Q. Does paraquat cause harm to humans when entering the respiratory tracts?

A. No. Paraquat is not volatile and vapor from the product cannot enter into the respiratory system. Additionally, the spray droplets produced by knapsack or tractor sprayers used to apply products containing paraquat, or any other CPP, are too large to be respired. Most droplets emitted from spray equipment are between 100 and 200 microns in diameter, but a particle must be 10 microns or less to enter the air spaces in the lungs. The large spray droplets cannot be inhaled into the respiratory system. The US EPA concluded that, “particles used in agricultural practices are well beyond the respirable range and therefore inhalation toxicity is not a toxicological endpoint of concern” (US EPA, 1997).