Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: Ian on 22/01/2009 09:30:02

Title: Are re-used plastic bottles harmful?
Post by: Ian on 22/01/2009 09:30:02
Ian asked the Naked Scientists:
There are several stores that if one reuses time after time the 1 & 2 litre
clear plastic (PFT) soft drinks bottle that the plastic will breakdown and has a carcinogenic affect on the body. Is this correct or not?

Ian Mackie

What do you think?
Title: Are re-used plastic bottles harmful?
Post by: dentstudent on 22/01/2009 09:36:55
Skeptoid #60 (

Today we're going to place our plastic water bottle, which has already been used three or four times, in the car on a hot sunny day, and then drink its noxious chemical contents to see if we get sick and die. The idea is that chemicals in the plastic get released into the bottle's contents when the bottle is reused, and especially if it's heated up.

So let's point our skeptical eye at the issue and see whether it has any merit. Do we need to be concerned about this? The only really fair answer is that it's a complicated question. "Plastic" is not a single compound. There are almost as many different types of plastic as there are types of substances contained by them. Some plastics do contain poisonous chemicals. Some plastics do leech chemicals into liquids. In some plastics, this process can be accelerated by heat. The reason for this variety is to provide the product distributor with enough choices that they can select a plastic type that's best for their product. This permits a distributor of drinking water to use a bottle that is absolutely safe to contain water for humans under the whole temperature range that the bottle is likely to be subjected to. But, put gasoline into that same bottle, and you might see that plastic dissolve away. Plastics are designed for their particular application, and misusing a plastic product can produce undesired consequences.

One time, in college, I was moving to a new apartment a block or two away. My brother and I had built a koi pond, and we needed to move the fish and store them long enough to build a new pond at the new place. We went out and bought a cheap plastic kids' wading pool. We put it in the garage and filled it with the hose, treated the water with all the usual fish-friendly chemicals, and walked the koi over in buckets and placed them in their new temporary home. Well, we learned a harsh lesson about chemicals in plastics. After a day or two the koi didn't look so good. Some of them died. Then all of them died. It was pretty horrible, because, and I'll spare you the details, they didn't look very good. We had no idea what the problem was. Was it the shock of being transported? Did we not add enough stuff to kill the chlorine? On a whim I called the manufacturer of the swimming pool and asked if they knew any reason why this would happen. They did. On products like this, they always add a mold inhibitor to the plastic. In this case, they used cyanide. For a children's pool, they add a safe low level of cyanide that's harmless to the children, but is enough to prevent mold from growing that would make the pool gross and unsightly. Evidently, a level of cyanide that's safe for a human is lethal for a fish, since they breathe it directly into their blood through their gills. The guy we spoke to was the company's head scientist, and he seemed to relish this rare opportunity to discuss his work. He went into all sorts of detail about their different products, and how they use the right plastic for each different job. Ever since then, whenever I work on a koi pond, I always call the manufacturer of any plastic products I'm using and talk to their chemists.

Here's the long and the short of it. Whether you're microwaving food in a plastic container, refilling your plastic water bottle, or making a koi pond, use plastic products that are intended for that use. The manufacturers do employ chemists to determine how best to package their products to ensure their safety, this process is strictly policed by the FDA, and this is always going to be more reliable than random information you read on the Internet or receive in a chain email.

And yes, it is our good old friend the Internet that seems to be the basis for this particular fear's place in popular culture. For example, there's one hoax email going around that says Sheryl Crow believes she contracted breast cancer from toxic chemicals by drinking water from a bottle that had been left in a car. Not true. Sheryl Crow doesn't claim this, there are no chemicals in water bottles that have been linked to cancer, and heating a water bottle to car temperatures does not leech anything into the water. There's another chain email that says freezing your water bottle, like so many people do, will leech dioxin into your water. Again, not true. No plastic containers designed for containing food or drinks contain dioxin, and colder temperatures stabilize plastics; it's heat that will accelerate their breakdown.

Most famously, a 2001 study by the University of Idaho found that reuse of plastic water bottles does release risky levels of diethylhexyl adipate (DEHA) into the water, which is potentially carcinogenic. This study was widely reported by the popular media and largely touched off the chain emails and most of the current perceived controversy. But is it true? No. Such a paper was written, but it was not a formal study. It was, in fact, merely the master's thesis of one student. It was not subjected to any peer review, and cannot accurately be characterized as a study performed by the university. It does not represent any position held by the University of Idaho. And unfortunately, it was not well performed research. DEHA is not classified by the FDA as a carcinogen, but more importantly, DEHA is not used in the type of plastic water bottles that the student evaluated. But it is used in many other plastics, and is present in a lab setting. "For this reason", concluded the International Bottled Water Association (which is, granted, not a very objective source), "the student's detection is likely to have been the result of inadvertent lab contamination." The FDA requires a higher level of scrutiny than that applied by the student writing his paper. DEHA is actually approved for food contact applications, but the fact that it's not present in the type of plastic that was studied, discredits the entire paper. But the mass media is often more interested in headlines than facts, so the dangers of reusing water bottles had no trouble becoming a fixture in pop culture.

