Risks of exceeding health-based guidance values for toxic metals and metalloids through seaweed and halophyte consumption

The present study aims to determine the risks of exceeding health-based guidance values for toxic metals (cadmium, lead and mercury) and metalloids (arsenic) associated with the growing consumption of wild-harvested seaweed and halophyte species in western countries. The risk associated with excessive iodine intake from the consumption of these new greens was also studied. In addition, the study quantitatively determined seaweed and halophyte multi-metal accumulation potential, as well as the suitability of the selected sampling areas for potentially developing marine agriculture. The wild samples were collected off the coasts of Portugal and Denmark (N = 113), and commercially available products supplied unprocessed in Portugal and Spain were acquired (N = 18). A wide literature review was performed to increase the datasets for those countries. Results indicate that concentration levels are related to studied groups (Chlorophyta, Phaeophyceae, Rhodophyta and Halophytes), geographical origin and species behaviour (e.g., perennial vs . annual). Arsenic and iodine are the limiting factors for seaweed consumption, and the Phaeophyceae species are the major contributors. Nevertheless, 27.9 % of the samples also exceeded the regulatory limits set out for cadmium. Despite the limited data available for halophytes, they seem to be a secure food alternative if not cultivated in contaminated areas. Data from the pollution index shows that estuarine areas are not suitable for marine agriculture, but the Portuguese rocky coastline seems to offer a safe option. The following gradient of accumulation potential was obtained: Halophytes < Chlorophyta < Rhodophyta < Phaeophyceae. The present study alerts that seaweed products commercially available in Portugal and Spain may not guarantee safety due to high levels of arsenic and iodine. • The metal and iodine accumulation potential of seaweeds and halophytes was assessed. • The risk to human health of seaweed and halophyte consumption was evaluated. • Levels are related to taxonomic groups, geographical origin and species behaviour. • Accumulation potential rank Halophytes < Chlorophyta < Rhodophyta < Phaeophyceae. • Arsenic and iodine are the limiting factors for seaweed consumption.