A patient presents with severe bradycardia and excessive tearing. What agent is MOST likely causing the symptoms?

The symptoms of severe bradycardia and excessive tearing are indicative of exposure to a nerve agent, with soman being a well-known example. Soman is a type of organophosphate, which inhibits the enzyme acetylcholinesterase, leading to an accumulation of acetylcholine at nerve endings. This accumulation results in overstimulation of the parasympathetic nervous system, which manifests as symptoms like bradycardia (slow heart rate) and excessive salivation or tearing due to increased glandular secretions.

The other agents listed do not typically cause these specific symptoms. Anthrax, primarily an infectious bacterium, usually presents with respiratory or gastrointestinal symptoms rather than bradycardia. Phosgene is a harmful gas that leads to respiratory distress but does not typically result in bradycardia or excessive tearing. Chlorine, while also a harmful irritant, primarily causes respiratory reactions and does not have the same neurological effects as nerve agents. Therefore, the presentation of severe bradycardia and excessive tearing aligns most closely with exposure to soman.