Assessment of heavy metals and aflatoxins in cottonii and spinosum seaweeds from Tanzania

There has been little research on heavy metals and aflatoxins in Tanzanian seaweeds. Concentra- tions of lead (Pb), cadmium (Cd), total mercury (THg), and methyl mercury (MeHg) were meas- ured in cottonii (Kappaphycus alvarezii) and spinosum (Eucheuma denticilatum) seaweeds from Tanzania. Seaweeds were collected in February 2024 from Tanga, Pwani, and North Unguja. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to assess Cd and Pb, a direct mercury analyzer (DMA-80) was used to analyze THg and MeHg, and high-perfor- mance liquid chromatography was used to determine anti-aflatoxigenic activity. Heavy metal concentrations were highest for Cd, followed by Hg, Pb and MeHg, and varied significantly (p<0.05) between species and sampling locations. The concentrations of Cd, Pb, and MeHg were below safety thresholds set by the European Union and Codex Standard, while THg concentra- tions exceeded Codex limits but were within European Union limits, and can therefore safely be consumed. Aflatoxins were not detected in the seaweed samples. Further research on heavy metal concentrations and moisture stability in Tanzanian seaweeds is recommended, over a period of at least a year.