Silcone is a plastic-like material based upon the chemistry of silicon instead of carbon. Like plastic, it lends itself to a vast number of applications and is the basis of an astonishing range of products, including car tyres, breast implants, prosthetics, cake tins, lubricants, sealants, solvents, gaskets, contact lenses and airbags.
Advantages of silicones
Compared to plastics, they are less toxic, recyclable, heat tolerant, more flexible and produced from resources as plentiful as the sand on the beach (silica). In contrast, chemicals found in plastics have long been known to cause cancer, infertility, allergies and immunological disorders. Disposing of plastic safely is almost impossible: in landfills it can take a thousand years for it to degrade. Even after it floats into our oceans, it breaks down into granules that are toxic to fish and often re-enters the human food chain.
Another quality where silicones excel over plastic, and most other materials, is their ability to impede the growth of bacteria. Nevertheless, modern regulations governing food production and storage are comprehensive and strict. Food grade silicone must not contain any residual chemicals from its manufacturing process nor be deliberately combined with other kinds of filler (for example fibreglass). In addition, of course, it must be kept and handled in ways that guarantee it is supplied hygienically clean.
In the past, concerns were raised about additives such as colourants combined into silicone cookware, especially as these products are exposed to high temperatures. Although no evidence has arisen to show harm, there have been anecdotal complaints of leeching at extra high temperatures. This Scientific American article concludes that even long-term use of good quality silicone cookware poses no evident safety risks, although it makes some criticisms about the lack of research: https://www.scientificamerican.com/article/earth-talk-silicone-tally/.
At least one silicone manufacturer has been caught substituting ordinary cheaper grades of silicone in products where safer grades were required by law (in breast implants in 2012). Consequently, inspections are now routine, and your best guarantee of a quality and regulation-compliant product is to buy only from a reputable silicone hose manufacturer, like Goodflex Rubber.
The real question is whether silicone is safer than the alternatives. In connection with food, the answer is a very clear yes. Toxic metals from saucepans have been leeching into our food for generations and plastic storage containers pose proven toxic dangers.