There's a hidden winter ecosystem between snowpack and soil.

Wherever you step, you can actually reach down where your foot was just at and you should feel a space right between the ground and the snow and that's the subnivium.

It's Friday, April 12th and it's the best day of the week. It's science Friday.

I'm Cy-Fi producer Shishana Bucksbaum.

Contrary to what many people might think, insects don't just die out when the weather

gets cold. Many of them head underground and wait out the season in this subnivium.

New research sheds more light onto this mysterious zone. We'll get into that in just a bit,

but first guest host and sci-fi producer

Kathleen Davis discusses the biggest science stories of the week.

This week the EPA unveiled national limits for the level of P-FAS chemicals that are

acceptable in drinking water supplies. Those are the so-called forever chemicals

that have commonly been used for things like fire retardants

and also oil and water repellent coatings. And now are found just about everywhere.

Water treatment plants will now have to test and treat for several varieties of the chemicals.

Here to explain that and other science stories of the week is Sophie Bushwick,

senior news editor at New Scientist. Welcome back, Sophie.

Thanks for having me.

So tell me about these P-fast chemicals. What are they and why is this such a big deal?

You've probably heard of P-FAS chemicals,

or at least the nickname Forever Chemicals.

These are substances that are really, really hard to destroy.

And they've been associated with health issues,

...