Is Stainless Steel Toxic? What Metal Migration Tests Reveal About Water Bottles

No. A properly made 304 or 316 stainless steel water bottle does not expose the person drinking from it to harmful amounts of metal. But “stainless steel” on its own is not a safety guarantee. Whether a bottle stays safe over years of daily use depends on three things: which grade of steel touches the drink, how the inner surface was finished in the factory, and how the bottle is used and cleaned afterwards.

We hear this question in many forms. Shoppers see “SUS 304” stamped on the base of a bottle and wonder what that mark actually means for their health. Brand owners and buyers need a clear, defensible answer for those shoppers before the first container ships. In this article, our product team walks through what can actually move from stainless steel into a drink, how regulators in China, Europe and the United States measure it, when the risk genuinely rises, and what evidence a buyer should ask a supplier for.

Table of Contents

The Short Answer: Food-Grade Stainless Steel Is Not Toxic — Under Defined Conditions

Stainless steel is not an inert material. It is an alloy of iron and chromium, with nickel added in the grades used for drinkware. Grade 304, the workhorse of the industry, is often called 18/8 because it contains roughly 18% chromium and 8% nickel. Grade 316 adds molybdenum, which gives it better resistance to chlorides such as salt.

Its safety does not come from the metal being “non-reactive”. It comes from a microscopically thin, chromium-rich oxide film that covers the surface. That film forms on its own: clean stainless steel exposed to oxygen in normal air builds and repairs this protective layer, and an electropolished surface passivates itself in air once it has been rinsed and dried (Nickel Institute, Pub. 9001). As long as the film is intact, very little metal can leave the surface. When it is damaged, by aggressive cleaners, long contact with salty or acidic liquids, deep scratches or poor finishing in the factory, metal release rises until the film re-forms.

So the honest answer is “safe, under defined conditions”. The rest of this article is about those conditions: what regulators test, under what assumptions, and what keeps a real bottle inside them. For the regulatory meaning of the term itself, our guide on how a stainless steel bottle earns food-grade status covers that ground.

What Can Migrate From Stainless Steel Into Your Drink

Food-contact rules do not ask whether a bottle contains nickel or chromium. Of course it does. They ask how much of each element ends up in the food or drink under defined test conditions. China’s national food-safety standard for metal food-contact articles, GB 4806.9-2023, sets migration limits for 13 elements. For a stainless steel bottle, two groups matter.

Alloying Elements: Chromium, Nickel, Manganese — and Molybdenum in 316

Chromium (limit 0.25 mg/kg). The form matters more than the name. Researchers at KTH Royal Institute of Technology tested grades 201 and 304 under the Council of Europe test protocol and found chromium released only as trivalent Cr(III). No hexavalent Cr(VI), the form of greatest toxicological concern, was released or detected (Hedberg et al., 2014).

Nickel (limit 0.14 mg/kg). For most people, a stainless steel bottle is a minor contributor. Diet is the largest source of nickel exposure, with cocoa, beans, seeds, nuts and grains among the richest foods (Nickel Institute, citing EFSA). The group that does need care is the small subset of nickel-allergic people who react to nickel taken in by mouth. We look at their options in a separate piece on nickel sensitivity and stainless steel bottles.

Manganese (limit 2.0 mg/kg in China). In its 2023 assessment, the European Food Safety Authority identified neurotoxicity as the critical effect of excess manganese. The data were not sufficient to set a tolerable upper intake level, so EFSA set a safe level of intake of 8 mg per day for adults (EFSA, 2023). Manganese is also where steel grade starts to matter: low-nickel 201 steel replaces much of its nickel with 5.5–7.5% manganese (ASTM A240, UNS S20100).

Molybdenum (limit 0.12 mg/kg). It is easy to overlook, but 316 contains molybdenum by design, so a 316-lined bottle should be tested for it as well.

Impurity Elements: Arsenic, Cadmium, Lead and Antimony

These are not intentional ingredients. They arrive as impurities in the raw material, and the limits are correspondingly tight: arsenic 0.002, cadmium 0.002, lead 0.01 and antimony 0.04 mg/kg. Because they track the quality of the steel coil rather than the grade name, they are the reason traceable raw material matters as much as the “304” on the label.

The first fill is the peak. In the KTH tests, most metal release happened within the first two hours of contact, and less was released with each repeat exposure as the surface stabilised. An Oregon State University study saw the same pattern under far harsher conditions: tomato sauce cooked for hours in stainless steel released nickel and chromium, but leaching fell with every cooking cycle and levelled off after the sixth (Kamerud et al., 2013). Water held in a bottle is a much gentler case than an acidic sauce simmered for hours, but the practical lesson carries over: wash a new bottle with warm, soapy water before its first use.

