An In Vitro Procedure for Estimation of Lead Relative Bioavailability: With Validation

ABSTRACT

The relative bioaccessibility leaching procedure (RBALP) is a simple, reproducible, and rapid in vitro procedure for estimating the in vivo (juvenile swine) relative bioavailability (RBA) of lead in solid media. Control of pH, temperature, and agitation are the most critical parameters of this in vitro procedure. The performance of the method was evaluated by triplicate analyses of each of 19 different test substances by the author and three independent laboratories, and comparison of the results to relative bioavailability (RBA) values measured in vivo. The results indicate that the RBALP measurements are strongly correlated with the in vivo RBA values (r² = 0.924, p < 0.0001), with an average absolute error of 10% and an average predictive error of 20%. Comparison of results within and between laboratories indicates that the procedure is highly reproducible, with inter-and intra-laboratory coefficients of variation of 4% and 6%, respectively, and within-sample precision of approximately 7%. Based on the results reported here, the RBALP can be effective in providing reliable estimates of lead RBA as predicted by the immature swine model. The method may also be valuable in evaluating site-specific differences in bioaccessibility, assessing remedial technologies intended to reduce lead RBA, providing a screening mechanism for futurein vivo studies, and providing insight into the chemical and physical factors that control lead bioavailability.

Keywords:

• lead
• bioaccessibility
• relative bioavailability
• in vitro–in vivo correlation
• RBA
• RBALP
• IVBA
• IVIVC

ACKNOWLEDGMENTS

The authors thank P. Mushak and G. Henningsen for their thoughtful review of the manuscript and M. Ruby, V. Post, W. Berti, C. Weis, and M. Carpenter for many enlightening discussions. The analyses by the three independent laboratories were funded by U.S. Environmental Protection Agency, Region VIII, under the direction of M. Goldade and S. Christiansen.

Notes

¹A full description of the RBALP may also be obtained at http://www.colorado.edu/geolsci/legs/.