About 70 years ago, humans invented a whole class of chemicals that improved things like this and
this and this, but it turns out they're probably bad for us. And they can last for ever forever.
Forever chemicals are usually per and poly floralalkyl substances or
PFAS, which are thousands of chemicals known for being water, heat, oil, and corrosion resistant,
which makes them really useful in jet engines and firefighting foams, but also more common things
like fast food wrappers so that that burger grease doesn't soak all the way through. Or
microwave popcorn bags so that they don't catch on fire.
Here's a typical forever chemical called PFOA. It's a chain of carbons surrounded by fluorine
atoms. Carbon fluorine bonds are covalent, meaning the atoms are sharing electrons. And as far as
bonds go, covalent bonds are pretty strong. But on top of that fluorine is the most electronegative
element on the periodic table. That means that although it's sharing electrons with carbon
fluorine, will pull those electrons closer to it, creating partial charges.
That makes the carbon and fluorine even more attracted to each other and less likely to
react with other molecules like water, different oils or corrosive compounds,
and less likely to break down even under extreme temperatures.
So do these chemicals really last forever? Depends. In the environment,
we don't know how long they last. In our bodies they seem to hang out for at least a few years,
but some PFAS might hang out for decades, which is a lot longer than any other chemicals we're
regularly eating or drinking. They stick around by binding to proteins in our blood, which is
probably why we're finding them in a bunch of different tissues, especially tissues that have a
lot of blood vessels like our liver or kidneys. In people they've been linked to higher cholesterol,
endocrine and immune system disruption, and even a higher risk of cancer.
In animal experiment they've caused reproductive and developmental defects and
tumors, and also messed with liver, kidney and immune system function.
We're still trying to figure out the chemistry behind why these compounds seem to be so bad for
us. So in the meantime, it would make sense for us to scale back on using them, right?
Here's the thing. We're super reliant on these chemicals for kind of good reasons. They're
useful, convenient, and they can do a lot of things that most chemicals can't. Why don't we
just invent new chemicals that don't last forever? Problem is the chemistry that makes PFAS so useful
is exactly what makes them stick around. So it's really hard to create alternatives that won't
last as long, but will still do their job. Take GenX, for example, first used in 2009 as a PFOA
alternative, it's a similar structure to PFOA, but instead of this carbon, there's an ether group.
Small switch was supposed to make GenX less stable and therefore less likely to stick around in the
environment. But now it's being found in our drinking water and animal studies are showing
that it's probably just as bad as PFOA. And we still don't know what GenX could do in humans.
It's not like there's been no effort to phase out PFAS. It's just been really limited. In 2006,
EPA and eight major manufacturers agreed to eliminate PFOA and other related PFAS from
their products by 2015. But remember there are still hundreds of other PFAS being used today
and they are everywhere. I mean, look at this map. As of January, 2021, over 2300 sites in 49 States
showed PFAS contamination and there's no federal limit for how much of it can be in our waters. EPA
has been collecting data on PFAS toxicities and is hopeful that we're now in a place where some PFAS
regulation might actually happen. But even if PFAS are fully phased out and we're no longer using
them, we still have over 70 years worth of PFAS sitting around in our environment. So chemists
are trying to figure out how to remove it. A recent approach actually has to do with microbes.