FAQs: Heavy Metals in Foods

Feel like everywhere you turn there’s a new report of lead or other heavy metals in the food products in your pantry? You’re not alone. While it can be unnerving to hear about contaminants ending up in food and personal care items, it’s important to start with the facts — the very same ones the in-house experts at Thrive Market use to ensure you can trust the products we carry for your family. 

To answer the most common questions we get from members and share our approach to monitoring levels of heavy metals in products, we went straight to the pros: the FSQA (Food Safety & Quality Assurance) team at Thrive Market led by Carla Hechler, VP of FSQA. 

What are heavy metals, and why are they concerning? 

“Heavy metals” is a broad term that describes a group of naturally occurring metallic elements of high molecular weight and density compared to water. You’ll probably recognize the names of common metals like lead, mercury, cadmium, and arsenic, which can be toxic at high levels because they can bioaccumulate in the body and/or replace other beneficial metals like magnesium, iron, calcium, and zinc. 

Heavy metals are found naturally in the environment, often at high levels because of past industrial uses, wastewater, and pollution. Over time and with prolonged exposure, they can cause harm — especially for infants and young children. While many factors are involved in a child’s development, excessive and prolonged exposure to heavy metals can affect cognitive and neurological development. 

How do heavy metals end up in food? 

Because heavy metals are naturally occurring elements in the Earth’s crust, they can get into water and soil through practices like mining, fracking, industrial agriculture, and using wastewater for irrigation. Arsenic and lead are two of many common contaminants found in soil (and in turn, the crops that grow in it). Other factors that can impact heavy metal concentrations include: 

• How foods grow: Root vegetables grow in soil, so they absorb more heavy metals than vegetables grown above ground. 
• A plant’s biology: Sometimes, it depends on the makeup of the plant itself. Rice, for example, is more likely to absorb arsenic, while onions are more likely to absorb lead.
• The food chain: A plant, animal, or living organism’s position on the food chain can affect its heavy metal concentration. When it comes to our oceans, fish at the top of the food chain, like tuna, can accumulate mercury more than algae, which is at the bottom. 

What regulations are in place for heavy metals, and how does Thrive Market determine if a product is at an acceptable level? 

There aren’t always overarching regulations for heavy metals, but there are certain laws, regulatory bodies, and organizations that we trust and use to set our own standards at Thrive Market:

California Prop 65

You may have seen a Prop 65 warning on a product before — the California law requires businesses to notify California consumers when they’re at risk for exposure to chemicals that are known to the state to cause cancer or reproductive toxicity. Established in 1986 by the Office of Environmental Health Hazard Assessment (OEHHA) of the California Environmental Protection Agency, Prop 65 designates safe levels for chemicals in products:

• Carcinogens: The no significant risk level, or NSRL, is the daily intake level of a carcinogen calculated to result in one excess case of cancer in an exposed population of 100,000, assuming a lifetime (70-year) exposure at the level in question. 
• Chemicals that cause reproductive toxicity: The maximum allowable dose level, or MADL, is the level at which the chemical would have no observable adverse reproductive effect, assuming exposure at 1,000 times that level. 

Since it was first published, Prop 65’s list of chemicals has grown to 900, and a warning on a product means it may expose you to one or more chemicals on the list. Thrive Market follows Prop 65 guidelines for the products we carry because it’s currently the most strict regulatory limit in the U.S. This includes monitoring these common heavy metals and their associated limits:

• Cadmium: 4.1mcg/day MADL (oral) 
• Arsenic: 10mcg/day NSRL (other than inhalation) 
• Lead: 0.5mcg/day MADL 

FDA Guidance

While the FDA has active working groups to address heavy metals in foods, it has only set regulations for a few food groups. When these regulations are in place, we work to ensure that our vendors comply with them. A few food examples with set regulations include:

• Juice: no more than 50 ppb of lead
• Candy intended for children: no more than 100 ppb of lead
• Bottled water: no more than 5 ppb of lead

The FDA has also issued draft guidance for action levels for lead in food intended for babies and young children, proposing the following limits:

• Fruits, vegetables (excluding single-ingredient root vegetables), mixtures (including grain and meat-based mixtures), yogurts, custards/puddings, and single-ingredient meats: 10 ppb of lead 
• Single-ingredient root vegetables: 20 ppb of lead
• Dry infant cereals: 20 ppb of lead

When it comes to cosmetics, the FDA also provides guidelines. Two examples include:

• Eye products: no more than 65 ppm of mercury
• Externally applied products like lipstick: no more than 10 ppm of lead

When the FDA provides guidance — as in the examples of babies and young children and cosmetics — we work with vendors to ensure they’re implementing these limits as part of their specifications and testing programs. 

