Identification of aniline as an air pollutant through biological assay with loblolly pine

Abstract

Investigation of death and injury to pine trees near Raleigh, North Carolina, points to air pollution, with aniline being the most likely causal agent. About 50% of the pine trees in the area were sensitive and responded with one or both of two syndromes, characterised by needle necrosis and needle abscission. Other species appeared to be more tolerant of the injurious agent. A combination of field and controlled exposures allowed four primary conclusions. First, development of injury symptoms could be delayed for several weeks after an exposure either in the field or in chambers under greenhouse conditions. This delay depended on the time of year and/or the dormant or active physiological condition of the plant, and indicated that the toxic effects might have been cumulative. Secondly, the needles on susceptible trees were injured, but the tree remained alive and new needles were formed. However, repeated defoliation resulted in mortality. Thirdly, under greenhouse conditions, genotypes of loblolly pine known to be sensitive or resistant from field trials responded to aniline with the same selectivity, that is to a degree predictable from field observations. Exposures of loblolly pine to other chemicals present in the affected area (biphenyl, toluene, xylene, acetic acid, acetic anhydride and nitrobenzene) either did not produce a response or did not show appropriate genetic selectivity in their effects. Fourthly, trees found to be resistant or sensitive to aniline in greenhouse exposures responded also with the expected genetic specificity in subsequent field exposures. Analyses of the ambient air show intermittent concentrations of aniline in the same order of magnitude as those that induced damage in experimental fumigations.