Methomyl, a carbamate insecticide, was introduced in India in 1988-89 for the control of boll worm pest on cotton. Soon after the introduction, there were some alleged cases of death due to insecticide exposure amongst spray operators in Andhra Pradesh. NIOH carried out a systematic study on the toxicity of methomyl on spray operators. It was observed that in spray operators with normal pre-exposure ECG, significant T-wave changes, including inversion, in most of the chest and limb leads, occurred following 5 days exposure to methomyl. The ECG changes observed in spray operators could be reproduced in rabbits in dose dependent manner.
This was the first report of the cardiac toxicity of methomyl in human beings and experimental animals. On the basis of the study results, the registration of Methomyl was cancelled by the Pesticide Registration Committee and large number of farmers were saved from the danger of exposure to this highly toxic compound.
Cardiac Toxicity in Pesticide Formulators Exposed to Organo-phosphate Insecticides
A number of studies indicate ECG and necropsy changes in cardiovascular system in persons accidentally or intentionally (suicidal) exposed to organophosphate group of insecticides. However, there are no reports on CVS changes in people chronically exposed to the insecticides. Studies carried out on pesticide formulators chronically exposed to organophosphate pesticides showed abnormalities of heart rate and ECG abnormalities like tall R wave, prolonged period of conduction (AV block or wide QRS complex) and ventricular premature beats. This is the first report of ECG abnormalities in occupationally exposed subjects.