In this guide, we outline:
– What silicone is
– How sustainable silicone is
– Whether silicone might be safe for human use (mainly from the perspective of using it for food and beverage/kitchen products, and also for contact with humans, such as with baby bottle nipples and feeders)
(Note – this guide contains general information only. The information in this guide is not professional health advice, and is not a substitute for the advice of a qualified health professional)
Summary – What Is Silicone, & Is It Sustainable & Safe?
What Is Silicone?
Silicone is a synthetic polymer made of various elements like silicon
Silicon vs Silicone – What’s The Difference
Silicon is an element, whilst silicone is a chemical compound that is made up of silicon, oxygen, and other elements along it’s molecule chain
Is Silicone Similar Or Different To Plastic?
Silicone is a synthetic polymer in the same way that some plastics are synthetic polymers (although some plastics are semi-synthetic)
Both silicone and plastic are man made materials
Both may also use hydrocarbons from fossil fuels in their polymer backbone, and this is why silicone may have plastic like qualities (such as the malleability of plastic)
The main difference between most plastics and silicones is that they are made of different atoms in their polymer backbones
Silicones are generally made with silicone and oxygen (amongst other elements), and plastics are generally made with hydrogen and carbon
Both silicone and plastic can be made in different types and with different chemistries
The different types and chemistries of plastic and silicone can each have different traits and properties
We’ve listed the different types of plastic in this guide
essentialchemicalindustry.org outlines some of the different types of silicone
Is Silicone A Rubber?
Technically no, but is might show elastic rubber like qualities.
Forms Of Silicone
Silicone comes in various different forms depending on the use
Types Of Silicone
Silicone comes in various different types, with the different types of silicone have different atoms that make up their polymer backbone
This leads to the different silicones having different physical properties
Uses For Silicone
We list some of the uses and industries where silicone is used in the guide below
Two examples of common everyday uses being as a sealant or glue around the house, and as a rubber in lids and containers for food and beverages.
Baby bottle nipples and baby feeders are further examples
Properties & Traits Of Silicone
Different types and chemistries of silicone have different properties and traits
We list some of the general traits/properties of silicone in general, and also of the different types of silicone, in the guide below
We also list what the traits/properties of some individual silicone products might be
Food Grade Silicone
Food grade silicone is a specific type/standard/quality of silicone
Different companies may make slightly different food grade silicones, so, it’s worth checking the traits and features of a company’s silicone material before buying. Be aware of any relevant safety regulations too.
Having said that, there isn’t uniform regulations or standards for silicone in some countries. So, each individual company may have to prove or certify the claims they are making about their material or product
Food grade silicones may in some instances be more eco friendly and less toxic than regular silicones or plastics
Some new silicone products are claiming to be made from 100% natural chemicals, as well as being recyclable, and BPA, BPS, phthalate, lead, latex and leachate/toxics free.
So, these products may be might favorable from a sustainability and human health point of view – depending on the specific product.
Is Silicone Sustainable?
Silicone is made from some abundant source materials. However, whilst some silicone is made without petroleum based chemicals, there is silicone that does contain hydrocarbons from fossil fuels
Silicone that lasts longer has an opportunity to average it’s sustainability footprint out over a greater number of years
Silicones that get into the environment can act like plastic and take a long time to decompose
Although some silicone is recyclable, some cities don’t have high recycling rates for silicone (for a range of reasons, such as not accepting it as a material)
wikipedia.org indicates that some silicone compounds can be pervasive in the environment, can pollute, and can possibly impact animals
It may be hard to gauge silicone’s true sustainability score because there doesn’t appear to be as much study done on it as plastic
Is Silicone Recyclable?
Silicone may generally have a low recycling rate because it isn’t accepted through many local recycling programs and streams
But, some recyclers do accept it
Is Silicone Safe?
There are differing reports on just how safe silicone might be for human health.
Some groups indicate that the use of undamaged silicone is generally safe and non-hazardous
Other groups indicate that either the research on the health effects of silicone are either not definitive (or there’s limited research and studies), or, that silicone might leach certain chemicals in some conditions and instances (such as when silicone is exposed to very high temperatures, or oil and substances with a high fat content)
Some groups sit in the middle and say that there might be reasons to be cautious when using silicone, or that there might be potential concerns
Some silicone is made without BPA, BPS, fillers or other potentially harmful or toxic additives or chemicals
Always do your own research on the individual silicone product, and investigate these claims for yourself for each individual type of silicone, product and company (as they can differ) before buying
What Is Silicone?
