Food and supplement makers should test for four heavy metals: arsenic, lead, cadmium, and mercury. For arsenic, the inorganic form matters most. Test before you approve a supplier, on incoming lots of higher-risk ingredients, on finished product, after any change, and after an out-of-range result.

These four elements are not added to food. They come in with the soil, the water, and the ingredients.

The amount in any food depends on the amount in the environment and on how much the plant or animal takes up. FDA explains this in its Closer to Zero plan.

So the risk depends on your ingredients, not only on your product category. A good testing program starts there.

Why these four elements get the attention

They occur naturally in the earth's crust, and human activity adds to them. Levels in air, water, and soil vary by location and by past or current pollution. Grains, fruits, and vegetables take them up as they grow. Mercury is different. Seafood is the main dietary source, because mercury builds up in seafood.

The law expects you to manage this. Food makers must use preventive controls as needed to significantly minimize or prevent exposure to chemical hazards, including lead, arsenic, cadmium, and mercury. For dietary supplements, FDA's cGMP rule requires specifications that set limits on contamination, and verification that finished batches meet them.

Which heavy metals to test for

• Arsenic: ask for inorganic arsenic, not only total arsenic. The inorganic form is the more toxic one. In the rice samples FDA reviewed, it made up anywhere from about 12 percent to 100 percent of total arsenic. FDA's action level for inorganic arsenic in infant rice cereal is 100 parts per billion.
• Lead: FDA issued final guidance with action levels for lead in processed foods for babies and young children in January 2025. See FDA's Closer to Zero page for the current list.
• Cadmium: plants take cadmium up from soil. FDA's Closer to Zero plan lists cadmium action levels as work in progress. Check the page for the current status.
• Mercury: focus on seafood and seafood-derived ingredients, where mercury builds up.

Labs can often report other elements, such as chromium, in the same run. FDA's Elemental Analysis Manual method 4.7 covers arsenic, cadmium, chromium, lead, mercury, and other elements in food.

Which limits apply

No single limit covers every product. The limit depends on the product, the market, and the customer.

• FDA action levels apply to specific foods, such as infant rice cereal and foods for babies. An action level is not a permitted level, and FDA can take enforcement action without one (FDA).
• For supplements, you set limits in your own specifications. USP chapter <2232> also sets elemental contaminant limits for dietary supplements labeled as meeting USP standards.
• California's Prop 65 sets safe harbor levels for listed chemicals, including lead and cadmium. They matter if you sell into California.
• Retail buyers may ask for results against specific limits. A retail-ready test package often includes a heavy metals screen.

Write the limit that applies to each product into its specification, so every test result has something to be measured against.

When to test for heavy metals

A single test at a single point is a snapshot. A program tests where risk enters.

1. Before you approve an ingredient or supplier

Qualify the source with your own test, not only the supplier's paperwork. FDA has cited a supplement maker that relied on supplier COAs and did not test for contaminants such as heavy metals. See the warning letter.

2. On incoming lots of higher-risk ingredients

Rice, plant-based ingredients, and seafood-derived ingredients deserve more frequent checks. FDA's draft guidance on supplier programs suggests testing supplier lots more often at first, such as monthly, and less often once a supplier shows a good record.

3. On finished product

For supplements, FDA expects you to verify that finished batches meet your contamination limits. You can use a sound statistical sampling plan, or test every batch.

4. When anything changes

A new supplier, a new sourcing region, or a new formula can change the metals profile. Review the testing plan before the first batch runs. For food facilities with a food safety plan, 21 CFR 117.170 requires a reanalysis when a change creates a new hazard or raises a known one.

5. After an out-of-range result

Investigate the source, retest, and check other lots from the same supplier.

How labs test for heavy metals

Labs usually measure metals by inductively coupled plasma mass spectrometry (ICP-MS). When you need inorganic arsenic, the lab must separate it from the other forms first, as FDA's own scientists did for rice. Ask whether the lab speciates arsenic.

Genista's ISO/IEC 17025 scope of accreditation includes ICP-MS for 24 elements, including arsenic, cadmium, lead, and mercury, plus inorganic arsenic. To check any lab, ask whether the method you need is inside its accredited scope.

Questions to ask about your current program

• Which ingredients in your formulas carry the highest metals risk?
• For arsenic, do you test the inorganic form where it matters?
• Which limit applies to each product and market, and is it written into the specification?
• Do you rely on supplier COAs for metals, and do those COAs report results against your limits?
• When did you last test finished product, and how do you choose batches?
• What triggers an extra test: a new supplier, a new region, a new formula?

If you cannot answer one of these quickly, start there.

The bottom line

A heavy metals program covers the right ingredients, the right forms of each metal, and the right points in your process. One test, at one point, for one metal leaves the rest unchecked.

Genista is built for this: one connected system for product safety, with accredited testing, robotic automation, connected software, and services in a closed loop, instead of stitching together three or more vendors.

Want to see how heavy metals testing fits your ingredients and products? Book a Meeting →