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TOXIC BOTTLES?
CHAPTER 3 INFORMATION LITERACY
On the trail of chemicals in our everyday lives
Do Now
1. 1. Obtain a copy of “But It’s Just a Bottle of Water…”
2. 2. Read Part I.
3. 3. Answer the question on page 2. (please be specific)
4. 4. Share your answer with a neighbor.
5. 5. Share your answer with the class.
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Toxins are chemicals that cause direct damage upon exposure.
Toxins fall into two categories, natural and synthetic.
NATURAL TOXINS ARE NOT ALWAYS SAFE.
Arsenic, a basic element, can cause cancer and nervous
system damage in humans.
Synthetic toxins are a problem because many are persistent chemicals—they don’t readily
degrade over time.
According to the EPA:
1,000-2,000 new chemicals enter the market each year
More than 80,000 chemicals are used in the United States
Regulation of toxins begins with risk assessment—a
careful weighing of the risks and benefits associated with any given chemical.
Federal agencies (FDA, EPA) are mandated with protecting us
from harmful chemicals. They can heavily regulate or ban those deemed dangerous.
In 2008, the National Toxicology Program (NTP) analyzed studies
about Bisphenol A, or BPA, which is used in metal food cans and many
plastic products.
NTP stated it had “some concern” about the effects of BPA exposure on brain,
behavior, and prostate glands in fetuses, infants,
and children.
Canada and the European Union had recently banned
the use of BPA in baby bottles and baby food cans.
Most NTP panelists felt the data were too uncertain to
warrant a ban, but they applied the precautionary principle, saying it would
be prudent for industries to look for a BPA replacement.
Toxicologists create a dose-response curve to track the
effects of a dose of a chemical, such as BPA.
Toxicologists use this curve tocalculate the LD50 (lethal dose50%), the dose that would kill
50% of the population.
The lower the LD50, the more toxic the substance. In this example, Substance A is the more toxic
substance.
What is the LD50 of Substance B?a) 10 ppmb) 31ppmc) 17ppmd) 7ppm
Clicker Question
Dose (ppm)
5 10 15 20 25 30 35
Per
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Substance ASubstance B
Which substance is most toxic?a) Substance
Ab) Substance
Bc) Substances
A & B are equally as toxic
Clicker Question
Dose (ppm)
5 10 15 20 25 30 35
Per
cent
age
of te
st p
opul
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n k
illed
by
dose
0
10
20
30
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Substance ASubstance B
BPA is an endocrine disruptor:It mimics a hormone or preventsa hormone from having an effect
Endocrine disruptors have different effects at low and
high doses, so dose-response curves and LD50s are trickier to
calculate—and a “safe dose” is harder to
determine.
As scientists debated the safety of BPA, and
regulatory agencies struggled, people were left
to decide whether they should purge BPA from their
lives.
We can use critical thinking skillsto analyze reports on potential
toxins and help us determine whatsteps we should take to be safe.
To make decisions, we need toknow whether a chemical hasthe potential to harm us and
how great that harm might be.
First, we need to evaluate thesource of the information about
the chemical.
Next, we need to look for logical fallacies in arguments or claims about the chemical, so we
won’t be misled.
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Be skeptical. Require evidencebefore accepting a claim as
reasonable.
Evaluate the evidence:
• Did the researchers look at human populations?
• How relevant are the studies?
• Is the claim from actual scientific studies?
Be open-minded. Identify your own biases or pre-conceived
notions and follow the evidence where it takes you.
Watch out for biases:
• Is the author promoting a specific position?
• Are they financially tied to a specific conclusion?
• Are they trying to support a predetermined conclusion?
There are rarely easy answers and
science is never as straightforward as we would like
it to be.
We are constantly uncovering new information and as our understanding
grows, existing information often becomes obsolete.
Science is incremental: Each study is a piece of the puzzle.
“Sometimes, if there’s enough momentum from the public,
regulatory change will follow. But more often than not, because of
the way the system works, it really has to start with individual
consumers deciding for themselves that they won’t
purchase or use certain items.”
--Sarah Vogel
