In Vitro Bioaccessibility Testing for Arsenic, Lead, and Nickel in England and Wales

Abstract

MS1-08 Abstract: The paper presents information on a project commissioned by the Environment Agency for England and Wales on assessing arsenic, lead, and nickel bioaccessibility data produced by U.K. laboratories. Key findings from a questionnaire survey undertaken to ascertain the experiences of local authorities (LAs) in England and Wales on bioaccessibility testing in risk assessment are also presented. Three soil samples collected from U.K. contaminated sites with elevated arsenic, lead, and nickel levels were distributed to 9 U.K. and 2 overseas laboratories. A human in vivo tested lead-contaminated soil sample donated by the U.S. EPA was also distributed to selected laboratories. The laboratory exercise was conducted in the form of a ring test following the scheme of CONTEST soil proficiency testing. Laboratories were asked to report analytic results for total metal concentration and in vitro bioaccessibility estimates in their standard reporting format. The identification of laboratories was kept anonymous. Laboratories were found to vary in their analytic procedures in determining the total metal concentration. Moreover, variations in in vitro methods, operating procedures, and expression of bioaccessibility results were also reflected in the results. For example, for soil 1, in vitro bioaccessibility data for arsenic varied between 21% and 68% (expressed as the percent of total); for soil 2 for nickel between 3% and 17%; and for soil 3 for lead between 11% and 54%, respectively. Considerable variation in the in vitro data between the majority of U.K. laboratories and an overseas laboratory was observed reflecting differences in the types of methods used. Because none of the U.K. soils had any corresponding in vivo data, the reliability of any of the methods and/or laboratories in predicting the bioavailability is unknown. Lower lead in vitro data (mean, 17%), reported for the U.S. EPA sample in the study, compared with human in vivo data (26.2%) indicates in vitro studies are slightly underestimating lead bioaccessibility. The questionnaire survey consisted of 14 multiple-choice questions, and of 298 LAs contacted, 100 responded. The names of LAs were kept anonymous. The findings of the questionnaire survey indicated that arsenic is the main contaminant of concern in land contamination. A number of LAs reported consideration of in vitro data for arsenic in risk assessment on a site-specific basis. Although bioaccessibility has been reported to be very much site-specific, some LAs reported the extrapolation of in vitro data from other sites or from literature and used these data to aid their decision-making process.