Peroxyacetylnitrate (PANs) - A class of chemical substances found as a pollutant in the troposphere, formed by photolysis from natural and manufactured organic chemicals. These chemicals act as irritants and mutagens in mammals and are toxic to many plants. [Atmospheric Environment; v.22; p.973; 1988.] [Air and Waste; v.43; p.1221; 1993.] Atmospheric Chemistry Glossary