Embryotoxicity of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin in the ring‐necked pheasant

Abstract

Fertilized eggs of ring‐necked pheasants (Phasianus colchicus) were injected into the albumin or yolk with vehicle or graded doses of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) (0.01, 0.1, 1, 10, 100, 1,000, 10,000, or 100,000 pg TCDD/g egg) on day 0 of embryonic development and toxicity was assessed in 1‐d‐old hatchlings and 28‐d‐old chicks. The most sensitive effect of in ovo TCDD exposure was induction of hepatic ethoxyresorufin‐O‐deethylase (EROD) activity in 1‐d‐old hatchlings. The ED50 for this response was 312 pg TCDD/g egg. Embryo mortality was the most sensitive sign of toxicity. The TCDD dose that caused 50% mortality above control (LD50) when injected into the egg albumin or yolk was 1,354 and 2,182 pg TCDD/g egg, respectively. At egg TCDD doses up to and including 1,000 pg TCDD/g egg, no effect was detected in 1‐d‐old hatchlings and 28‐d‐old chicks in body growth, organ weights, carcass morphometrics, incidence of edema, or incidence of histological alterations in the liver, spleen, heart, Bursa of Fabricius, or thymus. Egg TCDD doses as high as 1,000 pg TCDD/g egg also had no effect on cardiac morphometrics or incidence of cardiac malformations in 1‐d‐old hatchlings, or on antibody‐mediated immunity in 28‐d‐old chicks. We conclude that embryo mortality is the most sensitive sign of TCDD toxicity in the ring‐necked pheasant following in ovo exposure. The ring‐necked pheasant embryo is less sensitive than the chicken (Gallus domesticus) embryo and more sensitive than the eastern bluebird (Sialia sialis) embryo to TCDD toxicity.

Effects on tree swallows exposed to dioxin‐like compounds associated with the Tittabawassee River and floodplain near Midland, Michigan, USA

“…Based on these findings, the TS was classified as a species with moderate sensitivity to dioxin-like compounds, which is the same classification given to the American robin (Turdus migratorius), eastern bluebird (Sialia sialis), house wren (Troglodytes aedon), and house sparrow (Passer domesticus), and is similar to the ring-necked pheasant. After considering a number of criteria, the TRVs used herein were based on studies of the ring-necked pheasant [9,10,59], and were less conservative compared to TRVs based on chicken exposures [11,56,57,[68][69][70]. For the dietary exposure-based HQs, the TRVs based on intraperitoneal injections of TCDD in hen ring-necked pheasants [9] would be expected to overestimate the effects thresholds for tree swallows.…”

“…Studies in which ring-necked pheasant eggs were injected with TCDD [9,10,59] were selected as the most applicable for deriving egg-based TRVs in the present study. The three studies that dosed ring-necked pheasant hens or eggs were combined to determine a geometric mean NOAEC of 710 ng/kg wet weight, and LOAEC of 7,940 ng/kg wet weight, as egg exposure-based TRVs [60].…”

“…In that study, hatching success was less at exposed sites; while beyond the scope of their conclusions, it is likely that adult dietary exposure prior to breeding was similar to measured nestling exposures. Maximum measured daily intake based on bolus concentrations of PCDD/DF-TEQs WHO-Avian in the present [10] (PCDD/DF-TEQs WHO-Avian ) daily dietary dose calculated from site-specific bolus-based (R-1 to T-6) and food web-based (S-7 to S-9) dietary exposure for adult tree swallows collected from 2005 to 2007 in the river floodplains near Midland, Michigan (USA), based on the noobservable-adverse-effect concentration (NOAEC) and the lowestobservable-adverse-effect concentration (LOAEC). The HQs based on measured concentration ranges are presented; left y axis for reference areas (R-1 and R-2); right y axis (broken from 10-50) for Tittabawassee River study areas (T-3 to T-6) and Saginaw River study areas (S-7 to S-9); food web-based dietary exposure is presented for S-7 to S-9 because no bolus samples were collected from those sites.…”

The H4IIE Cell Bioassay as an Indicator of Dioxin-like Chemicals in Wildlife and the Environment

“…These hazard categories can be based upon the toxicity of dioxin-like contaminants to a species most sensitive life stage, the developing embryo or fetus, and the expected potential for biomagnification. Toxicity reference values (TRVs) of TCDD in fish and wildlife range from 35 pg TCDD/g egg in fish based on lake trout early life stage (ELS) mortality (Walker et al, 1994), to 100 pg TCDD/g egg for avian embryo lethality taken from a feeding study with ring-necked pheasants (Nosek et al, 1993). Reproductive toxicity in mink occurs at 60 pg TCDD/g liver in the adult mink .…”

Long-Term Toxic Impact of 2,3,7,8-Tetrachlorodibenzo-p-dioxin on the Reproduction, Sexual Differentiation, and Development of Different Life Stages of Gobiocypris rarus and Daphnia magna

“…The toxic mechanism of TCDD is mediated through combining with the cellular Ah-receptor, after a series of synthesis of protein, the most sensitive biochemical response is considered to be the induction of 7-ethoxyresoru"n-O-deethylase (EROD) activity (Poland and Knutson, 1982;Landers and Brunce, 1991;Safe, 1994;Boening, 1998). Thus, the dose}response relationship between EROD activity and TCDD concentration is increasingly attracting attention throughout the world (Van der Weiden et al, 1992;Nosek et al, 1993;Palace et al, 1996;Wu et al, 1996). At present, because of the extreme toxicity and high cost of developing standards, most studies on TCDD toxicity have involved short-term or one-time exposure (Mehrle et al, 1988;Wisk and Cooper, 1990;Spitsbergen et al, 1991;Walker et al, 1994;Cantrell et al, 1996;Henry et al, 1997;Elonen et al, 1998;Hornung et al, 1999).…”