Silicone is synthetic polymer made up of silicon, oxygen and other elements
Explaining in more depth what silicone is from a scientific or chemistry perspective can get very complicated and technical.
A few of the more simple and shorter explanations from different sources include:
Silicones have unique properties amongst polymers because of the simultaneous presence of organic groups attached to a chain of inorganic atoms …
Silicones are synthetic polymers with a silicon-oxygen backbone similar to that in silicon dioxide (silica), but with organic groups attached to the silicon atoms by C-Si bonds.
The silicone chain exposes organic groups to the outside.
Silicone is, at it’s core, a silicon compound
Silicone is a synthetic polymer made up of silicon, oxygen and other elements, most typically carbon and hydrogen (livescience.com)
Silicones are inorganic polymers, that is, there are no carbon atoms in the backbone chain.
The backbone [of silicone] is a chain of alternating silicon and oxygen atoms.
Each silicone has two groups attached to it, and these can be any organic groups
Silicones, also known as polysiloxanes, are polymers that include any synthetic compound made up of repeating units of siloxane, which is a chain of alternating silicon atoms and oxygen atoms, combined with carbon, hydrogen, and sometimes other elements (en.wikipedia.org)
Difference Between Silicon, & Silicone
Apart from the obvious ‘e’, the difference is that silicon is one natural element that makes up silicone as a compound
So, silicon is one part of silicone, and silicon is an element, whilst silicone is a chemical compound
Silicon is a naturally occuring chemical element that makes up silicone, along with other elements such as oxygen, and carbon and hydrogen
… [silicon is a naturally occurring chemical element, whereas silicone is a synthetic substance]
Is Silicone A Plastic? What’s The Difference?
Silicone is not technically a plastic, but has several close similarities to plastic.
Some reports refer to silicone as a plastic because of these similarities.
The main difference between the two is the atoms in the polymer backbone of each chemical compound.
Both use hydrocarbons from fossil fuels.
Silicone is something of a hybrid between a synthetic rubber and a synthetic plastic polymer
The key difference [between] common carbon-based plastics [and silicone] … is that silicones have a backbone made of silicon and oxygen, and hydrocarbon side groups – all of which gives them plastic-like characteristics … [whilst] most plastics have a polymer backbone of hydrogen and carbon, silicones have a backbone made of silicon
‘… silicone is still a type of [plastic] synthetic polymer because hydrocarbons from fossil fuels are used in its manufacture (biome.com.au)
Is Silicone A Rubber?
According to some reports, silicone is closer to the rubber family than plastic
Like the plastic section above, silicone is not technically a rubber, but displays close similarities:
The correct way to describe silicone might be an ‘elastomer’, that displays elastic properties [like rubber] (silicone.co.uk)
Read more on silicone and synthetic rubbers in the wikipedia.org resources
Forms Of Silicone
From a general perspective, silicones we use mainly come in the form of fluids, gels, rubbers, and resins
essentialchemicalindustry.org outlines the different forms of silicone in more detail
Types Of Silicone
From a chemistry perspective, the types of silicones we use most commonly are … silane, siloxan, and poly(diphenylsiloxane)
The most widely used silicones are those which have methyl groups along the backbone
essentialchemicalindustry.org outlines the different types of silicone in more detail
They also list what atoms each type of silicone has in it
What Is Silicone Used For?
Silicone is used across a range of industries, and for a range of uses.
Some of those uses and industries include …
Silicones are used in many industries including … electronics, paints, construction and food … (essentialchemicalindustry.org)
[Silicone is used in the medical field, in personal care items, kitchenware, cookware coatings (because of non stick properties) food and beverage containers, lubricant for automotive parts, and more] (livescience.com)
Silicone can be used to make malleable rubber-like items, hard resins, and spreadable fluids …
Silicone is often used for baby nipples, cookware, bakeware, utensils, and toys.
Silicones are also used for insulation, sealants, adhesives, lubricants, gaskets, filters, medical applications (e.g., tubing), and casing for electrical components
Properties & Traits Of Silicone
The properties and traits of silicone depend on the chemistry of the silicone, so, different silicone can end up having different traits and properties.
Silicone’s chemistry can be modified at the production stage to suit the end use or application for the silicone.
Traits/properties of silicone material in general, the different chemistries of silicone, and the different silicone products are listed below.
