Association between exposure to o-chlorobenzylidene malononitrile (CS riot control agent) and urinary metabolite 2-chlorohippuric acid in U.S. Army Mask Confidence Training

ABSTRACT

This study was conducted among U.S. Army soldiers to evaluate the association between exposure to o-chlorobenzylidene malononitrile (CS riot control agent) and urinary metabolite 2-chlorohippuric acid (CHA) detected in test subjects (n = 87) after completion of Mask Confidence Training. CS exposures ranged 0.086–4.9 mg/m³ ( = 2.7 mg/m³). CHA levels (corrected for creatinine) at 2-, 8-, 24-, and 30-hr post-exposure resulted in ranges of 94.6–1120 µg/g-cr ( = 389 µg/g-cr), 15.80–1170 µg/g-cr ( = 341 µg/g-cr), 4.00–53.1 µg/g-cr ( = 19.3 µg/g-cr), and 1.99–28.4 µg/g-cr ( = 10.6 µg/g-cr), respectively. Spearman's correlation revealed CHA levels strongly correlated with time sampled (r = −0.748, p < 0.05) and weakly correlated with CS concentration (r = 0.270, p < 0.05). A linear relationship was observed between CHA, CS concentration, and time of urine sample according to the following regression equation: ln(CHA, μg/g-cr) = 5.423 + 0.316 (CS conc., mg/m³) – 0.002 (time sampled), (R = 0.910, R² = 0.827, p < 0.05). This relationship suggests that CHA has the potential to be an effective retrospective indicator of CS exposure in future biomarker developments.

KEYWORDS:

• 2-chlorohippuric acid
• biomarker
• CS riot control agent
• mask confidence training
• o-chlorobenzylidene malononitrile
• tear gas

Acknowledgments

Sampling efforts were made possible from support of the Army Medical Department Center & School of Industrial Hygiene technicians in San Antonio, TX. CS analysis was completed at the U.S. Navy Comprehensive Industrial Hygiene Laboratory in Norfolk, VA. CHA and creatinine quantification was conducted by the CDC in Atlanta, GA. Statistical support was provided by Dr. Cara Olsen at the Uniformed Services University of the Health Sciences in Bethesda, MD.

Funding

Project funding was awarded from the Henry M. Jackson Foundation for the Advancement of Military Medicine through the Uniformed Services University of the Health Sciences.