- Environmental Health -

Picking Your Way Through Plastics

For storing food and toting beverages, plastics are hard to beat. But not all plastics are right — or safe — for all jobs.

Takeya water bottles

Attempt to tally up your daily encounters with plastics, and you’ll probably lose count before lunch. From the plastic bottles and tubes that hold your toiletries to the plastic surfaces that pervade your car, office and home, odds are you’ve touched a dozen different kinds of plastic well before you’ve even checked the first item of your to-do list – probably using a plastic pen.

Plastics are especially pernicious wherever food and drink are found. There’s a good chance that the milk for your coffee came from a plastic jug, and that any bread or cereal you ate was stored in a plastic bag. Did you nuke your lunch in a plastic container? Guzzle water from a plastic bottle during your workout?

There’s a good reason for all this plastic – it helps keep foods fresh, handy and portable. It’s also durable and lightweight. And manufacturers love that it can be molded into an incredible variety of shapes, weights and textures. But plastics are made of petroleum-based chemicals that, in most states, are definitely not meant for human consumption. Which makes some experts nervous about the plastics that touch your food.

For the most part, the chemicals in finished plastic are stabilized, meaning they stay bonded together and can’t migrate into the food they contain. But recent research indicates that under certain circumstances, trace quantities of these chemical cans leach into food or liquid. The concern is that when exposed to heat or reused beyond their intended life span, plastic compounds can break down, mix with your food or drink, and be ingested. Once inside your body, critics say, such compounds increase your risk for cancer and other problems.

So how much reason is there for concern? Unfortunately, not all scientists agree. Certain informed experts claim that plastic can dangerously taint our food and water, while others insist there’s nothing to worry about. The truth, as in almost everything else, probably lies somewhere in the middle.

Not Created Equal

The first thing to keep in mind about plastics is that they come in different grades, and each grade has specific recommended uses. From a food-safety perspective, problems tend to arise when plastics are heated or used for a purpose other than what they were designed for.

Plastics are made from polymers, a family of chemical chains made up of such elements as carbon, hydrogen and oxygen. Some polymers are resistant to erosion by chemicals like bleach. Others insulate heat and electricity.

Polymers are suited for different uses depending on their chemical makeup and characteristics. For example, polypropylene’s high melting point makes it ideal for hot-liquid cups and containers that store and heat leftovers, such as GladWare and frozen-food trays. Polypropylene’s cousins, however, can’t always take the heat. One of the most common plastics is polyethylene terephthalate, or PET. It forms a clear, lightweight and almost indestructible kind of plastic – an optimal material for manufacturers of beverage bottles as well as plastic wrap. But PET may break down when exposed to heat, some experts contend, causing chemical compounds in plastic containers to migrate into food or liquids.

You can tell if a bottle is made with PET by looking for the recycling logo on the bottom or side of the container. Items made with PET are marked with a triangle of chasing arrows containing the number “1.” A triangle containing “5” correlates to polypropylene. Other numbers identify other kinds of plastics.

Wash, Rinse, Don’t Repeat

Bottles made from PET in particular have been scrutinized by researchers – and not exclusively for leaching. In a study published in 2002 in the Canadian Journal of Public Health, researchers at the University of Calgary analyzed samples of drinking water found in the personal water bottles of 76 elementary-school students. The researchers found significant bacterial contamination in roughly two-thirds of the samples, including fecal coliforms, which are found in human waste. The most likely source of the bacteria was unwashed hands, the researchers reported. Although some of the children brought new water bottles each morning, many simply refilled the same container day after day without washing it.

The American Plastics Council (APC) was quick to emphasize that poor cleaning, not plastic, was the culprit. “Plastic bottles are no more likely to harbor bacteria than other kinds of packaging or drink containers,” the APC said in a statement. “The fact that the bottles in this particular study were plastic is irrelevant.” Consumers should clean drinking containers with hot, soapy water between uses and let them dry thoroughly, the APC advised.

That seems like smart advice: Washing bottles between uses certainly makes for good hygiene, and reusing them helps reduce nonbiodegradable waste. But a 2001 study by a University of Idaho researcher suggests that reusing even clean PET bottles might be problematic. Deena Lilya, a graduate student in environmental engineering, found that using a PET bottle more than once may cause the plastic to become chemically unstable. As PET breaks down, compounds may be released and migrate into the water. Among the migrating compounds in PET is a plasticizer, diethylhexyl adipate, or DEHA, that some believe is linked to cancer.

Lilya tried to replicate the conditions to which a typical bottle might be subjected by a user, varying the temperature, light and agitation. Examining water taken from the reused bottles, she found traces of four compounds, including DEHA.

What’s more, the longer the bottles were reused, the greater the amount of chemicals in the water. Lilya deduced that DEHA had leached from the plastic into the water. “Only PET bottles reused for short periods of time – less than one week – and protected from light and heat, did not show increased migration,” she says. (The bottles were not exposed to heat from repeated washing in hot water or placed in a dishwasher.)

