Food safety in the seaweed food supply chain: Inventory of production, consumption and chemical and physical hazards

n the Netherlands, the main cultivated seaweed species are Ulva and Saccharina. There are possibilities to cultivate other brown seaweed species, like Laminaria digitata (oarweed) and Undaria pinnatifida (wakame). Compared to other European countries, current seaweed production in the Netherlands is small-scale. The European production of seaweed is also small compared to worldwide production. There are several new initiatives in the Netherlands, and therefore, the seaweed market is expected to grow. The main application of the Dutch seaweed is in the food sector, a significant part being directly sold to restaurants, and another part is dried and sold as ingredients for other food applications and supplements. Based on a literature study, the following chemical hazards may occur in edible seaweeds: heavy metals, arsenic, iodine, other elements, pesticides, polycyclic aromatic hydrocarbons (PAHs), persistent organic pollutants (POPs), radionuclides, marine biotoxins, pharmaceuticals, allergens, and microplastics. Occurrence data of arsenic, cadmium, lead, mercury, iodine, and aluminium in edible seaweeds were used to estimate the contribution towards the respective health-based guidance values (HBGVs), or other available reference points (BMDLs), taking into account the desired Margin of Exposure (MOE). For estimating the exposure, a moderate (3.3 g dry weight (dw)/day) and high (12.5 g dw/day) consumption of seaweed by adults was used. The heavy metals cadmium, lead, as well as aluminium, inorganic arsenic and iodine were concluded to be the main hazards in edible seaweeds as these contributed >25% to the HBGVs or reference points. Mercury was concluded to be a moderate hazard because the estimated seaweed consumption contributed substantially less to the HBGV (<5%). Very high levels of inorganic arsenic were identified in Sargassum fusiforme (hijiki); however, other brown seaweeds can also contain high levels of inorganic arsenic. High iodine levels can be found, especially in brown seaweeds (>10,000 mg/kg dw), but consumption of red and green seaweeds could also result in exceedance of the tolerable upper intake level (UL) for iodine. For vulnerable groups, the consumption of seaweed or seaweed products should be carefully evaluated. Other contaminants in the marine environment, such as fluorine, pesticides, PAHs, POPs, radionuclides, pharmaceuticals, and microplastics can attach to or be taken up by seaweeds. The information on these hazards was limited, but the available data did not reveal levels of concern in seaweeds. Marine biotoxins have been associated with seaweeds, due to dinoflagellates and cyanobacteria growing on seaweeds. However, no foodborne illnesses with frequently consumed seaweeds, Saccharina japonica (royal kombu), wakame, and Pyropia (nori) have been reported. Although, recently, in two samples harvested in the Netherlands, cyanobacterial toxins were detected. One sample contained an elevated dioxin level. A limited number of scientific publications suggested the possible presence of allergenic proteins in seaweed. In general, allergic effects related to seaweed seem to be rare compared to allergic effects related to other marine food products. Industrial or other anthropogenic activities (e.g. tourism), resulting in the contamination of the marine environment, can increase the likelihood for the accumulation of contaminants in seaweed. Furthermore, processing can influence the level of contamination. Washing seaweed can reduce microplastics or cyanobacteria and dinoflagellates that can produce marine biotoxins. Cooking and drying have also been shown to reduce the inorganic arsenic and iodine content of seaweeds. This report gives an overview of the production of seaweed in the Netherlands and can be used to prioritize hazards for monitoring of seaweeds for human consumption.