Environmental toxicants and human exposure


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Environmental toxicants and human exposure

  1. 1. Paracelsus “All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy.” Paracelsus (1493-1541)
  2. 2. Developmental Toxicology -Developmental is concerned with the investigation of chemically induced teratogenic effects or birth defects. -Studies involve examining any detrimental effect produced following exposure of a developing organism during development. - Currently, developmental biology is one of the most exciting fields of study which will facilitate a better understanding of how toxic substances perturb the complex regulation patterns required for normal development.
  3. 3. Congenital Malformation - A physical defect present in a baby at birth, irrespective of whether the defect is caused by a genetic factor or by prenatal events that are not genetic. -In a malformation, the development of a structure is arrested, delayed, or misdirected early in embryonic life and the effect is permanent. These malformation can include heart defects, cleft lip or palate, Down syndrome spina bifida and limb defects.
  4. 4. Terms Monster – abnormal or strange animal or plant. From Latin monstrum omen, from monere to warn (abnormal infants reflect the future). Teratology – The study of malformations. From the Greek word for monster – teras.
  5. 5. Human Reproductive Facts • 50% of pregnancies end in miscarriage or spontaneous abortion often before pregnancy is recognized • 15% of couples of reproductive age are infertile
  6. 6. Phocomelia- A birth defect in which the upper portion of a limb is absent orpoorly developed, so that the hand or foot attaches to the body by a short,flipperlike stump.
  7. 7. Reproductive Toxicants  Endocrine disruptors • DDT, Dioxin  Heavy metals • Lead (decreased sperm)  Organic Solvents • Toluene, benzene  Drugs • Alcohol
  8. 8. Thalidomide as sedative  Introduced in 1956 (sleeping pill) and to reduce nausea and vomiting during pregnancy  Withdrawn in 1961 Discovered to be a human teratogen causing absence of limbs or limb malformations in newborns 5000 to 7000 infants effected Resulted in new drug testing rules
  9. 9. Methylmercury (MeHg)  Mercury (quick silver) is converted to methylmercury by bacteria  Methylmercury accumulates in fish, which are consumed by humans  In 1950’s the developmental effects of MeHg were first recognized in Minamata, Japan  Across the world there a regulatory agencies set limits the amount of mercury in fish that is safe to consume
  10. 10. Life-Long Effects of MeHg
  11. 11. Iraq Infant - Effects of Mercury