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



been studied by several groups. The removal of 

 such contamination from fruits and vegetables 

 during processing is being studied at Berkeley, 

 Calif. Studies have recently been completed toward 

 improving the separation of strontium-90 from 

 wheat flour during milling. The commercial re- 

 moval of radioactive fission products from milk 

 by an ion-exchange process has been evaluated. 



Further studies of radiation effects on plants 

 and animals are being conducted by many groups. 

 The U.S. Department of Agriculture is cooperat- 

 ing with the Office of Civil Defense, Public Health 

 Service, and the University of Tennessee- Atomic 

 Energy Commission Agricultural Eesearch Labo- 

 ratory at Oak Ridge, Tenn., in a study of the 

 problem of beta radiation dose to plants. This 

 may be the most important source of radiation to 

 plants early after fallout, while many of the radio- 

 active particles remain on the plant surfaces. How- 

 ever, the problem has been largely neglected to 

 date. The University of Tennessee-Atomic Energy 

 Commission Agricultural Research Laboratory 

 and the New York State Veterinary College at 

 Ithaca, N.Y., have the most comprehensive studies 

 of radiation effects on farm animals. 



In research that has taken place and is under- 

 way on techniques for coping with radioactive con- 

 tamination, we are seeking information we ear- 

 nestly hope we will never need. But we cannot feel 

 complacent. We probably will never be able to 

 feel secure in the adequacy of our knowledge in 

 this area. If we should ever be lulled into a sense 

 of security, we could harshly learn the meaning of 

 the words by old Hecate, the Witch, in Shake- 

 speare's Macbeth: "And ye all know security is 

 mortals' chiefest enemy." 



Chemical Air Pollutants 



As to the vast production of air-polluting chemi- 

 cals by automobiles, industry, and metropolitan 

 activity, agriculture and forestry can do little. 

 Nevertheless, much work has been underway on 

 the sensitivity of plants and livestock to air pollu- 

 tants, the injurious components in polluted air, 

 the effects of pollutants in different plants and 

 animals, management practices to reduce the ad- 

 verse effects of air pollutants, and varieties of 

 plants with higher tolerance of air pollutants. Most 

 of the research with animals has been concerned 



with fluoride injury to cattle and sheep from eat- 

 ing forage with high levels of fluoride. 



The complexity of chemical air pollution prob- 

 lems is indicated by recent studies in the U.S. De- 

 partment of Agriculture. For example, the dis- 

 covery has been made that sulfur dioxide and ozone 

 act synergistically in mixed air to produce injury 

 to tobacco leaves when levels of the individual 

 gases used alone are too low to cause injury. The 

 effects of the combined gases are more than addi- 

 tive. There is an increasing amount of evidence, as 

 well, to show that the greatest loss from chemical 

 air pollutants is from chronic rather than acute 

 injury; that is, the continued exposure of plants, 

 such as citrus, for long intervals to toxicants in 

 photochemical smog significantly reduces growth 

 of the trees and yields of fruit. 



Tremendous quantities of hydrocarbons and 

 particulates enter the air each year from wild 

 forest fires so that research information that 

 enables better forest fire control is exceedingly 

 important. 



Chemical Air Pollutants From Industrial and 

 Metropolitan Activity 



The California Agricultural Experiment Sta- 

 tion began studies on smog damage to crops in the 

 Los Angeles area back in the forties. Also at this 

 time, the New Jersey and Washington stations 

 began research on fluorine injury to plants. About 

 this same time, several State agricultural experi- 

 ment stations (Michigan, Tennessee, Utah, Wash- 

 ington, and Wisconsin) started work on fluorine 

 injury to cattle. The U.S. Department of Agricul- 

 ture began investigations on sulfur dioxide injury 

 to forest trees and other vegetation at about the 

 turn of the century. U.S. Department of Agricul- 

 ture studies on S0 2 injury to plant life were re- 

 ported as early as 1905, and to animal life in 1910. 

 The U.S. Department of Agriculture began its in- 

 vestigations on fluorine damage to crops in the 

 early forties. 



Plant breeding offers the most promising route 

 towards minimizing air pollution injury to eco- 

 nomic crops. Because plant breeders select the most 

 vigorous plants to maintain a line or variety, they 

 have inadvertently selected plants within sensitive 

 species which are most tolerant to prevailing air 

 pollution. Thus, breeders of cigar- wrapper tobacco 

 selected plants that were weather fleck resistant for 



