Air Pollutants, especially photo- chemical smog and fluorides, are known to cause major damage to agricultural crops. Commercial production of leafy vegetables has been seriously hampered in the Los Angeles Basin because of oxidant lesions which reduce their quality or render them totally unsalable. High levels of fluorides can cause visible damage to crops; where no leaf lesions can be seen, careful environmentally controlled studies are required to determine the extent of injury attributable to fluorides.