost a factor of 2 within the past 7 years. 

TEQ calculations were made based on both - the WHO-TEFs and I-TEFs for seventeen 2,3,7,8-substituted PCDDs and PCDFs. Dioxin like PCBs were not measured. Total WHO-TEQ PCDD/F values for the analyzed samples range from 53.50 to 65.26 ng/kg dry mass. Calculations, based on I-TEFs were also made, to allow comparison with the literature data. The variation in the TEQ concentration may be attributed to varying loads during the sample collection period. Obtained results are higher, than medium... 

Toxicity Equivalency Factors (WHO-TEFs) for Dioxins and Dioxin-Like PCBs... 

The WHO-TEF values are internationally accepted toxic equivalent factors for dioxins, furans, and dioxin-like PCBs, as stated by the WHO and derived from both in vivo and in vitro studies. The relative toxic potency of dioxins, furans, and dioxin-like PCBs, relative to... 

European Commission, Scientific Committee on Food, Opinion of the Scientific Committee on Food on the Risk Assessment of Dioxins and Dioxin-Like PCBs in Food, Adopted on May 50, 2001. http //europa.eu.int/ comm/food/fs/sc/scf/out90 en.pdf. 

One of the most sensitive mammals to dioxin-like PCB and dioxin exposure is the mink. Effects have been documented in both farmed mink [65,66] and wild mink [67-72], Extensive work was done in the 1970s and 1980s by Auerlich, Ringer, and colleagues [65,66,73-76] that documented the impact of feeding Great Lakes fish to mink. These impacts included reproductive... 

Urban air concentrations were multiplied by relative potencies (REPs) (listed in Table 2) to calculate the contribution of PCNs to dioxin toxic equivalents (TEQ) and to compare the contributions of the dioxin-like PCBs using REPs from Giesy et al. (1997) [143]. On average, PCNs contributed 64% of total PCN and dioxin-like PCB (PCN+PCB) TEQ in downtown air and 48% in north Toronto. The PCN contribution to PCN+PCB TEQ in Chicago air was similar (68%) when recalculated using the same REPs [97,126]. Although PCNs are as important as PCBs in air on a TEQ basis, polychlorinated dioxins and furans remain the dominant contributors of TEQ in downtown Toronto air [126]. 

Concentrations of 12 dioxin-like PCBs, that is, non-ortho and mono-ortho PCB congeners, in 10 house dust samples from Kumagaya and Sendai city (Japan) were reported by Saito et al. (2003). They may sum up to 30.5 ng TEQ kg"1 (TEQ = toxicity equivalent). 

Breast-milk monitoring WHO has conducted global surveys of dioxins, dibenzofurans, dioxin-like PCBs in human milk. Fourth UNEP/WHO protocol includes analysis of at least 50 individual samples of breast milk in each participating country (WHO 2005). 

There has been considerable work on the individual congeners of PCBs, so much so that analysis for these is now commonplace. Toxicological review of these substances has also been extensive. This has identified dioxin-like PCBs, probably the first time that such close parallels have been drawn between the toxicological and other properties of two major groups of chemical contaminants in food. 

Other food samples like egg, animal fat and fish oil appear to behave very similarly to milk fat and extensive validation has not been carried out thus far. The suitability was, however, demonstrated by inclusion of positive or spiked samples. The assay was validated for blood samples from wildlife species for high concentrations of dioxins and dioxin-like PCBs.13 A special clean-up procedure was developed and validated for sediment, pore water and other environmental samples, allowing the use of the assay for official testing of these type of samples.14... 

AHLBORG U G, BECKING G C, BIRNBAUM L S, BROUWER A, DERKS H G M, FEELEY M, GOLOR G, HANBERG A, LARSEN J C, LIEM A K D, SAFE S H, SCHLATTER c, W/ERN f, younes M and YRJANHEIKKIE Toxic equivalency factors for dioxin-like PCBs Report on a WHO-ECEH and IPCS consultation, December 1993 , Chemosphere, 1994 28 1049-1067. 

