Polystyrene cups and plates In light of lots of eating during the Holiday Season I was asked about the safety of drinking from styrofoam cups and eating from styrofoam plates because of the possibility of contamination with styrene. As is always the case, when it comes to matters of toxicity, we have to look at both extent and mode of exposure. Styrofoam, which is actually Dow Chemical’s name for expanded polystyrene, is made by polymerizing styrene, a liquid that is produced by reacting benzene with ethylene and then expanding the polymer with a blowing agent. The original blowing agents were freons which were phased out because of their ozone-destroying properties and have been replaced with the likes of steam, hot air and pentane. Since no polymerization proceeds to completion, there will always be a small amount of styrene left in the finished product. The question then is how much of this can leach into a food or beverage and how that amount compares with levels that are known to be toxic. Measurement of leaching is relatively easy, and studies have shown that 5-10 parts per billion of styrene can migrate into a liquid contained in a foamed polystyrene cup, which is about 2.5 micrograms. Can this present a risk? Almost all the toxicological data available about styrene stems from occupational exposure which is through inhalation of vapours of the volatile liquid. Even with huge exposure there is debate about effects, with many studies dismissing risk but a few concluding that styrene may be potentially carcinogenic. But occupational exposures are orders of magnitude greater than what people can be exposed to. There is widespread agreement that there are no effects attributed to occupational exposure to styrene at levels below 20 parts per million in air. During an 8 hour shift a worker inhales roughly 5 kgs of air, which means roughly 100,000 micrograms of styrene that could end up in the bloodstream from the lungs. Compare that with the 2.5 micrograms leaching out from the coffee cup, a good portion of which would not be absorbed. Furthermore, coffee beans contain styrene, naturally occurring. There is more styrene in the coffee than what leaches out from the cup! Beer contains even more styrene than coffee naturally, and cinnamon has thousands of times more. If you have concerns about styrene stay away from that cinnamon bun. (Of course there are far better reasons to stay away from the bun than styrene) A hamburger has far more naturally occurring styrene than any that can be picked up from the plastic plate on which it is sitting. So when we crunch the numbers, it is pretty clear that there is no issue about styrene leaching out from polystyrene cups or plates.
Posted on: Thu, 25 Dec 2014 18:16:51 +0000
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