Cleft Palate and Kidney-Urinary Tract Damage

Cleft palate may be caused by PCBs. Kidney damage or urinary tract damage may also be caused by PCBs

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Cleft Palate and Kidney/Urinary Tract Damage

Could PCB pollution contribute to these birth defects?

Wisconsin has 14.8 cases of cleft palate per 10,000 live births, or approximately 104 cases a year. Clefting, which involves either the palate or the lip, occurs at different rates within various ethnic gruops.
Nationally, the incidence is about 1 in 500 among Asians; 1 in 1,000 among whites; and 1 in 2,000 among blacks. Experts at Children’s Hospital of Wisconsin could not explain why the cleft palate rate was so high in the state.
According to a national report by the Pew Environmental Health Commission at the Johns Hopkins University School of Public Health, the frequency of infants born in the U.S. with complete or partial blockages of the urinary tract went from 9.7 cases per 10,000 births in 1989 to 15.5 cases in 1996, an increase of almost 60%.
Cleft Palate, Cleft Lip

One common form of urinary birth defect is "hydronephrosis" which develops when the pelvis and calyces (urine collecting structures of the kidneys) become distended because urine is unable to drain from the kidney down the ureters into the bladder. Hydronephrosis is not a separate disease entity; it is a physical phenomenon that occurs as a result of other problems, such as narrow ureters which restrict urine flow (hydroureter). Hydronephrosis can severely damage the kidneys.

According to the Pew Commission, 80% of birth defects in the U.S. have no known cause, but there are suggestions that environmental factors such as diet, tobacco, and toxins in water and air may play a large part.

Local Studies are Needed

No study has been done to determine whether areas along the Fox River, Green Bay or Lake Michigan, with higher PCB and dioxin contamination, have higher rates of cleft palate or kidney/urinary damage in newborns. National statistics show that people of Asian descent are at higher risk of cleft palate. Could this be due to inherited genetic traits or cultural traditions which include consumption of greater amounts of fish?
Apparently, no studies have been done to evaluate possible PCB effects on humans with cleft palate or congenital urinary tract birth defects, yet the 35 studies below show that certain types of PCBs and dioxin can dramatically increase the rate of these defects in mice and rats, and cause deformed chicken embryos.
Cleft Palate, Cleft Lip

Our government health agencies need to conduct proper studies that examine the rate of these birth defects in children of fish-eaters and compares their rates with the general non-fish-eating population. Better yet, researchers should take mothers’ blood and tissue samples for PCBs and dioxin, to look for correlations with the babys’ birth defect rate.

Abstracts of 38 Studies Linking PCBs with Cleft Palate and Kidney/Urinary Damage

The following studies all describe birth defects of the palate and urinary tract after exposure to PCBs and related chemicals. Keep in mind that these studies examined the effects of just a few of the 209 kinds of PCBs. Different PCB types produce different results. We have a large mixture of PCB types in the Fox River, Green Bay and Lake Michigan.

Study #1

Marks TA, Kimmel GL, Staples RE Influence of symmetrical polychlorinated biphenyl isomers on embryo and fetal development in mice: 1. Teratogenicity of 3,3',4,4',5,5'-hexachlorobiphenyl. TOXICOL APPL PHARMACOL; 61 (2). 1981. 269-276. Author Address: Teratol. and Reproduction, Upjohn Co., 301 Henrietta St., Kalamazoo, Mich. 49001.

cleft palate
kidney damage (hydronephrosis)
malformed fetuses
reduced fetal weight
fetal deaths
increased resorptions of fetus
decreased weight gain in pregnancy
liver discoloration
study used PCB 169 (a dioxin-like PCB type)
mothers dosed for 10 days during gestation

Pregnant outbred albino (CD-1) mice were given 3,3',4,4',5,5'-hexachlorobiphenyl (HCB) by gavage in cottonseed oil on days 6-15 of gestation at dosages of 0.1, 1, 2, 4, 8 and 16 mg/kg per day. The mice were killed on day 18, the general and reproductive health of the dams evaluated and the fetuses examined for external, visceral and skeletal malformations. HCB administration was followed by a significant (P < 0.01) increase in the average percent of malformed fetuses per litter at 2 (11.7%), 4 (36.9%), 8 (65.5%) and 16 (60.6%) mg/kg per day vs. the vehicle control group (0.9%). None of the dosages was lethal to any of the dams and only at 8 mg/kg per day did a significant decrease in weight gain during pregnancy occur. A significant increase in fetal deaths occurred at 4, 8 and 16 mg/kg per day and a significant decrease in average fetal weight and an increase in the percentage resorptions occurred at 8 and 16 mg/kg per day. Other signs of embryotoxicity (e.g., liver discoloration and small renal papillae) were seen at dosages as low as 1 mg/kg per day, a dose at which no significant increase in malformations occurred. Cleft palate (significantly increased at dosages \ 2 mg/kg per day) and hydronephrosis (significantly increased at dosages \ 4 mg/kg per day) were the predominant malformations. Teratogenic effects were observed in a high percentage of the fetuses from dams treated at several dosages, at least 2 of which had no apparent adverse effect on the dams.

Study #2

Watanabe M, Sugahara T Experimental formation of cleft palate in mice with polychlorinated biphenyls (PCB). Toxicology; VOL 19, ISS 1, 1981, P49-53 Author Address: Dep. Community Med., Fac. Med., Toyama Med. Pharm. Univ., Toyama.

cleft palate
daily injections from day 6 to 16 of pregnancy
brachydactyly
syndactyly
study used unspecified types of PCBs

The teratological effect of polychlorinated biphenyls (PCB) was examined using the ddY strain of mouse. PCB in 0.05 ml ethanol was injected daily, subcutaneously into the back of pregnant mice, for 10 days from day 6 of gestation. Cleft palates were found in fetuses at the 18th gestation, with a significant dose response between 10 mg and 50 mg as total body dose of PCB per pregnant mouse. Comparison of these results with simultaneous observations of body weight of dam or fetus, and number of resorbed and dead fetuses, indicated that cleft palate formation was due mainly to the specific effect of PCB and not to its general toxicity. Cleft lip, brachydactyly, and syndactyly were also found. In the control mice receiving no PCB and no treatment, no external malformations were found in 1765 live fetuses. These results demonstrate a teratogenic effect of PCB in the ddY strain of mouse after subcutaneous injection.

Study #3

Marks TA, Kimmel GL, Staples RE Influence of symmetrical polychlorinated biphenyl isomers on embryo and fetal development in mice. II. Comparison of 4,4'-dichlorobiphenyl, 3,3',4,4'-tetrachlorobiphenyl, 3,3',5,5'-tetrachlorobiphenyl, and 3,3',4,4'-tetramethylbiphenyl. Fundam Appl Toxicol 1989 Nov;13(4):681-93 Author Address: Research Triangle Institute, Research Triangle Park, North Carolina 27709.

cleft palate
kidney damage (hydronephrosis)
malformed fetuses
decreased maternal weight gain
reduced litter size, increased resorptions of fetuses
vaginal bleeding in mothers (abortifacient effects)
study used PCBs 15 (di), 77 (tetra), 80 (tetra) and 3,3’4,4’ tetramethylbiphenyl (TMB)
mothers were dosed for 10 days during gestation

Outbred albino (CD-1) mice were given the following biphenyl isomers by gavage in cottonseed oil on Days 6-15 of gestation: 4,4'-dichlorobiphenyl (DCB) at 16, 32, and 64 mg/kg/day; 3,3',4,4'-tetrachlorobiphenyl (3,4-TCB) at 1,2,4,8,16,32, and 64 mg/kg/day; 3,3',5,5'-tetrachlorobiphenyl (3,5-TCB) at 64 mg/kg/day; and 3,3',4,4'-tetramethylbiphenyl (TMB) at 64 mg/kg/day. The mice were killed on Day 18 of gestation, necropsies were performed on the dams, and the fetuses were examined for external, visceral, and skeletal malformations. Although DCB was toxic to the dams at 64 mg/kg/day, developmental toxicity was not detected. 3,4-TCB administration was followed by a significant (p less than 0.01) increase in the average percentage of malformed fetuses per litter at 4 (7.2%), 8 (9.8%), 16 (25.4%), 32 (50.0%), and 64 (75.0%) mg/kg/day versus the vehicle control group (1.1%). None of the dosages tested was lethal to any of the dams. Significant decreases in maternal weight gain were observed at 16 mg/kg/day and above; however, the differences from the control value most likely were due to significant decreases in the mean number of live fetuses per dam, as the result of reductions in the number of implants per dam, and significant increases in the incidence of resorptions. Vaginal bleeding and other evidence of abortifacient effects also were present in several dams in groups receiving 3,4-TCB at 16 mg/kg/day and above. Cleft palate and hydronephrosis (significantly increased at dosages of 4 mg/kg/day and above) were the predominant malformations detected. Thus, 3,4-TCB was found to be toxic to the conceptus at dosages of 4 mg/kg/day and above. Neither 3,5-TCB nor TMB showed indications of maternal or developmental toxicity at 64 mg/kg/day.

