Because of its low toxicity to fish, it is also used in water as an agent to control mosquito larvae. As with all organophosphates, coumaphos is readily absorbed through the skin. Skin and eye contact with this insecticide may cause mild irritation, as well as cholinesterase inhibition. Individuals with respiratory ailments, impaired cholinesterase production, or with liver malfunction may be at increased risk from exposure to coumaphos. Some of the symptoms of acute inhalation of coumaphos include headaches, dizziness and incoordination.
Moderate poisoning is characterized by muscle twitching and vomiting.
Some organophosphates may cause delayed symptoms beginning 1 to 4 weeks after an acute exposure that may or may not have produced immediate symptoms. In such cases, numbness, tingling, weakness, and cramping may appear in the lower limbs and progress to incoordination and paralysis. Other effects reported in workers repeatedly exposed include impaired memory and concentration, disorientation, severe depressions, irritability, confusion, headache, speech difficulties, delayed reaction times, nightmares, sleepwalking, and drowsiness or insomnia. No organ effects were seen in acute or chronic studies of coumaphos. These symptoms persisted in some survivors for up to 13 days, accompanied by weight loss.