1 Introduction 

The Nordic countries have a long history of using seaweed in various ways, but in modern times it has not been a tradition to use seaweed extensively as food, apart from in industrial production of polysaccharides such as alginate.

However, interest is now growing in using seaweed in Nordic and other European countries, mainly because of the focus on a greener and more sustainable economy and consumers’ search for healthy and sustainable food.

Seaweed is considered to be a valuable food resource in the world, and production has many sustainable characteristics (FAO, 2022). The European Commission has launched an initiative that will focus on how to increase sustainable algae production, ensure safe consumption, and boost the innovative use of algae and algae-based products in Europe (EC, 2021).

Despite seaweed being the biggest aquaculture product in the world, with significant global trade (FAO, 2020), there are still no international standards on food safety, such as Codex standards or guidelines. Some of the significant gaps in regulations for food safety in seaweed, along with an overview of food safety concerns in seaweeds, are identified in a FAO-WHO report (FAO and WHO, 2022).

The EU also lacks specific legislation on food safety in seaweed. The European Food Safety Authority (EFSA) has identified consumption of seaweed as an emerging risk, and the EU Commission has recommended monitoring of heavy metals and iodine in seaweed as a background for future risk management of seaweed as food and feed (EC, 2018).

There is limited experience of using seaweed as food, and knowledge is lacking about potential risks and benefits for human health relating to its consumption in Europe. Risk management of seaweed-based foodstuffs is a challenge, due to lack of knowledge and specific legislation and the many new business operators in the sector. Guidance for both producers and public agencies is required to ensure food safety, to facilitate uniform control and trade, and to support innovation and growth in this sector.

Regional differences, both globally and in Europe, in tradition, food culture, production methods, seawater quality, and types of seaweed species in use, favour a joint Nordic approach to the issue. This would support appropriate guidance for producers and food agencies in the Nordic region and ensure that Nordic species and production conditions are considered when legislation is developed in the EU.

The purpose of this report is to help develop a common Nordic approach to risk management of food safety in seaweed. The main goal is to identify food safety issues in seaweed in general, with a specific focus on conditions relevant for the Nordic countries involved in the project, i.e. Denmark, the Faroe Islands, Iceland, Norway, and Sweden.

The report can be used as a basis for developing guidance for food agencies and businesses, and for harmonising the risk management of seaweed used as food in the Nordic countries. The report may also contribute to future development of risk management of seaweed in the EU, as well as in Codex Alimentarius.

The report covers food safety aspects of seaweed used as foodstuff, with a main focus on chemical and microbiological food hazards.

Some aspects of seaweed are not included in the scope, i.e. refined industrial products such as alginate and carrageen, potential health benefits of eating seaweed, legislation on organic production, and self-picking of seaweed by consumers.

In order to understand food safety aspects in seaweed and to develop regulatory frameworks, it is important to have some familiarity with the properties and growing conditions of these organisms.

Seaweed, also named macroalgae, is a large and diverse group of multicellular photosynthesising algae, living predominantly in salt and brackish waters. Seaweed can be sub-divided into three groups: 

Only the green algae are classified together with terrestrial plants in the phylum Plantae, but all three groups of macroalgae are often named as plants. One group of seaweed is referred to as kelp, which are large brown algae seaweeds making up the order Laminariales.

The distribution of seaweed species varies according to water depth. Typically, green algae live in the top and middle depth layers, and brown algae are found in the middle layer. Red algae can be found at all depths but dominate at deep and middle sea depths. Some seaweeds are perennial, living for many years, while others are annuals. Annual seaweeds generally begin to grow in the spring and continue throughout the summer.

Seaweeds do not have roots but are attached with a basal structure (holdfast), allowing them to attach to solid substrates like stones. Unlike roots, holdfasts do not take up nutrients. Seaweed does not grow stems like terrestrial plants. A leaflike, often flattened structure (lamina or blade) emerges from a structure called a stipe. The youngest part of the blade is situated in the proximal end and may have different composition to the older parts. The blades of the kelp age, wear, and fall off over time, and thereby comprise annual parts of the kelp, whereas the stipe is perennial. The same applies to, for example, the red algae dulce, while the green algae sea lettuce is predominately annual.

The chemical composition of seaweed differs from other types of seafood and also from terrestrial plants, in the high content of specific polysaccharides in the structural components of the algae. The types of polysaccharides vary in the brown, red and green algae. The polysaccharides have metal-binding characteristics that may affect both the levels of metals and other components in the algae and the availability of these components through the human digestion processes (Duinker et al., 2016).

Both nutrients and contaminants are taken up and adsorbed directly through the blades. Seaweeds are not filter-feeders like mussels, so seaweed should not be treated in the same way as filter-feeders in legislation.

As seaweed also have quite different properties and growth environments to terrestrial plants, such as vegetables, fruits and mushrooms, seaweed should be classified in a specific group in respect to food legislation.

Seaweed can be produced by aquaculture or harvested from wild stocks in the sea. Aquaculture takes place mainly in the sea but can also be land-based. Seaweed can be grown as a monoculture or with other organisms in integrated multitrophic aquaculture (IMTA). Wild stocks are harvested through trawling, using smaller harvest equipment, or picked by hand.

Diseases and pests in seaweed aquaculture in Asia are described by Ward et al. (2019). In Nordic production, diseases, use of fertilisers, algicides, or pesticides are not yet reported, but agrochemicals can enter the marine environment through runoff from agricultural fields.

In land-based production the water quality can be manipulated for optimum conditions, giving the best yield and reducing levels of contaminants. For example, there is ongoing research on the effect of land-based production in different kinds of nutrient-rich food process waters (Stedt et al., 2022a and b).

There are some national regulations on wild harvesting and aquaculture of seaweed in the Nordic countries, such as requirements regarding where and how to harvest, but this is outside the scope of this report.

Seaweed is traditionally used for food, feed, soil fertilisers, and plant biostimulants in many countries, but is also used in cosmetics, medicine, biofuel, and packaging. There is an extensive production of several industrially produced hydrocolloids from seaweed for use as food additives, such as alginate, carrageen, and agar, used as thickeners, gelling agents, stabilisers, and emulsifying agents in a variety of food and other products. The amount of seaweed used for direct human consumption as food in Europe is still limited compared to Asian countries.

FAO (2022) reports on several properties of seaweed that are relevant for food and potential health aspects, such as mineral and vitamin content and high levels of soluble dietary fibres, and some species can be good sources of protein. Certain bioactive components from various seaweed species have been suggested to confer properties beneficial to health.

There is little specific legislation on food safety of seaweed, such as maximum levels (MLs) for actual food hazards. This is the status globally, including the EU. Discussions are ongoing regarding the need for more regulation on food safety in seaweed, both in the EU and in Codex Alimentarius.

However, general legislation on food applies for all types of food, including seaweed. Regulation (EC) No 178/2002 lays down the basic principles to protect human health and consumer interests. Article 14 in this regulation refers to general food safety requirements and stipulates that food must not be placed on the market if it is not safe to consume. More details about the EU legislation are given below for each hazard.

EU legislation concerning food safety also applies to Norway and Iceland through the EEA agreement.