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Lecture 4

EESA10H3 Lecture Notes - Lecture 4: Persistent Organic Pollutant, Distillation, Mirex

Environmental Science
Course Code
Jovan Stefanovic

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Lecture #4: Chemical Hazards and Human Health
Wednesday, February 9th/2011
Chemical Hazards
๎€Our bodies produce hormones from endocrine glands
๎€Some chemicals are able to mimic hormones because they are similar in
chemistry and structure etc.
๎€When these chemicals enter our body, our body isnโ€™t able to differentiate whether
it is a hormone or a foreign chemical; thus the chemical ends up disrupting the
endocrine functions of the hormone it is mimicking
๎€**Note: The data collected with regards to this matter is mostly from animal
studies, not much from human exposure
Endocrine disrupters
1.Direct Effects:
๎€Bind to hormone receptors
๎€Alter the appearance of some genes
๎€Changes in the level of produced proteins (unwanted proteins are
2. Indirect Effects:
๎€Altering hormone production
๎€Altering hormne transport
๎€Altering hormone metabolism
๎€Fetus is more sensitive than adults
๎€If we, as adults are exposed to chemicals/endocrine disrupters, weโ€™ll be able to
recover; we can cope quite well
๎€On the other hand, babies would be born with many defects if exposed to
chemicals in the womb, because fetuses are very sensitive to these substances
DES (diethlstilbesteol
โ€ขSynthetic estrogen used by physicians to prevent spontaneous abortion (1948-
โ€ขAdministered for early pregnancy until 35 weeks
โ€ขMore than 1 million women took it between 1960-1970
โ€ขDaughters whose mothers took DES have increased incidents of:
oReproductive organ dysfunction
oAbnormal pregnancies
oReduction in fertility
oImmune system disorders
๎€Effects were seen some 30-40 years later in kids of the mothers who had taken
the drug

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๎€No immediate effects were observed, both mother and babies were perfectly
healthy; however when it came time for these kids to grow and have children
themselves, the daughters had all sorts of problems as outlined above
Health Implications of Endocrine Disrupters
๎€Endocrine disrupters mostly effect the reproductive system
oFeminization of males
oAbnormal sexual behaviour
oBirth defects
oAltered time to puberty
oCancer of mammary glands or testis
oThyroid dysfunction
๎€Thyroid gland produces two major hormones (T4 & T3); another
hormone produced by pituitary gland ๎€‚ TSH (needed for
production of T4 and T3)
๎€Lower levels of these hormones will have severe effect on the
development of the fetus
Neurobehavioural Effects of Endocrine Disrupters
โ€ขPrenatal and early postnantal (shortly after birth) exposures
โ€ขPCBs (polychlorinated biphenyls):
oImpaired learning in nonhuman primates
๎€may also be seen in children; mental development is slowed e.g. a
7-yr-old will draw a picture as though he were a 3-yr-old
oDelayed psychomotor development
oPoor IQ tests
oOrganophosphates โ€“ brain development
๎€directly affect brain; not learning, but actual structure of the brain
Chemical body burdens
๎€Every single person has chemicals inside of them, therefore chemical burdens
affect everyone
๎€From air, clothing, etc, everywhere
๎€Our bodies fight back, maybe absorb, excrete, metabolize and break these
chemicals down to lower the quantity that stays within our body
๎€ The amount of chemicals ingested/inhaled is diff. (far greater) than found when
our body is analyzed
Chemical body burdens = quantity of chemicals accumulated in the body
โ€ขNot stable over time
โ€ขNot distributed homogenously in a body
oaccumulate in certain tissues in certain parts of the body
oe.g. arsenic likes to accumulate in males in hair, nails???
oe.g. DDT etc? accumulates in fats โ€“animals with more fats accumulate
more chemicals in their body
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