Biogeochemical dynamics of major elements in municipal solid waste landfills can induce health risks for nearly 1 billion people

Landfills remain the primary method for managing over a billion tonnes of municipal solid waste (MSW) every year worldwide. Landfills, meanwhile, cause various environmental issues that also threaten human health. However, complex biogeochemical conditions in landfills hinder the understanding of the long-term fates of disposed elements, limiting assessments and mitigations of environmental and health risks. In this review, we synthesized 2,387 data points from 754 studies to quantify landfill elemental dynamics. The results reveal that ∼20% of carbon, <1% of nitrogen, and ∼4% of sulfur convert to gas; ∼3% of carbon, ∼13% of nitrogen, and ∼1% of sulfur dissolve into leachate; and metals (>99%) alongside remaining elements persist in solid. Approximately 14% of the global population faces high exposure to fugitive landfill gas and leachate emissions, particularly in the Global South. These findings fill a critical knowledge gap and highlight the need for targeted remediation to mitigate environmental and health impacts from landfills.