Organophosphate Pesticide Poisoning

A total of 118 workers from a 120-person grape picking crew became ill in early September 1976. Of these (108 men and 10 women), 85 received medical attention and three of the 85 were admitted to hospital. The symptoms were typical for organophosphate poisoning. Average plasma and red cell cholinesterase values for the affected workers were depressed more than 60 percent. Most were treated with atropine and some were also treated with 2-PAM (pralidoxime). The exposure to residues of the organophosphate pesticides dialifor (Torak^®) and phosalone (Zolone^®) occurred in one grower''s vineyards near Madera, California.It appeared that workers had been allowed into recently-treated areas before the expiration of the required 30-day safety interval for dialifor, and that excessive skin exposure to residues of this pesticide had resulted. The clinical management of these cases and the occupational surveillance of the workplace became quite complex.The grower sustained significant losses of grapes during the period in which some of his vineyards were under quarantine and he had to pay substantial medical expenses as well as a fine for violating state regulations concerning the proper use of pesticides.Organophosphate pesticides decay more slowly under hot, dry weather conditions than they do when rainfall is frequent. California has imposed a number of specific safety intervals to be observed after the application of these pesticides to certain crops. If, in violation of these regulations, workers are permitted to enter fields too soon, poisoning can occur.