Comparison of arsenic bioaccessibility in housedust and contaminated soils based on four in vitro assays

Few studies have assessed As bioaccessibility in housedust using different in vitro assays and compared to those in contaminated soils. We determined As bioaccessibility in 24 housedust samples (4.48-38.2 mg kg(-1)) using SBRC, IVG, DIN, and PBET assays and they averaged 73, 68, 53, and 48% in the gastric phase and 26, 46, 55 and 43% in the intestinal phase of the 4 assays. The corresponding As bioaccessibility in 34 As-contaminated soils (22-6899 mg kg(-1)) were 34, 25, 22, and 22% in the gastric phase and 18, 19, 21, and 20% in the intestinal phase, which was 1.5-2.7 fold lower than those in housedust possibly due to differences in contamination sources and properties. Based on the gastric phase of SBRC assay, As bioaccessibility was 44-96% in housedust and 2.3-80% in soils. Variation in As bioaccessibility among assays was similar for housedust and soils, with SBRC assay providing the highest bioaccessibility in gastric phase. In intestinal phase, dissolved As was probably adsorbed onto precipitated iron oxides, causing a sharp decrease in As bioaccessibility by SBRC assay. Unlike SBRC assay, gastric constituents (pepsin, mucin, phosphate, and citrate) in other 3 assays inhibited As adsorption and/or enhanced As dissolution, leading to greater As bioaccessibility. The greater As bioaccessibility in housedust than soil suggests the potential of greater health risk from As exposure to housedust than soil.