Study #4

Haake JM, Safe S, Mayura K, Phillips TD Aroclor 1254 as an Antagonist of the Teratogenicity of 2,3,7,8-Tetrachlorodibenzo-p-dioxin Toxicology Letters, Vol. 38, No. 3, pages 299-306, 43 references, 1987 Author Address: Department of Physiology and Pharmacology, College of Veterinary Medicine, Texas A&M University, College Station 77843.

cleft palate
kidney damage (hydronephrosis)
PCB Aroclor 1254 is a partial antagonist (neutralizer) of the cleft palate effect caused by dioxin, at certain doses
study used PCB commercial mixture Aroclor 1254, and dioxin
single dose on day 9 of pregnancy

The teratogenic effects of combined exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (1746016) (TCDD) and Aroclor-1254 (11097691) were assessed in pregnant C57BL/6N-mice that had been mated to male C57BL/6J-mice. Pregnant mice were given Aroclor-1254 at a dose of 244mg/kg on day nine of pregnancy, TCDD at a dose of 20 micrograms per kilogram (microg/kg) on day ten of pregnancy, dexamethasone at a dose of 90mg/kg on day 13 of pregnancy, or Aroclor-1254 followed by either dexamethasone or TCDD. All agents were administered by oral gavage. None of the agents showed any maternal toxic effects. The percentage of fetuses with hydronephrosis was 1.3, 5.7, 33.4, 87.8, 96, 3.2, and 3.7 for untreated controls, vehicle controls, Aroclor-1254 alone, TCDD alone, Aroclor-1254 plus TCDD, dexamethasone alone, and Aroclor-1254 plus dexamethasone. Cotreatment of pregnant mice with Aroclor-1254 and TCDD significantly decreased the occurrence of TCDD induced fetal cleft palate (from 61.8 to 8.2 percent) but had no effect on dexamethasone induced teratogenic alterations. The authors conclude that Aroclor-1254 can act as a partial antagonist of TCDD teratogenicity in mice and suggest that nontoxic levels of environmental polychlorinated biphenyls may afford some protection from congeners of polychlorinated dibenzo-p-dioxins and dibenzofurans. They hypothesize that the compounds compete for the aryl hydrocarbon receptor, reducing its availability for the teratogen.

Study #5

Safe S, Bannister R, Davis D, Haake JM, Zacharewski T, Mayura K, Phillips TD Aroclor 1254 as a 2,3,7,8-tetrachlorodibenzo-p-dioxin antagonist in mice. Chemosphere 1989;18(1-6):709-14 Author Address: Department of Physiology and Pharmacology, College of Veterinary Medicine,Texas A&M University, College Station TX 77843

cleft palate
PCB Aroclor 1254 is a partial antagonist (neutralizer) of the cleft palate effect caused by dioxin, at certain doses
study used PCB commercial mixture Aroclor 1254, and dioxin

Both Aroclor 1254, a commercial polychlorinated biphenyl (PCB), and 2,3, 7,8-tetrachlorodibenzo-p-dioxin (TCDD) elicit common aryl hydrocarbon (Ah) receptor-mediated effects including the induction of aryl hydrocarbon hydroxylase (AHH), a cytochrome P-450-dependent monooxygenase, the inhibition of the T-cell dependent plaque forming cells in response to sheep red blood cells (in C57BL/6 mice) and cleft palate in C57BL/6 mice. However based on ED50 values from dose-response studies with Aroclor 1254 and 2,3,7,8-TCDD, it was apparent that the latter compound is at least 10(5) times more potent. Cotreatment of rat hepatoma H-4-II E cells or C57BL/6 mice with ED80-100 dose of 2,3,7,8-TCDD plus various sub-toxic (or effective) doses of Aroclor 1254 clearly shows that the commercial PCB can significantly antagonize 2,3,7,8-TCDD-mediated AHH induction (in vivo and in vitro), immunotoxicity and teratogenicity. In vitro Ah receptor binding studies suggests that Aroclor 1254 competitively inhibits the Ah receptor binding of 2,3,7,8-TCDD and this may account for the antagonist activity of the commercial PCB.

Study #6

Bannister R, Biegel L, Davis D, Astroff B, Safe S 6-Methyl-1,3,8-trichlorodibenzofuran (MCDF) as a 2,3,7,8-tetrachlorodibenzo-p-dioxin antagonist in C57BL/6 mice. Toxicology 1989 Feb;54(2):139-50 Author Address: Department of Physiology and Pharmacology, College of Veterinary Medicine, Texas A & M University, College Station 77843.

cleft palate
furan is a partial antagonist (neutralizer) of the cleft palate effect caused by dioxin, at certain doses --- but the results differ for rats versus mice
study used furan and dioxin (which are frequent co-contaminants with PCBs)

6-Methyl-1,3,8-trichlorodibenzofuran (MCDF), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and TCDD plus MCDF were administered to C57BL/6 mice and their effects on several aryl hydrocarbon (Ah) receptor-mediated responses including hepatic microsomal aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) induction, immunotoxicity and teratogenicity were determined. MCDF did not induce hepatic microsomal AHH and EROD at doses up to 500 mumol/kg, however, co-administration of MCDF (50 mumol/kg) with a dose of TCDD which elicited a submaximal induction response (i.e. ED80-100, 15 nmol/kg) resulted in some small but significant inhibition of the induction of hepatic microsomal AHH and EROD (14 and 17%, respectively) compared to that observed with TCDD alone. Co-administration of TCDD and other doses of MCDF (10, 100, 200 or 500 mumol/kg) did not effect the induction response. These results were in contrast to the effectiveness of MCDF as an antagonist of the induction of AHH and EROD by TCDD in the rat (up to 50% inhibition of monooxygenase induction). Administration of MCDF (4, 20 and 40 mumol/kg) to C57BL/6 mice caused some inhibition of the splenic plaque-forming cell response to sheep erythrocytes only at the highest dose (26% decrease); the interaction of MCDF (4, 20 and 40 mumol/kg) and an immunotoxic dose of TCDD (3.7 nmol/kg) resulted in significant protection from the immunotoxic effects of TCDD at the 2 higher dose levels of MCDF. Similarly, MCDF (400 mumol/kg) did not cause cleft palate in mice but at this dose level MCDF afforded some protection from TCDD (20 micrograms/kg)-mediated cleft palate in mice. However, studies utilizing [3H]TCDD suggested that the protective effects may be due to modulation of TCDD reaching the palate in the co-treated animals (MCDF plus TCDD). Although both MCDF and Aroclor 1254 were both weak Ah receptor agonists in C57BL/6 mice, the former compound was much less effective as a TCDD antagonist. The observed species-specific effects for these 2 TCDD antagonists may be related species-dependent differences in receptor structure and receptor-ligand (i.e. agonist or antagonist) interactions.

Study #7

Biegel L, Howie L, Safe S Polychlorinated biphenyl (PCB) congeners as 2,3,7,8-TCDD antagonists: teratogenicity studies. Chemosphere 1989;19(1-6):955-8 Author Address: Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, Texas.

PCB Aroclor 1254 is a partial antagonist (neutralizer) of cleft palates caused by dioxin, but only at certain doses
study used PCB commercial mixture Aroclor 1254, and dioxin

Administration of 2,3,7,8-TCDD (20 ug/kg) to female C57BL/6 mice gave greater than 60% cleft palate in the litters. Previous studies have shown that cotreatment of the pregnant mice with 2,3,7,8-TCDD (20 ug/kg) and Aroclor 1254 (750 umol/kg) resulted in complete protection of the animals from cleft palate. In contrast, a lower dose of Aroclor 1254 (250 umol/kg) was a less effective 2,3,7,8-TCDD antagonist. Several PCB congeners, including 2,2',5,5'-tetrachlorobiphenyl and 2,2',4,4',5,5'-hexachlorobiphenyl, which exhibit some Ah receptor binding activity were investigated as 2,3,7,8-TCDD antagonists in the in vivo teratogenicity assay system. Both PCB congeners significantly protected the mice from 2,3,7,8-TCDD-mediated cleft palate. The significance of these results and their mechanistic implications will be discussed.