Environmental Working Group (EWG) Guidance

The EWG isn’t a regulatory body like the FDA, but it is a trusted resource that publishes ingredient restrictions — including heavy metals — for personal care and cleaning products. At Thrive Market, we take guidance from EWG’s ingredient standards and vet the formulations for every personal care and cleaning product we carry, including requesting and reviewing test results for the presence of heavy metals. 

Do any foods or products carry a higher risk of containing heavy metals? 

Yes. While buying from a responsible source that tests for heavy metals can limit your exposure, certain foods and products are more susceptible to heavy metal contamination because of where or how they grow. 

Foods & beverages:

• Seafood: Ocean pollution can lead to mercury, lead, and cadmium in seafood like tuna, swordfish, and shellfish.
• Rice: Rice — especially brown rice — absorbs more arsenic from water and soil than most other plants. Arsenic is more prevalent in whole grains like brown rice because they accumulate arsenic in their outer layers, which are not processed out. 
• Cacao & chocolate: Heavy metals like cadmium can accumulate in cacao beans. 
• Leafy greens & root vegetables: Plants and leafy greens like cassava, spinach, brassicas (e.g. kale and Brussels sprouts), lettuce, and carrots are prone to cadmium contamination because they hyper-accumulate metals from the soil. 
• Fruit juices & baby foods: Apple and grape juices, along with products made from vegetables, can contain arsenic and lead when they grow in contaminated soil or water. 

Cosmetics & personal care products: 

• Lipsticks: Lip color may contain lead and even cadmium.
• Eyeliners & eyeshadows: These products may contain trace amounts of heavy metals like lead, mercury, and arsenic. 
• Skin-lightening creams: While it’s more common in unregulated or counterfeit products, these may contain mercury. 

Does organic food have fewer heavy metals than conventionally grown food? 

The USDA National Organic Program (NOP) prohibits the use of harsh synthetic fertilizers and many pesticides, but it does not have requirements in place for heavy metals. Because they’re inherently present in soil and water, heavy metals are also present on organic farms.

Does Thrive Market test the products it carries for heavy metals? If so, how often? 

We work closely with our brand and vendor partners to help ensure they have monitoring programs for their supply chains and/or finished products and set clear standards for the items they produce, including unacceptable levels of heavy metals. While Thrive Market does not perform any testing on its own, we routinely analyze the results of third-party testing conducted by vendors for products and ingredients considered to be at high risk for elevated heavy metal levels. In most cases, when setting expectations for our brand and vendor partners, we follow the limits established by Prop 65 because they’re the most stringent, and we work to ensure that products don’t exceed them wherever possible. 

Why does Thrive Market sell products containing ingredients known to be at risk for heavy metals? 

While we work closely with our partners to establish clear testing, monitoring, and supply chain restrictions, you’ll understand by now that some products are still at higher risk for heavy metals because of how their ingredients are grown or processed. And because we carry products that fit a wide range of diets and lifestyles, there are times when a product happens to be one of the only options of its kind for members with dietary restrictions (e.g. gluten), even if it is at higher risk of containing heavy metals. That said, we’re always committed to sourcing products with the best-possible formulations, and we never hesitate to remove a product when we find a better, safer alternative or if we cannot confirm a product’s safety after new data is revealed. 

What about the heavy metal limits proposed as part of the Baby Food Safety Act of 2021 — why are you using Prop 65 limits instead? 

The heavy metal action levels proposed as part of the Baby Food Safety Act of 2021 were significantly lower than other science-backed action levels based on risk. Actual test results for the majority of products on the market are above these limits based on the inherent presence of heavy metals in the environment. Because the levels weren’t feasible, the act was never passed and is not supported or recognized by any regulatory agencies. What’s more, you might see a report that uses the Baby Food Safety Act of 2021 to compare heavy metal levels, but it’s for a product that is not intended for babies or toddlers, meaning the levels are not relevant to the target consumer and the serving size for the product that is usually consumed is not taken into consideration. 

The FDA is working on an action plan for certain types of foods intended for babies and young children that’s achievable for food processors and for which Thrive Market vendors are able to meet. In the meantime, Prop 65 is still the only science-backed, established regulatory limit to reference. 

