It’s more than impressive to think about how pervasive plastic use has become. Despite only being around for the past century or so, plastics have become staple in every day life. From grocery bags to drinking bottles, IV bags to the teflon on non-stick pans, plastics really do make everything possible. They’re incredibly versatile: the final product can very in hardness, be shaped in almost any way imaginable, and is chemically inert, all for a bargain basement price. Really, it’s a magical substance.

Its everywhere…

Unfortunately, the very properties which make it so useful in so many industries are the same properties which make it one of the worst physical pollutant in the world. Despite recycling efforts, a large amount of plastic ends up in garbage cans (if we’re lucky) or littering the environment. Since the 1950s, one billion tons of plastic has been discarded by people. The ecological impact of all this plastic is devastating. Plastics make up at least 2/3 of marine litter, killing animals of all shapes and sizes. It takes over 450 years for a plastic bottle to degrade – that’s at least twice as long as it takes for an aluminum can to dissolve. And if that’s not bad enough, the forms of plastic that do degrade faster are even worse. Polystyrene – better know by the brand name “Styrofoam” – has been shown to degrade easily in seawater, but it leaves behind potentially damaging styrene molecules.

But this isn’t an article about the ecological impact of plastics – there’s enough on that for an entire book. The key question isn’t how does it affect the environment, it’s how does it affect us.

Plastic Chemistry 101

Plastics are very complex compounds chemically. They are made from combining various carbon-based compounds, called “monomers,” to create long chains, called “polymers.” The most common forms of plastic used are polyethylene, polypropylene and polystyrene. Their names explain what compounds are used to create them – polyethylene is made from strings of elthylene, polypropylene from strings of propylene, and polystyrene from strings of styrene. Another well-known plastic is polyvinyl chloride, better known as PVC. Another kind of plastic, polycarbonate, is made from bisphenol A (BPA), and is used extensively in our households in items like bottles, plastic glasses, tupperwares, even DVDs and CDs. There are actually hundreds of different types of plastic, all made from different carbon-based monomers. The different compounds lead to different properties, including different levels of hardness, flexibility, and heat resistance.

PVC Pipe, one of the most familiar forms of the common plastic

But there’s a lot more that goes into plastics than just the monomers. Other compounds can be added to further change the textural properties of the plastic. PVC, for example, often has phthalaes added to it to make it less brittle. These compounds are referred to as “plasticizers,” as they add to the fluidity of plastics. Some plasticizers eventually evaporate from the plastics they’re put into – for example, the “new car smell” we associate with a brand new Mercedes is caused mostly by trimelliate plasticizers evaporating from the car’s interior. Others leech out of plastics as they degrade or are exposed to extreme conditions, like the heat in microwave ovens. Bisphenol A is added to certain PVC to make it harder, and other compounds, like brominated flame retardants, make plastics less vulnerable to heat.

Luckily for us, most pure plastics that are free of such additives are fairly harmless. They are ecologically devastating because they take forever to degrade and ensnare marine and terrestrial animals, but as far as human use goes, they’re non-toxic. Unfortunately, most plastics we use aren’t pure. And even still, the compounds that make up pure plastics can be toxic, as the much more toxic, single monomers can be trapped in the plastic-making process only to be released later into our foods.

So what’s the harm, exactly?

What exactly do the chemicals in plastics do to the human body? A lot. And it depends on the compound. I’m going to dive into some of the big players and why you should know about them. First up is the one you’ve probably heard the most about: Bisphenol A, or BPA.

Bisphenol A

If you’ve paid attention to the news in the past year, you’ve probably heard a lot of talk about Bisphenol A. Like I mentioned before, it’s a monomer used to create polycarbonate plastics, labeled type 7, and also as a plasticizer in type 3 PVC plastics. It can leech out of either kind into food and water placed in contact with them.

Plastic ‘resin’ code #7

BPA is what is called an “endocrine disruptor“. Our endocrine system is the system of signals and hormones which constantly communicate information between cells. The problem with BPA is that it looks similar enough to estrogen that our bodies can’t really tell the difference. Because estrogen is such an important hormone in our bodies (in men as well as women, by the way), the potential affects of BPA on our bodies are severe and range widely.

The first problem is that, so far, we’re not really sure how much BPA it takes to have a negative effect on our bodies, especially over a lifetime. It’s clear that a high, acute dose is bad, but where the bottom threshold is for humans is unclear. It wasn’t until 1997 that low-dose effects on laboratory animals were reported, though since then a variety of studies have used animal models to warn of the dangers of BPA.