Study #8

Biegel L, Harris M, Davis D, Rosengren R, Safe L, Safe S 2,2',4,4',5,5'-hexachlorobiphenyl as a 2,3,7,8-tetrachlorodibenzo-p-dioxin antagonist in C57BL/6J mice. Toxicol Appl Pharmacol 1989 Mar 1;97(3):561-71 Author Address: Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station 77843.

cleft palate
Certain types of PCBs are partial antagonists (neutralizers) of cleft palates effect caused by dioxin, at certain doses
study used PCB 153 and dioxin

At doses as high as 750 to 1000 mumol/kg, 2,2',4,4',5,5'-hexachlorobiphenyl (HCBP) did not cause fetal cleft palate, suppress the splenic plaque-forming cell response to sheep red blood cells, or induce hepatic microsomal ethoxyresorufin O-deethylase (EROD) in C57BL/6J mice. Despite the lack of activity of HCBP in eliciting any of these aryl hydrocarbon (Ah) receptor-mediated responses, competitive binding studies indicated that HCBP competitively displaced 2,3,7,8-[3H]tetrachlorodibenzo-p-dioxin (TCDD) from the murine hepatic cytosolic receptor. Cotreatment of C57BL/6J mice with TCDD (3.7 nmol/kg) and HCBP or 4,4'-diiodo-2,2',5,5'-tetrachlorobiphenyl (I2-TCBP) (400 or 1000 mumol/kg) showed that both compounds partially antagonized TCDD-mediated cleft palate and immunotoxicity (i.e., suppression of the splenic plaque-forming cell response to sheep red blood cells), and HCBP antagonized TCDD-mediated hepatic microsomal EROD induction. Thus, HCBP and I2-TCBP, like the commercial polychlorinated biphenyl mixture Aroclor 1254, were partial antagonists of TCDD action in C57BL/6J mice; however, it was also apparent from the results that Aroclor 1254 was the more effective antagonist at lower doses. Using [3H]TCDD, it was also shown that some of the effects of HCBP on TCDD-mediated cleft palate may be due to the decreased levels of TCDD found in the fetal palates after cotreatment with TCDD and HCBP. 4,4'-[125I2]diiodo-2,2',5,5'-tetrachlorobiphenyl ([125I2]TCBP) of high specific activity (3350 Ci/mmol) was synthesized and used to investigate the direct binding of this compound to the murine hepatic Ah receptor or other cytosolic proteins. No direct specific binding was observed between 125I2-TCBP and any cytosolic proteins using a sucrose density gradient assay procedure. These results contrasted with previous studies with Aroclor 1254 that suggested that this mixture acted as a competitive Ah receptor antagonist.

Study #9

Mayura K, Clement BA, Safe S, Phillips TD Teratogenic effects of 3,3',4,4',5-penta-chlorobiphenyl in C57BL/6 mice.
Toxicologist 1992 Feb;12(1):104 Author Address: Department of Veterinary Anatomy and Public Health, Texas A&M University, College Station, TX.

cleft palate
kidney damage (hydronephrosis)
study used PCB 126
single dose on day 10 of gestation

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related toxic halogenated aromatic hydrocarbons elicit a broad spectrum of toxic and biochemical responses including the formation of hydronephrosis and cleft palate in C57BL/6 mice. Recent reports have shown that 3,3',4,4',5-Pentachlorobiphenyl (PeCB) is one of the major environmental contaminants that result in TCDD-like activity. This study was designed to determine the teratogenic potential of 3,3',4,4',5-PeCB in C57BL/6 mice and further quantitatively compare the developmental effects of this compound with TCDD. Mice were administered orally a single dose fo PeCB at varying concentrations ranging from 0 to 522 ug/kg body weight on day 10 of gestation. Fetuses were examined on day 17 of gestation for the presence of cleft palate and hydronephrosis. The results indicated a concentration-dependent increase in the incidences of fetal cleft palate in the treatment groups. At the highest concentration, 92.3% of fetuses exhibited cleft palate. All fetuses in the treatment groups showed hydronephrosis. Previous studies in this laboratory have shown that TCDD at a concentration of 20 ug/kg resulted in 61.8% of fetal cleft palate in mice. The results of this study suggest that PeCB is approximately 15 times less toxic than TCDD with respect to the induction of cleft palate in C57BL/6 mice.

Study #10

Mayura K, Spainhour CB, Howie L, Safe S, Phillips TD Teratogenicity and immunotoxicity of 3,3',4,4',5-pentachlorobiphenyl in C57BL/6 mice. Toxicology 1993 Jan 29;77(1-2):123-31 Author Address: Department of Veterinary Anatomy and Public Health, Texas A&M University, College Station 77843.

cleft palate
kidney damage (hydronephrosis)
immune system suppression from PCB more closely comparable to dioxin potency than other effects
study used PCBs 126 (penta), 169 (hexa) and 77 (tetra)

Administration of 3,3',4,4',5-pentachlorobiphenyl (pentaCB) to female C57BL/6 mice at doses from 130.5 to 522 micrograms/kg body weight resulted in the dose-dependent formation of fetal cleft palate and hydronephrosis. The estimated relative potency of 3,3',4,4',5-pentaCB compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was in the range of < 0.07-0.04. The immunotoxicity of 3,3',4,4',5-pentaCB and two structurally-related congeners, 3,3',4,4'-tetraCB and 3,3',4,4',5,5'-hexaCB, was investigated in male C57BL/6 mice by determining their suppression of the splenic plaque-forming cell response to sheep red blood cells. The potencies of these compounds relative to TCDD were determined from the ratios of their corresponding ED50 values and were 0.77-0.55 (3,3',4,4',5-pentaCB), 1.1-0.29 (3,3',4,4',5,5'-hexaCB) and 0.14-0.03 (3,3',4,4'-tetraCB). These results demonstrate that the immunosuppressive activities of the PCB congeners relative to TCDD were much higher than observed for many other TCDD-like responses in mice and other laboratory animals.

Study #11

Zhao F, Mayura K, Safe S, Phillips TD 2,2',4,4',5,5'-Hexachlorobiphenyl as an antagonist of the teratogenicity of 3,3',4,4',5-pentachlorobiphenyl in C57BL/6 mice. Toxicologist 1995 Mar;15(1):157 Author Address: Faculty of Toxicology, Texas A&M University, College Station, TX.

cleft palate --- dose-dependent
kidney damage (hydronephrosis)
certain types of PCBs are partial antagonists (neutralizers) of cleft palates and immune suppression caused by other PCBs, at certain doses, but did not neutralize or prevent the kidney damage caused by the PCBs
study used PCBs 126 (penta) and 169 (hexa)
single dose on day 10 of pregnancy

Polychlorinated biphenyls (PCBs) are widespread environmental contaminants. Among the PCBs, 3,3',4,4',5-pentachlorobiphenyl (PeCB) is the most toxic coplanar PCB congener. Recent studies have demonstrated the teratogenicity of PeCB in mice. This study was designed to investigate the potential of 2,2',4,4',5,5'-hexachlorobiphenyl (HeCB) as an antagonist of the teratogenicity of PeCB in C57BL/6 mice. Pregnant mice were administered orally a single dose of PeCB (dissolved in corn oil) at concentrations ranging from 522 to 2088 ug/kg body weight, either alone or in combination with a dose of HeCB (271 mg/kg) on day 10 of gestation. Fetuses were examined on day 17 for the presence of cleft palate and hydronephrosis. The results indicated a concentration-dependent increase in the incidences of cleft palate (ranging from 21 to 100%) in PeCB treatment groups. HeCB alone did not induce cleft palate. Cotreatment of dams with PeCB plus HeCB significantly reduced the number of fetuses with cleft palate in all treatment groups, except the group treated with the highest dose of PeCB (i.e., 2088 ug/kg). PeCB (1044, 783 or 522 ug/kg) produced 64, 45 and 21% of fetuses with cleft palate, respectively; whereas, the same doses of PeCB plus HeCB resulted in only 13, 4 and 0% of fetal cleft palate. Interestingly, HeCB did not antagonize PeCB-induced hydronephrosis in any of the treatment groups. The results from this study demonstrate that HeCB is a partial antagonist of PeCB-induced teratogenicity in C57BL/6 mice.

