BARGE Method

Preservation of simulated stomach & intestinal fluids from the Unified BARGE Method

BARGE logo

Contaminants such as arsenic, cadmium and lead can be naturally occurring as a result of the underlying geology or as a result of mans activity. Under current contaminated land and planning guidelines there is a requirement to determine whether exposure to the presence of such contaminants, where the contaminant concentration is above the applicable soil guideline value, justifies taking remedial action or a more detailed assessment of the risk to human health.

Human health risk assessment in the UK applies the source-pathway-receptor paradigm; where in simple terms, the contaminant is the source, a person occupying that space, i.e. using a garden is the receptor and the route of exposure to that contaminant i.e. soil ingestion through hand to mouth activities is the pathway and a pollutant linkage has to be present. If there is no pollutant linkage, e.g. no exposure pathway, the hazard may still be present but it may not be a risk.

In vitro methodologies

In order to determine whether contaminants present in soils are available to cause harm to human health if ingested/inhaled, scientists study an area of science known as bioaccessibility/bioavailability. This research area has brought together scientists from different disciplines, such as chemists, geochemists, pharmaco-kineticists, geologists and risk assessment practitioners amongst others. A priority area for this field of science is the correct estimation of bioaccessibility, which is a parameter which can be included in the assessment of risk from contaminated soil. As such, in vitro methodologies, which simulate the pathways of exposure, gastro-intestinal tract for ingestion and lungs for inhalation, have been developed.

This research describes a preliminary study undertaken to investigate methods of preservation of simulated 'stomach' and 'stomach & intestinal' fluids prior to an international inter-laboratory project by the BioAccessibility Research Group of Europe (BARGE).

Cartoon showing soil samples being being offered to a human volunteer.

Who are BARGE?

BARGE is a European network of international institutes and research groups to study human bioaccessibility of priority contaminants in soils such as arsenic, lead and cadmium via the gastrointestinal tract.

Why was the research undertaken for the preservation method?

The BARGE inter-laboratory project was international in nature, with samples expected for analysis by BGS from Europe and North America and potential delays were expected in sample transportation.

  • To ensure the stability of sample solutions a method of preservation was required
  • To ensure consistency in the sample matrices for analysis, a digestion procedure was required

What was the research?

Preservation

  • 0.1M Nitric acid preservation in a ratio of 1:10 was compared to unpreserved extraction samples for the two simulated gastrointestinal phases.
  • Measurements for a suite of analytes (including As, Cd, Ni and Pb) were collected over a period of c. 1 month
  • Data were evaluated to give an indication of extract stability

Digestion

  • Application of a HNO3/H2O2 hotblock digestion to stop further sample degredation and ensure uniformity of sample matrix prior to analysis by ICP-AES

Contact

Contact Mark Cave for further information about the Medical Geology team