Before revision: Environmental studies deal with the sum of all social,economical,biological ,physical,and chemical interrelations with our surroundings Contaminant A contaminant is a substance present in nature at a level higher than fixed levels or that would not otherwise be there.American Meteorological Society.
After revision: Contaminant A contaminant is a substance present in nature at a level higher than fixed levels or that would not otherwise be there.American Meteorological Society.