June, 1917.] ARSENICAL RESIDUES AFTER SPRAYING. 35> 



SUMMARY AND CONCLUSIONS. 



Considering the various experiments so far described in this- 

 bulletin, the writers propose the following conclusions as to the 

 danger of poisoning human beings thru residues of arsenic re- 

 maining on fruits or vegetables following spraying with arsenate- 

 of lead. 



In the case of apples, the maximum amount of the poison in 

 terms of AS2O3 that may be expected to occur on apples in the- 

 ordinary course of events would not exceed .5 milligram per fruit. 

 It is true that the surface of an apple may contain more than this,, 

 even as much as 5 milligrams, as made clear by experiments al- 

 ready described in direct spraying of poison on the surface of the- 

 fruit. But as pointed out in that place, such fruit would cer- 

 tainly attract attention and in picking and handling would cer- 

 tainly lose a material part of this residue, even if no rains inter- 

 vened. It is believed, therefore, that under ordinary conditions 

 no apples will reach the consumer carrying such amounts of 

 arsenate of lead per fruit that a healthy human adult can eat 

 enough at one time to cause fatal poisoning. In offering this 

 conclusion the writers are taking into account the result obtained 

 in feeding equivalent amounts of the poison to guinea pigs and 

 other data already mentioned, which have a bearing on the toxic 

 properties of arsenate of lead. 



The possibilities in the case of strawberries appear a little dif- 

 ferent. The surface of this fruit is of such nature that larger 

 amounts of the poison may be retained and quite possibly may 

 escape notice. These residues also would be much less likely 

 to be rubbed off in handling and probably would wash off less 

 readily. One portion of strawberries, consisting of one-fourth 

 quart of the berries, may carry as much as 8 milligrams AS2O3. 

 This would probably seldom or never constitute a dangerous dose 

 for an adult person in good health, but it might for a child or for 

 an adult in weakened condition. The writers believe, therefore, 

 that strawberries that are fully formed or nearly so, should not 

 be directly sprayed with arsenate of lead, unless they are to be 

 thoroly scrubbed before using. 



In the case of blackberries and currants there is the possibility 

 that a portion of these fruits suitable for an adult might carry 

 a questionable amount of the poison. The possibility appears. 



