﻿2 BULLETIN 1149, U. S. DEPARTMENT OF AGRICULTURE. 



has been employed at ports of entry (9, 17) to prevent the intro- 

 duction from foreign countries of many injurious insect pests that 

 have not yet gained a foothold here. Among the most important 

 of these pests are the pink boll worm and the citrus black fly. Fumi- 

 gation With hydrocyanic acid gas is also a means for the prevention 

 of epidemics of yellow fever (5) and bubonic plague (6, IS, 19). 

 Ships coming from ports where these diseases exist are fumigated 

 on arrival in order to kill mosquitoes and rats which carry the 

 causative organisms. 



Food products fumigated to destroy the insects with which they 

 are infested come into contact with hydrocyanic acid. This is true 

 in the fumigation of imported fruits and vegetables at ports of entry 

 and in the fumigation of flour and grains in mills and warehouses. 

 In destroying insects and rats in dwellings and ships, foodstuffs 

 ma)* not be removed during exposure to the gas. In any case there 

 is the possibility of exposure to the fumigant of products intended 

 for food. 



Since hydrocyanic acid is extremely poisonous to man, it is impor- 

 tant to know how much of it is absorbed and retained by foods. Very 

 little work on this subject seems to have been done, although appar- 

 ently the opinion that there is no danger in the fumigation of dry 

 foods 5 is fairly general. 



REVIEW OF LITERATURE. 



Guthrie (10) was unable to find a trace of residual gas in oranges 

 that had been fumigated with hydrocyanic acid gas, in the propor- 

 tions recommended for actual practice, for three hours and then 

 allowed to remain in the open air for a half hour. He states that 

 "similar experiments were made on samples of apples and lemons 

 * * * with the same result." 



Townsend (22) reports that seeds, whether dry or moist, are 

 capable of absorbing hydrocyanic acid, even when its concentration 

 in the atmosphere is very low. He fed fumigated seeds (corn and 

 wheat) to mice and concludes from his experiments that "dry grains 

 and other seeds treated for several days with hydrocyanic acid gas 

 of any strength will not be injured for food. * * * Damp 

 grains and other seeds treated with hydrocyanic acid gas of any 

 strength, even for short periods of time, should not be used for food 

 until several hours after removing from the gas." 



Schmidt (21) fumigated peaches, plums, pears, lemons, and apples 

 with hydrocyanic acid gas, apparently in rather high concentration. 

 He placed his material in a chamber of 9.4 liters capacity and, in the 

 course of a half hour, carried over into it by means of a stream of air 

 the acid freed from 20 grams of potassium cyanide. He gives no 

 values for the rate at which the air entered. If the stream of air 

 was just strong enough to get all the hydrocyanic acid over into the 

 chamber, without carrying any out, the atmosphere surrounding 

 the fruit would contain about 78 per cent of the fumigant. This is 

 equivalent to treatment with the gas from 213 ounces of potassium 

 cyanide or 160 ounces of sodium cyanide per hundred cubic feet, 

 which would be from 50 to 150 times as concentrated as that used 



* H. D. Young reports that the workmen engaged in citrus fruit fumigation in California often hang 

 their lunches in the trees which they expect to finish about lunch time. Immediately after fumigation 

 the lunches are removed and eaten with no ill effects. 



