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MISCELLANEOUS PUBLICATION NO. 10 65, U.S. DEPARTMENT OF AGRICULTURE 



active fallout should increase substantially by (a) 

 accidental release from underground tests; (b) 

 breaking of the ban on atmospheric testing now in 

 effect by the U.S.S.R., the United States, and the 

 United Kingdom; or (<?) intensification of atmos- 

 pheric testing of nuclear explosions by nations re- 

 specting no bans; then, our problems will be much 

 more serious. 



If nuclear warheads should become the last re- 

 sort in deciding international disputes, then we are 

 going to need a great deal more information 

 on decontamination and other defensive pro- 

 cedures than we have. One suspects that the 

 United States is better supplied with these war- 

 heads than with countervailing information to 

 cope with those that might come to us. 



We need far better information on the duration 

 and effects of retained fallout particles on plants in 

 order to improve validity of prediction of radia- 

 tion doses to plants and animals. Information is 

 especially needed on heavy fallout conditions. "We 

 need to more fully evaluate the forces tending to 

 dislodge fallout particles from plants. These 

 forces include wind, rain, shaking, and brushing. 

 Characteristics of leaves that affect ease of dis- 

 lodgment need far better evaluation. Distribution 

 of retained particles on plant surface needs to be 

 measured. 



The foregoing information is needed to develop 

 more expedient and practical procedures for de- 

 contaminating forage in the field. This capability 

 is urgent. Research will probably find certain crops 

 are far more easily decontaminated under field 

 conditions than others. A sprinkler irrigation sys- 

 tem could have new uses, but it would be necessary 

 to know optimal time of sprinkling during fallout. 



Radically new techniques are needed to reduce 

 the thickness of surface soil that must be removed 

 to decontaminate soils. For example, it should be 

 possible to develop mechanical methods for re- 

 moving thin plastic coatings that have been al- 

 lowed to harden on contaminated soil surfaces. 



Much research information is needed on the 

 physiological specificity of different varieties of 

 crop plants to (a) exclude most entities in radio- 

 active fallout from absorption by the roots; (b) 

 exclude these entities from entry into the vascular 

 system even if absorbed by the fine roots; and (c) 

 exclude these entities from foliar absorption. A 

 crop plant that would not absorb radioactive ma- 



terials under heavy fallout would indeed be the 

 nonpareil in a nuclear emergency.. 



Chemical Air Pollutants 



Improved Technology for Evaluation of Damages 

 From Airborne Toxicants 



Evidence of significant damage by airborne toxi- 

 cants to farm crops, ornamentals, and forest trees 

 continues to grow each year. There is no question 

 that vegetation is very sensitive to air pollutants. 

 Adverse effects occur around every industrial and 

 populated area. For example, in Metropolitan 

 Washington, D.C., an ozone-sensitive variety of 

 tobacco only makes half as much growth in pre- 

 vailing air as when grown in the same environment 

 but with carbon-filtered air. Even a resistant vari- 

 ety of tobacco accumulated one-third less dry 

 weight in the prevailing air. 



Losses due to various airborne toxicants are 

 difficult to estimate and reliable data are very lim- 

 ited. Estimates published in 1956 (83), 1961 (81, 

 p. 4U), and 1965 (5, pp. VI 1-280) show that 

 photochemical air pollution causes millions of dol- 

 lars of damage annually to crops in California and 

 that the amount of damage has been increasing 

 rapidly. In 1959, there was an estimated 12 to 20 

 percent loss to cigar-wrapper tobacco growers in 

 the Connecticut Valley (54, 97). In 1965 and 1966, 

 ozone-induced weather fleck caused significant 

 damage to Florida shade-grown tobacco (27, 29). 

 The damage was more general over the area in 

 1966 and resulted in greater economic loss. It was 

 estimated that fleck damage in 1966 averaged at 

 least one leaf per plant for every acre planted. 



In view of the gross evidence of mounting losses 

 from these airborne toxicants, there is an urgent 

 need to improve the validity of the techniques 

 available for assessing damages, particularly 

 chronic damages. Valuable information can be ob- 

 tained by comparing plant growth in ambient 

 versus carbon-filtered air. If adverse effects in the 

 ambient air are noted, it is essential to ascertain 

 the entities that are responsible. Further informa- 

 tion is needed to enable identification of the spe- 

 cific effects of each toxicant on the many different 

 plant species of concern. 



Physical facilities must be available that enable 

 controlled exposures of plants for long periods to 

 low levels of toxicants. Methods of identifying 



