# Presentation: 036318

**Federal Advisory Committee on**
**Detection and Quantitation**
**Approaches and Uses in**
**EPA’s Clean Water Act Programs**
**Common Base of Information**
**June 22, 2005**

## Presentation Overview

- EPA and Clean Water Act (CWA) mandates
- Statutory authority for analytical methods in EPA’s CWA programs
- History of detection and quantitation
- Chronological
- Emphasis on history in EPA’s CWA programs
- Where we are today
- Note:  information is intended for those not intimately familiar with detection and quantitation, and may be largely repetitive for those involved over the years

## EPA and Clean Water Act Mandates

- EPA’s mandate is to “protect human health and the environment”
- CWA’s mandate is to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters”
- Detection and quantitation limits must support these mandates
- Examples
- Measurements need to be made at ambient water quality criteria levels to assure protection of aquatic life
- Measurements need to be made to support waste load allocations for total maximum daily loads (TMDLs)

## Congressional Authority for Analytical Methods

- Clean Water Act (CWA) Sections 301(a), 304(h), and 501(a) provide the statutory authority for test procedures (analytical methods)
- Section 301(a) prohibits discharge of a pollutant without a permit
- Section 304(h) requires EPA to promulgate guidelines establishing test procedures for the analysis of pollutants
- Section 501(a) authorizes the EPA Administrator to prescribe regulations necessary to carry out CWA functions
- CWA methods are promulgated at Title 40, parts 136 and 405 – 599, of the *Code of Federal Regulations* (CFR), written as, e.g., 40 CFR part 136

## Characteristics of an Analytical Method

- In environmental analytical chemistry, a *method* is a series of steps (a *procedure*) that leads to a *result* (concentration or amount) for an *analyte* in a *sample*
- Method performance characteristics include
- Precision
- Recovery
- Specificity
- Detection and quantitation limit (sometimes termed “sensitivity”)
- The focus of this FACA is on how to establish, evaluate, and apply detection and quantitation limits

## Detection/quantitation Limit History

- Seminal work on detection and quantitation is by Lloyd Currie, recently retired from NIST
- Published in *Analytical Chemistry* in 1968 (**40**, p586)
- Introduced terms of
- “critical level” (LC), “critical value” (CRV); the “detection decision”; sometimes “detection limit”
- “minimum detectable value” (MDV), “detection limit” (LD)
- “determination limit”, “minimum quantifiable value” (MQV); limit of quantitation” (LOQ); commonly “quantitation limit” (LQ)
- Currie’s work forms the basis the ISO/IUPAC nomenclature and standards, and nearly all other approaches

## Detection/quantitation History – ML

- On December 3, 1979, EPA proposed the 600-Series organic methods (44 FR 69463)
- GC/MS Methods 624 and 625 contained a “limit of detection” for each compound
- In Method 624, the LOD was defined as defined as the “minimum level at which entire system must recognizable mass spectra and acceptable calibration points”
- In Method 625, the LOD was defined as the “minimum level at which the analytical system must give mass spectral confirmation.”
- The LOD in Methods 624 and 625
- Were estimates of the lowest level that could be measured and the basis for the minimum level of quantitation (ML)

## Detection/quantitation Limit - MDL

- Method detection limit (MDL) was first published in a paper by John Glaser and others at EPA’s laboratory in Cincinnati in 1981 in *Environmental Science and Technology* (**15**, p1426)
- MDL based on Currie’s work
- Employs low-level spikes rather than backgrounds
- Uses Student’s t-test to allow for varying number of replicates
- Has remained largely unchanged since publication

## Detection/quantitation - ACS

- In 1980 and 1983, the American Chemical Society’s (ACS’s) Committee on Environmental Improvement adopted an approach similar to Currie’s
- “Limit of detection” (LOD) nearly identical to Currie’s “critical value” (LC) and EPA’s MDL
- “Limit of quantitation” nearly the same as Currie’s “limit of quantitation” (LQ)

