Isofenphos is an organophosphate insecticide used to control soil-dwelling insects.

• Acute toxicity: Isofenphos is highly toxic via the oral route, with a reported acute oral LD50 of 28 to 38 mg/kg in rats and 91.3 to 127 mg/kg in mice . It is moderately toxic via the dermal route, with a reported dermal LD50 of 188 mg/kg in rats. Typical of other organophosphate insecticides, this compound is a cholinesterase inhibitor. Effects that may occur from exposure include: increased secretions, difficulty in breathing, diarrhea, urination, pupil contraction, and slowness of the heart . At very high doses, convulsions and coma may ensue. Isofenphos may be more toxic when it is combined with the insecticide malathion.

• Chronic toxicity: The primary chronic effect of isofenphos in animals and in humans is suppression of cholinesterase activity. Doses in the diets of rats and mice below 0.05 mg/kg/day had no effect on blood stream (plasma) cholinesterase activity.^[1]