It's next to impossible to avoid. Today you will find it in bowls, wraps, bottles and bags used to store various foods and beverages, but is it safe?
Studies have found that certain chemicals in the plastic can leach out of the plastic and into the food and drinks we consume. Some of these chemicals have been linked to health problems such as metabolic disorders (including obesity) and reduced fertility. This leaching can occur even faster and greater when plastic is exposed to heat. This means you might be getting an even higher dose of potentially harmful chemicals simply by microwaving your leftovers in a plastic container.
Should we be worried?
First, we need to understand that there are many types of plastics, such as polypropylene, polyethylene, polyethylene terephthalate, and polycarbonate, and contain various chemicals with different properties such as plasticizers, antioxidants, and colourants. According to Dr. Russ Hauser, chair of the Department of Environmental, Health Harvard T.H. Chan School of Public Health, "We're talking about very low-dose chemical exposures," says Dr. Hauser. "But even though single exposures to a specific chemical are small, if they repeatedly occur over long periods, their effects may be cumulative, leading to a variety of adverse health outcomes down the road. Furthermore, and most importantly, we are exposed to many chemicals simultaneously (i.e., chemical mixtures) that may have additive adverse effects." At particular risk are pregnant women and their fetuses. Many of these chemicals cross the placenta, so the fetus is exposed. Experts say childhood exposure is also of great concern.
Among the more troubling chemicals are phthalates and bisphenol A (BPA). Both are endocrine disrupters, which are substances that interfere with the actions of human hormones.
Phthalates are known to toxicologists as male reproductive toxicants (harmful substances). But this group of chemicals is also known to have ill effects in females. Phthalates sometimes referred to as plasticizers, are often used to make vinyl plastics soft and #exible. They are widely used in baby toys, food processing equipment and materials, medical devices, and vinyl building products, in addition to other items.
A 2003-04 analysis by the CDC and the National Health and Nutrition Examination Survey (NHANES) found that exposure to phthalates was widespread in the U.S. population. Adult women had higher exposure than men, likely because some phthalates are also found in many cosmetics and personal care products such as soaps, shampoo, and body washes.
Bisphenol A (BPA) has gotten a lot of attention in recent years because studies have shown it has reproductive effects in humans and rodents.
Polycarbonate is a clear, lightweight, heat resistant, and shatter-resistant type of plastic, making it an optimal material for a wide variety of applications, many of them involving direct contact with foods and beverages, such as lining the inside of food storage cans. Even some thermal paper receipts can contain BPA as a component of the heat-sensitive coating that allows for inkless printing.
That same 2003-04 CDC/NHANES report estimated that 93% of people in the United States ages six and older had the chemical in their urine.
While these two chemicals get the most attention, many other chemicals in plastics could be related to health problems.
Is it safe to microwave plastic?
Depending on the type of plastics you are using, heating them in the microwave can release various chemicals into the foods or liquids that you are reheating. Fatty foods, particularly meats and cheeses, seem more prone to absorbing high amounts of these chemicals.
While microwaves accelerate chemical leaching from plastic, this isn't the only way that chemicals from the plastic can wind up in your food or drinks. "Even if it's not microwaved, chemicals can still enter food stored in plastic containers or bags," says Dr. Hauser. "There were studies done a few years ago in Japan that show that plastics used to store foods and liquids allowed chemicals to leach into the foods and liquids."
Dr. Hauser was involved in another study that found liquids stored in plastic bottles subject to heat and sunlight passed chemicals into the liquids. And acidic foods, like tomatoes, can also absorb chemicals from the linings of food cans. Even types of vinyl or plastics used in homes or offices can release gases, putting measurable amounts of chemicals, such as phthalates, into the air over time. In the same way, plastic vapours can introduce chemicals to food, even if the plastic isn't touching the food, albeit in smaller amounts than would occur with direct contact. This might happen if you use a plastic splatter lid over a bowl in the microwave.
BPA Free, OK?
Are you safe if you use plastics that are free of problematic chemicals such as phthalates and BPA?
It's hard to say whether plastics that don't contain such chemicals are risk-free, says Dr. Hauser. Often what happens when a manufacturer removes a problematic ingredient from plastic is that it substitutes another chemical that we know little about, he says. For example, suppose a manufacturer takes phthalates out of its vinyl plastic recipe. In that case, it still needs something that will make the plastic soft, so it replaces the phthalates with another softening chemical. The problem is that the new chemical isn't safer; there is just a little or no evidence about its risk. "Initially, companies looking to avoid using BPA in products switched to a different chemical called bisphenol S, or BPS," he says. "Much less was known about it at the time. But more recently it's been shown to be harmful as well."
A 2011 study published in Environmental Health Perspectives reported that when scientists tested commercially available plastic products labelled as BPA-free, almost all of them leached out chemicals known to have estrogenic activity, meaning that they mimicked human estrogen. Some of the substances had even more estrogenic activity than the BPA they replaced.
So now what? Use heat wisely. Plastics release more chemicals when heated, so avoid heating foods in plastic containers in the microwave. Whenever possible, skip the packaging.