Spatial and seasonal variation of diarrheic shellfish poisoning (DSP) toxins in bivalve mollusks from some coastal regions of Vietnam and assessment of potential health risks.

The occurrence of okadaic acid (OA) group toxins in bivalve mollusk collected from Vietnamese coastal areas was investigated from April 2016 to April 2017. OA group toxins were detected in mollusk by UPLC-MS/MS with the highest level of 11.3 ng/g and detection frequency of 11.8%. Toxins were detected more frequently in dry season (14.4% of analyzed samples) than in wet season (7.9%). Toxins were also detected more frequently at sampling locations in the northern parts (≥10.4%) than in the southern part (≤8.3%) of Vietnamese coastline. Results of this study were similar to those obtained in long-term studies in regions geographically close to Vietnam, confirming decisive influence of geographic location on the accumulation of toxins in mollusks. Within the scope of the study, toxin levels in all contaminated samples were below the regulation limit (160 ng/g), but the presence of OA group toxins in bivalve mollusk suggests the need of a more stringent control of toxins in bivalve mollusk in Vietnam.