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ch 9_

3 Pages
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Department
Environmental Science
Course Code
EESA10H3
Professor
Jovan Stefanovic

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Chapter 9: Endocrine Disruption
- Tens of thousands of synthetic chemicals have been synthesized and released into our
environment for the past 50 years
- These chemicals can interfere with hormone function
- There is debate whether there are evidence of significant health risks to human
population from exposure to these chemicals
- There is research for the past few years demonstrating how chemicals in environment can
interfere with endocrine function
o For adults, there is the ability to recover
o In the fetus though, even minor changes in hormone levels can lead to lifelong
effects
- Endocrine disruption is gaining public attention and many public policy decisions today
involve chemicals known or suspected to interfere with hormone function.
Historical Background
- Endocrine disruption is not a new phenomenon
o Eg. 1930 test on animals demonstrated estrogenic properties of a number of
industrial chemicals (eg. Bisphenol A ± used in many plastics)
o Eg. 1950s studied feminizing effect of DDT in roosters
- In 1971, a synthetic estrogen diethylstilbestrol (DES) was used for pregnant women
o Linked to epidemic of vaginal clear cell carcinoma to young pregnant women in
use
o DES daughters had higher risk of reproductive and immunological abnormalities
o Sons were at risk of genital anomalities and abnormal spermatogenesis
o In animals (and possibly humans) it alters male/female typical behaviour patterns
o Fetus is most at risk, not the adult
Mechanisms of Action and Fetal Vulnerability
- Some pesticides and other industrial chemicals directly bind to or block hormone
receptors, therefore initiating or blocking receptor-activated gene transcription
(production of proteins)
- Other chemicals act indirectly by altering hormone production, hormone transport on
binding proteins, receptor numbers on target organs, or hormone metabolism.
- Polychlorinated biphenyls (PCBs)
o Interferes with thyroid hormone T4 by increasing metabolism of T4, interfering
with T4 delivery or interfering with conversion of T4 to T3
- Fetus more sensitive to low level exposures.
o Eg. Mild hypothyroidism in adult does not have long term effects but subtle
hypothyroidism during fetal and neonatal life causes disruption of
neurotransmitters, growth and development
Potential Health Implications
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Description
Chapter 9: Endocrine Disruption - Tens of thousands of synthetic chemicals have been synthesized and released into our environment for the past 50 years - These chemicals can interfere with hormone function - There is debate whether there are evidence of significant health risks to human population from exposure to these chemicals - There is research for the past few years demonstrating how chemicals in environment can interfere with endocrine function o For adults, there is the ability to recover o In the fetus though, even minor changes in hormone levels can lead to lifelong effects - Endocrine disruption is gaining public attention and many public policy decisions today involve chemicals known or suspected to interfere with hormone function. Historical Background - Endocrine disruption is not a new phenomenon o Eg. 1930 test on animals demonstrated estrogenic properties of a number of industrial chemicals (eg. Bisphenol A used in many plastics) o Eg. 1950s studied feminizing effect of DDT in roosters - In 1971, a synthetic estrogen diethylstilbestrol (DES) was used for pregnant women o Linked to epidemic of vaginal clear cell carcinoma to young pregnant women in
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