Heavy metals in food: Carrageenan as an example of the need to improve ingredient quality

Tom Neltner, J.D., Chemicals Policy Director, and Maricel Maffini, Ph.D., Independent Consultant.


Arsenic, cadmium and lead levels in carrageenan varied widely but were within international standards. This is not reassuring since current specifications for the heavy metals are inadequate. Food manufacturers can and should set tighter limits to better protect their customers. Consumers, especially those buying from internet-only retailers, need to ask the ingredient supplier how much of the heavy metals is acceptable.


In the fall of 2013, the Food and Drug Administration (FDA) bought 10 samples of carrageenan from 5 companies sold through internet-only retailers to test for three heavy metals – lead, arsenic (total and inorganic), and cadmium. The agency published the results on its combination metals testing webpage in September 2016.

Each of these metals are carcinogens. In addition, lead and inorganic arsenic are widely acknowledged as harming children’s brain development even at low levels of exposure. EDF found that more than one million children consume lead in amounts that exceeds the maximum exposure level set by FDA in 1993, a level that subsequent research shows is of great risk to children’s health. Further, recent research has strengthened evidence of the relationship between low levels of lead exposure in adults and cardiovascular deaths. In 2011, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) took the extraordinary step of withdrawing its previous tolerable intake level for lead because it could not determine a safe level of exposure for children.

In light of these risks, we must make every effort to reduce the levels of these heavy metals in food to the greatest extent possible – without undermining other food safety measures or compromising quality. A key step to success is examining the levels of heavy metals in all ingredients used to make a food since the risk is based on the cumulative exposure – even if the amounts in individual additives are small. With this in mind, we revisited FDA’s analysis of carrageenan.

FDA’s testing for heavy metals in carrageenan

Derived from red seaweed, carrageenan is widely used in the food industry as a thickener and stabilizer, especially in dairy and meat products. It is also advertised as a food ingredient for home and restaurant use, especially in the so-called molecular gastronomy or to make vegan gelatin.

FDA does not usually test individual food ingredients, so we asked the agency why they performed this analysis. They told us that because carrageenan is manufactured from species of red seaweed that may grow in environments (e.g., soil or water) where some contaminants may occur naturally and, thereby, be absorbed, the agency tested it as part of its Toxic Elements Program.

From its testing data, FDA concluded the levels of the three metals were below the limits established by the Food Chemicals Codex (FCC) and the Joint FAO/WHO Expert Committee on Food Additives (JECFA). While within FCC and JECFA specifications, FDA’s analysis showed some wide variations in heavy metal levels; there was a 20- to 37-fold difference between the highest and the lowest levels. Specifically:

  • Arsenic: Levels ranged from 97 to 2,011 ppb (FCC and JECFA limits are 3,000 ppb);
  • Cadmium: Levels ranged from 35 to 1,292 ppb (FCC and JECFA limits are 2,000 ppb); and
  • Lead: Levels ranged from 38 to 1,065 ppb (FCC and JECFA[1] limits are 5,000 ppb).

After securing the brand information through a Freedom of Information Act request, we examined whether certain brands or forms of the ingredient had lower levels than others. As shown in the figure below, each of the brands with multiple samples had one with relatively high levels of each heavy metal and one with much lower levels. We saw the same variation in the three forms of carrageenan – iota, kappa, and lambda – that are extracted from the different stages in the lifecycle of the seaweed.

Carrageenan[2] is used at relatively low levels in food, so at even the higher levels of heavy metal contamination seen in some of these samples, it is unlikely to force any recalls on its own due to an immediate health risk. But widely-used ingredients like carrageenan that have heavy metal tolerances in the thousands parts per billion can contribute to a significant cumulative dietary exposure for children.


FDA’s testing of carrageenan offers a glimpse at the importance of quality control of food ingredients in general and their potential to be meaningful sources of heavy metals in children’s diets. From what we have learned, we conclude that:

  • JECFA and FCC specifications for the heavy metals are inadequate. The limits are not based on the health risks posed by these chemicals. Rather they are based on the ability to measure the chemicals using the standard analytical method available in 2002. In 2014, FDA adopted a much more sensitive analytical method called ICP-MS that can reliably quantify these heavy metals at levels below 10 parts per billion (ppb). In light of JECFA’s conclusion in 2011 that there is no level of lead that is sufficient to protect children’s health and with better analytical methods available, JECFA and FCC specifications need to be revised. Since carrageenan is unlikely to be unique, the revision should address other additives as well.
  • Food manufacturers can and should set tighter limits to better protect their customers. The variation shown in heavy metals in carrageenan indicate that individual producers can significantly reduce the levels in their products by determining what is causing the variation, setting tighter standards, and better managing their testing and quality control programs. Food manufacturers should demand that ingredient producers take the necessary steps to strengthen their quality controls and drive down levels of heavy metals.
  • Consumers, especially those buying from internet-only retailers, need to ask the company how much of the heavy metals is acceptable in the ingredient. Consumers may not be aware of the limitations of current standards or deficiencies in quality control. And when they use additives like carrageenan in their food, they may not use the ingredients at the low amounts on which those standards may have been set, based on industrial food manufacturing. This could put consumers and their families at risk of greater exposures to heavy metals.

[1] In 2007, JECFA increased the limit for lead from 2,000 to 5,000 ppb claiming it had made a typographical error in 2002.

[2] Carrageenan has been controversial in some uses. We don’t have an opinion on the concerns at this time.

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