One widely marketed alternative is silicone, a flexible polymer made of silicon and oxygen that can be made into a rubbery substance. It’s advertised as safer and more environmentally friendly than plastic. Silicone sandwich bags, muffin tins, ice cube trays, baby bottles, and a plethora of other objects are available. But while the science on silicone is sparser than that on plastic, there is enough information to suggest we should be cautious about welcoming it into our kitchens, some experts say. Silicones have many interesting properties, says biologist Birgit Geueke of nonprofit Food Packaging Forum. But “they are not inert at all.” 

Do silicone baking pans leach chemicals into food? 

Some of the best evidence that silicones should be used with care comes from studies where scientists bake with silicone bakeware and check the finished products for chemicals. A 2009 study found that more silicone molecules wound up in fatty foods heated in silicone pans than in leaner ones. In a 2010 study, scientists cooked meatloaf and found that startling quantities of silicone migrated into the food. Over time, a great deal of fat from the food also wound up migrating into the material of the pan, which may contribute to the rancid smell users of silicone rubber products sometimes notice after repeated use.

However, a 2012 study found that some silicone baking pans do seem to perform as promised. Scientists analyzed silicone pans used in a commercial pizzeria and found that in these there was very little migration. They noted that silicones that had been tempered, or post-cured, by manufacturers seemed to be more stable. Elizabeth Beckwith of the industry group American Chemistry Council's Silicones Environmental, Health, and Safety Center, wrote in an email that "silicone materials have been subject to hundreds of scientific studies showing that they are safe for human health, when used for their intended purposes."

One way to post-cure silicones is with heat, baking them at the end of manufacturing, says Pelle Moos, a senior advisor at the European Consumer Organisation, a consumer advocacy group. This is an energy-intensive process, though, and manufacturers may skip it. There is also no reliable way for a consumer to know whether a product has been post-cured.

In 2022, Moos and his colleagues reported that in an assortment of silicone bakeware purchased in shops and online, more than 80% of samples released substances of concern into food, while a small number performed well and were very stable. There was no way to tell which was which ahead of time. “You can buy from an online marketplace, and it can be the worst product in the bunch, or it can be one of the best,” says Moos. “So as a consumer, you can't tell up front what kind of product you're actually buying.”

Some of the substances that can migrate from silicones into food have known health risks, but many others are still mysterious. More research is needed to explore exactly what chemicals migrate into food from silicone and what health effects there may be, says Geueke. She points to the Food Packaging Forum’s database of papers on substances that can migrate into food. There are only about 30 published papers on this subject in silicones, which is a very small number compared to the hundreds on plastics, she says. 

Is silicone better for the environment?

Unfortunately, silicone rubber products strike out here, too, says Beyond Plastic’s science director Trisha Vaidyanathan. “I don't think it's a direct replacement for plastic. It has a lot of the same problems. It is still dependent on fossil fuels to make, it's a very energy intensive process to manufacture, and at the end of its life, it is going to end up in a landfill, or it's going to be incinerated, just like plastic,” she says. “It cannot be recycled. It doesn't biodegrade.”

The Wirecutter dug into this question and found that from a carbon emissions perspective, reusable silicone bags must be reused for a very long period of time to start to break even with the disposable plastics they’re meant to replace—and some may never get there, because of the heat and water required to clean them over their lifetime. 

What should you use instead of silicone?

Glass and metal are still the best choices for materials that come into contact with food, says Geueke. Glass in particular is inert; it has the properties that we expect of a food container.

If you decide to use a silicone product, make sure you are using it for its intended purpose. Moos recalls a moment that sent chills down the spines of folks in the food packaging world: A viral trend showed people using silicone fidget popper toys as chocolate candy molds. 

Moos watched in horror as people poured hot liquid into the toys, made of a silicone not for kitchen use. “That material is really not meant for that,” he says. “When you work on this topic, and you see this, you think, ‘You cannot do this! Please stop!’”