Florida Agricultural Experiment Stations


 exposure to spray drift; nevertheless, parathion poisoning among
 them was a rarity. It was noted that many spray operators were
 so afraid of handling parathion that they often thought they
 were sick. Such psychosomatic cases emphasize the fact that
 some test such as one for blood cholinesterase is necessary to
 make positive diagnoses of parathion poisoning. Mild poisoning
 cases could exhibit nausea and headache, and these same symp-
 toms would be shown by individuals who were working in fear
 of the material. This study indicated that parathion, if handled
 properly, can be used with a minimum hazard to the spray oper-
 ator.
 The amount of parathion necessary to produce poisoning
 symptoms for man has not been definitely determined, but some
 information concerning its toxicity is available. Parathion has
 been estimated to be as much as 70 times more toxic to man
 than DDT (16). Results from different sources vary, but in
 general the oral LD,,, dosage for experimental animals varied
 between as little as 3 and as high as 30 mg. per kg. (12, 13, 16).
 LD.,o means the amount of parathion at which 50 percent of the
 animals received lethal dosages. In terms of parts per million in
 the diet over a period of two years, animals fed as high as 50 parts
 per million showed no symptoms and no evidence of parathion
 storage. At 100 parts per million in the diet, occasional symp-
 toms were manifested (8). Based on data similar to these,
 Lehman (17) stated that 2 to 5 parts per million of parathion
 in the diet would not represent a health hazard. Even on a whole
 fruit weight basis the amount of parathion found in the fruit
 has always been lower than 1 part per million (21). Thus,
 there appear to be no health hazards associated with parathion
 residues in citrus fruit.
 It is of major importance to determine the way in which citrus
 grove labor may be poisoned. When parathion work was first
 begun, emphasis was placed upon the wearing of respirators
 with organic vapor cartridges. This is of considerable import-
 ance, but data collected during the 1950 spray season indicated
 that other factors were of even greater importance (7, 25). Most
 of the cases of authentic parathion poisoning reported were in
 spite of the wearing of respirators. Parathion vapors in a grove
 are probably not particularly hazardous. Animals which were
 exposed in a grove for 10 days following an extremely heavy
 application of parathion showed no effect on blood cholinesterase
and no parathion poisoning symptoms (7). However, respira-