Organophosphate Splash at a Farm-Supply Warehouse
At a farm-supply warehouse, a 38-year-old mixer is transferring chlorpyrifos 4E from a 250-gallon nurse tank into 55-gallon drums. A hose clamp fails, and a stream of concentrate soaks his forearms and soaks through both nitrile gloves; he estimates the exposure lasted about 40 seconds before he shut off the pump. He is wearing a disposable dust mask, safety glasses, and a cotton coverall. He rinses his arms at a hose for 30 seconds and returns to work because the crew is behind schedule. Roughly 50 minutes later he reports blurred vision, a runny nose, heavy sweating, and nausea, and he vomits once. His pulse is 52, his pupils are pinpoint, and his skin is cool and clammy. A coworker wants to drive him to a clinic 25 minutes away; the supervisor wants him to wait until the 17:00 shift change so the crew is not short-handed. The SDS lists chlorpyrifos as an organophosphate with a dermal LD50 of about 200 mg/kg.
1. Explain the toxicological mechanism and why the dermal route dominates this exposure.
Read the worked answer
Chlorpyrifos is an organophosphate. It phosphorylates acetylcholinesterase, so acetylcholine accumulates at muscarinic and nicotinic receptors and in the CNS. The muscarinic picture - salivation, lacrimation, urination, diarrhea, GI cramping, emesis - plus bronchorrhea, bradycardia, miosis, and later muscle fasciculations fits this patient: pinpoint pupils, pulse of 52, vomiting 50 minutes after a splash are diagnostic until proven otherwise.
Route matters. Organophosphates absorb readily through intact skin, and an emulsifiable concentrate is formulated in a solvent carrier that attacks gloves. Thin nitrile gives minutes, not hours, of resistance to aromatic carriers, and a 40-second soak through both gloves plus a forearm splash is a substantial dose. The dust mask is irrelevant: it filters particles, not liquid or vapor, and the exposure was dermal, not inhaled. This is systemic poisoning, and absorption from skin and soaked clothing continues after the splash ends. At a dermal LD50 near 200 mg/kg, a few grams is a serious dose for a 70-kg worker.
2. What is the priority sequence of actions, and how do you respond to the supervisor's proposal to wait until 17:00?
Read the worked answer
Decontaminate first, then transport - and do both in minutes. Remove and bag the coverall, gloves, and boots; wash skin and hair with soap and water; flush the eyes if there was any splash. No solvents, no bleach. Rescuers need gloves and a splash suit, because the patient is contaminated.
Then it is an emergency transport, not a drive to a clinic. He has vomiting, bradycardia, and copious secretions, and the trajectory of organophosphate poisoning is downward - the cause of death is bronchorrhea and respiratory muscle weakness. Call EMS, state the agent, and have them start an IV en route. Tell the receiving facility to prepare atropine titrated to drying secretions and pralidoxime for nicotinic weakness, with oxygen and suction ready.
The supervisor's proposal is indefensible. Even the 25-minute ride in a coworker's vehicle is poor practice once symptoms are systemic, because he can deteriorate en route with no airway management available.
3. What was wrong with the PPE selection, and what program failures sit behind it?
Read the worked answer
Nothing in his ensemble matched the task. A cotton coverall wicks a solvent-based concentrate straight to the skin, and a disposable dust mask protects against neither liquid nor vapor. Nitrile is a poor choice for an aromatic carrier; a laminate film or butyl glove with a tested breakthrough time, worn with the sleeve overlapping the glove cuff, is what a glove-selection chart would support. A full-facepiece respirator with the correct cartridge and chemical goggles would protect the eyes and face, which are also a mucous-membrane route.
Behind the PPE, the program failed. A 250-gallon transfer should use a drip pan, a self-closing valve, and a pre-use hose inspection. The worker should have been trained to stop, decontaminate, and report immediately instead of rinsing and continuing. Anyone handling organophosphates regularly belongs in a cholinesterase monitoring program with a documented baseline. Finally, this is an OSHA-recordable injury that requires a medical evaluation and entry on the exposure record.