“It seemed like a good idea at the time” – Plastics additives


Today’s topic is a scary-nerdy one, endocrine-disrupting chemicals and choices. This column discusses the manufactured controversy, but so many people hear big scary science words and get confused.

Like a lot of problems, this one started as a solution to something else.

We’ve been here before. Lead in gasoline was a terrific solution to making gas burn more efficiently on cheaper fuel. (Remember the Fred Flintstone cartoon where the gas pump was a dinosaur named “Ethel”? That was a reference to tetra-ethyl lead.) Oops, turns out lead is bad for you and causes Tea Party activists brain damage. Well, that’s a problem, so we had to ban leaded gasoline.
Chlorofluorocarbons were a great invention, making possible safe refrigeration and air conditioning, so food spoilage was reduced. They’re so safe you can even use them in inhalers for asthma medicine. Unfortunately, they are also responsible for ozone depletion. The greenhouse gas issue is the same. Fossil fuels have done great things for the economy and bad things to the environment.

In all these cases, the theme is the same. “It seemed like a good idea at the time.” And, in general, the problem solved was more significant than the problem created. What causes trouble is when we as a society, or the people who can make those decisions, refuse to modify the problem-causing part of their product or process. Usually, there is a burden of proof: if there is possible harm, then it is important to show the harm is real and that the benefits of alleviating the harm outweigh the cost of finding a solution. So, a significant threat from lead in gasoline was bad enough to force a change, and the change was not that onerous. For CFCs, the change of formula to a less-dangerous substance (decomposing before it can get up to the ozone layer and/or chlorine-free) was a technological and engineering hurdle. But it’s been solved with relatively little pain.

A more serious problem happens when the solution involves a more dramatic shift or even abandoning the problem-causing issue. Thus, the tobacco companies fought a long and vicious fight against the tobacco/cancer link, because the best (and generally viable) fix is to avoid tobacco. Similarly with fossil fuels, where the stakes are extremely high. Vast profits, and globally severe consequences, have made a bitter battle since there isn’t an easy replacement.

So the question for the plastics industry is, will you devote your efforts to searching for alternative additives, or to fighting to keep your existing processes? And the question for opponents is, how can you make a scientifically valid and publicly persuasive case that these additives are dangerous? Current standard tests for toxicity aren’t good at analyzing subtle hormone effects that may not show up for a generation or even two, and where the contamination is so low and so widely dispersed that the “background” level of problems is significant. (Actually, the same questions apply to genetically engineered crops!)

Right now, it seems like market pressures are having a far more significant impact than regulation or law. Look at the water-bottle selection at Target and they are mostly advertised as “BPA-free”. But that doesn’t help with the non-water-bottle market.

So, why are these chemicals are even around?

Background – Plastic Basics

Plastics are terrifically cheap and versatile materials, but they don’t always have exactly the right properties manufacturers need. By mixing other chemicals into the plastic, its properties like color, flexibility, sunlight resistance, or ability to be shaped and molded can be tweaked.
Imagine a huge pile of cooked spaghetti noodles, without sauce.

Dump it out onto a cookie sheet so you can spread them into a thin layer. Let the noodles dry out in their tangled mass and you have a decent model of plastics. You can imagine that you might get different properties from thick linguini vs. thin angel-hair pasta, or maybe the more tangly Ramen noodles or the more transparent rice noodles. Maybe you’d get different properties if you let them air-dry vs. oven-drying, and how dry are you going to get them? All the way back to the original state, or more leathery-tough?
But sometimes, instead of the brittleness of dried noodles, you might need a little flexibility. So, you add some oil to the noodles so they won’t be quite so dry and can slide past each other al little, as the mat of dried noodles bends. That works great, but after a while you notice that the olive oil you used isn’t quite as good as it could be, plus it’s attracting ants. Since you weren’t going to eat this stuff anyway, go ahead and use motor oil instead. Perfect!
Or maybe you want the noodle-plastic to be harder – okay, throw a little glue in there, or maybe some wagon-wheel noodles to increase tangling.

The polymer (meaning long chain of many molecular units) industry has gotten really good at finding the exact type of noodles and oil for whatever product it wants to make. The “oil” additives are called plasticizers. These are substances that improve the flexibility of a polymer so that a vinyl raincoat or a PVC plumbing pipe (same noodles) can have very different characteristics.

So far, so good. We have a terrific invention, making useful products that make people’s lives easier and save energy. Remember when you couldn’t get soda in plastic bottles, just glass? Think about how much more fuel it took to haul that extra weight around. Or if you’re older, think about when plastic meant cheap and brittle.

So, what are these molecules, and what’s the problem?

The problem comes about because those little plasticizer or hardener molecules sometimes come out of the plastic and get loose. If you have a vinyl shower curtain, and it’s getting old, take a look at it and you’ll see that it’s still pretty flexible at the top, but the bottom is getting more stiff and crinkly. That’s because the plasticizers are slowly leaching* out as the plastic gets “washed” every day. Where do those plasticizers go? Down the drain, into the sewers, to the waste water treatment plant, and back into the environment. So, someone downstream from me, in maybe Dubuque, or St. Louis or Memphis or New Orleans is drinking coffee made with river water that has a few molecules of my shower curtain in it. (And that’s passed through my kidneys, but that’s another story….)


One of the more common plasticizers is dioctyl phthalate (right). Another substance of concern is the stabilizer Bisphenol A (left). These substances, as they leach out of plastics and into food or water, seem to sort of fit the same places in the body that some hormones do. This causes the systems that depend on those hormones to get confused and not work properly. Because plastics are everywhere and their breakdown products are present in tiny quantities, it’s hard to avoid exposure.



Thanks to the coders who finally fixed the bugs that caused the WordPress iPad app to crash all the time. Working on such a long post would have been incredibly frustrating with the buggy edition.


*pet peeve: homonym abuse. “Leaching” means gradually losing some substance or property; “leeching” means parasitically taking, like the animal does. Misuse homonyms and I’ll disrespect the content of your writing as well as its substance. Also, I wish autocorrect would learn that “its” (possessive) is different from “it’s” (contraction of “it is”). When confused about which it’s to use, it’s best to try substituting its short form for the long form “it is”. It is ridiculous to say, “my car is great, except for it is uncomfortable seats”, so it’s appropriate to use “its uncomfortable seats”, with no apostrophe. That one’s for you, Mom.

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