Surgical masks have been part of essential personal protection equipment during the Covid-19 pandemic. Vast application and inappropriate disposal of surgical masks can potentially bring serious pollution of microplastics (MPs) into coastal marine environments worldwide. This study aimed to investigate the kinetic release of MPs from polypropylene SMs (PP-SMs) in seawater and evaluate the chronic toxicity of the released MPs to the marine copepod Tigriopus japonicus. Based on the kinetic study results and available relevant data, it is estimated that 0.88 million to 1.17 million MPs would be released during the complete decomposition of a single surgical mask. It has been reported that about 1.56 billion masks ended up in the ocean in 2020, and this amount of MPs can seriously pollute 137 million cubic meters of seawater, which is equivalent to filling up more than 54800 Olympic swimming pools with a release rate of 396 billion MPs per day. To evaluate the ecotoxicological impacts of the MPs release from surgical marks, we conducted a chronic exposure using marine copepod (Tigriopus japonicus), which is one of the most important secondary producer in the marine food chain. The results demonstrated that MPs can be ingested and accumulated in the intestines of marine copepods, resulting in 22% reduction in reproductive fecundity and 5.6% longer time in maturation. The results evidently suggested the MPs released from improperly discarded surgical masks could pose a long-term domino effect on coastal marine ecosystems. To minimize the risk of this emerging threat, better environmental management, policy and law enforcement for ensuring proper disposal of SMs are deemed to be necessary.