WASTES IN RELATION TO AGRICULTURE AND FORESTRY 



21 



S0 2 injury to forest trees, horticultural plantings, 

 and field crops can be expected. 



Fluoride 



Airborne fluorides have become a serious toxi- 

 cant to vegetation and animals over the last few 

 decades. The industries mainly responsible are 

 aluminum reduction, smelting of iron and nonfer- 

 rous metals, ceramics, and phosphate fertilizer 

 manufacture. Some manufacturers have been mak- 

 ing good progress over the last decade in installing 

 equipment to curb fluoride effluent. 



Fluorides appear to act as cumulative poisons 

 to the plant. In 150 hours, corn foliage will con- 

 centrate 0.005 p.p.m. of atmospheric hydrogen 

 fluoride to 178 p.p.m. dry weight of plant. Gladio- 

 lus, prunes, peaches, and grapes are also sensitive 

 to this low level of hydrogen fluoride. More than 

 500 p.p.m. of fluoride can be concentrated in foli- 

 age during a single season from an atmospheric 

 fluoride level of 0.5 part per billion. Fluoride in- 

 jury on ponderosa. pines has been detected 20 miles 

 from an aluminum smelting plant. 



Most agricultural soils contain 100 to 150 p.p.m. 

 of fluoride, but most plants absorb very little of 

 this element from the soil because of the low solu- 

 bility of calcium fluoride (1.6 mg./lOO ml. H 2 0) ; 

 that is, it is nearly as insoluble as calcium oxalate. 

 ( 'onsequently, when plant leaves contain more 

 rlian a few parts per million of fluoride, 

 atmospheric contamination with fluoride can be 

 suspected. 



When one considers that air samples from a 

 heavily industrialized city such as Baltimore re- 

 veal 0.08 part per million of fluoride, the potential 

 for damage to vegetation by this air contaminant 

 is extant. In fact, legal claims for fluoride damage 

 to crops within three States — Utah. Florida, and 

 I daho— totaled nearly S3 million in 1957. 



Chronic fluorosis may develop in livestock from 

 ingestion of small amounts of fluoride over several 

 months or years. Fating contaminated forage 

 growth near industrial areas emitting fluorides will 

 induce fluorosis. If the animals receive mineral 

 mixture or water containing fluoride the effect of 

 the contaminated forage will be accentuated. All 

 kinds of livestock may be affected by accumulation 

 of fluoride in their systems, but cattle are most 

 sensitive followed by sheep, swine, horses, and 

 poultry. Cattle may ingest 1 to "2 milligrams of 



fluorine per kilogram of body weight without 

 harmful effects if they are in good health. 



Symptoms of fluorosis involve excessive wear- 

 ing of the teeth, staining, pitting of the enamel, 

 and exposure of the dentine. In severe cases, the leg 

 joints may become enlarged and the shaft of the 

 long bones may thicken. 



In past years, numerous dairy herds in central 

 Utah have shown extensive symptoms of fluorosis. 



Peroxyacetylnitrate and Ozone 



Peroxyacetylnitrate (PAN) and ozone are the 

 two most important plant toxicants that are pro- 

 duced in smog that has been activated by light en- 

 ergy. There are many sources of compounds that 

 will react in the presence of sunlight to produce 

 PAX and ozone, but the automobile exhaust ap- 

 pears to be the worst offender. 



PAX is extremely toxic to citrus, forage, salad 

 crops, ornamentals, and coniferous trees. Acute 

 leaf damage by PAX to sensitive species has been 

 observed at 0.005 p.p.m. in the air. PAX tends to 

 produce injury symptoms on the lower surface 

 of leaves, whereas ozone primarily affects the up- 

 per surface. PAX may also seriously retard 

 growth and stimulate leaf abscission. Crops of 

 romaine lettuce have been so badly damaged by 

 PAX as to be unsalable. Cigar-wrapper tobacco 

 grown beneath cloth shade, as in the Connecticut 

 Valley and Florida, has been seriously damaged 

 by "weather fleck" caused by ozone injury. Sensi- 

 tive plant species such as tomato, tobacco, radish. 

 and white pine may be damaged after exposure to 

 0.06 p.p.m. ozone for 3 to 4 hours. 



Annual losses to crops in California from dam- 

 age caused by photochemical smog have been - 

 timated at millions of dollars; the estimates also 

 show that these losses have been rising rapidly. 

 Damage of this type has been observed in 27 States 

 and the District of Columbia. For example, east- 

 ern white pine has been killed, discolored, or 

 stunted by photochemical smog in Tennessee and 

 Pennsylvania. 



Oxides of Nitrogen 



Nitrogen oxides are produced by high tempera- 

 ture combustion; thus they may be emitted by any 

 fuel combustion source. Nitrogen dioxide is more 

 injurious to living cells than nitric oxide and 

 causes irregular blotches o( collapsed tissue near 



