Does Microwaving Plastics Make Microplastics? Maybe Not

There were many reports in early August breathlessly warning about new research showing that microwaving plastics causes millions and billions of micro- and nano-plastic particles to form. Maybe you saw one of these reports online. They were tough to miss with headlines such as: “For the love of God, stop microwaving plastic” and “After seeing this terrifying study, we’re never microwaving plastic again.” Pretty strong statements — I hope the research is there to back it up.

It isn’t.

Looking through the published report, I was shocked to see something really important missing from the analysis. Something really important.

Before I get to that, let me explain the research. In brief, the researchers took some plastic containers, filled them with water, microwaved them, filtered the water, and then looked at what was filtered out. They determined the size of the particles, the quantity, and so forth. They put together some graphs — not very good ones, but I’ll talk about that shortly — and estimated how much of them someone might consume on a daily basis. Sounds pretty straightforward, right?

Where's the plastic?

Well, they left out some critically important information about the particles — where’s the plastic? Seriously, where is the plastic? With all the discussion and concern over these particles, how do we know they are plastic? We don’t.

The researchers did an extremely brief chemical analysis of the particles — Raman IR at a single wavelength and some x-ray diffraction — but that’s not enough to prove they are plastic. This merely showed that the particles are hydrocarbons, and crystalline ones at that. Those elements are common to a vast array of chemicals, even something as mundane as soap.

But if only plastic and water are being microwaved, then the particles have to be made of plastic, right? No, there can be other contaminants, such as the detergent that was used to wash the containers. It’s stated that Hellmanex was used. On the Hellmanex website, the manufacturer states that the detergent is “filtered to 1 micrometer and, therefore, is virtually free of solid particles.” (Unless, of course, you are extremely interested in studying particles that are 1 micrometer or less.) Even beyond the detergent, the surfaces of polymers are documented to readily absorb chemicals, with that absorption ruining many, many experiments of people not aware of or suspicious of this phenomenon.

The researchers really need to prove that the particles are plastic and not something else.

You could say that I’m being picky, that I found one little problem and am making the most of it, but just my initial reading of the report raised some other concerns.

The plot thickens

Many of the graphs make the mistake of not starting at zero. This is a favorite tactic of politicians. If the Honorable Senator Phil E. Buster wants to strenuously object to spending increases from the opposite side of the aisle, he can make a very small difference look huge by changing the axis so that it doesn’t start at zero. By starting the plot at $1 trillion, he can make even a $10 hike look like an out-of-control spending increase that must be stopped.

I expect graphs like this from politicians, not from people with a PhD or people attempting to obtain one. Seeing dubious plots like this makes me start to question how biased the researchers are and the validity of the results. And it makes all those silly headlines look that much more like exaggerations.

John Spevacek earned a B.ChE. from the University of Minnesota (Twin Cities) and a PhD in chemical engineering from the University of Illinois (Urbana). He worked in the plastics industry for 25 years for several companies, large and small, in the Minneapolis-St. Paul area.