## MDL and ML Promulgation

- On October 26, 1984 (49 FR 43234), EPA promulgated:
- The 600- and 1600- Series organic methods at 40 CFR 136, appendix A
- The 600-Series methods contained MDLs as detection limits
- Methods 1624 and 1625 contained MLs as detection limits
- The MDL procedure at 40 CFR 136, appendix B
- Method 200.7 for metals by ICP/MS at 40 CFR 136, appendix C
- Method 200.7 contained MDLs as detection limits

## VEPCO Suit and Settlement

- In early 1985, members of the power industry brought suit against EPA
- The suit claimed, among other things, that the MDL procedure in appendix B should be applicable to the organic methods in appendix A only
- On July 12, 1985, EPA signed a settlement agreeing to industry’s condition
- The settlement did not preclude future use of the MDL by EPA or the right of the litigants to bring suit over future use

## Use of ML in OCPSF Rule

- On November 5, 1987 (52 FR 42522), EPA published a final rule for the Organic Chemicals, Plastics, and Synthetic Fibers (OCPSF) industrial category
- The rule was the first use of the ML as an effluent limit and data censoring point
- Data below the MLs listed in Methods 1624 and 1625 were not considered in calculating effluent limits
- No limit was set below 10 μg/L
- Significant because MDLs were not used for effluent limits or regulatory compliance; instead, MLs were used
- Nearly all subsequent effluent guidelines were censored to the ML

## WQBEL Guidance

- In 1994, EPA published draft “National Guidance for the Permitting, Monitoring, and Enforcement of Water Quality-based Effluent Limitations Set Below Analytical Detection/Quantitation Levels” (WQBEL Guidance)
- Guidance suggested use of the ML as a compliance evaluation threshold when the ambient water quality criterion was below the detection limit of the most sensitive analytical method
- Opposition
- Industry - ML too low
- States - ML not as protective as the MDL.
- EPA did not finalize WQBEL Guidance, but it precipitated further discussions of detection and quantitation limits

## Refinement of ML

- In support of the WQBEL Guidance, EPA refined the ML to be consistent with the ISO/IUPAC LOQ (at the time) and the ACS LOD
- ML = 10 times the standard deviation of 7 replicates
- ML = 3.18 times the MDL
- Directed at 10% RSD, although 10% RSD may not be achievable for some analytes in some methods

## Alternate Minimum Level (AML)

- In 1995, in response to the WQBEL Guidance, the Inter-Industry Analytical Group (IIAG) advanced the “alternate minimum level” (AML)
- AML = 10 times the interlaboratory standard deviation, adjusted to the true concentration and a 95 % prediction limit
- Standard deviation modeled linearly as a function of concentration
- AML led to modeling standard deviation vs concentration

## Rocke and Lorenzato Two-component Model

- In 1995, David Rocke and Stefan Lorenzato published a paper (*Technometrics* **37** p176) giving details of a two-component model of variability (as standard deviation) vs concentration
- Region in which standard deviation remains constant with increasing concentration
- Region of Currie’s critical value (LC) and EPA’s MDL
- Region in which standard deviation increases proportional to concentration
- Region of quantitation
- Region between constant and proportional standard deviation
- Transition region

## ASTM IDE and IQE

- In the mid- to late- 1990s, Robert Gibbons, David Coleman, Nancy Grams, and others worked through IIAG and within ASTM Committee D19 to develop the “interlaboratory detection estimate” (IDE) and “interlaboratory quantitation estimate” (IQE)
- IDE and IQE used a model of standard deviation or relative standard deviation (RSD) as a function of concentration as the basis for establishing detection and quantitation estimates

## EPA Method 1631 for Mercury

- On June 8, 1999 (64 FR 30417), EPA promulgated Revision B to EPA Method 1631for determination of mercury by purge-and-trap and atomic fluorescence
- MDL established at 0.2 ng/L
- ML established at 0.5 ng/L
- The Alliance of Automobile Manufacturers, Inc. and others  brought suit over, among other things, the detection and quantitation limits in EPA Method 1631 and how they were developed