Study #12

Zhao F, Mayura K, Kocurek N, Edwards JF, Kubena LF, Safe S, Philips TD Effects of 2,2',4,4',5,5'-hexachlorobiphenyl and indole-3-carbinol on 3,3',4,4',5-pentachlorobiphenyl-induced teratogenesis in chicken embryos and C57BL/6 mice. Toxicologist 1996 Mar;30(1 Pt 2):197 Author Address: Faculty of Toxicology, Texas A&M University, College Station, TX.

cleft palate
chick embryo toxicity
chick embryo death
deformed chick embryos
chick edema
liver lesions
antagonism (neutralization) between PCB congeners may not follow predicted patterns
study used PCBs 126 (penta) and 169 (hexa)

Polychlorinated biphenyls (PCBs) are widespread environmental chemicals. Previous studies have reported that 2,2',4,4',5,5'-hexachlorobiphenyl (hexaCB), a diortho PCB congener antagonized 3,3',4,4',5-pentachlorobiphenyl (pentaCB)-induced teratogenesis (cleft palate) in C57BL/6 mice. In this study, our objectives were two-fold: 1) investigate if hexaCB could antagonize the teratogenic effects of pentaCB utilizing the chick embryotoxicity screening test (CHEST) bioassay, and 2) evaluate the effects of 13C (indole-3-carbinol) on pentaCB-induced teratogenesis in the CHEST assay and C57BL/6 mice. Fertilized hen eggs were injected into the yolk with pentaCB at concentrations ranging from 0.5-12.0 ug/kg egg weight either alone or in combination with hexaCB (10, 25, or 50 mg/kg egg weight) on day 4 of incubation. The experiment was terminated on day 18 and live embryos were subjected to embryonic and histological evaluations. PentaCB alone produced dose-dependent increases in mortality, toxicity and malformations in the embryos. A concentration of 2.0 ug pentaCB/kg resulted in 16% embryonic malformations, 56% edema, and 63% liver lesions. HexaCB, at 25 or 50 mg/kg, antagonized the embryotoxic and teratogenic effects of pentaCB (2.0 ug/kg) in the chicken embryos. Studies have demonstrated that 13C binds to the Ah receptor. Our results indicated that exposure to 13C alone at 2.0 mg/kg in chicken embryos and 200 mg/kg in mice did not result in any toxic effects. Cotreatment of 2.0 ug penta CB/kg plus 2.0 mg 13C/kg (in the CHEST assay) and 1044 ug pentaCB/kg plus 200 mg 13C/kg (in C57BL/6 mice) revealed neither agonist nor antagonist effects on pentaCB-induced teratogenic effects. The CHEST bioassay confirmed results in C57BL/6 mice and may be useful to delineate interactions between complex mixtures of environmental toxins.

Study #13

Zhao F In vitro and in vivo evaluation of the developmental toxicity of various polychlorinated biphenyls, chlorophenols and related compounds. Diss Abstr Int Sci 1997 Feb;57(8):4957B-4958B Author Address: Texas A&M University, TX.

cleft palate
kidney damage (hydronephrosis
mortality
toxicity
malformations
study used PCBs 126 (penta) and 169 (hexa), and indole-3-carbinol

Data pertaining to the developmental toxicity of PCBs are very limited in the literature. Studies were performed to determine the teratogenicity of 3,3',4,4',5-pentachlorobiphenyl utilizing the chick embryotoxicity screening test (CHEST), and to evaluate the effects of 2,2',4,4',5,5'-hexachlorobiphenyl and indole-3-carbinol (I3C) on 3,3',4,4',5-pentachlorobiphenyl-induced teratogenesis in the CHEST bioassay and C57BL/6 mice. 3,3',4,4',5-Pentachlorobiphenyl alone produced dose-dependent increases in mortality, toxicity and malformations in chicken embryos. 2,2',4,4',5,5'-Hexachlorobiphenyl antagonized the embryotoxic and teratogenic effects of 3,3',4,4',5-pentachlorobiphenyl (2.0 ug/kg) in chicken embryos. A concentration-dependent increase in the incidence of cleft palate was observed in mice treated with 3,3',4,4',5-pentachlorobiphenyl. Cotreatment of the dams with 3,3',4,4',5-pentachlorobiphenyl plus 2,2',4,4',5,5'-hexachlorobiphenyl significantly reduced the number of cleft palate in all treatment groups except in the highest treatment group. 2,2',4,4',5,5'-Hexachlorobiphenyl did not antagonize the 3,3',4,4',5-pentachlorobiphenyl-induced hydronephrosis. While I3C alone did not induce any toxic effect, cotreatment of 2.0 ug/kg 3,3',4,4',5-pentachlorobiphenyl plus 2.0 mg I3C/kg (in the CHEST assay) and 1044 ug 3,3',4,4',5-pentachlorobiphenyl/kg plus 200 mg I3C/kg (in mice) revealed neither agonist nor antagonist effects on 3,3',4,4',5-pentachlorobiphenyl-induced teratogenic effects. The CHEST bioassay confirmed the results in mice and may be useful to delineate interactions between complex mixtures of environmental toxins. Human embryonic palatal mesenchymal (HEPM) cell growth inhibition bioassay was used to evaluate the developmental toxicity of chlorophenols (CPs). This assay demonstrated a linear relationship between the IC50 values of the CPs and degree of chlorine substitution. A clear structure-activity relationship was observed between toxicity of CPs and the degree of chlorine substitution. The rank order of CP toxicity (i.e., C5P greater than C4P greater than C3P greater than C2P greater than CP greater than phenol) was in excellent agreement with previous in vitro and in vivo studies. However, contrary to published reports, the HEPM assay predicted that all CPs were teratogenic (false positives). These findings suggest that the HEPM cell growth inhibition bioassay may be useful to discriminate between subtle differences in structure-activity of diverse chemicals. Also, this assay in combination with other bioassays, might facilitate the rapid detection and prioritization of various developmental toxicants. Importantly, conclusions about the teratogenicity of a test chemical (via HEPM testing) should be approached with caution and confirmed with other teratogen-sensitive systems.

Study #14

Zhao F, Mayura K, Harper N, Safe SH, Phillips TD. Inhibition of 3,3',4,4',5-pentachlorobiphenyl-induced fetal cleft palate and immunotoxicity in C57BL/6 mice by 2,2',4,4',5,5'-hexachlorobiphenyl. Chemosphere 1997 Mar-Apr;34(5-7):1605-13 Author Address: Department of Veterinary Anatomy and Public Health, Texas A&M University, College Station 77843-4466, USA.

cleft palate
immune system damage
single dose on day 10 of pregnancy
study used PCBs 126 (penta) and 153 (hexa)

3,3',4,4',5-Pentachlorobiphenyl (pentaCB) caused a dose-dependent induction of fetal cleft palate in offspring from pregnant C57BL/6 mice exposed to a single dose (783 or 1044 micrograms/kg) of this compound on gestation day 10. In contrast, 2,2',4,4',5,5'-hexaCB did not cause cleft palate at a dose of 271 mg/kg and, in pregnant mice cotreated with 2,2',4,4',5,5'-hexaCB (271 mg/kg) plus 783 or 1044 micrograms/kg 3,3',4,4',5-pentaCB, fetal cleft palate formation was significantly inhibited. 3,3',4,4',5-PentaCB (6 micrograms/kg) also inhibited the splenic plaque-forming cell (PFC) response and serum IgM levels in C57BL/6 mice treated with the T cell-independent antigen trinitrophenyl-lipopolysaccharide. At doses as high as 72 mg/kg, 2,2',4,4'-5,5'-hexaCB was not immunotoxic; however, in mice cotreated with a immunotoxic dose of 3,3',4,4',5-pentaCB plus different doses of 2,2',4,4',5,5'-hexaCB (18, 36 and 72 mg/kg), there was a dose-dependent inhibition of 3,3',4,4',5-pentaCB-induced immunotoxicity. These non-additive (antagonistic) interactions of prototypical polychlorinated biphenyl (PCB) congeners may be an important consideration in development of a toxic equivalency factor approach for hazard and risk assessment of PCB mixtures.

Study #15

Yamashita K, Takagi T, Miwa I, Yasuda M Teratogenicity of 3,3',4,4',5-pentachlorobiphenyl in the mouse: dose-response and comparison with teratogenicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin. Teratology 1996 Oct;54(4):12A Author Address: Department of Anatomy, Hiroshima University School of Medicine, Hiroshima, Japan.

cleft palate
kidney damage (hydronephrosis)
fetal death
single dose on day 12.5 of pregnancy
study used PCB 126 (penta), and dioxin

Polychlorinated biphenyls (PCBs) are notorious as environmental pollutants. Among PCBs non-ortho coplanar PCBs are more toxic than other mono-ortho or di-ortho congeners. 3,3',4,4'-Tetrachlorobiphenyl, 3,3',4,4',5-pentaCB (CB = chlorobiphenyl), and 3,3',4,4',5,5'-hexaCB are non-ortho coplanar PCBs. These congeners act through the aryl hydrocarbon (Ah) receptor as dibenzodioxins and dibenzofurans do. They elicit similar responses to dioxins and are called dioxin-like PCBs. 3,3',4,4',5-PentaCB (PeCB) is the most toxic among the non-ortho coplanar PCBs. In this study teratogenicity of PeCB was investigated in the mouse and compared with that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Pregnant Jcl:ICR mice were given a single dose of 0 (vehicle control, corn oil), 50, 100, 200, and 400 ug of PeCB at GD12.5 (GD0 = vaginal plug positive) by gavage. Fetuses were examined at GD18.5. The incidences of fetal death at doses of 0, 50, 100, 200, and 400 ug of PeCB were 2.2, 1.1, 0, 0, and 11.8%, those of cleft palate; 2.4, 0, 2.0, 17.3, and 68.0%, those of hydronephrosis (dilated pelvis); 2.9, 33.4, 70.5, 64.5, and 97.2%, respectively. The ED50 (median effective dose) to induce cleft palate is estimated to be 300 ug for PeCB and 30 ug for TCDD. The toxic equivalent factor (TEF), which shows the toxicity of a given congener relative to a standard toxin, i.e., TCDD, was estimated to be 0.1 for PeCB in this study. This value is equivalent to the TEF for PeCB (0.1) proposed by the WHO-the International Program on Chemical Safety (IPCS). The present value is larger than the value of PeCB (less than 0.07-0.04) estimated for teratogenicity in C57BL/6 mice (Mayura et al., 1993). The difference in estimated potencies may reflect the difference in mouse strain.

