A Teratogen

I didn t know what a teratogen is. I was not the only person scampering to a dictionary for a definition. 

Industry had no choice other than to discontinue manufacturing NTA, for use in the United States. This one announcement murdered the product for use in the United States, forever, but not in Canada where it is still used without deforming Canadians. It has always been a bit baffling to me why the Canadian people are so very different from those of us who live south of their border. Canadians can use NTA with no problems, but we must not use NTA because it will deform us. Perhaps the closer to the equator one moves, the more toxic NTA becomes. 

A second case study is the well-known saccharine story. An official announced that saccharine is a carcinogen. The public answer was  

Back to sweeteners far less damning evidence completely destroyed calcium cyclamates. There were rumors in the scientific community that the data killing cyclamates were intentionally designed to kill them. This may or may not be true, but in view of some other things happening at that time, I am inclined to believe that it is true. 

The political poison, dioxin, ranks high on the list of trumped-up charges. If Agent Orange had not contained traces of dioxin, few people would ever have known there are such compounds. Some leading household and office products had contained traces of dioxin for many years with no obvious harm to the users. As 

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Tellurium is not an essential element, and teUurium compounds are in general more toxic than their selenium counterparts. MetaUic teUurium is known to have a teratogenic effect in rats, though no studies have been done on the toxicity of teUurium donor compounds (35). 

Formaldehyde is not considered a teratogen and has not been reported to cause adverse reproductive effects (138,139). vitro mutagenicity assays... 

The amino acids L-leucine, T-phenylalanine, L-tyrosine, and L-tryptophan all taste bitter, whereas their D-enantiomers taste sweet (5) (see Amino ACIDS). D-Penicillamine [52-67-5] a chelating agent used to remove heavy metals from the body, is a relatively nontoxic dmg effective in the treatment of rheumatoid arthritis, but T.-penicillamine [1113-41 -3] produces optic atrophy and subsequent blindness (6). T.-Penicillamine is roughly eight times more mutagenic than its enantiomer. Such enantioselective mutagenicity is likely due to differences in renal metaboHsm (7). (R)-ThaHdomide (3) is a sedative—hypnotic (3)-thaHdomide (4) is a teratogen (8). 

The effects of a teratogen on a fetus depend on the timing of the exposure, i.e., at which stage of organogenesis the exposure takes place. Exposure to a teratogen before implantation usually leads to death and abortion of the fetus. How-... 

Edwards, M. J. (1986). Hyperthermia as a teratogen A review of experimental. studies. and their clinical significance. Teratog. Carcinog. Mutag. 6, 56.3-S82. 

A teratogen (the word is of Greek origin, meaning the induction of a monster) is a chemical, physical or viral factor causing birth defects. Exposure to teratogens can result in a wide range of structural abnormalities. 

DOE. 1985a. Environmental impact of a teratogenic actinide A case study of americium-241. Washington, DC U.S. Department of Energy. NTIS/DE86001795. 

Weis, J.S. and K. Kim. 1988. Tributyltin is a teratogen in producing deformities in limbs of the fiddler crab, Uca pugilator. Arch. Environ. Contam. Toxicol. 17 583-587. 

There has been no comprehensive evaluation of the reproductive and developmental effects of hexachloroethane. Limited data indicate that it is maternally toxic and retards fetal development. It does not appear to be a teratogen. 

Some variations exist between the susceptibility of mammalian species to the teratogenic action of nickel salts. No detrimental reproductive and developmental effects have been documented in humans [422], Yet exposure to nickel salts must be assumed to constitute a teratogenic risk. 

In addition, nickel chloride has a teratogenic potential in developing chick embryos, with malformations such as exencephaly, everted viscera, short and twisted neck and limbs, microphthalmia, haemorrhage and reduced body size being obtained [428]. 

Khera KS, Villeneuve DC, Terry G, et al. 1976. Mirex A teratogenicity, dominant lethal and tissue distribution study in rats. Food Cosmet Toxicol 14 25-29. 

Villeneuve DC, Khera KS, Trivett G, et al. 1979a. Photomirex A teratogenicity and tissue distribution study in the rabbit. J Environ Sci Health [B] 14(2) 171-180. 

TCDD (a dioxin derivative) tested positive as a teratogen in rats. 

A well known example of tragic consequences is provided by "Thalidomide" (or "Contergan") which was commercialised in the 60 s whereas the (/ )-enantiomer shows a weak sedative activity, the enantiomer of (5)-configuration, administered together in the racemate, caused in the expectant mothers a teratogenic effect (malformations) on the foetus. 

Most cases of mercury poisoning led to handicap, chronic disease, or death. The most frequent symptoms include numbness of limbs, lips and tongue, speech abnormalities, limb function disorders, visual acuity disorders, deafness, and muscular atrophy. Insomnia, hyperactivity, and coma have also been reported. Methylmercury penetrates the blood-brain barrier and causes central nervous system injuries. Mercury also has a teratogenic effect, leading to congenital abnormalities or congenital Minamata disease. 

A teratogen and suspected human carcinogen having a low toxicity (Patnaik, 1992). 

However, here, too much of a good thing is not so hot. If retinoic acid is administered systemically during embryo formation (in experimental animals to be sure), severe malformations result in the offspring. Thus, retinoic acid is a teratogen. 

Q7 has an increased risk of neonatal haemolysis during the third trimester Q8 may cause vestibular or auditory nerve damage Q9 should be stopped at least 2 days before delivery Q10 consists of a folate antagonist that poses a teratogenic risk... 

Co-trimoxazole is a folate antagonist and should be avoided in the first and the third trimesters of pregnancy. In the third trimester there is an increased risk of neonatal haemolysis and methaemoglobinaemia, whereas in the first trimester there is a teratogenic risk caused by the trimethoprim (folate antagonist) component. 

The developmental effects of 1,4-dichlorobenzene have been evaluated in New Zealand White rabbits (Hayes et al. 1985). Pregnant rabbits were exposed to 1,4-dichlorobenzene by inhalation at 800 ppm for 6 hours per day on Gd 6-18. At 300 ppm, there was a significant increase in the number of litters with resorptions and the percentages of resorbed implantations per litter however, this effect was not seen at 800 ppm and was thus probably not treatment-related. An increased incidence of retroesophageal right subclavian artery present in the offspring was noted it was not considered to constitute a teratogenic response to exposure to 1,4-dichlorobenzene, but was considered only a minor variation. Based on the NOAEL of 300 ppm, an acute-duration MRL of 0.8 ppm was calculated as described in the footnote to Table 2-1 and Appendix A (Hayes et al. 1985). 

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