In January, a shopper in Nanning, southern China, bought a steamer pot online that was listed as 304 stainless steel.1 When it arrived, she dabbed a test liquid on it and it quickly turned red, which by the test's markings meant it was 201 manganese steel.1
The Chinese newspaper Guangming Daily has described the same pattern more widely: steel goods sold as 304 or 316 that held too much manganese and were really 201 or 202.2 ‘Stainless steel’ is a family of grades with different mixes of manganese, chromium and nickel, and the 200-series grades resist corrosion poorly, so they are not recommended for containers that hold acidic or hot food for long periods.1,2
The reassuring part is that lab tests of genuine grades have found the metal they release stays below the release limits in the Council of Europe test protocol the researchers used.3 The people with most reason to care are those with a nickel allergy, and anyone cooking acidic food in mislabelled or 200-series steel.
YAN's view: stainless steel is one of the best materials for a long-lasting kitchen, but only when it is the grade it claims to be. The amounts of metal genuine steel releases in tests are small, but small is not proof that it is safe for everyone, so we choose genuine good-grade steel and keep it away from the jobs it does badly.
What you need to know
- A label saying ‘stainless’ or ‘food-grade’ does not tell you the grade, and even a printed grade can be wrong.
- The 200-series grades resist corrosion poorly and are not recommended for holding acidic or hot food for long.1
- New, unused pots, acidic food and long cooking release the most metal, and repeated use brings it down.3,4
- If you have a nickel allergy, you have the most reason to choose carefully and to cook acidic dishes in something else.
- Buy 304 or 316 steel from a seller who will take it back, cook a few plain meals in a new pan first, and keep acidic leftovers in glass.
What ‘food-grade’ stainless steel actually is
Stainless steel is iron mixed with chromium, which forms a thin, invisible skin on the surface that stops the metal underneath from rusting. France, for example, requires steel that touches food to contain a minimum share of chromium, and allows nickel and manganese in the mix.5
The grades shoppers meet most often, 201, 304 and 316, are each made with a different mix of manganese, chromium and nickel, and the raw materials for each grade differ hugely in price.2 That price gap gives a seller a reason to pass a cheaper grade off as a dearer one. So what really separates one grade from another is the recipe of metals inside, which no shopper can see by looking at a shiny pan.
When the technical guide that Europe's manufacturers and regulators use for food contact metals was updated in 2024, its migration limit for manganese (the most of that metal allowed to seep into food) was tightened from 1.8 to 0.55 milligrams per kilo.6,7,8 That is less than a third of the old figure, which means far less manganese is now allowed to pass from the pan into the meal on your plate, and a pot that passed the old test could fail the new one.
China's food-contact standard judges a steel product mainly by how much metal moves out of it into food, not by the grade stamped on it, so in theory a pot sold as 304 can fail and a 200-series one can pass.1 Wang Qingjie, speaking to Xinhua about the standard, was frank about the 200 series: it resists corrosion poorly and “only suits short-term contact with water-type items, for example an ordinary vegetable-washing basin.”1 In other words, 200-series steel can handle quick jobs with plain water, like rinsing vegetables, but it is the wrong metal for simmering tomato sauce or keeping coffee hot all day.
Why acid, heat and a new pan make the difference
At the University of Messina in Italy, researchers cooked tomato sauce and lemon marmalade for an hour in new and used stainless steel pots from different manufacturers.4 More nickel and chromium came out the longer the food cooked, more from new pots than used ones, and more when the food was more acidic, and the amount sometimes differed a lot from one maker to another.4 In every test the amounts stayed below the levels known to trigger an allergy, though the researchers warned that nickel already in food plus nickel from the pot could be too much for highly sensitive people.4
A study of metal kitchen utensils in Korea found that how much metal came out was highly dependent on pH, the measure of how acidic a food is.9 Chromium and nickel release from its stainless steel samples was also much higher in the first test than in the third.9 Another set of laboratory tests likewise saw less metal released each time the steel was exposed again, and generally more when it was hotter.3
Put together, the picture is consistent: acid, heat, long cooking and a brand-new surface each pull more metal out, and ordinary use settles it down.
