Introduction
Evolutionary Health
Co-Evolution of Disease & Living Conditions
Diabetes
Malaria
Health Effects
What is Risk?
Environmental Risk
Risk Assessment
Risk Abatement
Risk Perception
Risk Management
Uncertainty & Other Features of Risk Assessment
Precautionary Principle
Appendix 1: Contaminants
Appendix 2: Environmnet & Reproductive Health
Exercises
Internet Links
Other Resources
Health & Risk System PDF
Printer-Friendly Web Version

APPENDIX 2 – CASE STUDY:
Environment and Reproductive Health

 

Special populations may be particularly susceptible to certain types of risks. Thus on days of “ozone alert” (high trophoshpric ozone due to traffic and weather conditions), older people and children are asked to stay indoors. Another gropu at risk from specific environmtnal agents are organisms – including human beings – during their early developmental stages.

“Reproductive health” includes fertility, sexual function, and fetal developmental health. We are just learning the effects of one huge class of synthetic chemicals – organochlorines – and their effects on fertility. DDT (Dichloro-diphenyl-trichloroethane) the pesticide, has been shown to have the effect of estrogen given to young male bids such as roosters. Young roosters treated with DDT are “feminized,” with severely underdeveloped testes, and even combs. DES, Diethylstilbestrol, invented the same year as DDT (1938) as DDT, was used to prevent miscarriages. Given to women with history of miscarriages in early stages of pregnancy, DES is a synthetic estrogen in1940’s and 50’s. Not thinking of long-term effects, the chemical company that produced it advertised it for all pregnancies, with a claim that it produced “bigger and stronger babies,” a claim that had no evidence. Doctors also gave DES for various other uses, such as suppressing milk production in new mothers, for prostate cancer, gonorrhea, and even to limit the height of teenage girls who were growing “too tall.”

In the ‘70’s it was discovered that female children of mothers who had taken DES during pregnancy developed a rare vaginal cancer as young women. Many of these women then had to undergo surgery to remove their uterus and vagina to limit the spread of cancer. It is suspected, but hard to prove that DES sons are at greater risk of various genital defects, had abnormal sperm, and perhaps had greater risk of testicular cancer as adults.

This stark case paints the picture of delayed effects from a critical exposure during fetal development. While the placenta protects the mammalian fetus to some extent, the period of organ development or organogenesis called the fetal period is the most susceptible in terms of birth defects (teratogenesis; terato=monsters). In humans, this period is for about 18-20 days since conception to about days 55-60 of gestation. This is why doctors have developed the role of no lower abdominal x-rays, for example, in young women, especially during the first 3 months of pregnancy. Figure 6, from Wilson shows the degree of susceptibility to agents during the prenatal developmental span of time.

 

 

 

Figure 6: Susceptibility to Teratogenesis


The type of malformation in the newborn changes depending on the time of exposure, even for the same agent., or due to lack of nutrition. Drugs and chemicals shown to be teratogenic in experimental mammals include: aspirin, caffeine, antihistamine, anesthetics, antibiotics, steroids, pesticides, ionizing radiation, nicotine, and alcohol. Fetal alcohol syndrome affecting children on women who drank heavily during pregnancy manifest in attention deficits and other nervous system problems manifested later in the life of the offspring.

About 20-25% of developmental defects are known to be genetic. Known environmental agents cause about 8% of defects. These include radiation; infections (e.g. rubella virus, syphilis); maternal metabolic imbalance (e.g. diabetes, vitamin deficiency); drugs; and environmental chemicals. The attention to environmental chemicals is important because their effect may be subtle, may interact with other categories, and are preventable.

 

References:

Theo Colborn, Dianne Dumanosky, and John Myers, Our Stolen Future. Plume (Penguin); NY, 1997

James G. Wilson, Environment and Birth Defects. Academic Press; NY, 1973.

 

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  ©Copyright 2003 Carnegie Mellon University
This material is based upon work supported by the National Science Foundation under Grant Number 9653194. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.