Peroxyacetyl nitrate, which is in equilibrium with the peroxyacetyl radical and NO2,
was initially discovered by agricultural researchers who had identified a new type of
plant damage in the Los Angeles air basin. The damage, leaf bronzing of a number of
plant species, did not resemble known damage due to ozone, sulfur dioxide, or other air
pollutants. The damage, originally attributed to “Compound X”, led to studies
conducted at the Franklin Institute in Philadelphia and at the University of California,
Riverside, where PAN was discovered and isolated and its phytotoxicity was confirmed.