BECHER G Dietary exposure and human body burden of dioxins and dioxin-like PCBs in Norway , Organohalogen Compounds, 1998 38 79-82. 

Figure 1.11. Dioxin levels in environmental media. Left axis for air, surface water, ground water right axis for sediments, soil. Note that the data are sum of PCDDs, PCDFs and dioxin-like PCBs.

Masunaga, S., Takasuga, T., Nakanishi, J., 2001. Dioxin and dioxin-like PCB impurities in some Japanese agrochemical formulations. Chemosphere 44, 873-885. 

In the present study, 17 compounds including dirty dozen POPs (OCPs, PCDDs/DFs, PCBs), two emerging POPs (PBDEs and PFAs), and two potential POPs (APs and PAHs) in the South Korean environment were reviewed (Table 2.1 and 2.2). Among the 17 POPs, the most studied pollutant was determined to be chlorinated dioxins and dioxin-like compounds such as PCDDs/DFs and dioxin-like PCBs for which occurrence, distribution, contamination level, fate, exposure, and control techniques have been fairly thoroughly investigated. The literature on dioxin research included 42 SCI articles and 57 domestic articles. Because most of... 

Loutfy, N., Fuerhacker, M., Tundo, P., Raccanelli, S., El Dien, A.G., Ahmed, M.T., 2006. Dietary intake of dioxins and dioxin-like PCBs, due to the consumption of dairy products, fish/seafood and meat from Ismailia city. Egypt. Sci. Total Environ. 370, 1-8. 

Sasamoto, T., Ushio, F., Kikutani, N., Saitoh, Y., Yamaki, Y., Hashimoto, T., Horri, S., Nakagawa, J., Ibe, A., 2006. Estimation of 1999-2004 dietary daily intake of PCDDs, PCDFs and dioxin-like PCBs by a total diet study in metropolitan Tokyo, Japan. Chemosphere 64, 634-641. 

Tsutsumi, T., Yanagi, T., Nakamura, M., Kono, Y., Uchibe, H., Iida, T., Hori, T., Nakagawa, R., Tobiishi, K., Matsuda, R., Sasaki, K., Toyoda, M., 2001. Update of daily intake of PCDDs, PCDFs, and dioxin-like PCBs from food in Japan. Chemosphere 45, 1129-1137. 

There are 209 PCB congeners, differentiated by the numbers and positions of the substituted chlorine atoms. The 12 PCB congeners with 4 or more chlorines with just 1 or no substitution in the ortho position are thought to have dioxin-like toxicity and are often called dioxin-like PCBs . PCBs have been used commercially since 1929 as dielectric and heat exchange fluids, as well as in a variety of other applications. The total amount of PCBs produced worldwide has been estimated to be 1.5 million metric tons (t). The majority of the PCBs in the environment are thought to be the result of leaks from PCB-containing electrical capacitors and transformers. Waste incineration is also a potential air emission source of PCBs. 

MSWI has been identified as an important existing potential PCBs emission source, but currently no information on stack gas concentrations of PCBs in MSWI has been reported in China. Dioxin-like PCBs are not categorized as dioxins in China so there are no regulations for PCBs in stack gas from MSWI and other combustion processes. 

There was comparatively little information on the release of PCBs as unintentionally produced POPs. PCBs are known to be produced as unintentional combustion by-products of incineration and combustion processes. The current UNEP Toolkit (2003) does not give EFs for PCBs. There was little information on the release of PCBs from known local emission sources. A few measured emission data were available from a number of incinerators, crematoria and power plants to permit local EFs to be derived and the annual release of dioxin-like PCBs to be estimated for these processes. Results indicated that the measured total annual air emission of dioxin-like PCBs was very low (less than 0.1 g TEQ). Compilation of the local dioxin-like PCB emission profile would await further emission data from other potential sources. 

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