The conversation around heavy metals in food has gotten loud, and it’s not hard to understand why. Consumer Reports published findings that shook up the chocolate industry. Lawsuits followed. Brands scrambled. And somewhere in between the panic and the corporate spin, the average person trying to eat well was left with almost no usable information.
This page exists to fix that, at least partially.
The goal here isn’t to scare anyone or to hand out a clean bill of health to products that don’t deserve one. It’s to give you the framework that most companies won’t: what contamination actually means in a practical diet, how your body handles these metals, and why those two things together change how you should read a test result.
Quick Disclaimer: This article is an opinion piece using publicly available documentation. While I do my best to make sure everything is accurate, I am not a scientist nor medical expert. Please do not take this article as fact, but instead as a starting point to inform yourself about your diet and what’s in it.
There is no clean plate
Start with the uncomfortable truth: there is no diet that is free of heavy metals. Not organic. Not locally sourced. Not ceremonial grade. Not whatever label the marketing department landed on this quarter.
Metals like lead, cadmium, and arsenic are in the soil. They’re in the water. They’ve been deposited by decades of industrial agriculture, leaded gasoline, phosphate fertilizers, and in some regions, centuries of mining and colonial land use. Plants absorb them through their root systems whether the farmer wants them to or not. Cacao grown in volcanic Central and South American soil pulls cadmium from the earth at elevated rates regardless of how carefully the farm is managed.
Pesticides follow the same logic. EWG’s 2025 Dirty Dozen report found that more than 90% of samples from the twelve most-contaminated fruits and vegetables tested positive for potentially harmful pesticide residues, with spinach leading the list for total pesticide residue by weight. The point of that finding isn’t that you should stop eating spinach. It’s that contamination at trace levels is the default condition of a modern food supply, not an exception.
This matters as a baseline because the entire conversation about acceptable contamination levels in any product only makes sense once you accept that zero isn’t an option on the table. The question was never “contaminated or not.” It was always “how much, from what sources, and what does my body actually do with it.”
Accumulation is the real concern
Trace contamination in a single meal isn’t what causes harm. What causes harm is the same low-level exposure, repeated daily, over years and decades, in a body that stores certain metals far better than it eliminates them.
This is what half-life means in a biological context. It describes how long it takes for your body to eliminate half of what it absorbed. And for some metals, that number is genuinely alarming.
Lead circulates in your blood with a half-life of roughly 28 to 36 days, which sounds manageable. What doesn’t sound manageable is that once lead migrates from blood into bone, the half-life extends to somewhere between 20 and 30 years. Your skeleton essentially becomes a long-term storage depot. Over 95% of the body’s total lead burden in adults lives in bone and teeth. It doesn’t stay there permanently either: pregnancy, lactation, osteoporosis, and normal aging can all remobilize bone lead back into the bloodstream decades after the original exposure occurred.
The “eat paint chips” association most people have with lead poisoning is not a meme. It tracks directly from this biology. Children absorb lead at dramatically higher rates than adults (more on that shortly), and their developing neurological systems are far more vulnerable to its effects. The paint chip image stuck in the cultural memory because children were actually being poisoned, at scale, in ways that weren’t immediately visible. Blood lead levels that cause no obvious symptoms in an adult can produce lasting cognitive harm in a child.
Cadmium is, in some ways, worse. Its half-life in the kidney and liver is approximately 30 years. Healthy adults absorb only 3 to 8% of dietary cadmium from any single exposure, which sounds reassuring until you account for the fact that nearly all of what does get absorbed stays. Cadmium accumulates in the kidneys over a lifetime, and kidney damage from cadmium exposure is largely irreversible once it begins. Renal dysfunction, bone demineralization, and increased cancer risk are the long-term endpoints. Unlike lead, there’s no physiological process that meaningfully clears it.
Arsenic is the outlier in this group, and not in the direction most people expect. Inorganic arsenic, the form that matters for toxicity, is actually highly bioavailable: research shows roughly 45 to 80% of inorganic arsenic from food is absorbed after ingestion, with some studies reporting even higher figures for soluble forms. It doesn’t sit around in the body the way cadmium does; arsenic exits primarily through urine with a half-life of roughly two to three days.
