Global seafood production practices and trade patterns contribute to disparities in exposure to methylmercury.

Seafood consumption is a major pathway for exposure to methylmercury (MeHg), a globally pervasive neurotoxin. Yet, how upstream processes in the seafood value chain influence MeHg exposure remains poorly understood. Here we quantified MeHg in seafood production, trade and consumption in 2019 around the world. We found that countries with seafood-MeHg exposures beyond the recommended threshold by the World Health Organization were predominately high-income countries. These countries experienced a tenfold increase in exposure levels compared with low-income countries, due to greater consumption and long-overlooked higher MeHg concentrations in seafood inherited from production. Notably, 43% of seafood MeHg in production was redistributed through seafood trade, marked by inequality, as exports from high-income to lower-income countries contained higher seafood-MeHg concentrations. These exposures may have resulted in 61,800 global premature deaths and economic losses of around US$2.87 trillion, underscoring the need to change seafood production practices and trade patterns.