Heavy Metal Testing: Built for Supplement Compliance

​

Heavy metals don't discriminate. Lead, arsenic, cadmium, and mercury can enter your supply chain through raw botanical ingredients, mineral sources, soil contamination, and processing equipment, and they won't show up on a visual inspection. By the time a problem surfaces, it's already a recall risk.

​

At Twin Arbor Labs, we use ICP-MS to detect trace-level elemental impurities with the sensitivity the USP framework requires. Our testing follows USP <233> analytical procedures and is benchmarked against USP <232> elemental impurity limits, the standard the FDA has adopted for finished dietary supplements.
 

​

​

Understanding Your Limits: It's Not One-Size-Fits-All

​

One of the most common questions we get from clients is: "What ppm limit should I be testing against?" The honest answer is, it depends on your product's maximum daily dose.

​

Under USP <232>, heavy metal safety limits are established as Permitted Daily Exposures (PDEs), expressed in micrograms per day. Because a consumer taking a 500 mg capsule is ingesting far less material than someone scooping 40 grams of protein powder, the allowable concentration in ppm looks very different between those two products, even though the underlying safety threshold is identical.

​

The PDEs for oral products are:

• Lead (Pb): 5 µg/day

• Cadmium (Cd): 5 µg/day

• Arsenic (As): 15 µg/day

• Mercury (Hg): 30 µg/day

​

A quick note on units that trips up a lot of clients: these regulatory limits are expressed in ppm (parts per million), not ppb. A spec written in ppb that looks numerically close to an FDA ppm limit is 1,000 times more stringent than what the regulation requires. If your internal specs or supplier COAs are currently in ppb, confirm that tighter standard is intentional — and that your suppliers can consistently meet it.

​

​

Calculate Your Spec: The Formula

​

To find your maximum allowable concentration, divide the PDE by your product's maximum daily dose in grams:

​

Maximum Allowed Concentration (ppm) = PDE (µg/day) ÷ Maximum Daily Dose (g/day)

Note: 1 ppm = 1 µg/g, so the units work out cleanly.

​

Example A — High-Dose Protein Powder A meal replacement taken at 2 scoops per day (40 g total): Lead limit = 5 µg ÷ 40 g = 0.125 ppm

​

Example B — Low-Dose Capsule A 500 mg (0.5 g) botanical capsule taken once daily: Lead limit = 5 µg ÷ 0.5 g = 10 ppm

​

Same element. Same regulation. Vastly different specifications — which is exactly why getting your daily dose right before setting specs matters so much.

​

Use the calculator below to find the limits for your specific product.