This course covers chemicals in our environment and in our bodies and how they impact our health. It addresses policies and practices related to chemicals, particularly related to how they get into our bodies (exposures), what they do when they get there (toxicology), how we measure them (biomonitoring) and their impact on our health. Most examples are drawn from the US.
The Chemical Revolution - Megan Latshaw
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From the course by Johns Hopkins University
Chemicals and Health
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From the lesson
Week 1: Welcome & Introduction
Start off this week with the peer assessment (we know, we know. . .how can we have an assessment before the course even starts, right?). We simply hope to gauge your initial understanding of the topics that we’ll cover (so grade easy).
Then we get into a quick overview of the course, a discussion of chemicals & how we are exposed (in three parts) and an introduction to chemical production & regulation. The module ends with a fun homework assignment: watch an eight-minute video and discuss amongst yourselves (and with us too).
Meet the Instructors
Dr. Megan Weil Latshaw, PhDCo-Director of the Masters Programs in Environmental Health
Bloomberg School of Public Health
Beth A. Resnick, MPHAssociate Scientist
Health Policy and Management
Hi.
This is Meghan Latshaw and I'm going to talk about the chemical revolution.
This is the idea that,
as we've explored it,
in a number of chemicals out there and our understanding of chemistry,
along with those amazing things that that has brought to our lives,
it has also brought some questions and some fears.
I'll cover common misunderstandings that surround chemicals and our health.
I'm going to emphasize again how important dose is in understanding
risk and I will discuss the downside that often comes from banning certain chemicals.
So let's start off by talking about the benefits of chemicals in our lives.
DuPont Chemical Company, which was where my father worked for decades,
had, as their slogan,
"Better Living Through Chemistry."
In this website from the American Chemistry Council of which DuPont is a member,
highlights how innovation in the chemistry industry has benefited our lives.
From solar powered aircrafts to pharmaceuticals,
the chemical industry has, in 2016 alone,
invested almost $100 billion in research and development.
Remember this slide?
Imagine life without plastic.
Here you see a picture of glass bottles.
Imagine glass baby bottles, IV bottles,
even phone screens or imagine life without laundry detergents.
Here you see a woman who's probably using some homemade soap to
wash out her laundry or imagine life without antibiotics.
There's a picture of an old advertisement
for a mixture that was supposed to treat cholera,
and also a picture of beds lined up from back in the TB days.
Or imagine life without chemotherapy or even toys.
We used to make our toys,
like this car pictured here, out of metal.
All of these products,
laundry detergent, scotch tape, antibiotics,
chemotherapy, plastics, all of these are possible because of chemistry.
As DuPont said, "Better Living Through Chemistry."
Let's shift now to debunk some myths about chemicals.
Some people have an irrational fear of chemicals.
Sometimes we call that chemophobia.
You can see that at the top of the slide.
But after this course,
I am sure you will not be one of these people.
As you can see in the silly meme on the left where it says,
"President Obama banned the use of dihydrogen monoxide to
torture detainee yet still allows it to be given to our children at school",
you can see it might be easy to scare people
about chemicals since they often have scary names,
like in this instance dihydrogen monoxide,
which literally means two hydrogens and one oxygen,
which is the same as saying H2O.
In other words, water.
Remember water is a chemical,
so are the molecules that make up our air.
Everything is a chemical.
So not all chemicals are bad.
In the right, you see a picture of vegetables that
say everything is grown without chemicals or pesticides.
But we know, again,
even water is a chemical.
So nothing can grow without chemicals.
A common misconception is that any natural product must be safe.
But from the title of this slide,
you should know by now that natural does not mean safe.
As my father would say, "Wrong.
Arsenic is natural.
So is snake venom.
Natural does not mean safe."
Similarly, green doesn't mean healthy.
You can see a label on this slide that says Eco-Green.
Even though green chemicals might break down quickly in the environment,
they can still impact our health if humans come into contact with them.
Green does not mean healthy.
Looking at this slide,
there's two that mentioned toxic, non toxic.
I'm not even sure what that means since everything is toxic at a high enough dose.
The USDA organic label on this slide however is highly regulated.
It means that certain man-made pesticides were not used in the production of the food.
Labeling is so important as is our understanding of what these labels mean.
I once wrote to Burts Bees who is famous for
making products in the US that are considered organic and natural.
And I wrote to them because a lip balm that I bought said, "Chemical Free".
Now, you've heard me say it,
you should know by now that this is impossible because everything is a chemical.
The bottom line is that there are so many labels out
there and they're basically meant to make you buy something.
So, think about them before taking them at
face value and remember natural does not mean safe.