The Idaho study has yet to be published, and sev eral critics have dismissed the research as flawed. The U.S. Food and Drug Administration (FDA), in particular, remains skeptical. PET bottles don’t contain DEHA, according to FDA consumer-safety officer Kenneth McAdams. The FDA also noted that DEHA isn’t even used during the PET-manufacturing process.

So where did the DEHA in Lilya’s samples come from? Researchers still don’t know for sure. But it turns out that DEHA, while not an ingredient in the plastic used for water bottles, is used in caps and seals for many food and beverage containers, suggesting a source for the migrating compounds.

Such debate is beside the point, says Lilya’s adviser Margrit von Braun, PhD, head of the University of Idaho’s environmental-science program. In general, she says, too little is known about the health risks associated with leaching and plastics to be sure about much of anything. “The fact is,” von Braun asserts, “a lot of these compounds [in plastics] have not really been adequately studied in terms of their human health effects.”

A Safer Alternative?

If you’re concerned about PET plastics, you might think you’re better off reaching for the reusable and sturdy polycarbonate plastic bottles popular with athletes and hikers. (Nalgene is perhaps the best-known producer.) Polycarbonate, a strong, lightweight, heat-resistant plastic, is used to make other items, too, including reusable food containers and baby bottles. But don’t assume that it’s the Holy Grail of plastics, says Frederick vom Saal, PhD, a professor of biological sciences at the University of Missouri-Columbia and one of the leading plastics researchers in America.

Vom Saal has conducted numerous studies that convince him that polycarbonate bottles may leach a chemical called Bisphenol A, or BPA, as they age, making them unsafe. Sunlight and heat hasten this process, he says. And even traces of BPA can be toxic to humans, he asserts.

BPA is believed to be an endocrine disruptor, a compound that confuses the endocrine systems of humans and animals. Endocrine disruptors have been found to mimic sex hormones like estrogen and testosterone, for example, potentially interfering with development and reproduction. In animal studies, BPA has been shown to contribute to an increase in breast and prostate cancers, reduced sperm production and chromosome damage, which can result in miscarriages. A 2003 study by a researcher at Case Western Reserve University School of Medicine found that very low doses of BPA damaged the egg cells of female mice. (The mice lived in polycarbonate cages and drank from polycarbonate water bottles that had been washed and reused.)

The FDA, however, currently condones small amounts of BPA in food packaging and other products. Why? “The culture of the FDA is that to admit a mistake is unacceptable,” says vom Saal. “The government has told people this is safe. Regardless of the science, they are going to hold on to this until the house of cards collapses.”

The plastics industry, of course, sees it differently. “The safety of BPA has been extensively tested … for more than four decades,” according to a statement issued by the American Plastics Council in 2003. It went on to say, “Consumers would have to eat more than 500 pounds of food and beverages in contact with polycarbonate plastic every day of their lives to exceed the reference dose for BPA.” Vom Saal, meanwhile, says the industry has no evidence to support such a claim.

To Use or Not To Use

So what should you do? That depends on whose arguments sound most convincing to you. But there are precautions that you can take if you want to avoid risks. Consider these basic, better-safe-than-sorry strategies:

  • Consider plastic’s purpose. Containers made from any type of plastic are great for storing lunches and leftovers. Freezing them is OK, too. But you should generally not expose PET plastic to high temperatures.
  • Double-check the number on plastic containers you plan to heat, and don’t nuke margarine tubs or carryout containers. The best solution for heating food? Opt for glass or ceramic containers.
  • Adopt a one-and-done philosophy. When it comes to commercial water bottles, the jury is still out as to whether PET bottles can stand the heat of hot washing, in the sink or dishwasher. But high temperatures may be a culprit, so play it safe and limit yourself to a single refill. In between uses, clean the bottles by hand in warm, soapy water and let dry completely before using to reduce bacteria buildup
  • Pump up with polypropylene. For sports bottles, switch to polypropylene (5). As of yet, no studies have linked this plastic and the leaching of harmful substances. High-density polyethylene, or HDPE (2), and low-density polyethylene, or LDPE (4), are other good choices, says Case Western’s Hunt.
  • Know the rap on wrap. Some experts worry about plastic wraps, especially those that contain DEHA, which helps the plastic cling to container surfaces. It’s true that DEHA can migrate into food that comes in contact with plastic (particularly fatty foods like meat and cheese, where the fat speeds up migration), but the FDA, at least, considers the levels so low as to be negligible. Want to play it safe? Use plastic wrap as you see fit, but never microwave it.

For busy but conscientious consumers, hard and fast rules on plastics are difficult to come by. Are these guidelines sufficient for reducing risk? Or should you instead avoid all plastics, as vom Saal recommends? The answer, of course, depends on your approach to health. But the most logical position might be a bit like plastics themselves: sometimes flexible, sometimes tough – if not always clear.

Alice Lesch Kelly is a freelance writer based in Newton, Mass.

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