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Abbr. PAN A toxic organic compound, C2H3NO5, formed photochemically in smog, causing eye irritation and damage to vegetation. Due to the stability of this compound, it may be transported in air over long distances before breaking down into smaller reactive compounds.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.