Identifying degradation products responsible for increased toxicity of UV-Degraded insensitive munitions

Comparative Toxicological Evaluation of UV‐Degraded versus Parent‐Insensitive Munition Compound 1‐Methyl‐3‐Nitroguanidine in Fathead Minnow

“…Despite similar concentrations of MeNQ parent compound in the exposure water (716 and 709 mg/L for parent compound and UV‐treated solutions, respectively), survival was significantly decreased in the UV‐treated MeNQ exposure (14% mean survival) relative to the exposure to non‐UV‐treated MeNQ parent compound (100% survival). Even though UV treatment clearly caused increased toxicity of MeNQ in fathead minnows (Table ), the magnitude of increased toxicity is lower than has been reported for UV‐degraded NQ in previous experiments (Gust et al ; Kennedy et al ; Moores et al ). Kennedy et al () reported a 73‐fold lower LC50 for UV‐treated NQ compared with NQ parent compound in C. dubia .…”

“…Information on subchronic or chronic toxicity of NQ to fathead minnows was not found in the available literature; therefore, future studies comparing the chronic toxicity of parent MeNQ and NQ including concentrations approaching their limit of solubility in water are warranted to determine if these compounds elicit lethal and sublethal effects in fathead minnows. (Table 3), the magnitude of increased toxicity is lower than has been reported for UVdegraded NQ in previous experiments Kennedy et al 2017;Moores et al 2020b). Kennedy et al (2017) reported a 73-fold lower LC50 for UV-treated NQ compared with NQ parent compound in C. dubia.…”

“…Kennedy et al () reported a 73‐fold lower LC50 for UV‐treated NQ compared with NQ parent compound in C. dubia . Moores et al () demonstrated the greatest increase in toxicity yet observed for UV‐degraded NQ, where 90% UV degradation of NQ elicited a 1240‐fold increase in toxicity in Daphnia pulex . Comparatively, the effect of UV‐degraded NQ was perhaps less severe in fish compared with cladocerans, where 69.2% UV degradation of NQ caused a 17‐fold increase in toxicity in larval zebrafish (Gust et al ), whereas 7% UV degradation of NQ elicited an 85‐fold increase in toxicity for D. pulex (Kennedy et al ).…”

“…This contrasts with the 42 and 99% reductions reported by Kennedy et al () for 1619 and 108 mg/L solutions, respectively, and the 69.2% reduction reported by Gust et al () for a 3000 mg/L solution. The present study used the same UV‐irradiation method as used previously (Gust et al ; Kennedy et al ; Moores et al ), and all were conducted in the same laboratory. Therefore, the transformation system has remained constant among studies; however, starting concentrations have varied as well as the test species investigated to assess toxicity.…”

“…Kennedy et al (2017) reported a 73-fold lower LC50 for UV-treated NQ compared with NQ parent compound in C. dubia. Moores et al (2020b) demonstrated the greatest increase in toxicity yet observed for UV-degraded NQ, where 90% UV degradation of NQ elicited a 1240-fold increase in toxicity in Daphnia pulex.…”