government cooperated in an extensive program to obtain the necessary data. All the 
common fumigants are now covered by tolerances or exemptions for use on all the major 
grains. 
The establishment of tolerances has brought about some new problems. Repeated 
fumigation of grain may be required during long-term storage and may build up excessive 
residues from continued use of certainmaterials. Alternate fumigants have had to be used 
in some storage programs. Those in the grain industry are also faced with the problem 
of not knowing the previous treatment history of grain they receive. Until they have 
chemical analyses made, they do not know how much residue may be present or whether 
they dare to fumigate again without exceeding the tolerance. 
We have learned that some fumigants do not air out of grain as readily as we 
formerly thought they did. There has been some indication that an excessive amount of 
ethylene dibromide in oats fed to laying hens may have an adverse effect on egg produc- 
tion. The Department issued a press release towarn the poultry industry of this potential 
hazard and to caution that poultry feed should be aerated thoroughly after fumigation. We 
are having research conducted under contract to learn more about the problem. 
Large numbers of flat storage facilities for grainare being built. There is wide var- 
iation in the design of the aeration systems and some are poorly engineered. We must 
learn how best to use these systems for forced-distribution fumigation. Uneven distribu- 
tion of fumigant will produce poor insect kill in areas of low gas concentration and ex- 
cessive residues in areas of high concentration. 
Another problem facing us is the need for tolerances or exemptions under the Food 
Additive Amendment to cover the fumigation of processed foods and animal feeds. The 
only fumigant tolerance established is 15 p.p.m. of ethyl formate for the fumigation of 
cashew nuts. Several extensions have been granted, only two of which carry tolerance 
specifications. One is for 25 p.p.m. of hydrogen cyanide as a fumigant. The other is for 
50 pepem. of inorganic bromides in processed foods resulting from methyl bromide fumi- 
gation. An extension for ethylene oxide specifies a dosage rate of 0.4 ml. per pound of 
dried fruit. There are extensions for carbon tetrachloride, chloropicrin, ethylene di- 
bromide, and ethylene dichloride as fumigants for foodplant use. Presumably this covers 
their use on processed foods in a food plant but a strict interpretation would preclude 
their use in a warehouse. An extension granted for propylene oxide permits its use asa 
fumigant in foods. As stated in the extensions, none of the materials except hydrogen 
cyanide could be used on mixedor processedanimal feeds. It appears obvious that a large 
amount of residue data will have to be obtained to establish all the final tolerances or 
exemptions needed. 
We also need to do a great deal of basic research on background factors related to 
fumigation. It is surprising to find how little is known about the behavior and distribution 
of fumigant gases in mixtures or under vacuum, the fundamental aspects of penetration 
and sorption, and the performance of fumigants atlower temperatures. There should also 
be a search for new fumigants with improved properties. Our Branch is now in the process 
of initiating some limited work of this nature. 
FOOD PROCESSING PLANTS 
One of the most urgent problem areas is that relating to the use of pesticides in food 
processing plants. The foodand pest control industries, not to mention many in government 
circles, are thoroughly confused as to what pesticides can be used safely in food plants, 
or where and how they can be applied without coming into conflict with the Food Additive 
Amendment. The industry is concerned because on the one hand they must use pesticides 
to prevent the insect infestations that would be in violation of the Food, Drug, and Cosmetic 
Act, and on the other hand they greatly fear that some unintended or unknowing misuse of a 
pesticide may bring about a Food and Drugaction. Where the reputation and good will of a 
brand name is concerned, a Foodand Drug citation causes an unfavorable and costly public 
reaction. 
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