Almost a quarter of edible seaweed samples analysed recently had cadmium concentrations above the maximum level of 0.5 milligram per kilogram set by the French High Council for Public Health (CSHPF). Because cadmium is classified as carcinogenic to humans and is used in foods whose consumption is increasing, the Agency was asked by the Directorate General for Competition, Consumer Affairs and Fraud Control to recommend maximum cadmium levels for seaweed intended for human consumption. As consumers are already exposed to cadmium in their daily lives, through diet or active and passive inhalation of tobacco smoke, the Agency recommends that maximum concentrations of cadmium in edible seaweed be set as low as possible to avoid the population being overexposed to cadmium through its consumption.
Although seaweed consumption is traditional in many Asian countries, it is a growing phenomenon in France and more widely in Europe, driven in particular by the popularity of Japanese restaurants and the consumption of certain makis. Consumed as vegetables or processed (dried, salted, fresh, bottled, etc.), some species of seaweed are also used in food supplements.
Seaweed has a propensity to easily bind to environmental contaminants (cadmium, arsenic, lead, etc.)
Because it is high in polysaccharides, seaweed tends to become loaded with trace metal elements such as cadmium, lead or arsenic. Analysis of around 250 samples of unprocessed seaweed revealed that 26% of them had cadmium concentrations that exceeded the maximum value of 0.5 mg/kg dry weight recommended by the CHSPF.
Cadmium is a contaminant that is widespread in the environment in its natural state and as a result of human activity, particularly agriculture and industry. It is readily available for uptake by plants through their roots, by which it enters the food chain.
Cadmium is known to be carcinogenic, mutagenic and toxic to reproduction, and prolonged exposure causes kidney damage and bone fragility in humans, particularly from oral exposure via food and drinking water.
Aim for the lowest possible cadmium levels in edible seaweed to limit overexposure of consumers
In a context where the European Commission is considering setting maximum levels for arsenic, lead and cadmium in seaweed, the Agency recommends:
- setting the lowest possible maximum cadmium concentrations in edible seaweed, since part of the French population is already exposed to cadmium above the tolerable intake level through its normal diet.
Taking into account the overall cadmium intake from a normal diet, ANSES proposes a maximum cadmium level of 0.35 milligram per kilogram of dry matter in edible seaweed. This level would ensure that the tolerable daily intake of cadmium is not exceeded in 95% of cases. As seaweed makes a major contribution to cadmium dietary exposure among consumers of this food, such a level would reduce seaweed’s contribution to the tolerable daily intake of cadmium to 11.5%, compared to the 19% currently observed, which would be 15.5% if the seaweed consumed complied with the CSHPF value of 0.5 mg/kg dry matter.
In order to limit cadmium exposure from food, ANSES stresses that it is now up to the competent authorities to define the most appropriate ways of setting maximum levels, taking into account both seaweed and other sources of cadmium intake.
- conducting a new survey to collect more data on edible seaweed consumption habits in France. The results would make it possible to issue more precise consumption recommendations: maximum amount of seaweed or cadmium concentration level not to be exceeded, depending on the type of seaweed (microalgae, red, green or brown macroalgae, etc.).
The Agency also reminds consumers that cadmium contamination is higher for brown (such as wakame, often eaten in salads) and red macroalgae (such as nori, used dried in sheet form or as an ingredient in makis, for example).
Lastly, the expert appraisal underlined the risk of higher overexposure to chemical contaminants when combining consumption of seaweed with that of other foods. This is particularly the case for inorganic arsenic when the seaweed hijiki (Hizikia fusiforme) is consumed with rice.