How Migration Testing Works

Migration tests are designed to model a bottle’s worst realistic day, not an average one. Three frameworks matter for drinkware sold internationally.

China: GB 4806.9-2023

The standard has applied since 6 September 2024. The test liquid, or food simulant, is chosen by what the product will hold: an artificial tap water for most drinks, and a citric acid solution for acidic foods with a pH below 5. Time and temperature follow the intended use as well. A bottle that may be filled hot and left at room temperature for up to a day is tested at 70 °C for 2 hours, followed by 40 °C for 24 hours. Because the surface of a reusable article changes after its first contact, the standard requires three consecutive migration tests and judges stainless steel on the third result.

One point often causes confusion. China’s product standard for vacuum flasks, GB/T 29606, covers quality requirements such as steel grade, heat retention and sealing. Its 2026 revision, for which Haers is the first-listed drafting organisation, leaves food safety entirely to the GB 4806 series. A GB/T 29606 test report on its own is therefore not a food-safety report.

Europe: The EDQM Technical Guide

The EU has no harmonised regulation for metals in food contact. Laboratories and authorities instead rely widely on a technical guide published by the Council of Europe’s EDQM. Its second edition (2024) tightened several limits: manganese fell from 1.8 to 0.55 mg/kg, and chromium is now assessed as Cr(III) at 1 mg/kg. Aqueous testing uses EN 16889:2016 artificial tap water, with citric acid for acidic foods.

United States: Case-by-Case Review

No metals are listed in the U.S. Code of Federal Regulations as food-contact substances; FDA reviews metal uses case by case. In its correspondence on stainless steel, FDA describes acceptable food-contact grades as containing at least 16% chromium, accepts the 200 and 300 series with an appropriate finish, and points to the FDA Food Code requirement that food-contact materials be safe, durable, corrosion-resistant and free of deleterious migration (FDA, 2015).

Element	China GB 4806.9-2023 (mg/kg)	EDQM Technical Guide, 2nd ed. 2024 (mg/kg)
Chromium	0.25 (total chromium)	1 (as Cr(III))
Nickel	0.14	0.14
Manganese	2.0	0.55
Molybdenum	0.12	0.12
Lead	0.01	0.010
Cadmium	0.002	0.005
Arsenic	0.002	0.002

Specific migration or release limits, expressed per kilogram of food. Sources: GB 4806.9-2023; EDQM, Metals and Alloys Used in Food Contact Materials and Articles, 2nd edition.

The two frameworks do not line up perfectly. A bottle sold into both markets should be checked against the stricter value for each element, and manganese is the one most likely to catch a supplier out.

When the Risk Actually Goes Up

The wrong steel grade. China’s vacuum flask standard requires the inner liner to be made from 304-type austenitic steel or a grade with at least equivalent corrosion resistance. Grade 201 replaces much of its nickel with manganese, which leaves it with less corrosion headroom. It is worth being precise here: 201 is not “toxic”. FDA accepts the 200 series for food equipment, and in the KTH tests 201 stayed within release limits. The problem is margin. Over years of contact with acidic or salty drinks, a lower-alloy surface is more likely to pit, and a pitted surface releases more metal. That is why 201 is not permitted for liners under the national standard, and why the 201 versus 304 question is worth settling before an order is placed. If you are unsure what you are being offered, these simple checks for genuine 304 are a useful first filter.

An unfinished inner surface. Steel that is formed, welded and polished picks up residues along the way. In our own process, the inner liner is cleaned and dried before the base is welded on. After the vacuum is drawn, the liner is electropolished, then acid-washed, rinsed in cold and then hot water, and dried. Electropolishing smooths the fine roughness where contamination can hide and leaves a surface that passivates evenly in air. A liner that skips or rushes these steps can carry polishing residue and an uneven oxide film into its very first fill.

Long contact with acidic or salty drinks. Short-term use is well within what the passive film can handle. Days of storage are a different matter, because acids and chlorides keep working on the film. We cover the practical limits in our articles on lemon water in stainless steel and carbonated drinks and corrosion. To check how our own bottles hold up, we expose them to a 5% salt spray at 35 °C for 24 hours, and the visible surfaces must show no spots, pinholes or rust.

