A review of laboratory results for bioaccessibility values of arsenic, lead and nickel in contaminated UK soils

This paper presents the key findings of an Environment Agency's project aimed to ascertain what types of in vitro bioaccessibility methods are currently being used in the United Kingdom, what information is being reported and how they compare. Three samples of soil with elevated levels of arsenic, lead and nickel were collected from contaminated sites. The prepared and homogenised soils were sent as blind triplicate samples to 11 participating laboratories, of which 2 were from outside the UK. Analysis for total arsenic, lead and nickel content and the in vitro bioaccessible fraction was requested. An aqua regia extract was also prepared and sent with the soil samples for analysis. Whilst laboratory identification remains anonymous, codes A, B, C, D, E, F, G, H, J, K and L were assigned to individual laboratories. Three different types of in vitro methods were identified in the project producing bioaccessibility data. Each laboratory used the same bioaccessibility method for all three contaminants, irrespective of concentration or matrix. The results varied between laboratories and the variability is largely attributed to the difference in the in vitro methods used.