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



the edges of the leaves. Pinto beans and tomatoes 

 will show reduced growth and leaf distortion when 

 exposed to 0.5 p.p.m. of nitrogen dioxide for 10 

 to 22 days. Most of the time, concentration of ni- 

 trogen dioxide in the atmosphere near sources of 

 effluent are below 0.3 p.p.m. 



Ethylene 



Cotton plants growing downwind from indus- 

 trial establishments making polyethylene were 

 found to be seriously damaged by ethylene con- 

 taminated air. Air samples revealed 0.04 to 3 p.p.m. 

 ethylene. Ethylene in the atmosphere has caused 

 considerable loss to orchid growers in California. 

 Exposure for 6 hours at 0.05 p.p.m. will cause sepal 

 damage to Cattleya orchids. Carnation flowers 

 often fail to open after a 6-hour exposure to 0.1 

 p.p.m. ethylene. 



Lead Compounds 



In the middle twenties, tetra-ethyl lead began 

 to be added to gasoline, enabling use of engines 

 with higher compression and higher efficiency 

 in energy conversion. Since that time, millions 

 of pounds of lead have been poured into the 

 atmosphere from motor vehicle exhausts. Most 

 of this was eventually deposited on soil and plants. 

 In Los Angeles, the average air concentration is 

 2.5 micrograms of lead per cubic meter of air. 



Pasture grasses collected at the intersection 

 of two U.S. highways near Denver contained 

 3,000 p.p.m. lead, while grasses collected next to 

 a less-traveled roadway contained 700 p.p.m. 

 Grasses collected 50 to 100 feet away from the 

 latter road contained 5 to 50 p.p.m. of lead. When 

 the lead from auto exhausts is fortified by airborne 

 particulate lead from certain smelters, the lead 

 content of forage may become a hazard to the 

 health of livestock. Although there is little 

 evidence of lead poisoning to livestock from 

 combustion products up to the present time, 

 numerous authorities believe the situation is be- 

 coming critical. 



Summary 



Judging from past trends, the adverse effects of 

 air pollutants on agriculture, ornamentals, and for- 

 ests are going to become worse before they get bet- 

 ter. Eecent evidence was obtained showing a syn- 

 ergistic (more than additive) action of low concen- 

 trations of ozone and sulfur dioxide. The mixed 

 gases caused plant injury, whereas there was no 



damage from the same concentration of individual 

 gases. As several toxicants are usually present in 

 polluted air, we must be concerned about the addi- 

 tive effect of the various toxicants on vegetation. 

 Middleton (82) stated in 1964: 



The industrialization of California has resulted in 

 an increase in air pollution which has, in turn, 

 caused extensive and serious damage to vegeta- 

 tion. About 14,000 square miles in California are 

 now known to be affected by oxidants, ozone, and 

 ethylene, which are typically emitted from com- 

 bustion processes and motor vehicles, and by fluo- 

 ride and sulfur dioxide which are typically 

 emitted from industrial sources. 



Crop losses from air contaminants are exhibited 

 by suppression of yield, delay of maturity, and 

 reduction in quality. As the flood of these noxious 

 chemicals continues to pour forth into the atmos- 

 phere, and as capability in diagnosing their dam- 

 ages to plants and animals increases, we can expect 

 estimates of annual damages by air pollutants to 

 crops, ornamentals, forests, and livestock to soar. 



Airborne Dusts 



'"May the gusty wind that blows the ladies' 

 skirts knee-high, also blow dust in the naughty 

 man's eye." Although this ditty penned by a 

 woman many years ago involves extreme bias, it 

 probably represents the only case wherein a benefit 

 was attributed to airborne dusts in day-to-day 

 living. 



Dusts in the atmosphere derive from natural 

 dune-lands; inadequately protected farm and 

 rangelands; highway and industrial construction 

 sites; certain mining operations, such as strip 

 mines; mineral processing operations, such as 

 cement plants; fly ash from smelters; dust from 

 cotton gins, feed mills, and feed lots ; and volcanic 

 action. 



Photographs of farmsteads in the Great Plains 

 half buried in windblown soil as a result of the 

 duststorms of the thirties are stark reminders that 

 agriculture and agricultural people may suffer 

 grievously from airborne dusts. In addition to the 

 mess incurred on the afflicted farmsteads, the air- 

 borne dust threatened the health of people and 

 livestock, damaged buildings and machinery, 

 filled ditches and waterways, buried fences, dam- 

 aged or destroyed crops, and removed topsoil from 

 millions of acres of land. Finnell (36) reported 

 that 6,541,000 acres of land were put out of cultiva- 



