I have spent years arguing that nickel is the heavy metal the food-safety world is going to be forced to reckon with: that it drives pathogenic virulence, that it appears in vegetable-based baby foods during the worst possible developmental window, and that it acts as a catalytic driver of necrotizing enterocolitis in preterm infants. For most of that time the standard response has been that I am early, speculative, ahead of the evidence. So I want to point at a document, because it changes the conversation, and because it isn't mine.
It's California's.
What the State of California already says, in writing
The Office of Environmental Health Hazard Assessment (OEHHA), the California agency that administers Proposition 65, publishes a dedicated fact sheet on nickel and nickel compounds, dated February 2025. Read it for yourself (direct PDF). Here is what a state government agency states plainly on that page:
- Nickel and nickel compounds are on the Proposition 65 list for cancer. Exposure can cause cancer of the nasal cavity, paranasal sinus, and lungs.
- Certain soluble nickel compounds, and nickel carbonyl, are also on the Proposition 65 list for reproductive toxicity.
- "During pregnancy, exposure to soluble nickel compounds or nickel carbonyl may affect the baby's development."
- Exposure to soluble nickel compounds "may also harm the male reproductive system."
- And, in the agency's own words, "during pregnancy, nickel and nickel compounds can pass from mother to baby."
Sit with that. This isn't an activist blog or my journal. It's the formal, published position of the state agency whose entire job is to identify chemicals that cause cancer and reproductive harm. California has already concluded, and committed to print, that nickel is a carcinogen, that it is a developmental and reproductive toxicant, and that it crosses the placenta from a mother to her unborn child.
So why can't anyone find it?
Here is the part that I cannot stop thinking about. Having concluded all of that, the agency appears to have done the bare minimum to surface it. The fact sheet exists, but it is the kind of page you only ever reach if you already know to go looking for it: sparsely linked, buried under the general machinery of the Proposition 65 chemical list, easy to publish and easier to overlook. It reads almost as though it were prepared to satisfy an obligation rather than to inform a parent.
I am not going to tell you why a government builds a page documenting that a common environmental and dietary contaminant can harm a developing baby and then declines to put it anywhere a developing baby's mother would actually see it. I do not have to. I am only going to note that this is what happened, and ask the obvious question: if the science were not solid, the page would not exist in this form. And if the science is solid, solid enough for the state to warn about cancer and to warn pregnant women specifically, then the quiet is the story.
There is an enormous difference between knowing something and acting on it, and an even larger difference between acting on it and making it findable. The warning about nickel and pregnancy clears the first bar. It does not come close to clearing the others. The most generous reading is bureaucratic inertia. The least generous reading is that fully surfacing nickel's developmental toxicity would raise an uncomfortable question the food system is not ready to answer: if nickel can harm a developing baby, and nickel is in the food, then what about the food?
It is not just California, and the dietary numbers are the part that should stop you
If California were the only agency saying this, you could write it off as one state being cautious. But it is the third voice in a pattern of three, and the other two are worse.
Start with the federal government. The U.S. Environmental Protection Agency publishes a document called the Nickel Compounds Hazard Summary. Its framing on diet is reassuring: the soluble nickel that occurs naturally in foods like chocolate, oats, and nuts is bound up inside organic plant matrices, and ordinary diet, on this reading, does not deliver anything close to the dose associated with reproductive harm. (That same summary concedes, in its own animal-study findings, that oral exposure to soluble nickel compounds produced fetal loss, reduced survival, and skeletal abnormalities, so the reassurance is about dose, not about whether the harm is real.) Take the dietary framing at face value for a moment anyway, and notice two things. First, the document lives at a URL that spells the element "nickle", as in epa.gov/sites/default/files/2016-09/documents/nickle-compounds.pdf. A misspelling baked into the federal filename itself is a small but real drag on whether a worried parent searching "nickel in baby food" ever lands on it. The most safety-relevant federal page on this metal is, quite literally, filed under the wrong name. Second, the "diet is fine" framing is a claim about adults eating whole foods, and it is not the last word. The agency that actually sat down and modeled dietary nickel exposure across the whole population reached a very different conclusion.
That agency is the European Food Safety Authority. In its 2015 Scientific Opinion on nickel in food and drinking water (EFSA Journal 2015;13(2):4002), EFSA did the work that turns a hazard into a number. It set a Tolerable Daily Intake (TDI) of 2.8 micrograms of nickel per kilogram of body weight per day, and, critically, it identified reproductive and developmental toxicity as the critical effect: the most sensitive endpoint, the one the safe limit is built to protect. This is the same conclusion California reached, expressed as a dose.
Then EFSA compared that limit to what people actually eat. The finding is the part that should stop you. Current dietary exposure to nickel already exceeds the TDI, and the exceedance is largest in the youngest eaters. At the 95th percentile, EFSA put chronic dietary nickel exposure as high as 20.1 µg/kg body weight per day in toddlers, roughly seven times the 2.8 µg TDI, with exposure generally above the TDI in toddlers and other children, and in infants in some surveys. The reason is mechanical: small children eat far more food relative to their tiny body mass, and that food skews toward exactly the plant-based, grain-and-vegetable items that carry nickel. EFSA also confirmed the mechanism California only gestures at: nickel crosses the placenta, so maternal dietary exposure is fetal exposure.
Put the three documents side by side and the picture is not subtle:
- EPA says the diet is fine, in a file misspelled badly enough to dent its own findability.
- California (OEHHA) says nickel can harm a developing baby and crosses from mother to child, on a page almost no one is steered to.
- EFSA actually ran the dietary numbers and found that the most vulnerable population on earth, infants and toddlers, is already over the safe limit, with developmental toxicity as the very reason that limit exists.
The reassuring document is the one that is easy to find. The alarming document is the one that did the arithmetic. And the population the arithmetic flags hardest is the one that cannot read any of it.
Why this matters to me specifically
Because I have already mapped the mechanism the fact sheet stops short of. OEHHA tells you nickel can affect a baby's development and can cross from mother to child. My work explains part of how the damage compounds once it is inside: nickel is an essential cofactor for the virulence machinery of multiple WHO priority pathogens (ureases, [NiFe]-hydrogenases, glyoxalases), enzymes the human host does not need but that bacteria use to survive immune attack and colonize inflamed tissue. In the preterm gut, that abstraction becomes the difference between a microbiome that stabilizes and one that tips into necrotizing enterocolitis. The state warns about the metal. I have been documenting what the metal does to the microbial ecosystem of the most vulnerable patients alive.
The European Union has already begun regulating nickel in foods. California has published the warning. The pieces are assembling in plain sight. What is missing is the connective tissue: the willingness to link the dedicated nickel page to the baby-food aisle, to the NICU, to the certification standards that do not yet exist. That connective tissue is exactly what I build, and it is why I built HMTc: the certification infrastructure has to exist before the regulatory wave crests, because by the time the fact sheet stops being quiet, the demand will be deafening.
The prediction
I have a documented habit of being right about direction and early about timing, and here is the call. The OEHHA nickel fact sheet is a tell. It is the regulatory equivalent of a tremor before the quake: the moment a state agency commits the dangerous conclusion to paper while declining, for now, to act on its full implications. That gap does not last. Push comes to shove; the science does not un-happen; and a warning a government has already written down does not stay buried forever. When it surfaces, when "nickel can affect your baby's development" moves from a PDF nobody links to the front of the conversation about what we feed infants, the people who saw it coming will be the ones who read the fact sheet before it was famous.
I read it. Now you have too.