Organic waste-borne ZnS nanoparticles: The forgotten ones

•Considerably more ZnS-NPs are released into the environment than most commercial NPs.•The fate of incidental ZnS-NPs formed in organic waste has been completely overlooked.•ZnS-NPs that form in organic waste are small and exhibit unique structural properties.•The reactivity and ecotoxicity of ZnS-NPs may be enhanced due to their small size.