Roofing materials as reservoirs of persistent chemical warfare agents: Fate and detectability

Persistent chemical warfare agents (CWAs), designed for deposition as liquid droplets or coarse aerosols, pose prolonged environmental and forensic risks due to their persistence on contaminated surfaces. Roofing materials represent large, exposed areas in urban environments and may act as important reservoirs of CWAs following a release. However, their role in controlling contaminant fate and forensic detectability remains poorly understood. In this study, the behavior of four persistent CWAs - A-230, A-234 (Novichoks), cyclosarin (GF), and sulfur mustard (HD) - was investigated on five representative roofing materials differing in composition. Extraction efficiency, long-term persistence, and the divergence between matrix-retained and surface-accessible contamination were systematically evaluated using comparative bulk extraction and wipe sampling approaches. Dissipation half-lives, degradation-product formation, and long-term forensic detectability were assessed using gas chromatography-mass spectrometry. Results showed strong matrix-dependent behavior. A-series agents exhibited the highest persistence, particularly in porous cement-based materials. Wipe sampling consistently recovered only a fraction of the deposited mass and declined faster than bulk extraction, indicating rapid migration of agents into the matrix interior. Transformation products remained detectable in all materials after 90 days, even when parent compounds were substantially depleted. These findings demonstrate that roofing materials represent significant but often neglected reservoirs controlling the long-term retention, transformation, and forensic detectability of persistent CWAs. The results highlight the need to extend current decontamination and risk-assessment paradigms to include such surfaces and emphasize the importance of matrix-adapted sampling and analytical strategies in urban contamination scenarios.