Study #16

Yasuda M, Takagi T, Matsui KA, Miwa I, Yamashita K Palatal ruga anomalies induced by coplanar polychlorinated biphenyl in the mouse. Teratology 1996 Oct;54(4):44A-45A Author Address: Department of Anatomy, Hiroshima University School of Medicine, Hiroshima, Japan.

cleft palate
single dose on day 12.5 of pregnancy
study used PCB 126 (penta)

The oral surface of the mouse palate has eight or nine pairs of transverse ridges, or rugae. Abnormal patterns of palatal rugae in mice may be indicators of environmental teratogens. In the present study, we examined palatal ruga anomalies induced by 3,3',4,4',5-pentachlorobiphenyl (PeCB), one of the toxic coplanar PCBs. Pregnant Jcl:ICR mice were orally given PeCB at 25, 50, 100, 200, or 400 ug/kg at gestational day (GD) 12.5 (vaginal plug = GD 0). Fetuses were harvested at GD 18.5, fixed in Bouin's solution, and their palates were examined under a dissection microscope. Frequencies of cleft palate in groups treated with PeCB at 0 (vehicle control), 25, 50, 100, 200, and 400 ug/kg were 0, 0, 0, 4, 9, and 66%, respectively, and those of abnormal patterns of palatal rugae were 9, 5, 10, 23, 40, and 73%, respectively. TD50 for cleft palate induction was calculated to be about 350 ug/kg, that for palatal ruga anomalies about 250 ug/kg. The most frequent type of ruga anomalies was shortness, the same as observed in fetuses treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). These results indicate that the basic mechanism of developmental toxicity of both substances is similar. The TCDD-toxic equivalency factor (TEF) for PeCB was calculated to be about 0.1.

Study #17

Yasuda M, Yamashita K, Takagi T, Miwa I. Relationship between palatal ruga anomalies and enlarged renal pelvis induced by 3,3',4,4',5-pentachlorobiphenyl in mice. Teratology 1997 Jan;55(1):62 Author Address: Department of Anatomy, Hiroshima University School of Medicine, Hiroshima, Japan.

cleft palate
kidney damage (enlarged renal pelvis, hydronephrosis)
single dose on day 12.5 of pregnancy
study used PCB 126 (penta)

We have reported that variant patterns of palatal rugae may be indicators of developmental toxicity of chemicals. The purpose of the present study was to evaluate value of observation of palatal ruga anomalies (PRA) by analyzing relationship between PRA and enlarged renal pelvis (ERP) in a developmental toxicity study with one of the dioxin-like coplanar PCBs, 3,3',4,4',5-pentachlorobiphenyl (PeCB) in mice. Pregnant Jcl:ICR mice were orally given PeCB in a mixture of isooctane and corn oil at 25, 50, 100, 200, 400, or 800 ug/kg at gestational day (GD) 12.5 (VP = GD 0). Control mice received the vehicle. The fetuses were harvested at GD 18.5, individually numbered, and examined for cleft palate (CP), PRA, and ERP. Fetal mortality rates were comparable among the dose groups. In the control, 25, 50, 100, 200, 400, and 800 ug/kg groups, frequencies of CP were 0, 0, 0, 4, 9, 66, and 93%; those of PRA were 9, 5, 10, 23, 40, 73, and 100%; and those of ERP were 6, 26, 35, 65, 66, 98, and 100%, respectively. In each dose group, the frequency of fetuses with ERP was compared between CP+ and CP-, or PRA+ and PRA- fetal groups. In the majority of dose groups, the differences were statistically not significant. This result indicates that PeCB affects the palate and kidney rather independently, hence PRA are of value for observation.

Study #18

Morrissey RE, Harris MW, Diliberto JJ, Birnbaum LS Limited PCB antagonism of TCDD-induced malformations in mice. Toxicol Lett 1992 Jan;60(1):19-25 Author Address: Systemic Toxicology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27711.

cleft palate
kidney damage (hydronephrosis)
hydroureter
maternal weight changes
lower fetal body weight
single dose on day 9 of pregnancy
study used PCB 153 (hexa) and dioxin

C57BL/6N mice used to model induction of cleft palate and kidney malformations in offspring following maternal treatment with TCDD, were dosed on gestation day (gd) 9 with 2,2',4,4',5,5'-hexachlorobiphenyl (HCB) (62.5, 125, 250, 500, 1000 mg/kg) and/or gd 10 with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (15 or 18 micrograms/kg) to investigate the potential protective effects of HCB against TCDD-induced teratogenicity. Maternal body weight gain was increased by combinations of 15 micrograms TCDD/kg and 125-500 mg HCB/kg and decreased at doses of 15 micrograms TCDD/kg + 1000 HCB mg/kg. At the doses used in this study, there was no effect of either compound on number of live or dead offspring. Fetal body weight was slightly decreased in all groups dosed with greater than or equal to 250 mg HCB/kg. HCB did not induce cleft palate at a dose of 1000 mg/kg, but did induce increases in hydronephrosis and hydroureter at 500 and 1000 mg/kg. Combinations of HCB and TCDD decreased the incidence of cleft palate induced by TCDD alone, but only at doses of 15 micrograms TCDD/kg combined with 125-500 mg HCB/kg. The antagonism of hydronephrosis (incidence and severity) appeared over a narrower dose range (15 micrograms TCDD/kg + 500 mg HCB/kg). HCB induced increases (3-fold) in ethoxyresorufin-O-deethylase (EROD) activity at doses of 500 and 1000 mg/kg, suggesting that the limited antagonism of TCDD teratogenicity by HCB could be under the control of the Ah-receptor.

Study #19

Morrissey RE, Harris MW, Diliberto JJ, Birnbaum LS. Limited PCB Antagonism of TCDD-Induced Malformations in Mice. Govt Reports Announcements & Index (GRA&I), Issue 14, 1992 Author Address: Health Effects Research Lab., Research Triangle Park, NC. Environmental Toxicology Div. Merck, Sharp and Dohme, West Point, PA.

cleft palate
kidney damage (hydronephrosis
hydroureter
single dose on day 1 of pregnancy
study used either PCB 153 or 169 (abstract doesn’t say which) and dioxin

TD3: Mice used to model induction of cleft palate and kidney malformations in offspring following maternal treatment with TCDD, were dosed on gestation day with hexachlorobiphenyl (HCB) and/or with tetrachlorodibenzo-p-dioxin (TCDD) to investigate the potential protective effects of HCB against TCDD-induced teratogenicity. At the doses used in the study, there was no effect of either compound on number of live or dead offspring. Fetal body weight was slightly decreased in all groups dosed with = or > 250 mg HCB/kg. HCB did not induce cleft palate at a dose of 1000 mg/kg, but did induce increases in hydronephrosis and hydroureter at 500 and 1000 mg/kg. Combinations of HCB and TCDD decreased the incidence of cleft palate induced by TCDD alone, but only at doses of 15 microgram TCDD/kg combined with 125-500 mg HCB/kg. The window for antagonism of hydronephrosis (incidence and severity) appeared narrower (15 microgram TCDD/kg + 500 mg HCB/kg). HCB induced increases (3 fold) in EROD activity at doses of 500 and 1000 mg/kg, suggesting that the limited antagonism of TCDD teratogenicity by HCB would be consistent with control by Ah receptor. (Copyright (c) 1992 Elsevier Science Publishers B.V.) Journal article. Pub. in Toxicology Letters, v60 n1 p19-25 1992. Prepared in cooperation with Merck, Sharp and Dohme, West Point, PA.

Study #20

U.S. EPA. Drinking water criteria document for 2,3,7,8-tetrachlorodibenzo-p-dioxin. NTIS Technical Report (NTIS/PB90-215294) 1988 Apr;:344 PP.

dioxins are recognized teratogens in animals and possible teratogens in humans (several PCBs are dioxin-like)
cleft palate
edema (fluid retention)
hemorrhage
kidney anomalies
fetus death

2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is one of the most toxic and environmentally stable tricyclic aromatic compounds belonging to chlorinated dibenzo-p-dioxins. 2,3,7,8-TCDD has been demonstrated to be teratogenic in rats, mice and rabbits, and feticidal in monkeys. The major toxic signs and terata observed were cleft palate in mice, edema, hemorrhage, and kidney anomalies in rats and extra ribs in rabbits. Some epidemiological studies have indicated a possible teratogenic effect in humans, but the evidence is not sufficient to reach a firm conclusion.