The wrong cleaning routine. Household cleaners containing chlorine bleach can lead to corrosion if they are left on stainless steel, so thorough rinsing matters (Nickel Institute, Pub. 9001). Mild detergent and a bottle brush are enough for daily care. For bottles marketed as dishwasher-safe, we run 25 full dishwasher cycles and require that no metal part rusts; see our notes on dishwasher use for stainless steel cups.

Physical damage. Deep scratches and dents disturb the surface and can trap residue. A small cosmetic dent on the outer wall is usually harmless; damage to the liner is worth a closer look, as we explain in whether a dented bottle is still safe to use.

Can a Metal Water Bottle Make You Sick? Separating Real Causes From Myths

When someone feels unwell after drinking from a bottle, the cause is far more often hygiene than metal. Lids, gaskets and straws trap moisture and residue, which is where biofilm and mold tend to take hold, and it is why the water trapped inside a lid deserves attention. Warm dairy is a particular risk. China’s 2013 vacuum flask standard required manufacturers to warn against keeping milk or baby food warm for long periods because of bacterial growth.

A metallic taste is a separate issue. It usually comes from residue on a new bottle or from acidic contents, and it is not in itself a sign of harmful exposure.

For the small group of people with nickel allergy, the choice of liner material is a reasonable precaution. A 316 liner is one option, and we explain the trade-offs in why 316 is used for bottle interiors. Commercially pure titanium is another: it protects itself with its own dense oxide film and contains no nickel at all.

What Brand Buyers Should Ask For Before Placing an Order

A material name on a specification sheet is a claim. A migration report on the finished product is evidence. Before committing to a supplier, these five questions separate the two:

A migration report for your target market, on the finished product. That means the full bottle including lid, gasket and straw, with each material tested against its own standard: metal, plastics, silicone. For Europe, check results against the EDQM limits, not only the Chinese ones.
Which simulant and conditions were used. If the bottle will be marketed for lemon water, juice or sports drinks, ask whether the acidic (citric acid) condition was tested, not only tap water.
Evidence of the steel grade. A mill certificate plus an independent composition check, rather than a supplier’s declaration alone.
The scope of any “lead-free” claim. In a vacuum bottle, solder seals the evacuation hole at the base, outside the drinking chamber. Ask for the lead content of that solder; we specify no more than 100 mg/kg for products marked lead-free.
Re-testing rules. Results should be refreshed periodically and whenever material, structure or process changes.

This is how we approach it at Haers. Every steel part of our vacuum bottles, from the outer shell and inner liner to any steel accessory that touches the drink, is made from 304, 316 or 316L. We do not use 201 anywhere on the bottle, even where the national standard would allow it on the outer shell. Steel composition is verified by spectral analysis, finished products go through full type testing at least once a year, and our CNAS-accredited in-house laboratory carries out routine verification between those cycles.

Final Word

Stainless steel earns its reputation for safety, but it earns it under conditions: the right grade, a properly finished surface, sensible use and cleaning, and testing that matches both the drink and the market. When those conditions are met, the amounts that migrate are small, highest at first use, and well inside the limits regulators set.

For brands, the practical step is to make those conditions visible: specify the grade, ask for the right report, and understand what each market expects. Our overview of what BSCI, LFGB, FDA and REACH tests actually mean is a good next read. If you are specifying a new bottle and would like to map a test plan to your target markets, our team is glad to walk through it with you.

Frequently Asked Questions

Is 304 stainless steel safe for drinking water?

Yes. 304 (18/8) is the standard food-contact grade for drinkware. A finished 304 bottle that passes migration testing under GB 4806.9-2023 or the EDQM technical guide releases only trace amounts of metal, well below regulatory limits.

Does stainless steel leach metals into water?

In trace amounts, yes. Release is highest during the first contact and falls with repeated use as the protective oxide film stabilises. Long storage of acidic or salty drinks increases it, which is why testing uses an acidic simulant for products intended for such drinks.

Is 18/8 stainless steel toxic?

No. 18/8 is another name for 304. Studies of food-contact stainless steel show chromium released as trivalent Cr(III), with no hexavalent chromium detected.

Can a stainless steel water bottle make you sick?

Rarely because of the metal. Most problems come from hygiene: residue and mold in lids, gaskets and straws, or warm dairy stored for too long. Clean the lid parts as carefully as the bottle itself.

Is 201 stainless steel safe for drinking water?

201 is not toxic, and FDA accepts the 200 series for food equipment. However, it has lower corrosion resistance than 304. China’s vacuum flask standard therefore requires 304-equivalent steel for liners, and we do not use 201 in our bottles.