This TED Talk features public health scientist Michael Hendrix, recorded live at TEDmed 2017.

Let's say that you wanted to conduct an experiment. In this experiment, you randomly assign people to live in blasting zones or in control locations without explosives going off over their heads.

They live in a community for years, just downwind and downstream from sites where tons of explosives are used, almost daily,

and millions of gallons of water contaminated.

With random assignment, you could carefully study the long-term health effects of living in these blasting communities without a bunch of annoying confounders and covariance.

Random assignment does wonders.

That would be a rigorous, powerful, scientific inquiry into the effects of these environmental exposures.

Of course, such a study could never be done. Most scientists wouldn't have the stomach for it.

The Institutional Review Board would never approve it. It would never pass human subjects review

because it would be unethical, immoral.

And yet, in effect, it is happening right now. In my mind, this prompts some questions.

What is the ethical obligation of the scientist who believes populations are in danger?

How much evidence is enough to be confident of our conclusions.

Where is the line between scientific certainty and the need to act?

The unplanned experiment that is happening right now is called mountaintop removal.

The abbreviation for it is MTR.

It is a form of surface coal mining that takes place in Appalachia here in the United States.

MTR occurs in four states, Virginia, West Virginia, Kentucky, and Tennessee.

Over 1.2 million acres have been mined in this way.

This is an area about the size of Delaware, but it

is spread over a footprint as large as Vermont and New Hampshire combined. The process involves

clear-cutting ancient Appalachian forests home to some of the richest biodiversity on the planet.

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