In another study, researchers collected 124 new stainless steel items, from cutlery to kettles, from supermarkets, shopping malls and online shops.10 Items in one test group, including the cutlery and the kettles, were boiled for half an hour in 4% acetic acid, standing in for food, then left in it for 24 hours at room temperature.10 Acetic acid is the acid that gives vinegar its sour taste. One item stood out: on grill grids, the spot welds were not stainless steel at all and appeared to have corroded in the acid.11 A steel product is only as good as its weakest part, so welds, rivets and any other metal that touches food count too.
Drinking bottles have tested well: when the German magazine ÖKO-TEST checked two stainless steel bottles for allergenic nickel, no bottle in its test released pollutants into the drink.12 Stiftung Warentest filled steel travel mugs with a mild acid to imitate coffee and found nothing moved from the steel into the drink.13 Cold water in a bottle is an easy job for good steel; a long simmer of tomato sauce in a cheap pot is the hard one.
Who has most reason to care
About 10 percent of people, mostly women, have a contact allergy to nickel.5 For them, nickel swallowed in food can also trigger skin reactions or make them worse, says Germany's food-risk agency, the BfR.14 That is why the European guideline for metal kitchenware sets its nickel limit using data from people already sensitised to nickel.5
Most of the nickel people take in comes from food itself.14 Europe's food safety authority, EFSA, found that the most heavily exposed toddlers and young children already take in more nickel from everyday food than the tolerable daily intake, the amount judged safe to eat every day for life, which it says may raise a health concern.15 That finding is about nickel in food rather than from pans, but it means the most exposed young children have little room to spare, which is one more reason not to let the pan add to it.
This investigation continues below.
Want the next one in your inbox?
What the rules say
The Council of Europe guide that sets release limits for metal kitchenware is not legally binding, but because there is no specific EU-wide law for food-contact metals, manufacturers and regulators use it as their reference.5,8 It expects every metal in the steel, not only chromium, to stay within its own limit.5 Italy goes further and keeps an approved list of stainless steel grades for food use.5
Plated items, ordinary metal with a thin coating such as nickel on top, are not suitable for direct contact with food.5 The grade stamped on the base is only the maker's claim; the test that counts is how much metal comes out.
What nobody has tested yet
We found no test of the steel actually sold in children's cups, bowls and bottles, of the lids and seals that come with them, or of real family pans after months of use. The nickel industry's own fact sheet says the nickel that moves into food from common stainless steel is very small next to what many foods naturally contain.8 That is an interested party speaking, but independent tests from Italy, Korea and Germany point the same way for genuine steel; none of them tells us how much comes out of a pan that is not the grade it claims to be.
EFSA also notes real uncertainty about how swallowed nickel affects people.15 Tests of real children's products, and of cheap or mislabelled pans after months of family cooking, would tell us whether our caution here is too much or too little.
What to choose
At YAN we would keep genuine 304 or 316 steel for cooking and drinking, and glass or ceramic for keeping acidic food. The worse option is a 200-series pot or flask, or one wrongly sold as 304. Genuine 304 or 316 is clearly better, though even a good new pan releases the most metal in its first uses.
- Free, with a new pan: cook a few plain meals, such as pasta or steamed vegetables, before the first long tomato or lemon dish.
- When buying: choose pots, flasks and bottles marked 304 or 316 on the base or product page, and skip unmarked ‘stainless’ and anything nickel- or chrome-plated for food.
- Buy from a seller who will take it back, and if it helps, ask once: “Is every part that touches food, inside and out, 304 or 316 steel, and will you refund me if it isn't?”
- If a pan sold as 304 or 316 shows rust within months, return it: the good grades are made to resist exactly that.
- If you can't replace a pan you suspect is a cheap grade, keep it for boiling water, pasta and steaming, and cook acidic dishes in something else.
- If you or your child has a nickel allergy, ask your doctor whether to avoid long-cooked acidic food in steel; an enamelled or glass pot for those dishes is a simple fix.
Steel can be recycled again and again, and a good pan can last for decades. That is why we would rather you buy one genuine pot once than three cheap ones that look the same: it is better for your food, your money and the scrap heap. If you do only one thing tonight, make it the free one: move tomato sauce, citrus, pickles and vinegar dressings out of steel pots into glass or ceramic before they go in the fridge.