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Lecture 4

EESA10H3 Lecture Notes - Lecture 4: Herbicide, Miscarriage, Lipophilicity


Department
Environmental Science
Course Code
EESA10H3
Professor
Jovan Stefanovic
Lecture
4

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Lecture 4: Chemical Hazards and Human Health
From Last Class
Transformation of nitrates to nitrites – in the book it says that it is happening in our body, professor
said here in class that it is happening in water (both things are true)
It actually depends if we have bacteria to do this transformation process in water
We always have them in our body but if we have in water this process will definitely happen
Other thing is what is the temperature of the water – if it gets warmer this process will speed up - i.e.
reheating spinach, if spinach is fertilized heavily with nitrogen fertilizers definitely will at least have
high amount of nitrogen – nitrates
When we first eat it fresh it won’t be very dangerous for us – not a risk
But if we reheat that spinach process transformation between nitrates and nitrites will speed up
because of that heat
Chemical Hazards
Why chemical hazards all contaminants all pollutants that we discussed until now are basically
chemical hazards – in water, in air
This lecture will be about the chemical hazards that are spread everywhere – in every medium be soil,
food, plants, meat, water, even in air
Endocrine disruptors
Chemical body burdens of industrial chemicals
Some chemicals that are body burdens are also endocrine disruptors and on the other hand endocrine
disruptors can accumulate in the body and we call them body burdens and they also do the same in
industrial because endocrine disruptors can be industrial
What is the biggest problem with these chemicals? We don’t know much about it especially not how
these chemicals affect human health
Most of our conclusions are assumptions or they are based on animal studies – many experimental
animals have a similar physiology with humans but not the same and who knows
That is what we have right now and science is working on that very hard so soon we will have some
better answers
What are Endocrine disruptors?
First you have to know what endocrine glands are
Picture posted to show what are the endocrine glands – these organs in our body produce hormones
What are the hormones? Chemicals that regulate many different processes that are very important
processes in our body and they regulate the processes in very tiny amounts
What do endocrine disruptors do to these functions? Hormones are carried through our body by some
receptor also some chemical that carry the hormone
Because of the similarity between the hormone and our pollutant our endocrine disruptor receptor is
confused
What is happening? Some genes can be altered because these receptors bind with DNA and alter the
appearance of the gene
What the genes do is regulate the production of different proteins and as a result of their changes and
alterations so changes are reliable to produce proteins are seen in a body – that is all about direct
effects
Also there are many types of indirect affects – production of the hormones, metabolism of the
hormones, transport of the hormones through the body

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What is specific for endocrine disruptors? Adults are not that sensitive (adverse affects are not very
visible on adults), fetuses are much more sensitive
Fetuses are more sensitive on the changes of the hormones than adults
Thyroid hormone affects mental brain development of fetuses
DES (diethylstilbestrol)
Problems are not seen if a pregnant mother is exposed to endocrine disruptor – not much problems
can be seen to your health
But the problem is changes in health and life of daughters and sons – we have to wait 20 to 30 years
to see this adverse affect until the daughter or son reach maturity to have own kids
An example of this is DES, a synthetic estrogen hormone that physicians prescribe to prevent
spontaneous abortion
Lasted for almost 30 years from 1948 to 1971
More than one million women took this in a period of ten years from 1960 to 1970
During the 1980s started facing significant increases in some health problems such as reproduction
organ dysfunction, abnormal pregnancies in daughters, reduction in fertility when daughters and sons
try to have their own kids, immune system disorders, and some type of carcinoma (adenocarcinoma)
This is lack of knowledge in a time when some medication is prescribed (when we discuss risk
assessment later we will come back to this problem again)
Mothers didn’t suffer that much but kids did
Endocrine disruptors – Health Implications
Other problems with the endocrine disruptors affects our health – feminization of the males, some
strange abnormal sexual behaviour, birth defects, cancer, altered time to puberty, and thyroid
dysfunction especially PCBs affect function of the thyroid gland
Endocrine disruptors – neurobehavioural effects
Besides these factors, affects on a sexual behaviour and sexual problems neural behavioural affects
are also seen
As a result of prenatal or postnatal exposure
What is the postnatal exposure? Mostly from the breast milk and other exposures
Gave example of PCBs – PCBs can greatly affect thyroid function but later as a neural behaviour
affect can be some problem with mental developments of the kids, learning disabilities, some poor IQ
tests later in life
In animal studies some impaired learning in non-human primates seen
Organophosphates affect directly brain development
Chemical body burdens
What are these chemicals – industrial chemicals many of them called body burdens because during
the time they accumulate in the body
Quantity of these chemicals accumulated in the body are called body burdens
Why is it difficult to do research in this area and to solve some of these problems?
These chemicals are not stable over time inside our body – partially they can be metabolized, changed
into other forms, degraded (but not much), most of them are very persistent, and some of them can be
execrated through the urine or other forms of execration
They are not distributed evenly through our body – some are accumulated in the liver, some can be
accumulated in the nails or skin, hair (arsenic particularly accumulates in the hair)
Because of that more organs are exposed and the concentration is higher
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