A faster half-life doesn’t mean arsenic is safe to ignore, though. Two separate issues are worth understanding here. First, arsenic is a known carcinogen, and repeated daily exposure at elevated levels accumulates risk even when the arsenic itself clears quickly. The damage isn’t purely from what’s stored; it’s from what the arsenic does to cells during transit. Second, arsenic contamination has shown up beyond agricultural soil in recent years. Rice is a well-documented concern because the rice plant is particularly efficient at absorbing arsenic from paddy water and soil, which is why rice-based products, rice cakes, and certain snack foods have drawn scrutiny from food safety researchers. The arsenic conversation isn’t only a soil and cacao problem. It’s a commodity food problem.
So while the short half-life of arsenic is genuinely different from lead and cadmium biology, it doesn’t remove it from the watch list. High absorption, carcinogenic mechanism, and widespread presence in staple foods make it worth tracking in your overall diet load.
What Prop 65 is, why it’s stricter than most people realize, and why companies push back
California’s Proposition 65, formally the Safe Drinking Water and Toxic Enforcement Act of 1986, requires businesses to warn consumers before knowingly exposing them to chemicals on the state’s list of known carcinogens and reproductive toxins. For cadmium, the Maximum Allowable Dose Level (MADL) is 4.1mcg per day. For lead, it’s 0.5mcg per day.
These thresholds are set at 1/1000th of the No Observable Effect Level, the concentration at which researchers found no measurable harm in controlled studies. The 1,000x safety buffer is intentional. Regulators building this framework understood that people don’t eat one food a day; they eat dozens, each contributing its own trace load of metals. The threshold isn’t “the amount that hurts you.” It’s “the amount at which, if every source in your diet hits this level simultaneously, you might approach concern.”
Companies push back on these thresholds constantly. Some of the criticism has a factual basis. Prop 65 was originally written for drinking water, not food matrices. California has revised its safe harbor levels upward since the original MADL figures were published, and the updated thresholds are more aligned with international standards like those used by the EU. The Consumer Reports investigation in 2022 that generated significant media coverage used the older, stricter MADL numbers, not the revised safe harbor levels.
When a brand responds to contamination findings by arguing that the regulatory framework is flawed, that Prop 65 was designed for water not chocolate, that the MADL is overly conservative, that Canada has different standards, that bioavailability means the real absorbed dose is lower: all of that may contain fragments of truth. What it doesn’t do is tell you how much of each metal is in their product per serving. The deflection toward regulatory criticism, rather than toward disclosure, is doing a specific kind of work. It’s moving the conversation away from numbers you can evaluate and toward a debate about methodology that most readers don’t have the background to adjudicate.
A brand that clears the Prop 65 safe harbor threshold on its own product in isolation has demonstrated one thing: that single product, eaten alone, sits below the California limit. It has not demonstrated that a person eating that product daily, alongside all the other foods in a normal diet, is operating at a safe cumulative load. The threshold is a floor. Some brands market it as a ceiling.
What bioavailability actually means, and the math behind it
Here’s where the picture gets more honest in the consumer’s favor.
Bioavailability is the fraction of what you ingest that your body actually absorbs into the bloodstream and distributes to tissues. The number on a heavy metals test result is the total concentration in the product. That is not the same as the number your body processes.
For a healthy adult, the absorption rates break down roughly like this:
Lead: Adults absorb approximately 5 to 10% of dietary lead from the gastrointestinal tract. That number varies based on whether the lead is ingested with food versus on an empty stomach, the nutritional status of the person, and the specific chemical form of the lead in question.
To put that in practical terms: if a product contains 5mcg of lead per serving, a healthy adult absorbs somewhere around 0.25 to 0.5mcg of it. The rest passes through. That doesn’t make 5mcg of lead in a product acceptable; 5mcg is already 10x the Prop 65 MADL. But it does mean the raw test number and your actual internal exposure aren’t the same figure.
Cadmium: Healthy adults absorb approximately 3 to 8% of dietary cadmium from food. Again, a practical example: a product with 10mcg of cadmium per serving results in roughly 0.3 to 0.8mcg being absorbed by a healthy adult. The Prop 65 MADL is 4.1mcg per day total from all sources.
The reason this doesn’t resolve the concern is what was covered earlier: cadmium doesn’t leave. Nearly everything absorbed stays in the kidneys and liver. Over years and decades, even 3 to 8% of daily exposure from multiple dietary sources accumulates into a substantial body burden. The low absorption rate is not a long-term protection; it’s a slower clock toward the same problem.
Arsenic: As noted above, inorganic arsenic absorbs at a much higher rate, roughly 45 to 80% from food. There’s no similar “only a fraction enters your system” buffer for arsenic. What’s in the product is largely what you absorb.
