Toxicology laboratory analysis and human exposure to p-chloroaniline

Abstract

Introduction. p-Chloroaniline is more potent at producing methemoglobin than aniline in animal models. This case highlights the clinical presentation of an inhalation exposure to p-chloroaniline and associated laboratory analysis. An in-vitro study evaluating the metabolism of p-chloroaniline in human hepatocytes was undertaken to evaluate the metabolic fate more closely. Case presentation. A 20 year-old man was working at a chemical waste plant when he developed dizziness, abdominal pain, and nausea. The exam was remarkable for coma, tachycardia, cyanosis, and pulse oximetry of 75%. Arterial blood gases showed a pH 7.38, pCO₂ 41 mmHg, pO₂ 497 mmHg, bicarbonate 24 mEq/L and methemoglobin 69%. Methylene blue administration led to complete recovery without sequelae. p-Chloroaniline was later identified as the chemical involved. He denied direct contact with the chemical, but was not wearing a dust mask or respirator. GC/MS confirmed p-chloroaniline and metabolites in the patient's urine. Methods. Human hepatocytes were incubated with 100 μM p-chloroaniline for 24 hours, in both rifampicin- and vehicle only-treated cells. The cell culture medium was collected for GC/MS analysis for p-chloroaniline metabolites. Results. Similar to the patient sample, both p-chloroaniline and p-chloroacetanilide were identified by GC/MS in hepatocytes incubated with p-chloroaniline. Neither p-chloroaniline incubated in empty cell culture nor direct GC/MS injection of p-chloroaniline generated any p-chloroacetanilide via non-enzymatic degradation. Discussion/Conclusion. The seemingly innocuous dermal and inhalation exposure to p-chloroaniline dust can lead to life-threatening methemoglobinemia. The diagnosis can be confirmed with GC/MS analysis of the patient's urine, searching for p-chloroaniline and its primary metabolite p-chloroacetanilide.

Keywords:

• Analytical
• GC/MS
• Methemoglobinemia
• Occupational accident
• p-Chloroaniline

Acknowledgments

M.D.K. is supported by a physician-scientist career development grant K08-GM074238 from the National Institutes of Health (NIH). M.D.K. gratefully acknowledges advice regarding primary human hepatocyte studies from Dr. Stephen Strom of the University of Pittsburgh, Department of Pathology. J.C.R. is supported by Grant Number 1 KL2 RR024154-02 from the National Center for Research Resources (NCRR), a component of the NIH, and NIH Roadmap for Medical Research. Its contents are solely the responsibility of the authors and do not necessarily represent the official view of NCRR or NIH. J.C.R. is also supported by an unrestricted grant from the National Association of EMS Physicians/Zoll EMS Resuscitation Research Fellowship.

The authors also gratefully acknowledge Dr. Jesse T. Mann and Dr. Alex C. Mangili for providing detailed translations of the non-English literature.