Study #21

Birnbaum LS, Weber H, Harris MW, Lamb JC 4^th, McKinney JD Toxic interaction of specific polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin: Increased incidence of cleft palate in mice. Toxicol Appl Pharmacol; 77 (2). 1985. 292-302. Author Address: Toxicol. Res. and Test. Program, Natl. Inst. Environ. Health Sci., Research Triangle Park, NC 27709, USA.

cleft palate
hydronephrosis
renal abnormalities
dosed on days 10-13 of pregnancy
study used PCBs 153, 156 and dioxin

The induction of cleft palate in C57BL/6N mice is a reproducible and sensitive indicator of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicty. This endpoint was used to look for potential interactions between 2 polychlorinated biphenyl (PCB) congeners and TCDD. Both 2,3,4,5,3',4'-hexachlorobiphenyl (HCB) and 2,4,5,2',4',5'-HCB were of relatively low toxic potency, but their biological properties differed. Pregnant mice were treated with TCDD and HCB on gestation days 10-13, and the fetuses examined for the presence of cleft palate and renal abnormalities on gestation day 18. At a dose of TCDD which cauesd a low level of cleft palate, moderate hydronephrosis was observed. No renal or palatal anomalies were detected after 2,4,5,2',4',5'-HCB treatment, and the combination of this isomer with TCDD had no effect on the incidence of TCDD-induced cleft palate. 2,3,4,5,3',4'-HCB caused mild renal toxicity, but not cleft palate. Treatment of pregnant mice with a combination of TCDD and 2,3,4,5,3',4'-HCB resulted in a 10-fold increase in the incidence of cleft palate. The toxicity of compounds such as TCDD may have been enhanced by compounds of relatively low acute toxicity such as selected PCB. The widespread enviromental occurrence of such combinations suggested a need for further evaluation of the mechanism of this interaction.

Study #22

Birnbaum LS, Weber H, Harris MW, Lamb JC, McKinney JD Toxic Interaction Of Specific Polychlorinated Biphenyls And 2,3,7,8-Tetrachlorodibenzo-p-dioxin: Increased Incidence Of Cleft Palate In Mice.Toxicology and Applied Pharmacology, Vol. 77, No. 2, pages 292-302, 38 references,1985

cleft palate
hydronephrosis
renal abnormalities
increased maternal liver weight
dosed either once on day 11 or from days 10-13 of pregnancy
study used PCB 156 and dioxin
certain PCBs magnify the toxic effects of dioxin

The effect of specific polychlorinated biphenyls (PCB) on 2,3,7,8-tetrachlorodibenzo-p-dioxin (1746016) (TCDD) induced teratogenesis was investigated in mice. Pregnant female C57BL/6N-mice were dosed twice by gavage on either gestation day 11 or once daily on gestation days 10 to 13. Maternal body and hepatic weights and the numbers and position of live and dead fetuses and resorptions were recorded. The kidneys were sectioned and examined for presence of hydronephrosis; the extent of renal injury was graded for each kidney. Neither 2,3,4,5,3',4'-hexachlorobenzene (118741) (HCB) nor TCDD, alone or in combination, were clinically toxic to the dams. There was a significant increase in maternal liver weight per body weight ratio in all treated groups; there was no significant interaction between HCB and TCDD on the liver to body weight ratio. Significant differences occurred in the cleft palate response between the TCDD, HCB, and the combination treated fetuses. The PCB isomer failed to cause cleft palate in any of the treated litters. TCDD alone at 12 micrograms per kilogram resulted in 63 of 165 fetuses having cleft palates. Combined treatment with HCB resulted in a significant increase in the cleft palate incidence, 112 of 187 fetuses in the low dose and 90 of 140 in the high dose combination groups. Neither PCB isomer, TCDD, nor the combinations caused signs of clinical toxicity in the dams. At the TCDD dose used, 3 micrograms per kilogram on days 10 to 13, the renal damage was moderate to severe. Treatment with HCB alone resulted in significant dose related incidence of hydronephrosis; damage was less severe than that induced by TCDD. The authors conclude that certain PCBs of relatively low toxic potency such as HCB may greatly enhance the toxicity of halogenated aromatic hydrocarbons such as TCDD.

Study #23

Birnbaum LS, Harris MW, Barnhart ER, Morrissey RE Teratogenicity of Three Polychlorinated Dibenzofurans in C57BL/6N Mice Toxicology and Applied Pharmacology, Vol. 90, No. 2, pages 206-216, 48 references, 1987

cleft palate
hydronephrosis
renal abnormalities
increased maternal liver weight
dosed either once on day 11 or from days 10-13 of pregnancy
study used PCB 156 and dioxin
certain PCBs magnify the toxic effects of dioxin

The teratogenic effects of three polychlorinated dibenzofurans (PCDF) were studied in pregnant C57BL/6N-mice. The compounds were 2,3,4,7,8-pentachlorodibenzofuran (57117314) (4-PeCDF), 1,2,3,4,7,8-hexachlorodibenzofuran (70648269) (HCDF), and 1,2,3,7,8-pentachlorodibenzofuran (57117416) (1-PeCDF). The compounds were administered by gavage at 10 milliliters per kilogram body weight on days 10 to 13 of gestation. The mice were sacrificed on day 18. The toxic effects were assessed from the changes in maternal weight gain, maternal liver to body weight ratios, fetal viability, and fetal weight. The secondary palate and the kidney, the common target organs for TCDD toxicity, were scored for the presence of cleft palate and hydronephrosis, respectively. The results demonstrated that all three PCDFs produced teratogenic effects at doses below those that produced maternal or fetal toxic effects. The isomer, 4-PeCDF was the most teratogenic of the tested compounds. The authors conclude that PCDFs appear to induce the same type of teratogenic effects as 2,3,7,8-tetrachlorodibenzo-p-dioxin and suggest that their possible involvement in an increased incidence in human perinatal mortality should be investigated.

Study #24

Birnbaum LS, Harris MW, Crawford DD, Morrissey RE Teratogenic Effects of Polychlorinated Dibenzofurans in Combination in C57BL/6N Mice. Toxicology and Applied Pharmacology, Vol. 91, No. 2, pages 246-255, 38 references, 1987

cleft palate
kidney damage (hydronephrosis)
dosed on days 10-13 of pregnancy
study used PCB 156 and 2 kinds of furans

Teratogenic effects of 2,3,4,7,8-pentachlorodibenzofuran (57117314) (4-PeCDF) and 1,2,3,4,7,8-hexachlorodibenzofuran (70648269) (HCDF), alone or in combination, were studied in C57BL/6N-mice. Pregnant mice were dosed by gavage with 0, 5, 10, or 30 micrograms/kilogram (microg/kg) of 4-PeCDF in combination with 0, 100, 200, or 300microg/kg of HCDF on gestation days ten through 13. 4-PeCDF and HCDF, alone or in combination, produced no significant effect on maternal weight gain, fetal viability, or mortality was observed. Cleft palate was observed in offspring of females treated with either compound or the compounds in combination. Treatment with either polychlorinated dibenzofuran resulted in hydronephrosis. Combinations of 4-PeCDF and 2,3,4,5,3',4'-hexachlorobiphenyl (HCB) resulted in no significant effects on maternal weight, fetal weight, fetal viability or mortality. At the doses used, neither compound by itself induced a statistically significant incidence of cleft palate. Hydronephrosis was produced in all cases. HCB with 4-PeCDF induced cleft palate and hydronephrosis. The incidence of cleft palate induced by 4-PeCDF and HCDF in combination was compared with the expected incidence predicted by probit analyses. A slight synergistic effect was suggested. The observed incidence of cleft palate induced by the two chemicals was slightly lower than that predicted. The incidence of hydronephrosis observed for the combination of 4-PeCDF and HCDF was slightly greater than that expected. For teratogenic endpoints, the effect of 4-PeCDF and HCDF in combination appeared to be additive.

