Human Exposure to Toxic Metals (Cd, Pb, Hg) and Nitrates (NO3−) from Seaweed Consumption

Seaweed is now considered a functional food with a high nutritional value in Western countries, and the consumption of different species of edible algae has grown exponentially in recent decades. However, anthropogenic pressure on the seas has increased the presence of pollutants such as toxic metals and nitrates that can accumulate in algae. It is necessary to know the levels of these contaminants and the dietary exposure from the consumption of edible algae. The content of toxic metals (Cd, Pb, Hg) and nitrates (NO3−) was determined in 72 samples of edible algae marketed in the Canary Islands (Spain). Cd stands out in the Asian algae hijiki (1.196 mg/kg) and nori (1.005 mg/kg). Pb stands out in the Asian wakame seaweed (0.119 mg/kg). The highest mean concentration of Hg was in European arame algae (0.055 mg/kg). Some samples of the nori seaweed had NO3− concentrations of >8000 mg/kg. Considering the consumption recommended by the manufacturer of 4 g/day, the maximum admissible intake values are not exceeded, and, consequently, this does not pose a risk to health. However, in the case of Cd, Pb, Hg, and NO3−, legislation is necessary to regulate their content in edible algae.