Malathion: The Mosquito Fogger With a Nerve Agent Family Tree
Malathion is an organophosphate insecticide that shows up as a colorless to amber oily liquid with a smell most people describe as skunky, garlicky, or just plain rotten. It’s one of the most widely used pesticides in the world, sprayed over neighborhoods for mosquito control and sold in dilute form to treat head lice, which gives it a friendly, everyday reputation that its chemical relatives absolutely do not deserve.
You’ll find it in agriculture, public health vector control, landscaping, grain storage, and veterinary use. Like every organophosphate, it works by shutting down acetylcholinesterase, the enzyme that clears the neurotransmitter acetylcholine out of the synapse. Block that enzyme and the nervous system never gets the message to stop firing, which is the same mechanism military nerve agents use, just dialed down. The classic picture is SLUDGE: salivation, lacrimation, urination, defecation, GI distress, and emesis, plus pinpoint pupils, muscle twitching, and in serious cases respiratory failure.
Here’s what makes malathion sneakier than its mild reputation suggests. It’s relatively low in mammalian toxicity only because our bodies can break it down quickly, but heat, age, and poor storage convert it into malaoxon and isomalathion, degradation products that are dramatically more potent. A drum that’s been baking in a shed for two summers is not the same chemical that went into it. On top of that, most formulations are dissolved in flammable petroleum solvents, so you often have a fire problem riding along with the poisoning problem, and it’s absorbed readily right through intact skin.
Whether you’re working a crop duster crash, an agricultural warehouse fire, a tanker rollover, or an intentional exposure, treat malathion as a genuine cholinesterase emergency and don’t get talked out of it by the label on the jug. Approach upwind with respiratory protection and skin protection that actually blocks liquid contact, decontaminate patients thoroughly before they reach the ambulance so you don’t poison your own crew, and get atropine and pralidoxime into the treatment plan early rather than waiting to see how bad it gets.
Have fun and let us know how you did in researching the hazards.
Want to be alerted when a new Chemical of the Week is published? Click the button to sign up for our notifications.
About the Author:
Dave Donohue is a hazardous materials course developer, educator, and trainer with experience at the local, regional and national level. He is also a Master Exercise Practitioner, firefighter, and emergency manager.