Some people allege a conspiracy among distributors of bottled water, who know that their products are poisonous but who have analyzed the cost savings against the projected lawsuits from wrongful death and have concluded that it's more profitable to sell dangerous products. I do not find this theory very compelling. First, the products demonstrably do not contain the toxic agents claimed by the theory. Second, like all conspiracy theories, it's just too implausible that something of that magnitude could be kept secret for so long by so many people and so many victims, with nobody ever blowing a whistle or calling a newspaper. If corporate Men in Black were sent out to silence the whistleblowers and families of the victims, this would just multiply the number of reasons for someone to blow the whistle. This conspiracy theory just doesn't hold any water — pun intended.

There are absolutely plastics that are unsafe for containing or heating food. Look what happened to my koi. Or, let's say you sealed some food inside a length of PVC pipe and heated it over a campfire. Is that safe? I don't know, but I wouldn't eat it. Just like everything else in life, use products for their intended purpose, and you will not have any problem. Be assured that intended use of water bottles does include high temperature cycling. You will not get sick from any reasonable use of a water bottle or other food-containing plastic product.
Title: Are re-used plastic bottles harmful?
Post by: Chemistry4me on 22/01/2009 09:38:25
Most types of plastic bottles are safe to reuse at least a few times if properly washed with hot soapy water. But recent revelations about chemicals in Lexan (plastic #7) bottles are enough to scare even the most committed environmentalists from reusing them (or buying them in the first place).

Studies have indicated that food and drinks stored in such containers—including those ubiquitous clear Nalgene water bottles hanging from just about every hiker’s backpack—can contain trace amount of Bisphenol A (BPA), a synthetic chemical that interferes with the body’s natural hormonal messaging system.

The same studies found that repeated re-use of such bottles—which get dinged up through normal wear and tear and while being washed—increases the chance that chemicals will leak out of the tiny cracks and crevices that develop over time. According to the Environment California Research & Policy Center, which reviewed 130 studies on the topic, BPA has been linked to breast and uterine cancer, an increased risk of miscarriage, and decreased testosterone levels.

BPA can also wreak havoc on children’s developing systems. (Parents beware: Most baby bottles and sippy cups are made with plastics containing BPA.) Most experts agree that the amount of BPA that could leach into food and drinks through normal handling is probably very small, but there are concerns about the cumulative effect of small doses.

Title: Are re-used plastic bottles harmful?
Post by: Bored chemist on 22/01/2009 19:33:18
When the bottle is first in use it contains essentially water.
When you wash it it contains water.
When you refil it it contains water.
How is it meant to know when to start being poisonous?
Title: Are re-used plastic bottles harmful?
Post by: Chemistry4me on 23/01/2009 07:38:26
When it gets chewed and squashed and squeezed and bashed around.
Title: Are re-used plastic bottles harmful?
Post by: Karsten on 24/01/2009 21:57:51
You will not get sick from any reasonable use of a water bottle or other food-containing plastic product.

While I still feel that no one INTENDS to do any harm (at least in Europe and the USA), your statement is only true until someone finds out that what was scientifically true yesterday is not true any longer. Additionally, it ignores that profitable procedures are often not changed quickly. Just because one scientist says it is dangerous (and may even be right) does not mean the material will not be used any longer right away. Just because it cannot be measured today does not mean it is safe for consumption forever. I would be more skeptical. Big companies react slowly, people whose main interest is making money don't listen well, acceptable limits are adjusted up or down, etc.

We have had company owners ruin thousands of their own employees and leave them bankrupt and without any retirement savings after working for them for decades. This was done so they could get richer. People ruin other peoples lives to get wealthier. What makes you so sure (and unskeptical I dare say) that a similar mind-set cannot and will not appear in the food industry or agriculture?

I assume that those Chinese mothers who gave their children melamine tainted infant formula did not imagine that someone could be so cruel to add this stuff to milk to make more money. Sure, that was not in Europe or the USA, but those who added it to enrich themselves were humans. The difference is is a matter of degree, but not in principle. Josef Stalin once said "It's not the people who vote that matter. What matters are the people who count the votes." Regulation of industrial products could be viewed in a similar fashion: Product safety does not depend on regulations, it depends on the people who create and follow the regulations.
Title: Are re-used plastic bottles harmful?
Post by: FredL on 10/03/2010 18:22:49
I have a follow-up question.  I don't know how it is in the rest of the world, but, here in the US, a new type of plastic pipe is being used for household water plumbing.  It is called PEX (Cross-Linked Polyethelene).  Does anyone know if it contains BPA?
Title: Are re-used plastic bottles harmful?
Post by: Bored chemist on 10/03/2010 18:49:18
If PEX contains any BPA it's there by accident. There shouldn't be any.
Still your follow up question gives me a chance to clarify something that was said earlier.
When it gets chewed and squashed and squeezed and bashed around.
So, on the way to the store you bought it from then.
Title: Are re-used plastic bottles harmful?
Post by: daveshorts on 22/03/2010 15:40:41
Unless there is some kind of breakdown process (either with heat or UV) I would have thought that an old bottle would have less leaching out of it than a new one - There is going to be less leachant in an old bottle than a new one as some of it has already leached out.