Peculiar stimulatory action of high-energy chemicals: Fifty years of explosive-induced hormesis evidence.

Explosives, such as trinitrotoluene (TNT) and cyclic nitramines (cyclotrimethylene trinitramine, RDX, and cyclotetramethylene tetranitramine, HMX), are widespread environmental contaminants. Although high doses are toxic, the effects of low, environmentally relevant concentrations remain poorly characterized in risk assessment. This review synthesizes evidence from five decades of research to determine explosives-induced hormesis, a biphasic dose-response characterized by stimulation at low doses and inhibition at high doses. Hormetic responses to explosives have been documented across a vast range of life forms, including bacteria, algae, higher plants, annelid worms, crustaceans, insects, fish, reptiles, and mammalian cells. Stimulated endpoints include growth, reproduction, chlorophyll content, reduced DNA damage, and stem cell proliferation. Effective concentrations span seven orders of magnitude, from 0.0014 mg kg-1 to 21,750 mg kg-1. Key explosive classes inducing hormesis include nitroaromatics (TNT, 1,3,5-trinitrobenzene, TNB, picric acid), nitramines (RDX, HMX), and nitrate esters (nitroglycerin). These findings challenge traditional linear or threshold dose-response models used in ecological risk assessment, and highlight the need to revise standard testing protocols to include low-concentration treatments and hormesis modeling.