A note that applies to all three metals: these absorption figures are averages for healthy adults. Several factors push them significantly higher. Iron deficiency increases lead absorption substantially, because the body uses the same transport pathway for both iron and lead. Deficiencies in zinc and calcium can increase cadmium absorption by as much as tenfold in some research. Compromised gut health, gut microbiome disruption, and antibiotic use have all been shown to raise absorption rates for multiple metals. The 5 to 10% lead figure and the 3 to 8% cadmium figure describe a best-case healthy adult under normal dietary conditions. They describe a narrower population than most public health discussions assume.
Children are a separate calculation entirely
The bioavailability figures above apply to adults. For children, the numbers are substantially worse, and the stakes are higher.
Children absorb approximately 40 to 50% of ingested lead, compared to 5 to 10% in adults. That’s a four to five times higher absorption rate, in a body that weighs significantly less and a neurological system that’s still developing. Lead at concentrations that produce no detectable symptoms in an adult can cause lasting cognitive effects, reading and learning disabilities, reduced attention span, and behavioral problems in children. There is no established safe blood lead level for a developing child; the threshold for medical follow-up has been revised downward multiple times as research has improved.
This is the biological reality behind what most people treat as a historical footnote. When lead paint was common in housing and leaded gasoline was still in use, children were accumulating lead at rates that produced measurable, population-level neurological harm. The damage didn’t require dramatic acute poisoning. It came from routine daily exposure in developing bodies with absorption rates far above what adults experience.
The same pediatric vulnerability applies to cadmium, though the research there is less extensively documented in children specifically. The general principle holds: smaller body weight, higher absorption relative to body mass, and developing systems that are less equipped to handle toxic metal load.
This is relevant for any parent evaluating heavy metals in a product consumed regularly by children, not just occasionally by adults.
How bioavailability changes the way you read a test result
Pulling this together into a practical picture:
A test result showing elevated metals in a product is real information. It’s not alarmist, it’s not a technicality, and it’s not adequately explained away by regulatory debate. But the raw mcg figure on a certificate of analysis is also not a direct translation to what enters your body, at least for lead and cadmium.
Here’s a simplified version of the math that most brands never show you:
Say a product contains 2mcg of cadmium per serving. At the Prop 65 MADL of 4.1mcg per day, that’s already nearly half your daily limit from one source before you’ve eaten anything else. A healthy adult absorbing 3 to 8% of that means your body actually takes in roughly 0.06 to 0.16mcg from that serving. Over the course of a day eating multiple foods, each contributing small cadmium loads, your total absorbed dose is still a fraction of the ingested total.
That fraction matters. It’s the difference between a test result that should inform your consumption habits and one that should make you stop entirely. A product with 2mcg of cadmium per serving is worth knowing about. A product with 40mcg per serving from a company that has never published its test results is a different situation, both for total ingested dose and for what it tells you about the brand’s priorities.
The framework that serves most consumers well: pay attention to the total ingested dose first, because bioavailability percentages can’t rescue truly extreme contamination levels. Then factor in that your actual absorbed dose is lower, particularly for lead and cadmium. Then ask what else you’re eating that day and what your cumulative dietary load looks like across your whole diet, not just from a single product.
Transparency matters more than perfection
The final point, and the one that connects this page to every brand review on this site:
There is no such thing as a zero-contamination food product. Given the soil conditions in the regions where most cacao, rice, leafy greens, and root vegetables are grown, some contamination is not a sign of a negligent or dishonest company. It’s a sign that they grow food on Earth.
What separates a brand worth supporting from one that isn’t is not whether they have metals in their product. It’s whether they tell you. A company that publishes its test results, states the numbers per serving in plain language, and doesn’t argue against the regulatory framework when those numbers are inconvenient is doing more for consumer safety than a brand with slightly lower numbers that hasn’t published anything and deflects every question about contamination with marketing language.
Bioavailability means the math is more forgiving than the raw numbers first appear, but only for consumers who have access to the actual numbers. Companies that refuse to provide them are not protected by bioavailability. They’re protected by the gap they create between you and the information you’d need to evaluate the risk.
There is no safe level of heavy metal exposure in a strict biological sense. Accepting that as the baseline doesn’t mean treating all contaminated products as equivalent. It means asking better questions: how much, from what source, published by whom, and what does it look like across my whole diet. Those are the questions this site exists to help answer.