Arsenic　(As)　mobilisation　assists　in　remediating　As-contaminated　soils　but　might　increase　ecological　and　health　risks.　In　this　study,　risks　of　applying　two　mobilising　agents　were　assessed,　i.e.　an　emerging　reducing-chelating　composite　agent　[dithionite　(Na2S2O4)–EDTA]　and　a　classical　low-molecular-weight　organic　acid　(LMWOA)　[citric　acid　(C6H8O7)].　Results　showed　that　both　agents　induced　sharp　increase　in　leachability-based　ecological　risk　of　As.　Interestingly,　the　two　agents　had　opposite　performances　regarding　health　risks.　Na2S2O4–EDTA　significantly　increased　As　relative　bioavailability　(RBA)　to　1.83　times　that　in　controls　based　on　in　vivo　mouse　model,　and　As　bioaccessibility　to　1.96,　1.65　and　1.20　times　in　gastric,　small　intestinal　and　colon　phases　based　on　in　vitro　PBET-SHIME　model.　Besides,　it　caused　significant　increase　of　highly　toxic　As()　in　colon　fluid.　In　contrast,　C6H8O7　significantly　reduced　RBA　and　bioaccessibility　of　soil　As　in　colon　by　44.44%　and　14.65%,　respectively.　Importantly,　C6H8O7　restrained　bioaccessible　As(V)　reduction　and　promoted　bioaccessible　As()　methylation,　further　reducing　health　risk.　The　phenomena　could　mainly　be　attributed　to　excessive　metal　components　release　from　soil　by　C6H8O7　and　gut　microbiota　metabolism　of　C6H8O7.　In　summary,　C6H8O7　and　similar　LMWOAs　are　recommended.　The　study　contributes　to　mobilising　agent　selection　and　development　and　provides　a　reference　for　managing　remediation　sites.　©　2022　Elsevier　B.V.