We understand that the Proposition 65 warning labels found on our products, and on many, many other products in the marketplace, can  raise concerns and we welcome any questions you might have.  We will answer them clearly and forthrightly, based on the science and the available data.  We want you, our customers, to be fully informed.  Please read on to learn more about Proposition 65 and what it means for sea vegetables.

What is Proposition 65?

In 1986, California voters approved Proposition 65, the Safe Drinking Water and Toxic Enforcement Act.  Prop 65 requires companies doing business in California to give consumers a “clear and reasonable warning” when their products contain listed chemicals known to cause cancer, birth defects or reproductive harm. As of 2020, the list published by the California Office of Environmental Health Hazard Assessment (OEHHA) included about 900 chemicals.   

The OEHHA establishes a “Safe Harbor” level for each chemical and companies are responsible for warning consumers if their product or service exposes them to levels that exceed Safe Harbors. The law is sweeping in scope, requiring warnings not just on food and drink but also for numerous other products, services, and places that expose people to listed chemicals. Any person or group acting in the public interest can enforce Proposition 65 by filing a lawsuit against a business alleged to be in violation. Penalties for failing to provide warnings can be as high as $2,500 per violation per day and defending these lawsuits can be extremely expensive, especially for smaller companies. This is why some companies choose to post the warning even if their product contains listed chemicals below Safe Harbor levels. 

How are Safe Harbor Levels Determined for Each Chemical?

There are two kinds of Safe Harbor levels: one for chemicals known to cause reproductive harm and one for chemicals known to increase cancer risk.  Listed chemicals can have one or both kinds of Safe Harbors associated with them.  By design, Safe Harbors are established with very large safety margins, which is why the label doesn’t necessarily mean a product is in violation of product-safety standards or requirements. 

The Safe Harbor for reproductive harm is known as the MADL, or Maximum Allowable Dose Level.  The MADL is established by surveying all the available scientific evidence for a specific chemical to determine the maximum level where no observable effect on reproduction is seen, and then dividing that level by 1,000.  Put another way, the MADL is the level at which a chemical would have no observable effect, even if an individual were exposed to 1,000 times that level.

The Safe Harbor for avoiding cancer risk is known as the NSRL, or No Significant Risk Level. The NSRL is established as the level that would result in no more than one case of cancer out of every 100,000 individuals exposed to the chemical every day over a 70-year time frame. 

Why is There a Lead Warning on Seaweed?

As discussed elsewhere on our website, seaweed has an extraordinary capacity to absorb trace minerals, metals, and other elements from seawater and accumulate them in its tissues.  This is one of the reasons sea vegetables are so nutritious, but it also means they can absorb undesirable elements such as lead, cadmium, and arsenic.  These heavy metals are widespread in the world’s oceans from geological and human sources. 

Scientists have tested sea vegetables from all over the world for heavy metals and other contaminants, and everywhere they consistently find that most species contain lead, cadmium, and arsenic in their tissues. The majority of seaweed products on the market today likely contain traces of one or all three of these metals.  Levels may vary between species, but even within the same species they differ depending on local factors such as temperature, salinity, Ph, and influence from rivers, human populations, and industry.

We began placing Prop 65 warnings on our products in 2016, but not every seaweed company does so. For one thing, companies that don’t market into California don’t have to concern themselves with Prop 65. Some companies may not even be aware of the legal hazard due to unfamiliarity with the law or because they don’t have a testing program. In 2019, plaintiff groups issued over 150 Prop 65 Notices for cadmium and other heavy metals in seaweed and various dietary supplements.  In January 2020 alone, plaintiffs issued 14 Notices for various seaweed and seafood products including dried seaweed, dried shrimp, dried anchovies, and canned squid.  These Notices alleged that seaweed and seafood products contain arsenic, cadmium and/or lead (and related compounds) and therefore require a Prop 65 warning.

Numbers, Please!

Now, for some numerical context.  What are the Safe Harbor levels for the heavy metals cadmium, lead, and arsenic, and how do our products compare?  We can answer this question because we test every year and post the results on our Testing page.


Orally ingested cadmium is considered to pose a reproductive risk but not a cancer risk, so cadmium only has an MADL Safe Harbor, of 4.1 µg (micrograms) per day.  Exposure at 1,000 times that level (4,100 µg) is shown to have no observable effect.  In 2020, the most cadmium detected in any of our sea vegetables (laver) was 4.04 µg per gram (or 4.04 ppm – parts per million).  A seven-gram serving of laver would contain about 28 µg of cadmium; high enough to require a Prop 65 warning but certainly far below the no observable effect level.  The least amount of cadmium detected in any of our sea vegetables in 2020  was 0.21ppm.  This was for milled sea lettuce with a serving size of about 1 tsp (3 grams).  Three grams of sea lettuce powder contains about 0.6 µg of cadmium, which is well below the level requiring a Prop 65 warning.


Lead is the other metal that often triggers a Prop 65 warning on our sea vegetables. Lead causes both reproductive harm and poses a cancer risk, so it has both an MADL Safe Harbor (0.5 µg/day) and an NSRL Safe Harbor (15µg/day).  Usually, the lower Safe Harbor level is the one that triggers a warning; in this case the MADL of 0.5 µg/day.  Using our two earlier examples of laver and sea lettuce, we find their roles reversed; sea lettuce had one of the highest levels of lead detected in our products (0.6 ppm), and laver one of the lowest (0.1 ppm).  However, both of them require a Proposition 65 warning for lead because when consumed at suggested serving sizes they each exceed the MADL of 0.5 µg.  Since none of our products exceed the NSRL for lead, the warning is based on the reproductive Safe Harbor level but not the cancer Safe Harbor level.


Seaweed often contains arsenic, but most of it occurs in an 'organic' form known as arsenosugars, considered by scientists and the OEHHA to be relatively harmless because it's almost entirely excreted. However, inorganic arsenic is known to increase the risk of cancer, and some seaweed species can contain high levels.  For example, hijiki seaweed, which is enjoyed in Japan, contains about 44 ppm of inorganic arsenic. The NSRL Safe Harbor for inorganic arsenic is 10µg per day, so just ¼ gram of hijiki would cause exposure above the Safe Harbor level.  We don’t sell hijiki and all of our sea vegetable products are low in inorganic arsenic, so none of them require a Prop 65 warning for this element.  In 2020, Alaria contained the most inorganic arsenic (0.89ppm) of all our products. At this level a seven-gram serving of Alaria contains only 6µg of inorganic arsenic.

Ultimately, the decision is up to you—our customer. Our approach has always been to provide the best products and information we can, and allow consumers to make the choices that are right for them. We encourage you to seek out the information you need to make the best choices for yourself and your family.  We test most of our products every year for heavy metals and other contaminants, and post the results on our Product Testing page.  Our FAQ on heavy metals takes a closer look at regulatory standards for heavy metals in seaweed and other foods in the US and Europe.

For any follow-up questions you may have please email: questions@seaveg.com