Study #25

Kimbrough RD Laboratory And Human Studies On Polychlorinated Biphenyls (PCBs) And Related Compounds. Environmental Health Perspectives, Vol. 59, pages 99-106, 77 references, 1985

cleft palate
kidney damage (hydronephrosis)
numerous other health effects

Studies involving polychlorinated biphenyls (PCBs) are reviewed. PCBs are a class of halogenated aromatic compounds, including halogenated biphenyls, naphthalenes, dibenzodioxides, and dibenzofurans. PCBs persist in the environment and are retained in tissue because they are lipid soluble. They affect reproduction, suppress the immune system, cause tumors in laboratory rodents, cause hepatic porphyria, and cause chick edema in chickens. Cell mediated immunity is impaired by PCB, although the degree of impairment is determined by the type of isomers present. PCBs are not teratogenic, but they are fetotoxic, producing cleft palates, subcutaneous edema, and hemorrhage. PCBs are passed to mammalian offspring in the milk. 2,3,7,8-Tetrachloro-dibenzo-p-dioxin (1746016) (TCDD) is known to cause hepatocellular carcinomas and squamous carcinomas of the oropharynx and lungs. Subcutaneous sarcomas and tumors of the thyroid are also noted. The primary source of PCB exposure to the general United States population is fish from contaminated water. Serum cholesterol levels in humans are directly proportional to PCB levels. The concentration of PCB in human milk is particularly high. There is no clear evidence of harm to humans from PCB, but research is inconclusive. The author concludes that PCB may be a cancer promoter, but additional studies on exposed human cohorts, such as fishermen, must be done before any conclusions about the effects of PCB on humans can be reached.

Study #26

Birnbaum LS Developmental effects of dioxins and other endocrine disrupting chemicals. International Toxicologist 1995 Jul;7(1):AB# 79-S-5 Author Address: Environmental Toxicology Division, HERL, US EPA, Research Triangle Park, NC.

cleft palate
hydronephrosis
numerous other effects

Alteration of hormonal systems has long been known to cause developmental problems. TCDD and other structurally related PHAHs modulate the levels of many different hormones and their receptors. These effects are all mediated through binding to the Ah receptor. Dioxin and related compounds are developmental toxicants, causing a spectrum of morphological and functional deficits. At doses below those where maternal toxicity is observed, dioxins cause fetotoxicity. In the mouse, exposure of the dam results in hydronephrosis and cleft palate in the pups. Thymic atrophy and hemorrhage are observed in many species at doses which are not maternally toxic. Prenatal exposure to both rats and hamsters results in alterations to the genitourinary tract of the offspring, which is not detectable until puberty. Delays in puberty, permanent reduction in sperm counts, and long-term alterations in immune functions have also been observed. Prenatal exposure to PCBs has been shown to cause similar effects in rats and guinea pigs, as well as decrements in the auditory threshold. Children exposed prenatally to complex mixtures of PCBs and PCDFs are smaller and have problems at puberty, hearing deficits, increased respiratory disease, and IQ and behavioral deficits. Many of these effects are similar to those observed with known hormone modulators. The complex alteration of multiple endocrine systems is likely associated with the spectrum of adverse developmental effects caused by dioxin and related compounds.

Study #27

Brown MM, Schneider UA, Petrulis JR, Bunce NJ Additive binding of polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin to the murine hepatic Ah receptor. Toxicol Appl Pharmacol; VOL 129, ISS 2, 1994, P243-51 Author Address: Guelph-Waterloo Centre for Graduate Work in Chemistry, Department of Chemistry and Biochemistry, University of Guelph, Ontario, Canada.

cleft palate
certain PCBs compete partially with dioxin for Ah receptor site.

Fixed aliquots of both radiolabeled [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and hepatic Ah receptor from C57BL/6J mice were incubated competitively at 4, 23, and 30 degrees C with mixtures of 2,3,7,8-TCDD and several polychlorinated biphenyls (PCBs). The production of the radiolabeled receptor-ligand complex changed if the ligands were added sequentially, demonstrating that the competition between PCBs and TCDD for the Ah receptor in vitro is principally a kinetic rather than an equilibrium phenomenon and is irreversible on the time scale of our in vitro experiments. Examination of previous reports on the ability of TCDD, PCBs, and their mixtures to induce cleft palate in fetal mice suggests that the potency of receptor-ligand complexes is ligand-dependent. Receptor occupancy is not a sufficient condition for toxicity, and protection by one ligand against the toxic effect of a second, more potent one is only possible when a significant fraction of receptors is occupied.

Study #28

d'Argy R, Dencker L, Klasson-Wehler E, Bergman A, Darnerud PO, Brandt I 3,3'4,4'-Tetrachlorobiphenyl in pregnant mice: embryotoxicity, teratogenicity, and toxic effects on the cultured embryonic thymus. Pharmacol Toxicol; VOL 61, ISS 1, 1987, P53-7

cleft palate
kidney damage
thymus lymphoid cell damage
fetal resorptions
dosed on days 11,12 or 13 of pregnancy
study used PCB 77 and dioxin

3,3',4,4'-Tetrachlorobiphenyl (TCB) is a known ligand of the Ah-receptor. When TCB was given to Ah-responsive C57BL/6 mice at gestation day 11, 12 or 13, a pattern of embryotoxic effects similar to those of TCDD was produced. This pattern included death and resorptions of the conceptus (peak sensitivity at day 11), as well as characteristic malformations such as cleft palate, dilated kidney pelvis (peak sensitivity day 12), and thymus hypoplasia (peak sensitivity day 13). The ED50 for cleft palate induction was found to be about 100 mg/kg, as compared to 30 micrograms/kg for TCDD (earlier results). The binding affinity of TCB for the Ah-receptor has been reported to be two orders of magnitude lower than that of TCDD. When TCB was introduced into a thymus organ culture (thymi taken from day-14 embryos), the lymphoid cell development was inhibited with an approximate EC50 of 5 X 10(-8) M. This is approximately 100 times higher than that of TCDD and in good agreement with the receptor binding affinities

Study #29

Pohl H, Holler J Halogenated Aromatic Hydrocarbons and Toxicity Equivalency Factors (TEFs) from the Public Health Assessment Perspective. Chemosphere, Vol. 31, No. 1, pages 2547-2559, 43 references, 1995

cleft palate
liver effects
thymic effects
PCB and dioxin effects are not strictly additive, due to variable competition for binding sites in the body

The validity of using toxicity equivalency factors (TEFs) for estimating the toxicity of environmental mixtures of halogenated aromatic hydrocarbons was investigated. Minimal risk levels (MRLs) obtained from the scientific literature were used for comparison. The assumption has been that dioxin like chemicals act through a common mechanism of action and their toxicity outcomes and sensitive endpoints should be similar. Good correlation was found for intermediate duration values for 2,3,7,8-tetrachlorodibenzo-p-dioxin (1746016) (TCDD) and 2,3,4,7,8-pentachlorodibenzofuran (57117314) (2,3,4,7,8-pentaCDF). A high 25 fold discrepancy was found between the acute oral MRLs for TCDD and 2,3,4,7,8-pentaCDF, which was attributed to the quality of the database for each group of chemicals and the sensitivity of tests used for MRL derivation. The usefulness of TEFs was confirmed in studies of mixtures of TCDD and 2,3,4,7,8-pentaCDF on hepatic and thymic effects and cleft palates. In contrast, other studies showed no additive effects, including studies of coplanar congeners of polychlorinated biphenyls and Aroclor-1254 (27323188). Because individual congeners compete for the same receptor, toxicity is not always additive. The validity of the TEFs depended on the following specific criteria: a well defined group of chemicals, a broad database of information, consistency across endpoints, additivity of effects, and a common mechanism of action. Even when all these criteria are met, the authors conclude that the final behavior of all congeners in a particular mixture is uncertain.

Study #30

Letter from Dow Chemical Company to usepa regarding information on TCDD, chlorinated dioxins & phenols, PBB and PCB, environmental monitoring data with attachments. Source: EPA/OTS; Doc #88-7800209 Order Number: NTIS/OTS0200491, Classification Code: TSCA Sect. 8E Rec 07/05/78,Year of Publication: 1978, Secondary Source ID: TSCATS/408119

cleft palate (palate/nasal turbinates)
numerous other effects
study used PCBs, PBBs, dioxins, and phenols (all present in the Fox River and Green Bay)

Trace amounts of 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD), other chlorinated dioxins, chlorinated phenols, polybrominated biphenyls, and polychlorinated biphenyl were present in saples of fish taken from the lower Tittabawassee River in Michigan. Fact sheets containing results of toxicity studies indicate dietary doses of 0.001 ug/kg/day of TCDD for 2 years induces "some few" swollen liver cells in females, but causes no adverse effects in male rats, does not effect fertility, nor neonatal growth or survival. A similar regimen of 0.01 ug/kg/day is not lethal but leads to decreased litter size, while a diet 0.1 ug/kg/day for 2 years leads to increased incidence of liver cancer in females, lung and palate/nasal turbinates or tongue cancer in both sexes, and a marked decrease in reproductive capacity. The no-effect dose was 0.01 ug/kg/day when administered orally 5 days/week for 90 days, and 0.1 ug/kg/day caused toxic effects (not described). Acute oral LD50 values are: 22 ug/kg for male rats and 45 ug/kg for female rats; 0.6 ug/kg for male guinea pigs (21 ug/kg in another study); 115 ug/kg for rabbits; >300 ug/kg for dogs and monkeys.

