[Code of Federal Regulations] [Title 40, Volume 21] [Revised as of July 1, 2007] From the U.S. Government Printing Office via GPO Access [CITE: 40CFR116.2] [Page 108] TITLE 40--PROTECTION OF ENVIRONMENT CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PART 116_DESIGNATION OF HAZARDOUS SUBSTANCES--Table of Contents Sec. 116.2 Abbreviations. ppm=parts per million mg=milligram(s) kg=kilogram(s) mg/l=milligrams(s) per liter= (approx.) ppm mg/kg=milligram(s) per kilogram= (approx.) ppm [43 FR 10474, Mar. 13, 1978]