Buried biomarkers: Rubble affects urinary volatiles in earthquake wreckage

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  • Published: Jun 4, 2012
  • Author: Steve Down
  • Channels: Gas Chromatography
thumbnail image: Buried biomarkers: Rubble affects urinary volatiles in earthquake wreckage

Search and rescue

The profiles of urinary volatile compounds released over concrete or bricks have been measured by European researchers in a simulation of human entrapment in collapsed buildings following an earthquake.

The recent earthquakes in Italy, New Zealand, Japan and South America have reminded us of the precarious nature of some of our towns and cities and the ease with which hundreds of lives can be lost in a few disastrous seconds. Normally, the initial searches of collapsed buildings involve local people working by hand and listening for signs of life from people buried below. Then organised search and rescue teams arrive to locate victims using a variety of techniques.

One of the best rescue tools is the search dog which has a sensitive innate ability to detect the human scent as it drifts through pockets in the rubble. However, when used correctly, the dogs need to be rested regularly, so their search time is limited. Given that their training is time-consuming and expensive, it is easy to understand why the hunt for alternative technical instrumentation is gathering pace.

There are a number of probes based on sonar, infrared cameras, telescopic cameras and listening devices but some labs are trying to emulate the canine model by analysing the human scent with the aim of designing special probes. They would have to be extremely sensitive because any volatiles emitted by trapped people become diluted quickly as they are spread.

Another key problem with this approach is the selection of volatile compounds to monitor. They need to be unique to the human scent, which consists of a mixture of emissions from blood, urine, breath, sweat and tissue, and they need to be stable to allow their detection.

One team of European scientists has been studying how these compounds behave as they permeate the ruins of buildings, interacting with brick, concrete, wood, furnishings and other materials, looking specifically at those found in urine.

Pawel Mochalski and Anton Amann, both from the Breath Research Institute, Dorbirn, Austria, with affiliations to the Institute of Nuclear Physics, Krakow, Poland, and Innsbruck Medical University, respectively, collaborated with Agapios Agapiou and Milt Statheropoulos from the National Technical University of Athens.

Environmental chamber

The research team used an environmental chamber which they had designed to simulate a collapsed building. Pieces of brick or concrete were held on steel gauze above a reservoir of human urine while a flow of synthetic air through the vessel mimicked the natural air currents to carry the urinary volatiles through the rubble to exit via a small opening in the top.

The volatile compounds carried on the air flow were sampled by an SPME fibre inserted through a second hole in the top of the chamber. Sampling times of three minutes gave satisfactory detection limits while maintaining good resolution within the permeation profiles that were built up over time.

Immediately after removal from the chamber, the fibres were inserted into the inlet of a GC/MS system for desorption and analysis. They were resolved on a porous polymer column designed specifically for volatile solvents and hydrocarbons before electron ionisation in a quadrupole mass spectrometer. The volatiles were identified from their retention times and by matching the mass spectra against those in a commercial library.

Extractions were carried out every 36.4 minutes over 24 hours, an interval which equates to the length of the GC temperature program, but which also approximates the optimum active time of a search dog before it needs to be rested.

Ketones clue to success

A total of 22 volatile compounds were identified in the headspace above the urine, dominated by ketones (11) and aldehydes (5). Six of them were observed in all of the samples and the individual concentrations of all compounds were less than 10 ppb apart from acetone, 2-butanone and 2-pentanone. Acetone made up 80-90% of the total mass of volatiles with relatively high levels of at 300-630 ppb.

The permeation profiles measured over 24 hours showed the same shape for all compounds, increasing initially following urine injection to the chamber, then falling exponentially. When no rubble was present, the highest concentrations of most compounds were observed soon after injection, within 12 minutes, and they were removed completely within 1-2.5 hours, except for propanal, pyrrole and acetonitrile.

In the presence of the concrete and brick pieces, the more volatile and poorly soluble components like the furans and sulphur compounds had relatively short residence times, so their usefulness is limited in the context of search and rescue operations. The more persistent compounds like aldehydes and ketones are those that have good solubility in urine.

The ketones had long residence times in the chamber and their interactions with the rubble increased with their molecular masses. Concrete had a far greater effect than brick, drawing out the residence time profiles to provide clear maxima and strong tailing. The maximum concentrations of the aldehydes were relatively unaffected by the presence of brick or concrete but their residence profiles also showed strong tailing.

So, ketones emitted from people trapped under collapsed buildings will be the easiest target compounds to detect, given their long residence times and higher concentrations. “Knowledge about the emission evolution of urine volatiles and their behavior in the presence of typical debris materials is a critical factor for the selection of urine markers that would be useful in rescue operations,” say the team.

However, it must be borne in mind that this is a lab-based pilot study and the human scent profile will be affected under real conditions by factors such as smoke, heat and the presence of other contaminants from the buildings and their contents. Nonetheless, the data will be useful for choosing known markers of the human presence to be detected by portable, sensitive instrumentation at the scene of the disaster.  

Related Links

Analyst 2012 (Article in Press): "Permeation profiles of potential urine-borne biomarkers of human presence over brick and concrete"

Article by Steve Down

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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