Silicone Material In General
Silicone [might have …] Low toxicity and high heat resistance. It also provides good electrical insulation (livescience.com)
[Silicone might have] … many plastic-like properties: flexibility, malleability, clarity, temperature resistance, water resistance …
… it is a unique plastic because it is much more temperature resistant and durable than most plastics and has a low reactivity with chemicals.
And while water resistant, it is also highly gas permeable, making it useful for medical or industrial applications where air flow is required.
It’s also easy-to-clean, non-stick, and non-staining, making it popular for cookware and kitchen utensils
[Silicone elastomers specifically have] … high temperature resistance, excellent environmental resistance, low compression set, low level of flammable components, high physiological inertness, poor abrasion, poor oil/petroleum resistance (silicone.co.uk)
[Compared to plastics, silicone is longer lasting and endures extreme fluctuations in temperature without melting, cracking or otherwise degrading, and, it resists oxidative deterioration (normal aging) for decades on end … these things increase it’s product lifecycle] (clearandwell.com)
Different Types Of Silicone
Properties such as solubility in organic solvents, water-repellence and flexibility can be altered by substituting other organic groups for the methyl groups.
For example, silicones with phenyl groups are more flexible polymers than those with methyl groups.
They are also better lubricants and are superior solvents for organic compounds.
[Silicone bags can be] … lightweight, flexible, stretchy, washable, waterproof (treehugger.com)
[Silicone bakeware can be] … Highly functional, and can handle hot and cold temperatures … Microwave and dishwasher safe … [and] Non stick – can skip greasing (livegreen.recyclebank.com)
Silicone Food Containers
Ecolunchboxes.com notes that silicone may be the answer to food container lids that don’t leak, and don’t leach chemicals like plastic might.
What About The Properties Of Food Grade Silicone Specifically?
The properties of food grade silicone depend on the individual food silicone product and how the company produces it, so, consumers should check this before buying.
Food grade silicones may in some instances be more eco friendly and less toxic than regular silicones or plastics.
But some select silicone food grade products might have the following properties, or features …
Not a “100% natural” material like rubber
Is a non-toxic polymer mostly made from silica (sand).
Can withstand heating and freezing without leaching or off-gassing, hazardous chemicals – unlike plastics, which contaminate food in these environments.
It is also odor- and stain-resistant, hypoallergenic, and because of it’s smooth surface, very easy to clean.
For these reasons, and because it is soft life rubber and does not break, it is the perfect material for eco-friendly and non-toxic baby products in particular
[Food grade silicone made by some companies might be:]
Highly resistant to damage
Highly resistant to degradation from high temperatures
Doesn’t harden, crack, peel, crumble, dry out, rot or become brittle over time
Non-toxic and odorless – contains no BPA, latex, lead, or phthalates
May be 100% recycled at select locations
Considered a non-hazardous waste
[Note that Stasherbag does a specific type of food grade silicone called platinum food grade silicone – Stasher products are made of 100% pure platinum grade silicone — a standard even higher than food grade silicone, passing all U.S. safety requirements and even tougher European standards]
Some benefits of food grade silicone, and tips for choosing and using silicone dishes can be found at clearandwell.com
Is Silicone Sustainable?
More Sustainable Aspects To Silicone
[Silicone is made in part with silicon, which] … is the second most abundant element in the Earth’s crust, after oxygen (livescience.com)
[Some pure platinum food grade silicones are]… made from sand (silica) and carbon, natural resources (stasherbag.com)
[Some silicone products are food-grade silicone [that] is made without petroleum-based chemicals, BPA, BPS, or fillers] (stasherbag.com)
If disposed of at a landfill for incineration, the silicone (unlike plastic) is converted back into inorganic, harmless ingredients: amorphous silica, carbon dioxide, and water vapor (ecolunchboxes.com)
Silicone that lasts longer will have an opportunity to average it’s sustainability footprint out over a greater number of years
Less Sustainable Aspects To Silicone
But, most silicones use methyl groups attached to the backbone. [Methyl groups are hydrocarbon groups, and, most hydrocarbons found on Earth naturally occur in crude oil] (en.wikipedia.org)
[Silicone does] contain silica, which is derived from sand, it also contains synthetic and chemical additives that come from fossil fuels (treehugger.com)
Silicone does not biodegrade or decompose (certainly not in our lifetimes). Silicones are very persistent in the environment (lifewithoutplastic.com)
Silicone compounds are pervasive in the environment. Particular silicone compounds, cyclic siloxanes D4 and D5, are air and water pollutants and have negative health effects on test animals (en.wikipedia.org)
Some silicone products can be recycled in regular recycling, while most silicone products need specialised privatised recycling (and have a low recycling rate)
Is Silicone Recyclable?
