PHAHs

PCDDs and PCDEs, together with coplanar PCBs, can express Ah-receptor-mediated toxicity. TCDD (dioxin) is used as a reference compound in the determination of TEFs, which can be used to estimate TEQs (toxic equivalents) for residues of PHAHs found in wildlife samples. Biomarker assays for Ah-receptor-mediated toxicity have been based on the induction of P450 lAl. TEQs measured in field samples have sometimes been related to toxic effects upon individuals and associated ecological effects (e.g., reproductive success). 

Verhallen, E.Y., van den Berg, M., and Bosveld, A.T.C. (1997). Interactive effects of the EROD—inducing potency of PHAHs in the chicken embryo hepatocyte assay. Environmental Toxicology and Chemistry 16, 277-282. 

Several comprehensive reviews of the immunotoxicity of TCDD have been published.13 Therefore, the goal of this chapter is to highlight the most recent developments in the field, with particular attention given to studies that provide new insight into the possible cellular and molecular mechanisms of PHAH immunotoxicity. New data that address three less-studied aspects of TCDD immunotoxicity will also be reviewed, including altered innate responses, toxicity to the developing immune system, and deregulation of anamnestic immune responses. 

Compared to people in a noncontaminated area, plasma IgG levels were also significantly decreased in proportion to increasing plasma levels of TCDD in a cohort exposed in an industrial accident in Seveso, Italy.118 There was no effect on IgM or IgA levels, or on complement levels IgE was not measured. In separate studies, in vitro exposure to TCDD enhanced the spontaneous production of IgE by B cells isolated from atopic but not non-atopic individuals, but did not affect the levels of other isotypes.119 Other recent studies have reported small changes in immune cells from individuals exposed occupationally to PHAH.120121 For example, compared to unexposed controls, a cohort of men exposed occupationally to TCDD had diminished IFNy production in a recall response to tetanus toxin, while IFNy production following polyclonal activation was unaffected.120 This observation is consistent with mouse studies, in which antigen-specific responses are highly suppressed by TCDD, but mitogen-driven T cell responses are less susceptible to impairment.83 88122123... 

The aim of the present study was to identify the DR CALUX bioassay performance criteria for the analysis of PHAHs in sediment samples in order to implement the bioassay in the assessment of dredged materials for systematic monitoring in the eoming years. Therefore, both an intra-and interlaboratory validation study was performed. 

Murk, A.J., Bosveld, A.T.C., Berg, M. van den and Brouwer, A. (1994a). Effects of polyhalogenated aromatic hydrocarbons (PHAHs) on biochemical parameters in chicks of the common tern (Sterna Hirundo). Aquat. Toxicol. 30(2), 91-115. 

Schriks, M., Vrabie, C.M., Gutleb, A.C., Faassen, E., Rietjens, I.M.C.M, Murk, A.J. (2006). T-screen to quantify potentiating, antagonistic and thyroid hormone-like activities of poly halogenated aromatic hydrocarbons (PHAHs). Toxicology in vitro, Vol 20, no 4,490-498. 

M Hahn Boston University Utilize fish to investigate the mechanisms of animal sensitivity and resistance to 2,3,7,8-TCDD and related planar halogenated aromatic hydrocarbons (PHAH), especially the resistance which develops after long-term (multi-generation) exposure associated with hazardous waste sites ... 

Most of the research on xenobiotic receptors has been conducted in mammalian systems. These studies have identified three families of proteins as having important roles in regulating the response to xenobiotic chemicals (Table 1). The aryl hydrocarbon receptor (AHR), a member of the basic helix-loop-helix Per-ARNT-Sim (bHLH-PAS) family of transcription factors, is well known for its role in the altered gene expression and toxicity elicited by chlorinated dioxins and related planar halogenated aromatic hydrocarbons (PHAHs) as well as certain polynuclear aromatic hydrocarbons (PAHs)114 188 244. Several members of the nuclear/steroid... 

The functional characteristics of the AHR pathway in teleost fish are generally like those described in mammals. For example, most fish AHRs display high affinity for PHAHs such as TCDD2,106,137,159 207 260, regulate expression of CYP1A216,257, and exhibit ligand structure-activity relationships that are similar (though not identical) to those of mammalian AHRs . However, fish AHRs also exhibit novel features,... 

Several PHAHs, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), co-planar PCBs (PCB 77 and PCB 126), 2,3,4,7,8-pentachlorodibenzofuran (PCDF), and 2,3,7,8-tetra-chlordibenzofuran (TCDF) affect the retinoid status of fish. Short-term exposures (< 4 weeks) do not appear to deplete retinoid stores. Besselink et al.12 exposed flounder (Platichthys flesus) to TCDD by oral gavage and found few changes in plasma and hepatic retinoids after 10 d, but there was a 27-fold increase of CYP1A activity. 

PHAH planar halogenated aromatic hydro- UV ultraviolet... 

In the name of Raphael (Rah-phah-ale) the great archangel of the air, and in the Kerubic Sign of the Head of... 

Van der Plas SA, de Jongh J, Faassen-Peters M, et al. 1998. Toxicokinetics of an environmentally relevant-mixture of dioxin-like PHAHs with or without a non-dioxin-like PCB in a semi-chronic exposure study in female Sprague Dawley rats. Chemosphere 37 1941-1955. 

---