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Lead(Pb)in housedust and contaminated soils depends on their bioavailability,i.e.,the proportion that is absorbed into the systemic circulation.In vivo animal assays(i.e.,swine and mouse)to estimate As and Pb relative bioavailability(RBA; relative to the adsorption of sodium arsenate and lead acetate)are time-consuming and costly.As a result,in vitro assays to measure As bioaccessibility,i.e.,the amount of As and Pb dissolved in simulated gastrointestinal fluid,has been developed.However,they need be correlated to in vivo animal data before they can be used to estimate As/Pb bioavailability.In this study,24 housedust and 12 contaminated soils samples from different locations in China were subjected to As/Pb bioaccessibility analysis of 5 common in vitro assays,i.e.,SBRC,IVG,DIN,PBET and UBM.Based on the mouse blood model,As-RBA was 22–87 and 6.4–73%and Pb-RBA was 29–60 and 7.0–84%in housedust and contaminated soils,respectively.Based on the in vivo–in vitro correlation between As/Pb RBA and As/Pb bioaccessibility,SBRC assay can be used to predict As and Pb bioavailability in housedust,while UBM and IVG assays can be used to predict Pb and As bioavailability in contaminated soils,respectively.Those in vitro assays can be used to refine risk assessment of human exposure to As/Pb,but additional research is needed to valid the assays to improve their predictability of As and Pb bioavailability in housedust and contaminated soils.