Paired case report: hypothesized association between prolonged dermal contamination and delayed lung injury after shared-source occupational nitrobenzene exposure

Nitrobenzene poisoning causes severe methemoglobinemia and multi-organ injury; lipophilicity allows accumulation in adipose tissue, which may trigger delayed lung damage. Existing literature only contains isolated single-case reports, lacking paired patients with identical chemical exposure but different dermal decontamination strategies to verify the correlation between skin contamination duration and toxic organ complications. This paired occupational poisoning case generates testable clinical and toxicological hypotheses for emergency critical care management. Two male workers simultaneously splashed by >99% nitrobenzene at a chemical plant in 2025 were enrolled. Patient 1 completed full-body decontamination within 3 minutes, while Patient 2 kept nitrobenzene-soaked trousers for over 2 hours with sustained occlusive skin absorption. Both presented with initial methemoglobin (MetHb) >70%. Patient 1 received timely antidote and extracorporeal therapy, had rapid MetHb clearance, no acute respiratory distress syndrome (ARDS) or acute kidney injury (AKI), and was discharged on hospital day 30 with complete organ recovery at 2-month follow-up. Patient 2 had delayed methylene blue treatment, slower MetHb elimination, developed Berlin-criteria ARDS on day 6 requiring 6-day venovenous extracorporeal membrane oxygenation (VV-ECMO), complicated with KDIGO Stage 3 AKI, and was discharged on day 44. Serial laboratory and chest imaging confirmed more severe and prolonged organ dysfunction in Patient 2. Multiple combined interventions including methylene blue, partial blood exchange, hemoperfusion, plasma exchange and continuous renal replacement therapy were administered to both patients. Prolonged occlusive dermal nitrobenzene contamination is potentially associated with elevated risks of delayed ARDS and severe AKI, possibly explained by the adipose toxic depot hypothesis. Immediate full-body skin decontamination is the core frontline intervention for occupational nitrobenzene exposure. For high-risk patients with delayed decontamination, early partial blood exchange and urgent consultation with ECMO-capable critical care centers are recommended. This paired observation provides rare comparative clinical data, yet large prospective cohorts are needed to validate the predictive risk markers and toxicokinetic mechanism proposed herein.