I see a lot of reports and articles about heavy metals in food. How should I interpret them? Does Thrive Market monitor them? 

At Thrive Market, we do the heavy lifting and the research for you. We actively review reports published about heavy metals to make sure we’re on top of current trends, data, and concerns. We also review available data and current established regulatory limits so that we can provide factual information to our members. When appropriate, we conduct independent, third-party testing on risky products. 

If you’re doing your own research, it’s important to consider the standards to which some test results and studies are being compared — common issues include reports referencing standards that do not apply to the products being tested, testing products for the wrong method of exposure (e.g. oral vs. inhalation), testing for the wrong form of heavy metal (e.g. total arsenic vs. inorganic arsenic), or using standards that were never put into law because they were deemed unachievable due to levels of heavy metals naturally present in the environment. 

How do I interpret lab results I see in ppb or ppm to determine if the levels are safe? 

Before you review lab results, it’s important to understand that actual heavy metal levels in ppb or ppm vary between harvests and tests. While a single test can provide useful information, it may not provide a complete and accurate picture of heavy metal levels. Instead, a report can be considered a snapshot in time. Thrive Market’s in-house technical team uses reports to identify areas that warrant further investigation. 

Test results in ppb or ppm are the concentration of a heavy metal in the product, but to understand the full picture, you should also consider the product’s serving size — because of variations in consumption levels and the intended consumer for a product, there isn’t a single level that should be considered safe for all products across the board. Looking at results in relation to serving size also allows you to compare them with Prop 65 levels, which are the only enacted regulations with scientific limits concerning consumption and safety. 

Some of the most common concerning heavy metals studied in food products and their associated Prop 65 limits include:

• Cadmium (in non-cacao products*): 4.1 micrograms (mcg)/day (oral); 4.1 ppm per 1g (4,100 ppb) MADL
• Arsenic: 10mcg/day (other than inhalation); 10 ppm per 1g (10,000 ppb) NSRL 
• Lead (in non-cacao products*): 0.5mcg/day; 0.5 ppm per 1g (500 ppb) MADL 

*Note: Cacao products have a higher limit for heavy metals as part of the As You Sow Settlement Agreement.

Two examples showing how to compare lead and arsenic lab results to Prop 65 limits

Prop 65 limits are stated in mcg/serving. If you’re interpreting lab results and want to compare them to Prop 65’s limits, start by determining how many mcg/serving are in the stated serving size for the product using the following calculation: Lab result in ppm x serving size in kg x 1,000

Note: If lab results are in ppb, divide the result by 1,000 to convert the number to ppm. If the serving size on the label is in grams, convert it to kg. 

Here are two examples for how to interpret lab results for two common heavy metals:

Example Lead Calculation

This product has a 7g serving size and produced a lab lead result of 35.1 ppb. 

1. Convert serving size from g to kg: 0.007 kg
2. Convert lead result from ppb to ppm: 0.0351 ppm 
3. Determine how many mcg/serving for the stated serving size using the calculation of lab result in ppm x serving size in kg x 1,000: 0.0351 x 0.007 x 1,000 = 0.2547mcg/serving
4. Compare 0.2547mcg/serving to the Prop 65 limit for lead (in non-cacao products) of 0.5mcg/day MADL 

Based on these results, two servings of this product would meet the MADL, the maximum allowable dose level at which the chemical would have no observable adverse reproductive effect, assuming exposure at 1,000 times that level. 

Example Arsenic Calculation

This product has a 7g serving size and produced a lab arsenic result of 28.4 ppb. Note that when reviewing arsenic results, it’s important to know whether they’re for inorganic arsenic or total arsenic. Only inorganic results should be considered as only inorganic arsenic is carcinogenic. 

1. Convert serving size from g to kg: 0.007 kg
2. Convert lead result from ppb to ppm: 0.0284 ppm 
3. Determine how many mcg/serving for the stated serving size using the calculation of lab result in ppm x serving size in kg x 1,000: 0.0284 x 0.007 x 1000 = 0.1988mcg/serving
4. Compare 0.1988mcg/serving to the Prop 65 limit for arsenic of 10mcg/day

Based on these results, 50 servings of this product would meet the NSRL, the no significant risk level at which the daily intake level of a carcinogen is calculated to result in one excess case of cancer in an exposed population of 100,000, assuming a lifetime (70-year) exposure at the level in question.