In animals like mice and rate, doses as low as 0.025 µg/kg/day can causes permanent changes to the genital tract and predispose breast cells to cancerous activity. Between 1 and 30 µg/kg/day can lead to long-term reproductive changes like earlier puberty and longer periodsdecline in testicular testosterone, and prostate cell changes indicative of cancer, as well as behavioral effects like decreased maternal instincts and even reversed sex roles. Basically, BPA exposure can affect almost every system in our bodies, particularly those impacted by reproductive hormones.

Older polycarbonate bottles all contain BPA, thanks flickr user vitameatavegalynn

Think of anything that makes you manly or womanly – the shape of your body, your muscle mass, neurological systems – all are vulnerable to BPA’s toxic effects. Over 100 studies have been published which reveal different toxic impacts of BPA. The question isn’t “is it harmful,” it’s how harmful, and more specifically, at what dose.

After all, anything can be toxic when in excess. You can even die from drinking too much water. The big question now among scientists is what level of exposure to Bisphenol A is low enough that it won’t cause major, negative side effects in most people. They also are looking into how much BPA we get exposed to and from where. What they’ve found is that BPA exposure is particularly high in infants, when, of course, it has the most side effects. Developing people and animals are much more strongly affected by hormone levels and disruptors like BPA which mimic those hormones in our bodies. The younger the person, the more of an effect a lower dose of BPA has on them – which is bad news for pregnant moms and newborn infants. Levels that are safe for adults are likely to be unsafe for them. But, to date, no study has looked specifically at the effects of different doses of BPA on in-utero or newborn infant biology.

Exposure and Effects Still a Mystery

So what, you ask, is our daily exposure anyway? Well, we’re not entirely sure. Studies have found that infants can consume up to 13 µg/kg/day when fed formula from polycarbonate bottles. Remember – that’s a dose high enough to cause serious reproductive changes in animal models. Adults can get similar levels of BPA exposure from single servings of canned goods (they use a plastic lining to protect the metal) and some from plastic containers, particularly those that are warmed up in the microwave or run through the dishwasher. The EPA has said that 50 µg/kg/day is normal and safe, but recent studies in our closest relatives have shown that level causes adverse neurological effects, even in adults. And even worse, scientists have found that monkeys given 8 times that dose – 400 µg/kg/day – have blood concentrations lower than the average human being. It’s likely, therefore, that we’re getting a lot more BPA than we think, and its probably worse for us than we thought.

The first study of BPA’s effects on humans wasn’t published until September 2008. It looked at urine BPA levels in around 1,500 people to see if they correlated with disease. The researchers found that increased BPA levels were significantly associated with heart disease, diabetes, and high levels of certain liver enzymes. They concluded that “higher BPA exposure, reflected in higher urinary concentrations of BPA, may be associated with avoidable morbidity in the community-dwelling adult population.”  Many researchers claim we have known about this problem for far longer:

Despite the overwhelming evidence of the dangers of BPA, the FDA recently announced that it still deems the compound “safe.” This preliminary decision was attacked by scientists and consumer groups who said the FDA was being biased towards the industry and not taking into account the science and the safety of the American Public. Canadian officials have already banned BPA use in baby bottles, finding that levels were simply too close to unsafe for formula fed infants, a decision which lead to many leading companies like WalMart and Toys R Us to stop selling them in Canada and the U.S. In June 2009, the FDA decided to “reconsider” its assessment of BPA safety levels, though a new finding has yet to be announced.  Rumor has it that FDA’s next decision on BPA should come down the pipe in late November.

What To Do:

In the end, my recommendation is to steer clear of bisphenol A-containing plastics as much as possible, especially when it comes to your kids. Here is a list of easy ways you can avoid BPA:

  • Be wary of all plastics labeled type 7
  • Absolutely, positively, do not buy polycarbonate baby bottles
  • Keep baby from putting hard plastics (like toys) in their mouths
  • Replace older polycarbonate ‘Nalgene’-type water bottles with stainless steel bottles
  • Replace canned foods, especially acid rich tomatoes, with those bought in glass
  • Microwave your food in glass or ceramic containers instead of plastic ones like tupperware
  • Use metal colanders in place of harder plastic ones for straining boiling water
  • Hand-wash hard plastic kitchen cups and utensils in place of hot dishwasher cleaning

Sadly, BPA is only one of many toxic chemicals that can leech out of plastics. Next, I’ll tell you all about brominated flame retardants, called PBDEs, which unlike BPA, are found in almost every form of plastic.