Silicones can be one of the materials with a lower recycling rate.
There may be some challenges to recycling silicone.
Silicones are recyclable, but have a low recycling rate and are generally not recyclable through the average local recycling program … usually specialized private recycling companies downcycle silicone into oil (lifewithoutplastic.com)
[Some companies offer recyclable silicone products, and even offer to recycle and repurpose it themselves] (stasherbag.com)
While there is nothing about silicone chemically that would prevent it from being recycled, curbside recycling programs rarely accept it, and it can be difficult to find a silicone recycler to accept post-consumer products.
This is because many consumers confuse polyurethane with silicone.
From biome.com.au: [silicone] has an end of life issue because it is not able to be recycled through [most recycling systems]’
Is Silicone Safe? (Toxicity, BPA, & Human Health Concerns)
Some Reports Say Silicone Is Safe
Some major organisations indicate that silicone is safe at the current exposure levels in society.
… the FDA considers normal use of undamaged silicone cookware and other items to be safe (healthline.com)
Health Canada confirms … silicone does not react with food or drinks or produce any hazardous fumes (clearandwell.com)
Some Research, Studies & Reports Question The Safety Of Silicone
… there has not been a lot of research done to date on the health effects of silicone … [But, independent research and review of peer-reviewed scientific studies shows] they can leach certain synthetic chemicals at low levels, and the leaching is increased with fatty substances, such as oils [and food with fatty content] … silicone is not as inert, stable and chemically unreactive as many claim (lifewithoutplastic.com)
Some studies indicate even food grade silicone can leach siloxanes when exposed to very high heat, and fat (thetot.com)
… there haven’t really been many in-depth or subsequent studies into [silicone’s] long-term effects … [but there are] reasons to indicate that “we should begin to be cautious about silicone.”
… One study tested the release of siloxanes from silicone nipples and bakeware into milk, baby formula and a simulant solution of alcohol and water [and, after 72 hours, there were results that raised some questions]
Kitchen and bakeware products made from silicone are often marketed on the basis that they’re safe.
They’re non-toxic, inert, can be heated as well as frozen and do not release any odours into food when cooking …
However, some concerns still linger around the safety of silicone.
For example, there is concern that, when heated to high temperatures (above 149oC) silicone becomes less stable.
It may also leach certain undesirable compounds known as siloxanes …
Further studies are needed before we have a more complete picture of any health risks posed by silicone
There is limited research on its health effects, and silicone can leach chemicals when heated.
Silicone can contain varying additives and there is no regulation of what can be called silicone [in some countries].
Potential Safety Tips For Using Silicone
Use [silicone] with caution, and if you can find an alternative, use it
… use high quality, relatively stable [silicone] material, and leaching of chemicals from other plastics is of much greater concern
… use high quality, food grade or medical grade silicone
… other options are glass, ceramic and stainless steel options for cooking and baking
[Basic tips for using silicone can be found at lifewithoutplastic.com]
Try food safe/food grade silicone for plates, cups and mealtime travel gear (it is claimed to be non toxic and doesn’t leach or off gas)
Glass and metal work well for baby bottles
BPA substitutes can be hazardous to health – so watch out for BPS and similar substitutes
Specific silicone food grade products from some companies are claimed to have the following features [so you may look for companies and products with similar claims and research if they are accurate for yourself]:
No fillers or toxic products in Stasher bags — no BPA, BPS, lead, latex, or phthalates
Food grade silicone is a non-toxic type of silicone that doesn’t contain any chemical fillers or byproducts, making it safe for use with food.
Prepol.com makes a good point about silicone safety and compliance:
… manufacturers of silicone components must demonstrate – on an individual basis – the compliance of the finished product
[This is because] there is no automatic universal ‘approval’ of all silicone products or manufacturers
[In addition, bodies like the FDA in the case of the US, are responsible to protect the public from food hazards – where we are looking at silicone as a food grade product … so we can look at what these bodies have to say too]
Silicones do play a useful role as seals or gaskets in many reusable containers, but these do not generally come into contact with the food and are a tolerable use of the product [when using it] (treehugger.com)