Unveiling the Contamination of Thiocyanate, Perchlorate, and Chlorate in Edible Microalgae: Detection, Distribution, and Risk Assessment in Sustainable Food Sources

With the growing interest in microalgae as a sustainable food source, concerns about potential chemical contaminants in these products have emerged. In this study, a sensitive and reliable LC-MS/MS method was developed for the simultaneous detection of thiocyanate, perchlorate, and chlorate in edible microalgae samples. The method was validated with excellent linearity (R² > 0.998), low detection limits (LOD: 1-8 μg/kg), quantification limits (LOQ: 4-26 μg/kg), and high recovery rates (75-101.9%) across different sample types. We collected a total of 77 microalgae products based on the available varieties in the market, including 43 Spirulina powder samples, 10 Chlorella powder samples, and 24 microalgae-based food products, sourced from key microalgae production regions in China. The contamination levels for thiocyanate (median: 1843.06-2645.72 μg/kg) and perchlorate (median: 23.29-31.4 μg/kg) were consistently quantitated in all samples, while chlorate concentrations showed greater variability (median: 18.94-160.21 μg/kg). Risk assessment revealed a significant dietary exposure risk to thiocyanate, with estimated daily intake (EDI) values exceeding the EPA's subchronic reference dose, whereas no significant risk was identified for perchlorate or chlorate. Monte Carlo simulations further supported the conclusion that perchlorate and chlorate posed minimal dietary risks, while thiocyanate exposure warrants concern. This study not only provides a foundational method for monitoring these contaminants in microalgae but also contributes critical data for future food safety standards and regulatory practices regarding edible microalgae products.