Silicone baby teats can carry traces of chemicals Europe is now restricting

When scientists tested silicone baby-bottle teats, they found three chemicals, known as D4, D5 and D6, in all of them.¹ This June, a Europe-wide restriction on those same chemicals began to apply, to cut how much of them escapes into the environment.² It is aimed at cosmetics and other consumer products, such as personal care products you leave on the skin.³ As far as we can find, it says nothing about what is left inside a baby's teat.

D4, D5 and D6 are used in making silicone, and they can stay behind in the finished material as “hidden” impurities.^3,4 So a teat sold as “medical-grade” can still carry them, and the phrase tells you nothing about how much it holds or how much reaches your baby's mouth.

Lab tests have found little or nothing seeping out into milk or infant formula.¹ But Germany's food-risk agency, the BfR, says no exposure assessment is possible with current data.⁵ In other words, the agency found the data too thin to say how much of these chemicals a person, let alone a chewing baby, actually takes in. YAN's view: something that spends hours in a baby's mouth should be shown not to release these leftovers there, because no evidence of harm is not the same as evidence of safety.

What you need to know

• Read “medical-grade” on a teat or teether as the seller's words, not a safety test.
• In one lab test, every silicone teat held D4, D5 and D6.¹
• The worrying findings come mostly from studies where the chemicals were breathed in, and German risk assessors say their relevance for humans is unclear.⁵
• What a teething baby takes in through hours of chewing has barely been studied.
• No need to bin what you have: replace worn teats, keep teether time short, and look for silicone that was heat-treated after moulding.

Where the leftovers come from

D4, D5 and D6 are siloxanes, and short siloxane molecules are common by-products of making silicone.^1,6 Some of these by-products can be removed by heating the final product before use.⁶

When scientists surveyed silicone baking moulds and mats, muffin cups, kitchen utensils, boxes and teats, the amounts of siloxanes varied widely, and they suspected the items with the most had not been properly cured.⁷ Curing is the step that sets soft silicone into its finished, rubbery form. So how much an item holds seems to depend on how well it was made, not simply on its being silicone.

Why scientists keep an eye on them

Europe's chemicals agency has classed D4, D5 and D6 as “very persistent and very bioaccumulative”, which means they last a very long time in the environment and build up in living things, and it rated D4 as toxic too.⁸ In the EU, D4 is labelled as toxic to fertility, and Japan's food safety commission lists it as suspected of harming human reproduction.^6,9 In rats, D4 has been shown to dampen a surge of a reproductive hormone, resulting in smaller litters.¹⁰

But the major studies tested breathing the chemicals in, not swallowing them, which the BfR says adds uncertainty.⁵

What the tests found

To check what seeps out of silicone into food, which scientists call migration, the same teat-testing team used silicone baking sheets rather than teats.¹ In milk and infant formula kept against the sheets for 6 hours at 40°C, no siloxanes were detected.¹

In the liquids labs use as stand-ins for food, some did come out, which the authors described as “very limited migration”.¹ That is the closest the research comes to a bottle feed, and it is reassuring, though the silicone was a baking sheet, not a teat.

In the survey of moulds, utensils and teats, some samples held more than the limits the scientists proposed, but once they measured what actually moved into a food stand-in, none would exceed them.⁷

Silicone that is used again and again has sometimes released more than the legal limits, especially in its first cycles of use.⁶ So a brand-new teat or teether may give off more than one that has been in use for a while.

Another study found that D4 and D5 posed negligible risk.¹¹ But D6, found in over 90% of samples, went above a screening threshold in every age group, the level below which a chemical is assumed to need no closer look.¹¹ Crossing that line is a call for more study, not a sign that anyone was harmed.

What nobody has tested: a chewing baby

None of these tests copies a teether's life: hours of chewing, warm and wet with saliva, day after day. A study from China detected 14 methylsiloxanes, the chemical family that includes D4 and D5, in saliva extracts.¹¹ We have seen only a short mention of that study in a later paper, not the study itself, so it shows these chemicals can turn up in saliva tests, not how much a baby takes in.

On the reassuring side, a draft review of D4 by the US Environmental Protection Agency found no unreasonable risk to the general population from any use it looked at.¹² But the BfR's Merkel also set out what a real answer needs: “A complete risk assessment can only be made with the availability of migration data from real foodstuffs.”⁵ For a teether, the food is saliva, and that kind of data does not yet exist in anything we could find.

A study measuring what real teats and teethers release into saliva, over hours of chewing and through their first weeks of use, would change this picture either way. Until then, we would rather keep down the hours a baby spends chewing silicone than wait for that proof.

What the rules say

There is no specific regulation in the EU for silicone that touches food, according to the Danish report written for Norway's food safety authority.¹³ The Danish scientists proposed limits of their own, based on a 90-day study of D5 in rats which showed an increased liver weight.¹³ Those are proposals, not law.

Europe's new restriction stops D4, D5 and D6 being sold on their own, inside other substances or in mixtures at 0.1% by weight or more, but it allows their use in making silicone polymer.² That exemption sits right where a teat's leftovers come from: the making of silicone itself.

The silicone industry expressed strong reservations when the chemicals were first classified.⁸ Pierre Germain of the industry group Silicones Europe said: “We consider this new restriction to be unjustified, because it is not based on most recent scientific evidence and it will provide negligible environmental benefit.”³ His argument, like the restriction itself, was about the environment, not about what a baby swallows.

What to choose

Start with what costs nothing.

• Keep using the teats and teethers you have; there is no need to throw them out.
• Check them before each use and replace any that look cloudy, sticky, swollen, cracked or bitten through.
• Keep teether time short: offer it for a sore spell rather than all day, and try other comforts, such as a clean, cold, damp flannel to chew or a gentle rub of the gums with a clean finger.
• Don't treat “medical-grade” or “food-grade” as proof the silicone is free of leftovers.

When you buy silicone, look for a named maker whose product page says the silicone was heat-treated after moulding, often written “post-cured”. That is the step the research points to for removing leftovers, so it is a good sign, though not a guarantee. If the page doesn't say, one question to the seller is enough: “Is this silicone post-cured after moulding?”

We prefer natural rubber for teats and dummies where nobody in your home has a latex allergy, for what it is made from, not because tests show it releases less. Natural rubber has its own checks: prefer a teether whose pack or product page shows the code EN 71-12, part of the European toy-safety standard, skip any without a maker's name, and give it loose, never on a cord. A teether made wholly of natural rubber can go in the home compost at the end of its life, though cured rubber takes several years to break down.

If silicone suits your baby better, stay with it and lean on the free steps above.