Methamidophos, aka Monitor is an organophosphate insecticide. LD50 rates of 21 and 16 mg/kg for male and female rats, respectively. 10–30 mg/kg in rabbits, and dermal LD50 of 50 mg/kg in rats. It is rapidly absorbed through the stomach, lungs, and skin in humans, and eliminated primarily through urine. It is a cholinesterase inhibitor. Methamidophos is used in great quantities in ricefields in China. Rice–fish culture is common in the southern parts of China as well as in many other rice-producing countries (e.g., Thailand, Malaysia, and the Philippines). Brown rice (unpolished) in this study contained double the concentration of polished rice. Both plants and animals did not degrade the pesticide well, and fish for human consumption in these cases contains methamidophos in concentrations roughly similar to brown rice.
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