Human volunteer study of the decontamination of chemically contaminated hair and the consequences for systemic exposure

Abstract

The decontamination of exposed persons is a priority following the release of toxic chemicals. Efficacious decontamination reduces the risk of harm to those directly affected and prevents the uncontrolled spread of contamination. Human studies examining the effectiveness of emergency decontamination procedures have primarily focused on decontaminating skin, with few examining the decontamination of hair and scalp. We report the outcome of two studies designed to evaluate the efficacy of current United Kingdom (UK) improvised, interim and specialist mass casualty decontamination protocols when conducted in sequence. Decontamination efficacy was evaluated using two chemical simulants, methyl salicylate (MeS) and benzyl salicylate (BeS) applied to and recovered from the hair of volunteers. Twenty-four-hour urinary MeS and BeS were measured as a surrogate for systemic bioavailability. Current UK decontamination methods performed in sequence were partially effective at removing MeS and BeS from hair and underlying scalp. BeS and MeS levels in urine indicated that decontamination had no significant effect on systemic exposure raising important considerations with respect to the speed of decontamination. The decontamination of hair may therefore be challenging for first responders, requiring careful management of exposed persons following decontamination. Further work to extend these studies is required with a broader range of chemical simulants, a larger group of volunteers and at different intervention times.

Evaluating the impact of decontamination interventions performed in sequence for mass casualty chemical incidents

“…Ethical approval was given by Public Health England's Research Ethics Group. As part of a series of human volunteer studies eleven (power = .909, based upon 4 ) participants completed a controlled crossover study in which their skin was dosed separately with MeS (1:1 mixture with vegetable oil) and BeS (each with 4mg/ml of uorescent marker Invisible Red S 4,8 ) at sites on both shoulders (Figure S1). The shoulder was chosen as it was a site refractive to decontamination using improvised procedures 4 .…”

“…Table S1 details the participant and study characteristics. 1); improvised dry, improvised wet (RWR, 4 ), interim (a bespoke high-volume showering corridor 8 ), SOR (an MDU with detergent and annel, 8 ) and a no-decontamination control. Interventions were conducted at a time post simulant application equivalent to operational expectations (Figure S2).…”

“…Participants provided baseline 4 and t = 80 minute post-simulant application urine samples on day 1 and collected all subsequent urine for 24h. MeS and BeS remaining on skin was determined by skin sampling and UV image analysis 4,8 . Urine analysis, interpretation and statistics were conducted according to 4,8 .…”

Mass Casualty Decontamination for Chemical Incidents: Research Outcomes and Future Priorities

“…A series of human volunteer trials conducted by Collins et al [ 55 ] using improvised dry/wet, interim wet, and mass decontamination showering methods at realistic timescales showed variable removal of two chemical warfare agent simulants, MeS and benzyl salicylate (BeS) from the hair and scalp of volunteers. Noting the limitations associated with the semi-quantitative sampling methods, dry decontamination was shown to reduce the amount of MeS and BeS remaining on the hair although results were only significant for the removal of BeS.…”

“…Until recently, with the exception of one study in which an oil-based simulant was used [ 79 ] all human volunteer decontamination studies, including those that have informed UK and US guidance used the simulants MeS or ethyl lactate (EL) [ 18 , 34 , 78 , 80 , 81 , 82 , 83 ]; volatile compounds (vapour pressures 4.6 Pa and 500 Pa at 25 °C) with similar physicochemical properties to sulphur mustard and sarin, respectively [ 84 ]. The range of chemical simulants safe to apply to humans is understandably more limited compared to those for in vitro studies [ 84 ] but James et al [ 56 ] recently identified BeS as a simulant for more persistent, lipophilic chemicals such as Novichok [ 57 ] and subsequently demonstrated its suitability for evaluating decontamination efficacy in human trials [ 55 , 59 , 85 ].…”