EESA10H3 Lecture Notes - Lecture 4: Biomagnification, Bioaccumulation, Biomonitoring

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10 Apr 2012
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EESA10: Lecture 4
Chemical Hazards and Human Health
Chemical Hazards:
Endocrine disrupters: some chemicals released into the environment are very similar in their
properties (in there distribution and effects) to endocrine hormones.
o These chemicals mimic some hormones ; therefore our body sometimes confuses these
chemicals for the hormones
o They disrupt the hormone’s normal function in the body because the metabolism in our
body will be different when regulated by the chemical ( which can’t regulate normally)
o The effects can be direct and indirect:
Direct: chemicals bind to the hormone receptor. Some appearance of the gene can
be altered which may lead in the inaccurate protein production.
Indirect: can cause lower or higher level of the hormone production.
o These endocrine disrupters do not cause really severe effects in human adults. However,
fetuses are extremely sensitive. Example 1 : thyroid gland being one of the endocrine gland
produces T3 and T4 if the women has lower level of thyroid hormone (slightly lower), and
the women becomes pregnant it will tremendously affect the development of the fetus
(causes lower IQ, slower mental development). Example 2: DES prescribed to prevent
spontaneous abortion. Although the mothers and their kids were okay, the grandchildren
had problems (Listed on the slide).
Endocrine disrupters: Feminization of males in roosters. Bird defects caused by teratogenic
chemicals.
Besides physiological impacts, the behaviors were altered as well. Prenatally, PCB’s cause the
problems listed on the slide. This research is coming from animal studies and not human.
What are the body burdens?
o Every year 100’s of new chemicals are released into the environment.
o Those chemicals need to have approval, however sometimes the approval is not based on
research. Sometimes they are used even before we have a good risk assessment.
o There are no individuals on this planet without chemicals in their body.
o The quantity of these chemicals is called body burden. Our body is able to excrete some of
these chemicals, and it’s able to break down some of these chemicals. Therefore, the
amount is not stable over time; it’s changing due to our metabolism. The amount is not
distributed evenly in every part of our body. Arsenic has a tendency to be around the nails,
the skin. If we know where each of these chemicals tend to accumulate, they we know
which part to take a sample from. We have a very good knowledge to find out those
chemicals in our body. Computer modeling helps in this matter, they help model the
distribution of chemicals in the human body.
o If we biomonitor, and we see that a certain chemical is below detection, it does NOT mean
that the chemical does not exist in our body. Every year our body burden in terms of the
number of chemicals is rising. Who is responsible to monitor this? The government. People
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