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Correlation of In Vivo Relative Bioavailability to In Vitro Bioaccessibility for Arsenic in Household Dust from China and Its Implication for Human Exposure Assessment Hong-Bo Li, Jie Li, Albert L. Juhasz, and Lena Q. Ma Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/es5037354 • Publication Date (Web): 03 Nov 2014 Downloaded from http://pubs.acs.org on November 10, 2014
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Correlation of In Vivo Relative Bioavailability to In Vitro Bioaccessibility for Arsenic in
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Household Dust from China and Its Implication for Human Exposure Assessment
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Hong-Bo Li,† Jie Li,† Albert L. Juhasz,‡ and Lena Q. Ma*,†,§
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†
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Nanjing University, Nanjing 210046, People’s Republic of China
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‡
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Mawson Lakes, SA 5095, Australia
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§
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United States
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment,
Centre for Environmental Risk Assessment and Remediation, University of South Australia,
Soil and Water Science Department, University of Florida, Gainesville, Florida 32611,
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*Corresponding author, Tel./fax: +86 025 8969 0631, E-mail:
[email protected] 1 ACS Paragon Plus Environment
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TABLE OF CONTENT
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ABSTRACT: Incidental ingestion of household dust is an important arsenic (As) exposure
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pathway for children. However, compared to soils, assessment of As relative bioavailability
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(RBA) in household dust is limited. In this study, As-RBA in 12 household dust samples
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(7–38 mg kg–1) was measured using an in vivo mouse model and compared to As
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bioaccessibility determined using 4 assays [Solubility Bioaccessibility Research Consortium
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method (SBRC), in vitro gastrointestinal method (IVG), Deutsches Institut für Normunge.V.
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method (DIN), and physiologically based extraction test (PBET)]. Arsenic RBA ranged from
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21.8±1.6 to 85.6±7.2% with samples containing low Fe and high total organic carbon content
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having higher As-RBA. Strong in vivo–in vitro correlations (IVIVC) were found between
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As-RBA and As bioaccessibility for SBRC and DIN (r2 = 0.63–0.85), but weaker ones for
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IVG and PBET (r2 = 0.29–0.55). The developed IVIVC for SBRC and DIN were used to
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calculate As-RBA based on As bioaccessibility of an additional 12 household dust samples.
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Although As bioaccessibility differed significantly (by up to 7.7-fold) based on in vitro
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methods, predicted As-RBA was less variable (up to 3.0-fold) when calculating using As
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bioaccessibility data and the corresponding IVIVC. Our data suggested that both SBRC and
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DIN had potential to assess As bioavailability in household dust samples, however additional
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research is needed.
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INTRODUCTION Chronic exposure to arsenic (As), a group-I human carcinogen, has been linked to
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various adverse health effects including cancers, skin disorders, vascular disease, and
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diabetes mellitus.1–3 Arsenic exposure occurs via consumption of contaminated water and
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food,4–6 and incidental ingestion of contaminated soil and dust.7 In Asia, As exposure via
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drinking water and rice consumption are the predominant pathways.8,9 However, for other
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locations where food and water quality are high, incidental ingestion of As-contaminated soil
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and dust may be important.
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Assessment of soil As in environments has received considerable attention,10–15 but
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limited information is available regarding As in household dust. Arsenic contamination in
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household dust is particularly pertinent for toddlers who spent substantial time indoors with
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their propensity for hand-to-mouth contact. Given the current debate regarding the impact of
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low dose As exposure on human health,2,16 assessing As in household dust is important to
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quantify early childhood As exposure. Recent studies have demonstrated that As
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concentrations in household dust vary considerably (0.10–636 mg kg–1),17–21 depending on
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anthropogenic As sources, household construction, outdoor soil As concentrations, and the
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cleaning practices of occupants.
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Using total As concentration in household dust provides a worst case scenario for
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exposure assessment as all As is assumed to be absorbed into the systemic circulation (i.e.,
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100% bioavailability). However, absorption is influenced by As speciation, properties of the
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matrix besides physiological parameters of the individual.22,23 Although the influence of As
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speciation and matrix properties on As relative bioavailability (RBA, relative to the
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adsorption of soluble sodium arsenate) has been demonstrated in As-contaminated soils,11,14 it
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is lacking for household dust due to the paucity of in vivo studies. Only one study measured
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As-RBA for a composite household dust based on monkeys.24 Conceivably, As-RBA in
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household dust may differ from soils due to its higher organic carbon (OC) content and
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smaller particle size.25
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Although the assessment of As-RBA in household dust is scarce, several studies have
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assessed As bioaccessibility in household dust (i.e., the soluble As fraction in gastrointestinal
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fluid, which is potentially available for absorption). For example, Dodd et al.26 determined
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that As bioaccessibility in Canadian house dust samples is 34–52% using the gastric phase
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(GP) of the solubility bioaccessibility research consortium method (SBRC) while As
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bioaccessibility in household dust from a former mining area in southwest England is
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10–19% and 31–43% based on GP and intestinal phases (IP) of the physiologically based
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extraction test (PBET), respectively.18 Similarly, Huang et al.27 reported that the mean As
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bioaccessibility in 10 household dust samples from air conditioner filters is 32–34% using the
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PBET assay.
