Review of environmental, ecological, and public health impacts from municipal landfill leachates

Exposure due to chemical toxicants emanating from landfill leachates is considered among major global concerns. This study aims to critically review the impact of selected non-threshold heavy metals mainly lead, cadmium, arsenic, mercury, and chromium. The study also reviews their effects on groundwater and surface water resources. It also reviews their effects on fauna and flora ecosystems. Health burdens from air pollutants and odours emitted by landfills/leachates on human populations are discussed. In addition, greenhouse gas (GHG) emissions associated with leachates/landfills and emerging sustainable mitigation measures are summarised. Among these heavy metals, lead consistently contaminates surface water and groundwater, while mercury levels often fall below World Health Organisation guidelines. Studies show DNA damage in aquatic fauna and growth inhibition in flora due to pollutant exposure. Common air pollutants from landfills include particulate matter, hydrogen sulfide, and airborne bacteria/fungi, linked to respiratory issues, cancer risks, and cellular disruptions in humans. Methane is the predominant GHG emitted from landfills. While nature-based solutions effectively remove organic matter and major cations/anions, their efficacy in heavy metal removal remains limited. Further research, including source apportionment and epidemiological studies, is needed to understand the public health and climate change impacts of landfills/leachates as sources of environmental pollution.