Authors: Sarah A. Kane1, Lauren Fernandez1, Dr. Dillon E. Huff2, Dr. Paola A. Prada-Tiedemann2, Dr. Nathaniel J. Hall1

1 Animal and Food Sciences Department, Davis College, Texas Tech University; 2 Department of Environmental Toxicology, Texas Tech University

Canines are one of the best biological detectors of energetic materials available; however, there are a variety of factors that affect a canine’s ability to detect explosives. The objectives of this study were: 1) determine canine detection limits for various energetics based on temperature and humidity conditions while odorants are held in a constant environmental condition (measuring canine physiological factors); 2) determine how canine detection limits vary when both the canine and odorant are held in varying temperature and humidity conditions (canine and odor interactive effects); 3) and determine if an acclimatization plan can improve detection limits in an adverse environmental condition. Eight working line canines were trained to detect four explosives: prill ammonium nitrate (AN), C-4, trinitrotoluene (TNT) and double base smokeless powder. In Experiment 1 canines completed two Go/NoGo 3-down-1-up staircase threshold assessments in five environmental conditions: 40°C and 70% relative humidity (RH), 40°C and 40% RH, 0°C and 90% RH, 0°C and 50% RH and 21°C and 50% RH, while the odorant was held at stable conditions. In Experiment 2, canines completed a 3-alternative forced choice 3-down-1-up staircase threshold assessment within the same environmental conditions in experiment 1. In Experiment 3, the eight canines were split into two groups (n=4), control and acclimation groups. The control group completed the threshold assessment for C-4 at 21°C and 50% RH each day for 20 days. While the acclimation group completed the same assessment daily starting at 21°C and 50% RH but was incremented daily over the course of 6 days to the 40°C and 70% RH condition. After the initial six days, the acclimation group completed daily assessments at 40°C and 70% RH condition for the remainder of the experiment. Detection limits for C-4 were tested in 40°C and 70% RH on day 11 and day 22 of Experiment 3. In Experiment 1, detection limits were overall lowest for double-based smokeless powder (0.0026 v/v air dilution in 21°C and 50% RH), whereas TNT (0.56 v/v air dilution in 21°C and 50% RH), and AN (0.35 v/v air dilution in 21°C and 50% RH) both had higher (poorer) detection limits. Detection for all explosives was lower (better) in the standard condition when compared to the other four environmental conditions. In Experiment 2, canines had a 3.5-fold detection limit increase (poorer detection) for C-4 in 40°C and 70% RH compared to their detection limit at 21°C and 50% RH. In Experiment 3, acclimatization improved detection limits in the 40°C and 70% RH condition for C-4 compared to control. In this series of experiments, canine detection limits for four explosive odorants were found to vary based on environmental condition and were mostly driven by impacts on the canine rather than odor availability. The acclimatization plan did result in lower detection limits (i.e., increased performance).