Blue Shift: Will My Microwave Popcorn Bag Kill Me?

When a source of light moves toward you, its waves are compressed and pushed to a higher energy. We can’t always see this blue shift, but it’s there.

In the space of Internet science, there’s a lot of bad information floating around. In this biweekly column, Leigh Krietsch Boerner, chemistry PhD and science editor of Wirecutter, will tell you what you need to know on the science of home products, and what’s all around you.

If you’ve been paying attention to the news, some stories about the threats of chemicals used in food packaging may have led you to ask yourself an important question: “Have I been eating death popcorn?”

The answer probably depends on what you’re putting on that popcorn—lots of butter, a ton of salt—and how much you eat. A bad diet is much more likely to kill you than, say, exposure to trace amounts of fluorinated compounds through food packaging.

But although the chemicals in these cases pose little threat to you personally, you also have their effect on the environment to think about. Here’s what these compounds are, what has changed, and what, if anything, is actually worth your concern.

The Food and Drug Administration recently announced that it was banning the use of three perfluoroalkyl ethyl compounds, known as C8 compounds, in food packaging. Some food-packaging companies used to put these coatings on paper and paperboard to keep tasty grease stains from soaking through your pizza boxes and microwave popcorn bags. But notice I said “used to”: Longer-chain perfluoroalkyl ethyl–containing compounds, such as the banned three, haven’t been used for food packaging made in the US since 2011. The ban, effective January 14, 2016, is intended to keep companies from importing C8 food packaging from other countries. The FDA says that, given the available information, “there is no longer a reasonable certainty of no harm for the food contact use” of these three food-contact substances.

They’re called C8 compounds because they’re eight-carbon (or longer) hydrocarbons that have fluorine atoms instead of hydrogen atoms. Basically everything slips right off them, so they work especially well as nonstick and water-repellent coatings. The downside is that they stay in the environment for a long time, giving wildlife more of a chance to absorb them. An example of an eight-carbon perfluoroalkyl compound is PFOA, or perfluorooctanoic acid (that “octa” part means eight carbons—most chemicals follow naming conventions). PFOA, a carcinogen, has been in the news lately because it’s a persistent environmental pollutant and can cause birth defects in the children of people who drink contaminated water. This thing is quite nasty, to put it mildly.

The FDA writes, “The toxicological profile of extended perfluorinated alkyl chains varies with chain length,” meaning that the molecules with longer chains of carbons, eight or greater, stay in the environment longer. The ones with shorter chains, with fewer than six carbons, are more water-soluble and can wash away more easily instead of clumping together in one spot. It is important to note that PFOA, one type of C8 compound, is not one of the compounds used in food-grade packaging. Previously, manufacturers commonly used PFOA to make polytetrafluoroethylene, a nonstick coating, but it was due to be phased out of use by the end of 2015. The C8 compounds the FDA recently banned are like PFOA, but nowhere near as dangerous.

So, eight or more carbons? Out. Fewer than eight? A-OK. Going forward, companies are replacing the C8s with shorter-chain compounds, called C6s. Two examples of these are perfluorohexanoic acid (PFHxA) and 6-2 fluorotelomer alcohol (C6-FTOH), which both contain six-carbon chains.

C6 compounds seem to be less persistent in the environment and less toxic than their eight-carbon big brothers. In the Madrid Statement, scientists and environmentalists from all over the world declared that even though C6s seem to not accumulate in plants and animals (as a C8 compound did with cows near a DuPont plant), they still hang around in the environment for a long time or break down into compounds that hang around. C6 materials also don’t seem to work as well at their intended job, so companies have to use more of them to get the same product performance as with C8 materials. Because of the amount in use, switching to the shorter-chain compounds may not end up putting fewer fluorinated compounds into the environment.

In addition, you can’t find a lot of consumer safety info on all these C6 materials. PFHxA, a sub for PFOA, has been pretty well studied and is not a carcinogen like PFOA is. C6-FTOH is a bit more of a mystery, according to a toxicologist at the FDA Office of Food Safety Additives. Only a few studies look at C6-FTOH either in people or rats, and no studies at all have considered mice, which tend to be more sensitive to polyfluorinated compounds than rats. In short, the paper’s author says, we just don’t know that much about C6-FTOH yet. “Further study is needed” is a scientist cliche, but where C6-FTOH safety is concerned, further study really is needed. Here’s hoping that scientists will fill in these safety gaps soon so that we can know for sure whether C6 compounds are okay.

For real, though, heart disease was the leading cause of death in the US in 2013. So just go easy on the butter and salt.