Inhalation Exposure to 2,4-Dichlorophenoxyacetic Acid Causes Tracheal Damage—A Study in Rats

Exposure to 2,4-dichlorophenoxyacetic acid (2,4-D) occurs mainly by inhalation. Studies indicate that respiratory allergic reactions are induced by this pesticide. This study analyzed the effects of chronic inhalation exposure to 2,4-D in the trachea of rats. We exposed the animals during six months to three different concentrations of 2,4-D used for crop spraying. Animals exposed to low concentrations had an increase in the mast cells count, showing that this herbicide can cause allergic reactions in the airways. The tracheal epithelium thickness, the nuclear area and number of nucleolar organizing regions increased proportionally to the exposure concentration and in correlation with each other. These histological tissue changes correspond to epithelial hypertrophy and increased cell activity and multiplication, and show an adaptation to tissue damage caused by 2,4-D. There was a tendency for inversion in the mucus pattern to acid and a decrease in goblet cells in the groups exposed to 2,4-D, which alters the protective mechanisms of the respiratory tract. The 2,4-D induced adaptations in the tracheal epithelium associated with an increase in herbicide concentrations, which may compromise mucociliary function and predispose the epithelium to additional lesions over time. Therefore, it should be used with appropriate respiratory protection equipment to avoid injury.