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Compared to animal models, bioaccessibility methods offer a simple, inexpensive way
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to estimate As-RBA in household dust. However, it is important to establish the relationship
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between As bioaccessibility and As relative bioavailability (RBA) so the assay is valid to
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predict As-RBA in household dust. The objectives of this study were to: 1) determine
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As-RBA in 12 household dust samples from 9 cities in China using a mouse blood model; 2)
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correlate As-RBA to As bioaccessibility determined using 4 in vitro assays, and 3) compare
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the in vivo-in vitro correlations (IVIVC) for household dust to those for As-contaminated
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soils to determine if the relationship holds true for different sample matrices. In addition, the
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derived IVIVC were used to predict As-RBA in an additional 12 household dust samples to
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assess the influence of As-RBA adjustment on daily As intake values from household dust
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ingestion. This is first such a study to investigate the feasibility of in vitro assays to predict
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As-RBA in household dust. Our research helps to develop valid in vitro methods to assess As
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bioavailability in household dust.
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MATERIALS AND METHODS
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Household Dust Samples. The
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DIN > PBET. The difference in As bioaccessibility based on different methods was probably
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related to their differences in GP-pH (1.5, 1.8, 2.0, and 2.5 for SBRC, IVG, DIN, and PBET 10 ACS Paragon Plus Environment
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respectively). Arsenic bioaccessibility also differed in IP. For SBRC and IVG, As bioaccessibility was
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lower in the IP than GP, decreasing by 1.5–6.1 and 1.3–1.8 fold. However, with DIN and
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PBET, As bioaccessibility in most samples did not decrease. In IP, As bioaccessibility was
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12.2–59.3% for SBRC, being significantly lower (p 0.60,42 the IVG and
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PBET didn’t (r2 = 0.29–0.55). Although IVIVC have not been reported for household dust,
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they have for As-contaminated soils. Based on a swine AUC assay, Juhasz et al.12 reported
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that the SBRC (r2 = 0.75–0.65) and PBET (r2 = 0.64–0.67) provides a better prediction of
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As-RBA in 12 contaminated soils than the IVG (r2 = 0.57–0.57) and DIN (r2 = 0.55–0.53).
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Bradham et al.14 and Brattin et al.41 reported that the SBRC-GP provides good prediction
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(r2=0.92 and 0.72) of soil As-RBA based on mouse and swine steady state urinary excretion
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model. Using the same soils from Bradham et al.,14 Juhasz et al.43 showed that IVG, DIN, and
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PEBT also have strong predictive ability (r2 = 0.67–0.90) of As-RBA.
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In addition to r2, the y-intercepts and slopes of IVIVC also influence their predictive
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ability. For most IVIVC in this study, the slope was close to 1,44 but significant variability
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was observed in the y-intercept (−33.6 to 20.4) (Table 2). Wragg et al.44 suggested that the
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y-intercept should be close to zero. Although the y-intercept was small for IVG-IP and
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PBET-GP, r2 was poor at 0.29–0.42. In contrast, assays exhibiting a strong IVIVC (SBRC and
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DIN) had large y-intercepts (−33.6 to 20.4), which may introduce under- and over-estimation 11 ACS Paragon Plus Environment
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of As-RBA at low values. For example, if the IVIVC for SBRC-GP and DIN assays were
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used to predict As-RBA, an underestimation would occur in samples with low As-RBA due to
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their negative y-intercepts (−33.6 to −14.1). The opposite would be true if SBRC-IP were
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used. With a view of being conservative when estimating As-RBA for exposure assessment,
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the SBRC-IP assay with positive y-intercept and strongest r2 at 0.85 was the best predictor of
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As-RBA for the 12 household dusts. However, caution should be exercised for samples with
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low As-RBA due to the large y-intercept. For better prediction, additional research is needed
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to improve the IVIVC (e.g., smaller y-intercept). This may be accomplished by including
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more dust samples, especially those contaminated from other sources (e.g., mining, smelting,
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and arsenical pesticide), which increase the range of As bioavailability and bioaccessibility.
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For SBRC and DIN with the strongest IVIVC, a comparison was made between
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household dust and As-contaminated soils.12,14,42,43 Previous research on As-contaminated
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soils has found variability in the slopes and y-intercepts of the IVIVC (Table 3). Compared to
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IVIVC for As-contaminated soil, the IVIVC of the SBRC and DIN for household dust were
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not significantly different in slopes, but significantly different in y-intercepts. For example,
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the y-intercept of –29.0 for SBRC-GP IVIVC of household dust was significantly different
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from values (5.64–19.7) for soils reported by Juhasz et al.12 (p
