[en] Levels of ²¹⁰Po and its effective dose in green mussel (Perna viridis) collected from mussel farming area at the Samut Sakhon province during the period of 2012-2013 are presented. Several parameters including maximum shell length and the physiological performance of mussels using condition index and physical properties of seawater (pH, salinity, conductivity, TDS, DO and cation-anion elements) were measured. Each individual mussel was measured on its maximum shell length which was adopted as size class. The activity concentration of 210Po was determined spectroscopically through its 5.30 MeV alpha particle emission, using ²⁰⁹Po as an internal tracer. The ²¹⁰Po activity concentration in mussels was found to vary between 1.044 and 6.951 Bq.kg-1 wet weight. The ²¹⁰Po concentration was higher in smaller sized classes (>35 mm) and lowest in larger ones (40-70 mm). This confirms that larger mussels have lower 210Po levels on a weight basis. The ²¹⁰Po body burden (activity per mussel) ranged from 1.035 to 17.183 mBq. Contrary to the ²¹⁰Po concentrations, results of the body burden revealed the lower activities in smaller sized mussels (>35 mm) and the higher in larger sized ones (40-70 mm). The type of fluctuations observed with ²¹⁰Po concentrations are interpreted as a seasonal effect. Total annual effective ²¹⁰Po dose due to mussel consumption was calculated to be in the range of 3.081 to 16.401 μSv. Based on the international guideline, the average dose calculated due to ²¹⁰Po in mussels of Samut Sakhon would not pose any significant radiological impact on human health and the mussels are considered to be safe for intake.