A second takeaway message from this class is that according to
traditional toxicology the dose makes the poison.
The title of this slide you can see that this quote,
the "Dose Makes the Poison",
is attributed to Paracelsus,
who lived back in the 1400 to 1500.
So, we've known this for a long time.
Here's an example. On the left there's a Scientific American article.
It basically talks about a 28 year old woman who competed in
a radio station contest called Hold Your Wii for a Wii,
which for those of you who don't know a Wii is a Nintendo electronic game console.
So, this woman drank six liters of
water in three hours and was not allowed to use the bathroom.
While she was at the station, she vomited,
and then, she went home with a terrible headache, and later died.
Most people don't think of water as being toxic
but six liters in three hours clearly can be.
Now, on the right,
you see a picture of sodium cyanide and the word "poison" underneath it.
A single tablespoon of potassium cyanide would kill most people.
Compare the dose it takes for water to be lethal,
which is six liters,
to a dose for cyanide which is one tablespoon.
The dose makes the poison.
Also, I want to note,
cyanide is a naturally occurring chemical.
It's found in many plants and has actually been used in
conventional warfare and in poisoning for two millennia.
So, the message again is remember,
natural does not mean safe.
What often happens is people get
nervous about a single chemical and they say, "Get rid of it."
You heard an example of this in the video of
Zephany Jordan who talked about formaldehyde precursors in baby shampoo.
The problem is we often know even less about
the chemicals that are used to replace the chemicals that we wanted to get rid of,
and we may find that
those replacement chemicals are even worse than the original chemical.
One example of this relates to the picture associated with this course.
You can see it here.
It's a baby reaching first to pick up, and in the background,
you see a chemical formula,
and that's the formula for BPA also known as bisphenol A.
It affects the reproductive systems of laboratory animals,
and when folks found out that it was in baby bottles, they freaked out.
There was such outrage that manufacturers started taking
BPA out of the bottles and labeling them BPA-free.
So folks thought that was a victory.
They thought "Oh, now I'm safe."
But they replaced the BPA with BPS and BPF,
which we know even less about than BPA.
So, are we really safer with our BPA-free bottles?
Who knows? Another example is formaldehyde in vaccines.
People might get really upset by the idea that something used to preserve
old biology specimens and known to cause cancer is in vaccines.
But we have to think about it in perspective.
On the right, you can see that a pair
naturally contains 12,000 micrograms of formaldehyde,
whereas, vaccines contain less than one percent of that amount.
Remember what we talked about;
the dose makes the poison.
In this case, the use of formaldehyde assures that
the vaccines don't contain any microbes that could harm us,
or even lead to death.
Back in the day, asbestos was seen as a miracle.
It never got hot and it was incredibly flame-resistant.
On the left, you can see a cartoon, and it says,
"Trade is brisk in some lines," and it shows at the top a sign,
"Asbestos curtains for sale," and there's people scrambling to buy them.
"I'll take this one." "I want two."
Then, there's another sign on the wall, "Can't burn 'em."
We even put asbestos in children's pajamas in order to keep them safe,
but then, we found out it causes cancer.
As you can see in the danger sign taped to a door on the right says, "Danger asbestos.
Cancer and lung disease hazard.
Authorized personnel only."
So, we replaced asbestos with brominated flame retardants,
which were added to mattresses and couches
to slow down fires that might otherwise spread.
Sounds like a great idea.
Let's prevent the spread of fires,
but let's not use asbestos because we now know it causes cancer,
and let's use these other chemicals that we don't know much about.
Here, you can see a woman talking about CertiPUR-US Certified Foam.
This is basically a new effort that is not
using brominated flame retardants anymore in foam,
because we've now found an association between
these flame retardants and altered neurological development.
By the way, there's some really interesting stories behind how this industry,
the brominated flame retardant industry,
got started and policies that arose in order to protect public health.
So, you're interested in learning more about it,
you can Google tobacco industry flame retardants if you want to learn more.
So that's it.
The purpose of this lecture was to show that the chemical revolution that introduced
all sorts of new chemicals into our lives was a good thing;
that not all chemicals are bad.
Many have helped humankind and improved our lives and our health.
Remember, better living through chemistry.
The second purpose of this lecture was to remind
you that natural does not necessarily mean healthy.
The third takeaway message is the dose makes the poison.
You can be exposed to some chemicals in small doses and not have to worry.
Lastly, I want you to remember that banning or substituting
one chemical for another sometimes just creates new problems.
Thank you for your time.
If you have any questions,
you can email me at mlatshaw@jhu.edu.
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