Air Pollution by Gas-phase Boron Compounds

Plant damage, such as yellowing the outer rim of leaves, was reported in the vicinity of a steel-related factory. Various investigations revealed that boron concentration was high (up to 550 mg/kg) in the affected leaves and in the flu gas from the factory where boric acid is used in the industrial process, indicating boron from the factory was the cause of plant damage. Moreover, the geographic distribution of affected trees and distribution of affected leaves within a tree suggested direct uptake of gas-phase boron compounds from atmosphere, although the chemical form of it has not been identified. The technical advice to the factory led to process amelioration, which resulted in decreased boron emission in the flu gas.