Lecture 1B: Chemicals in Our Environment: What Is a Chemical and How Are We Exposed - Burke

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From the course by Johns Hopkins University

Chemicals and Health

118 ratings

Johns Hopkins University

Chemicals and Health

118 ratings

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.

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).

Lecture 1A: Chemicals in Our Environment: What Is a Chemical and How Are We Exposed - Burke7:21

Lecture 1B: Chemicals in Our Environment: What Is a Chemical and How Are We Exposed - Burke8:34

Lecture 1C: Chemicals in Our Environment: What Is a Chemical and How Are We Exposed - Burke21:25

Meet the Instructors

Dr. Megan Weil Latshaw, PhD
Co-Director of the Masters Programs in Environmental Health
Bloomberg School of Public Health
Beth A. Resnick, MPH
Associate Scientist
Health Policy and Management

So how are we exposed to chemicals?

I'm going to talk a little bit about it now.

And here in this picture, I want to show you kind of the classical framework,

or exposure pathway schematic it's called,

of how we might be exposed to chemical contaminants in our environment.

And here's a classic case.

So, imagine that's your house there on the left.

And these days it might not necessarily be a leaking drum of chemical waste,

but perhaps it's something like an oil well.

A fracking location where there is

the use of chemicals as lubricants in fracking operations or, in fact,

some of the byproducts of oil drilling getting into the groundwater.

So here in this picture, it tries to show the big kind of cycle of how things

leak into the environment and leech through the soil

into the groundwater, be carried through the groundwater and

perhaps then ingested either by somebody, who in this case has a well, or

by a population downstream who may drink from a river or a stream.

But if you could kind of follow this, imagine a chemical,

which is synthesized, gets delivered to the environment in some way.

Or it may travel through the air as a vapor or a mist,

settle down into the soil, then down through the soil into the water,

where it may also be picked up in the water table, not just as a drinking water

contaminant, but it might be picked up by wildlife.

So contamination that is in the water supplies or

the water ways might be taken up by organisms living in those streams and

amplified or brought to us through edible fish for instance.

Or, back to this diagram,

you see the, not that everybody has a cow in the background, but

just imagine you have fallout of a chemical from a smokestack nearby or

from some release nearby, or pesticide spraying.

And you have a cow eating the grass that's growing there.

This was a major concern for instance, when I was a kid.

We were terrified of the fallout from the nuclear bomb tests and

traveling all across the world.

And was our milk contaminated with strontium-90, a radioactive chemical?

So the picture really is to show you it's complicated and

we have to think about exposure.

So this conceptual model is a way to think about the multiple pathways

through air, through ingestion or drinking water, through eating, and

through direct contact that we can be exposed to chemicals.

And so there's the kind of conceptual world.

Now I want to bring you to Washington D.C.

and a picture that I took in my real world of environmental public health.

So this is actually a picture of a community that is very concerned about

arsenic and other components of, believe it or not, World War I chemical weapons.

This neighborhood is built on a site of an old army base,

where there was a testing of chemical weapon back in 1917.

And unfortunately, an incomplete cleanup before the neighborhood was developed,

way back in 20s.

And unfortunately also, in recent years, unexploded shells were discovered.

And as the EPA and others began to dig to try to remove these hazards,

working with the Department of Defense, widespread contamination of

the environment was revealed, so there's a major clean-up effort.

So take a look at that picture and imagine you live in a house there.

How might you be exposed to chemicals from the environment?

Well, it could be plants in your backyard that you're growing.

So it could be uptake by vegetation if there's arsenic in the soil.

It could be direct contact if you like to play in the dirt.

So nearby here is the university, and believe me, university students playing

sports in a nearby playing field might have a lot of contact with dirt.

Other ways you might be exposed perhaps are through the sub pump in your house,

perhaps some vapor exposures from other types of chemical contaminants

that might be there.

So, as you can see, it's pretty complicated.

Luckily, in Washington D.C.

they don't have many dairy farms here on the old weapons site.

But the exposure scenarios are complicated, because as you can also see,

when they began to excavate, look in that hole.

What do you see? You see a lot of water, right?

So nature likes to spread things around, and eventually,

anything we bury in the ground ends up in our water supplies one way or another.

It's a long process, but the environment is all interconnected.

So I thought you'd like to see that picture of the real world.

There's another cool thing there.

So you see that big blue tent?

Well, that kind of reminds me of the movie ET,

when they're trying to figure out about this alien from another planet.

It almost looked like that, because imagine I went over and visited that.

The crew working in full protection, digging through what

they had excavated from the ground there to see traces of things that might be

harmful from the old laboratories, little laboratory bottles and other debris.

So they created a pressurized environment to make sure that

off-site exposures didn't happen as they worked to remediate this facility here,

down in, believe it or not, Washington D.C..

Now, there are a lot of exposures that happen everyday that are a lot less

dramatic than chemical weapons from World War I, and a lot more common.

And I wanted to show you a couple of examples of those.

So imagine a newborn infant having a baby bottle, what's the exposure there?

Try to think of what the potential exposure might be.

Well, there might be contaminants in the infant formula.

Hopefully not.

There may have been contaminants in the water used to mix the formula.

Hopefully not.

But, very few people suspected that the plastics and the very fabric

used to make the nipple on that baby bottle nice and soft and

pliable contained a plasticizer that would have some chemical off gassing and

actually would expose that baby to phthalates.

So, there's lots of ways in the chemical world that we live in,

we are exposed to trace chemicals.

Recently we've had some strong recommendations, and

manufacturers have really tried to think how they manufacture products for kids.

Because we want to avoid the kinds of exposures that we now know about

through many plastics.

And then there are some other classical types of exposure.

I mentioned spraying of insecticides and DDT.

We all hate to get bitten by mosquitoes.

In many places, particularly when we have the emergence of a new threat like

West Nile disease will be at night using a fogger, as you see there on that pickup

truck, to spray certain low lying areas to control pests or control mosquitoes.

That's a good thing, right, but it's also something that might lead to exposure.

And then there's that thing in the right hand corner there.

What do you think that is?

And how might you be exposed there?

All right, so that's a can of tuna fish, I took the label off and opened it up.

And I know what you're thinking, right, oh tuna,

you read somewhere that there's mercury in tuna.

Okay so that's a chemical exposure, I'll grant you that.

But does anybody know the other potential exposure from canned goods?

Well, it turns out that most of our cans are also lined with something meant to

protect us from the harmful metals in the can, but also to increase shelf life

to protect us from harmful microorganisms that might grow and spoil food.

But the plastic kind of coating used there

contains a substance calls bisphenol A or BPA.

And we're very concerned that this compound

may have adverse affects on health.

So exposures are complicated.

They could be old traditional types of exposures, but

exposures happen at very low levels in many of the things that we do

in our everyday lives, from eating, to nursing, to breathing the air outside.

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