Study #31

Couture LA, Harris MW, Birnbaum LS Characterization of the peak period of sensitivity for the induction of hydronephrosis in C57BL/6N mice following exposure to 2,3,7, 8-tetrachlorodibenzo-p-dioxin. Fundam Appl Toxicol 1990 Jul;15(1):142-50 Author Address: Experimental Toxicology Branch, National Institute of Environmental Health, Sciences, Research Triangle Park, North Carolina 27709.

cleft palate
hydronephrosis
higher maternal liver weights
fetal mortality
study used dioxin
effects varied in response to timing of dose during pregnancy

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an extremely potent teratogen in mice. Hydronephrosis and cleft palate are the most sensitive measures of teratogenicity in mice following exposure to TCDD and other structurally related polyhalogenated aromatic hydrocarbons. Despite a relatively long half-life, investigators have identified a critical window for the induction of cleft palate in C57BL/6N mice. To characterize the critical period for renal teratogenesis, pregnant C57BL/6N mice were treated once by gavage with 0-24 micrograms TCDD/kg body wt on Gestation Day (GD) 6, 8, 10, 12, or 14. All dams were killed on GD 18, and the fetuses were examined for the presence of hydronephrosis and cleft palate. Maternal liver-to-body weight ratios were significantly elevated above controls on all days, while maternal weight gain was unaffected. Fetal mortality was increased relative to controls only at 24 micrograms TCDD/kg on GD 6. There was no significant difference in fetal body weights between control and TCDD-treated fetuses. The incidence of cleft palate increased in a dose-related fashion from GD 6 to GD 12, and identification of GD 12 as the critical window for induction of clefting of the hard palate was confirmed. Hydronephrosis was observed at all dose levels, regardless of exposure day, and the incidence was close to 100% at 3 micrograms TCDD/kg and higher doses on GD 12 and earlier. At all doses on GD 14, both the incidence and severity of hydronephrosis were decreased relative to all other days. There was a dose-related increase in the severity of the renal lesion on each day, but between GD 6 and 12 severity was constant. Thus, while palatal sensitivity to TCDD increased with gestational age between GD 6 and 12, there was no difference among these days in development of hydronephrosis. The data suggest, however, that on GD 14 the urinary tract may be less sensitive to TCDD.

Study #32

Yamashita K, Takagi T, Yasuda M Fine structural aspects of hydroureter in the mouse fetus after administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Teratology 1995 Oct;52(4):16B Author Address: Department of Anatomy, Hiroshima University School of Medicine, Hiroshima, Japan.

cleft palate
hydroureter (dilated renal pelvis)
epithelial cells proliferate and shed, blocking the ureter
single dose at day 12.5 of pregnancy
study used dioxin

It is well known that, among dioxins, TCDD is the most potent teratogen in mice and induces cleft palate and hydroureter (dilated renal pelvis). In order to clarify the effect of TCDD on the ureter, we observed the fine structure of the ureter by electron microscopy. Pregnant Jcl:ICR mice were given TCDD by gavage at a single dose of 0, 40, 80 ug/kg at day 12.5 of gestation (vaginal plug = day 0, GD0). Dams were killed at GD14.5, 15.5, 16.5 and 18.5. In controls, the ureteral epithelium, which is composed of a single cuboidal epithelial sheet at GD14.5, proliferates to become a two-cell thick layer at GD16.5. Adult-type superficial cells (Deckzellen) with fusiform vesicles appear first at GD18.5. No apparent ultrastructural difference could be detected at GD14.5 between TCDD-treated groups and controls. In TCDD-treated groups, epithelial cells proliferated at GD16.5 to a greater extent than in controls. In addition, profiles of cell deaths were seen in epithelial cells which faced the ureteral lumen or which lay on the basal lamina. At GD18.5 hydroureter was apparent. Under a dissection microscope, the middle portion of the ureter between the renal pelvis and urinary bladder was narrowed. In this portion cell debris were noticed filling the ureteral lumen. These data suggest that the ureter was narrowed due to the proliferation of ureteral epithelial cells and cell debris in the lumen, which are shed from the epithelium.

Study #33

Mandell J, Blyth BR, Peters CA, Retik AB, Estroff JA, Benacerraf BR Structural genitourinary defects detected in utero.

Radiology 1991 Jan;178(1):193-6 Author Address: Department of Surgery, Children's Hospital, Boston, MA 02115.

kidney and urinary tract birth defects
frequency in the population

Fetal genitourinary anomalies are detected with increasing frequency due to the large numbers of fetuses that undergo screening ultrasonography (US) for nonspecific indications. One hundred seventy-seven patients were evaluated for fetal urinary abnormalities over a 2-year period. Fetal hydronephrosis accounted for 154 (87%) of the cases, with the remaining diagnoses including multicystic dysplastic kidney, autosomal recessive polycystic kidney disease, and renal agenesis or hypodysplasia. Ureteropelvic junction obstruction was the most common postnatal anatomic abnormality (29%), with a large number of cases of prenatally diagnosed hydronephrosis resolving either prenatally (33%) or postnatally (24%). Prenatal US findings were retrospectively analyzed with regard to the degree of hydronephrosis at different stages of gestation. Data showed that there is a gradual rise in anteroposterior renal pelvic diameter during gestation and that there is a correlation between this diameter and the ultimate renal outcome in regard to surgical repair. This information can provide guidance in making recommendations to parents and physicians.

Study #34

Cortes D, Lee K, Thorup JM Renal and urinary tract abnormalities in small children. Ugeskr Laeger 1999 Jan 11;161(2):147-50 Author Address: Bárneafdelingen og organkirurgisk afdeling, Hillerád Sygehus.

kidney and urinary tract birth defects
frequency in the population

The purpose of this study was to investigate frequency and pattern of urological abnormalities in children younger than two years of age in the county of Frederiksborg, Denmark, with a catchment area of about 350,000 people, and furthermore to investigate in which way the urological abnormalities were diagnosed. From 1994-1996 a total of 35 children younger than two years of age were found to have urological abnormalities. Fourteen patients had a ultrasonographical prenatally diagnosed urological abnormality, which was confirmed postnatally. Twenty-one children were diagnosed with urological abnormalities after presentry with their first urinary tract infection. The obstructive urological diagnoses: congenital hydronephrosis, congenital megaureter and posterior urethral valves made up to 57% (20/35) of the abnormalities. Nine boys were operated upon; three for unilateral hydronephrosis, two for posterior urethral valves, one for unilateral megaureter and three for phimosis. Two girls were treated with oestrogen for labial fusion. Urological abnormalities which were treated were found among the ultrasonographically diagnosed abnormalities, apart from phimosis and labial fusion. The frequency of urological abnormalities was 0.25% in children younger than two years of age in Frederiksborg county. In conclusion, in 1994-1996 the frequency and pattern of urological abnormalities in Frederiksborg county was in accordance with the figures in the literature. Urological abnormalities requiring treatment were diagnosed in 11 children; 55% (6/11) ultrasonographically and 45% (5/11) by examination of the external genitalia of children younger than two years of age at the time of the first diagnosed urinary tract infection.

Study #35

Tan PH, Chiang GS, Tay AH Pathology of urinary tract malformations in a paediatric autopsy series. Ann Acad Med Singapore 1994 Nov;23(6):838-43 Author Address: Department of Pathology, Singapore General Hospital.

kidney and urinary tract birth defects
frequency in the population

In a series of 3172 consecutive autopsies of stillbirths, infants and children performed over a 12-year period from 1978 to 1989 at the Department of Pathology, Outram Road, Singapore, urinary tract malformations were found in 78 cases (2.5%). The urinary tract abnormalities were of 6 major groups: hydronephrosis and/or hydroureter (35.9%), cystic disorders (29.5%), renal agenesis (26.9%), horseshoe kidney (11.5%), renal hypoplasia (5.1%) and pelvic kidney (1.3%). Other series have reported incidences of urinary tract malformations ranging between 2.7% and 11%, depending on the source of the study material. Our local incidence appears to fall below the lower end of the scale, but may not reflect an accurate comparison because of the differences in the denominational base.

Study #36

Leck I Structural birth defects. Epidemiology of Childhood Disorders 1994;:66-117 Author Address: Epidemiology, University of Manchester, Manchester, England.

Study #37

Sugawara R, Kawakatsu K, Watanabe M Causes for incidence of abnormalities.3.rubella virus and pcb induced experimental cleft palate in mouse. Source: Nippon Koshu Eisei zasshi (Jpn J Public Health) 19(10 spec suppl):188,1972

Study #38

Watanabe M, Sugahara T Combined biological effects of environmental contaminants.2.a combined teratogenic effect of polychlorinated biphenyls (pcb) and rubella virus infection in the experimental cleft palate formation of mouse. Source: Hokuriku Koshu Eisei Gakkaishi 7:21-24,1980