Mass casualty decontamination following a chemical incident: evaluating improvised and interim decontamination protocols in a controlled cross-over volunteer study.

Background: On-scene improvised and interim decontamination protocols in the Initial Operational Response to chemical incidents aim for rapid intervention to minimise injury before specialist capabilities arrive. This study examines the effectiveness of UK improvised and interim protocols conducted in sequence.

Method: A simulant with methyl salicylate (MeS) in vegetable oil and a fluorophore was applied to participants' shoulders, arms and legs. Participants either received no decontamination or used one of four decontamination protocols: improvised dry, improvised wet, improvised dry followed by interim or improvised wet followed by interim. Remaining simulant on the skin was quantified using gas chromatography tandem mass spectrometry for MeS analysis and UV imaging for fluorophore detection. Additionally, urine samples were collected for 8 hours post application to analyse MeS levels.

Results: Significantly less simulant was recovered from the skin post decontamination compared with no decontamination. There were no differences in the total simulant recovered across all decontamination conditions. However, significantly more simulant was recovered from the shoulder compared with the arm and leg. Variation in simulant recovery from different application areas was significantly higher in improvised-only conditions than in combined conditions. Decontamination did not affect the amount of MeS excreted in urine over 8 hours.

Conclusion: This research supports current practice of starting decontamination as soon as possible after chemical exposure and highlights the importance of implementing interim decontamination following improvised decontamination.