Analytical control of chemical decontamination

The growing interest in certification of the absence of residual danger means that we need to take a very precise look at what this entails. This is the aim of this article.

When dealing with the control of chemical decontamination, we first need to recall what is meant by contamination and decontamination. Without claiming to be exhaustive, a few particularly significant examples taken from the hazards associated with different situations encountered by the military (mainly toxic warfare agents) are mentioned. The examples chosen relate to the NRBC (nuclear, radiological, biological, chemical) threat, but the elements presented can to some extent be extended to many other situations in the civilian world, particularly accidental situations such as attacks involving the use of chemical products.

In the second part, the conditions necessary and sufficient to set thresholds deemed acceptable for decontamination are detailed, drawing on two complementary scientific exercises: the setting of toxicological reference values and the development of exposure scenarios. Both exercises are inherently multi-disciplinary, requiring a sustained and comprehensible dialogue between decision-makers on the one hand, and scientific teams on the other. Numerical examples, mainly taken from North American literature, are given to illustrate the complexity of this exercise, its prerequisites and limitations, and the sensitivity of the final result to the choices made prior to the numerical calculations (exposure scenario, acceptability of minor health effects, etc.).

Finally, the third section describes the analytical tools that can be used today to verify compliance with previously calculated decontamination levels during simulations, in the field or in specialized laboratories.

This article illustrates that behind the apparently simple question of "how much to decontaminate after chemical contamination" lie complex considerations that take time to reach a consensus among stakeholders. In our view, it is essential that this reasoning be carried out before an incident or accident occurs: once an incident or accident has occurred, time and energy should be devoted to decontamination and its control, rather than to calculations.