We live in a world filled with chemicals. They're in our water, our air, our soil–and, as a result, they're in our bodies.
Some of the most worrisome chemicals in everyday use are in plastic, the ubiquitous material that makes up so much of modern life. How do we expose ourselves to the chemicals in plastic, and how safe are they?
As if to add to the anxiety, some experts fear that when we heat food in plastic in a microwave, we significantly increase our exposure to potentially harmful compounds in some plastics. Is it safe to microwave plastic?
What's In Plastic?
There is no single plastic: The term describes everything from polyvinyl chloride (the compound in familiar white PVC pipes) to acrylic paints to the Bakelite once used to make tableware. Plastics can be made of organic or inorganic chemical compounds. In chemistry, organic just means it contains carbon.
Typically, plastics are made from petrochemicals (aka oil). The toxicity of any particular plastic is a function of what's in it and how stable it is. Since most plastics are water-insoluble, they're fairly stable and chemically inert.
Two additives, however, stand out among toxicologists as potential human health hazards: bisphenol-A, or BPA, and phthalates. BPA is an additive used to make hard, clear plastics (such as CDs and water bottles).
Phthalates, on the other hand, are used in plastics to make them soft and pliable (think rubber duckies). Both BPA and phthalates are believed by many scientists to be endocrine disruptors, sometimes called hormone disruptors.
The hormone that BPA and phthalates are usually suspected of disrupting is estrogen. It's been linked to obesity in some research. Moreover, there are links between these chemicals (and other additives in plastic) to fertility problems, immune system issues, disease, and disability.
This is especially important to consider in pregnancy, as BPA exposure was correlated with an increased risk of miscarriage and low birth weight. Beyond pregnancy, in babies and children, there are also potential cognitive effects and an increased probability of childhood asthma with over-exposure to BPA and phthalates.
BPA and Phthalates in Food
Though BPA and phthalates are found everywhere–BPA is even in many cash register receipts–most human exposure is thought to occur through food. Both plastic additives are in food containers, some plastic wraps, and in the linings of food and drink cans.
But how dangerous are these plastics in everyday use? Not everyone agrees on this matter. Because most plastics are designed to be stable, it's not likely that every contact with food or drink results in significant ingestion of BPA or phthalates.
Food packaging materials must pass standards set by the Food and Drug Association, and while FDA has not issued specific regulations concerning microwaveable food packaging, clearance is required for the “intended use of a product” under the Food Contact Notification program. The exception to this is the list of “Generally Recognized as Safe” (GRAS) polymers that can be included without additional approvals. The GRAS list was intended as an approval shortcut for food additives with a long history of use (like caffeine or sugar) that “[have] been adequately shown to be safe under the conditions of its intended use”.
So by this logic, if a product is labeled “Microwave Safe,” it can be used in a microwave. Though that may not mean you want to. Critics of such FDA standards cite a lack of oversight, leaving the burden of providing testing data up to the manufacturers themselves. This conflict of interest leaves consumers susceptible to misinformation and possibly harmful side effects.
To further muddy the waters, and perhaps predictably, the American Chemistry Council (a trade association representing more than 190 companies) claims, "Bisphenol A (BPA) is one of the most thoroughly tested chemicals used today and has a safety track record of more than 50 years. Regulatory bodies around the world have reviewed the science and have found BPA to be safe." Lobbying from organizations such as this has perhaps slowed the additional oversight and regulatory updates health organizations would like to see from the FDA.
Is It Safe to Microwave Plastic?
There isn’t a yes or no answer to this question. The amounts of BPA and phthalates leaching into food depends on the type of plastic that's put in the microwave, the amount of time it's heated, and the condition of the container. Old, battered plastic containers and those that are heated – or stored – for longer periods of time pose the greatest risks. Likewise, higher fat foods like certain meats, and those heavy in cream and butter shouldn't be heated in plastic containers as fat is a greater carrier of chemicals.
Unfortunately, this may mean that reusing and/or reheating your plastic takeout boxes may not be the best idea if you are concerned about unfriendly compounds migrating into your leftovers.
How to Avoid BPA and Phthalates in Plastic
The first and best way to avoid phthalates and BPA is to use food containers that don't contain these compounds: glass, metal, and other containers are longer-lasting and – in the case of glass – can usually be microwaved.
Some people, including research scientists, avoid contact with cash register receipts since some of these are made with thermal printing techniques and contain surprisingly high levels of BPA.
Plastics that have the recycling symbol "7" usually contain higher levels of BPA and plastics marked with the recycling number "3" are more likely to contain phthalates. But because these markings aren't used to indicate the additives in plastic, they can't really be relied upon to tell if or how much BPA and phthalates plastics contain. (There's no consensus, for example, on whether "5" plastics contain BPA.)
Though there's probably no need for most people to go to extremes to avoid all plastics, it may be prudent for some populations, especially young children and women of child-bearing age.
Because the effects of hormone-disrupting chemicals are most pronounced on developing fetuses and very young children, it's common sense to do what we can to protect these vulnerable individuals from the potentially harmful effects of plastics.
Centers for Disease Control and Prevention. Bisphenol A (BPA) factsheet. Published April 7, 2017.
Centers for Disease Control and Prevention. Phthalates factsheet. Published April 5, 2021.
Cleveland Clinic. What are ‘hormone-disrupting chemicals’? Published March 24, 2020.
Lichtveld K, Thomas K, Tulve NS. Chemical and non-chemical stressors affecting childhood obesity: a systematic scoping review. J Expo Sci Environ Epidemiol. 2018;28(1):1-12. doi:10.1038/jes.2017.18
Trasande L, Shaffer RM, Sathyanarayana S, Council on Environmental Health. Food additives and child health. Pediatrics. 2018;142(2):e20181408. doi:10.1542/peds.2018-1408
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U.S. Food and Drug Administration. Food ingredients and packaging. Updated April 2021.
National Archives. Code of Federal Regulations. Indirect food substances affirmed as generally recognized as safe. 21 CFR Part 186.
U.S. Food and Drug Administration. Generally Recognized as Safe (GRAS). Updated September 6, 2019.
American Chemistry Council. Polycarbonate/Bisphenol A (BPA) global alliance.
Bhunia K, Sablani SS, Tang J, Rasco B. Migration of chemical compounds from packaging polymers during microwave, conventional heat treatment, and storage. Comprehensive Reviews in Food Science and Food Safety. 2013;12(5):523-545. doi:10.1111/1541-4337.12028