Spleen - Microsoft Word Toxicology and Exposure Guidelines doc

(Created 12/02)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu
• Male: Anesthetic gases (halothane, methoxyflurane) cadmium, mercury, lead, boron,
methyl mercury, vinyl chloride, DDT, kepone, chlordane, PCBs, dioxin, 2,4-D, 2,4,5-T,
carbaryl, paraquat, dibromochloropropane, ethylene dibromide, benzene, toluene, xylene,
ethanol,
radiation, and heat.
• Female: DDT, parathion, carbaryl, diethylstilbestrol (DES), PCBs, cadmium, methyl
mercury, hexafluoroacetone, and anesthetic gases.
Types of Toxic Effects
Teratogenic. Teratology is derived from Latin and means the study of monsters. In a modern
context, teratology is the study of congenital malformations. Teratology is a relatively new
discipline that started in 1941 with the correlation of German measles to birth defects. In the
1960s, the first industrial link to teratogens was discovered. The chemical involved was methyl
mercury.
The following conditions have been associated with
congenital malformations: heredity,
maternal diseases such as German measles and viral infections during pregnancy, maternal
malnutrition, physical injury, radiation, and exposure to chemicals.
Most major structural abnormalities occur during the embryonic period, 5-7 weeks, whereas
physiologic and minor defects occur during the fetal period, 8-36 weeks. Studies using lab
animals show the need to evaluate exposure of chemicals for each day of pregnancy.
Thalidomide, for example, caused birth defects in rats only when administered during the 12th
day of gestation.
A number of chemicals are reactive or can be activated in the body during the gestation period.
The degree and nature of the fetal effects then depend upon:
• Developmental state of embryo or fetus when chemical is administered.
• Dose of chemical, route, and exposure interval.
• Transplacental absorption of chemical and levels in tissues of embryo/fetus.
• Ability of maternal liver and placenta to metabolize or detoxify chemical.
• Biologic half-life of chemical or metabolites.
• State of cell cycle when chemical is at toxic concentrations.
• Capacity of embryonic/fetal tissues to detoxify or bioactivate chemicals.
• Ability of damaged cells to repair or recover.
Teratogenic potential has been suggested by animal studies under various conditions:
• Dietary deficiency: Vitamins A, D, E, C, riboflavin, thiamine, nicotinamide,
folic acid,
zinc, manganese, magnesium, and cobalt.
• Hormonal deficiency: Pituitary, thyroxin, and insulin.
• Hormonal excess: Cortisone, thyroxin, insulin, androgens, estrogens, and epinephrine.
• Hormone and vitamin antagonists: 3-acetylpyridine, 6-aminonicotinamide, and
thiouracils.
(Created 12/02)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu
• Vitamin excess: Vitamin A and nicotinic acid.
• Antibiotics: Penicillin, tetracyclines, and streptomycin.
• Heavy metals:
Methyl mercury, mercury salts, lead, thallium, selenium, and chelating
agents.
• Azo dyes: Trypan blue, Evans blue, and Niagara sky blue 6B.
• Producers of anoxia: Carbon monoxide and carbon dioxide.
• Chemicals: Quinine, thiadiazole, salicylate, 2,3,7,8-TCDD, caffeine, nitrosamines,
hydroxyurea,
boric acid, insecticides, pesticides, DMSO, chloroform, carbon
tetrachloride, benzene, xylene, cyclohexanone, propylene glycol, acetamides,
formamides, and sulfonamides.
• Physical conditions: hypothermia,
hyperthermia, radiation, and anoxia.
• Infections: Ten viruses (including German measles and cytomegalovirus), syphilis, and
gonorrhea.
Far fewer agents have been conclusively shown to be teratogenic in humans: anesthetic gases,
organic mercury compounds, ionizing radiation, german measles and thalidomide.