1. EPA’s Revised Minimum Quantification Levels Scott Wilson

2. MQL Background First developed in 1992 Adopted by EPA Region 6 states and most other EPA Regions Based on –Atomic Adsorption –Furnace –Gas Chromatography/Mass Spectrometry

3. Revised MQLs In 2004, examined MQLs which were greater than water quality criteria (37) Examined newer methods and MQLs commonly achieved by labs Issues with Mercury

4. Revised MQLs Concentrated review on routinely achievable levels Routine levels were lower than previous MQLs for 33 of the 37 parameters Routine levels were lower than criteria for 13 parameters

5. Revised MQLs Based on: –Inductively Coupled Plasma Mass Spectrometry for metals (EPA method 200.8) –Gas Chromatography/Mass Spectrometry for most organics (EPA Method 624/625) –Gas Chromatography with Electron Capture Detector for pesticides (EPA Method 608) –Spectrophotometric Method for Chlorine (EPA Method 330.5)

6. Revised MQLs Mercury –Priority due to numerous fish advisories nationally –Choice of EPA Methods 1631 or 245.7

7. Revised MQLs EPA has implemented in permits for New Mexico Specific Methods are not required –Required to meet the MQL –May use any EPA approved methods –May obtain approval for alternative methods Other States are in the process of implementing revised MQLs

8. Scott Wilson EPA Region 6 telephone: 214-665-7511 email: wilson.js@epa.gov