Evaluation of an Intervention to Reduce Tear Gas Exposures and Associated Acute Respiratory Illnesses in a US Army Basic Combat Training Cohort

Abstract

Exposing unmasked US Army recruits to elevated levels of o-chlorobenzylidene malononitrile (CS tear gas) during Mask Confidence Training (MCT) increases the risk of Acute Respiratory Illness (ARI) diagnosis in the period following CS exposure when compared to the period before exposure. All Army Activities Message (ALARACT) 051/2013 was implemented in March 2013 to reduce CS exposure concentrations during MCT and associated ARI rates. This observational, prospective cohort studied CS exposures and associated ARI health outcomes after implementation of ALARACT 051/2013 in 5 298 recruits attending US Army Basic Combat Training (BCT). These data indicate a 10-fold reduction (p<0.001) in CS exposure concentrations; recruit exposures ranged from 0.26 -2.78 mg/m 3 ( =1.04 mg/m 3 ) and chamber operator exposures from 0.05 -2.22 mg/m 3 ( =1.05 mg/m 3 ). The overall risk of ARI diagnosis following CS exposure also decreased when compared to period before exposure (RR=1.79, 95%CI=1.29, 2.47) resulting in 26.85% (95%CI=-0.17, 0.54) intervention effectiveness. Post-chamber ARI rates were dependent upon CS exposure concentration (p=0.02), and pre/post-chamber ARI rate ratios were significantly elevated at all concentration categories higher than the Threshold Limit Value Ceiling (TLV-C) (0.39 mg/m 3 ). Results support previous research suggesting risk of ARI diagnosis after CS exposure is positively associated with CS concentration.

Exposure to the Riot Control Agent CS and Potential Health Effects: A Systematic Review of the Evidence

“…Three (Attack Rate = 30%) belonged to the direct exposure group and six (Attack Rate: 25%) to the indirect exposure group. An article by Hout et al describes the incidence of acute respiratory illness (ARI) after CS exposure in US army military training populations [ 37 ]. Incidence increased after exposure ( p < 0.01) and was positively correlated with CS concentration ( p = 0.03).…”

“…However it should be noted that the number of subjects in this study was small. CS effects on human health seem to be correlated with concentration and a dose-response pattern has been found [ 37 , 38 ]. In addition, interventions which decreased concentration also decreased the relative risk of post exposure incidence of ARI [ 38 ].…”

Transient receptor potential channels in pulmonary chemical injuries and as countermeasure targets

“…194,195 Exposure to CS tear gas agents during mask confidence training in new military recruits is associated with a significantly increased risk of acute respiratory illness, such as influenza, bronchitis, pneumonia, and cough. 60,196 A recent retrospective study of 93 cases shows the long-term effects of tear gas agents. 194 Cough, phlegm, and rhinorrhea are commonly seen for more than 3 months in victims exposed to tear gas, compared with control subjects.…”

Tear gas: an epidemiological and mechanistic reassessment

“…CS exposures were also associated with an increase in respiratory infections, including influenza. Follow‐up studies demonstrated that lowering CS exposures during training effectively reduced the risk for respiratory illness . Whether these lower concentrations are also safe for diverse civilian populations remains unclear.…”

“…Follow-up studies demonstrated that lowering CS exposures during training effectively reduced the risk for respiratory illness. 38 Whether these lower concentrations are also safe for diverse civilian populations remains unclear. identify potential long-term health effects of tear gas exposures.…”