## Settlement Agreement

- In Clause 6 of a Settlement Agreement signed October 19, 2000, EPA agreed to:
- Re-assess procedures for determining detection and quantitation limits
- Peer review the re-assessment
- Provide opportunity for comment on the re-assessment
- Publish a notice and invite comment on the re-assessment by February 28, 2003
- Publish a notice of final action on the re-assessment by September 30, 2004

## Re-assessment Study Plan Peer Review

- In 2001, EPA developed a Study Plan for the re-assessment
- Although not required by the Settlement Agreement, EPA:
- Submitted the Study Plan to peer review and the litigants in December 2001
- Conducted the peer review in accordance with the EPA Science Policy Council’s *Peer-Review Handbook*
- Revised the Study Plan based on comments received from the peer review and the litigants
- EPA also conducted a literature search on detection and quantitation to support the re-assessment

## Study Plan for the Re-assessment

- The re-assessment Study Plan:
- Described roles and responsibilities for implementing the Plan
- Provided a background discussion of detection and quantitation limit concepts
- Outlined a series of 11 steps to the re-assessment.  Examples:
- Develop list of detection and quantitation concepts to be evaluated; e.g., ISO/IUPAC (Currie) LC, LD, LQ; ASTM IDE and IQE; ACS LOD and LOQ
- Develop a list of criteria against which the concepts would be evaluated
- Evaluate the concepts
- Peer review the evaluation/re-assessment

## Evaluation of Concepts

- Evaluation criteria for detection and quantitation
- The concept must be scientifically valid
- It can and has been tested
- It has been subjected to peer review and publication
- It is supported by a well-defined procedure
- It has been accepted by the scientific community
- The error rate is known or can be estimated
- The concept must include routine variability
- The concept must be applicable in a single laboratory
- The detection limit concept should identify the concentration at which there is 99% confidence that the analyte is present

## Evaluation of Concepts (cont’d)

- Evaluation criteria for detection and quantitation (cont’d)
- The quantitation limit should identify the concentration at which the reliability of the measurement is consistent with the capabilities of a method practiced by an experienced staff in a well-operated laboratory
- Detection and quantitation limits must be applicable to the variety of decisions made under CWA, and should support State and local obligations to implement measurement requirements at least as stringent as those set by the Federal Government

## Datasets Used in the Evaluation

- EPA evaluated each concept using datasets developed by EPA or submitted to EPA
- ICP/MS – 9 metals at 12 concentrations from 10 – 25,000 ng/L
- Multi-technique (Episode 6000) study
- 11 analytes/techniques; e.g., TSS, ammonia, phosphorus; organics by GC and GC/MS; metals by GFAA, ICP/OES, and ICP/MS
- 7 replicates at 16 concentrations, from 0.1 – 100x the MDL
- American Automobile Manufacturer Association’s study of 12 metals by ICP/MS and mercury by CVAA
- Method 1631 (mercury) interlaboratory method validation study

## Evaluation of Datasets

- EPA calculated detection and quantitation limits using the various concepts
- EPA MDL and ML; ACS LOD and LOQ; ISO/IUPAC LC, LD, and LQ; ASTM IDE and IQE
- Two concepts were combined because their implementation is identical
- EPA MDL and ACS LOD @ 3x the standard deviation
- EPA ML and ACS LOQ @ 10x the standard deviation
- Comparisons of results published in tables in Appendix C to the technical support document (TSD)

## Technical Support Document

- Results of EPA’s evaluation of detection and quantitation limits were published in a “technical support document” (TSD)
- TSD was subjected to peer review and submitted to litigants
- TSD was revised based on comments received

## Federal Register Proposal

- On March 12, 2003 (48 FR 11770), EPA published a proposal in the *Federal Register*.  The proposal:
- Met requirements in Clause 6.a. of the Settlement Agreement
- Announced the availability of the re-assessment, peer review, and TSD
- Proposed changes to the MDL procedure based on the re-assessment and comments received
- Proposed codification of the ML procedure at part 136
- Invited comments on the re-assessment and proposal
- Based on requests, EPA extended (re-opened) the comment period on the proposal to August 13, 2003

## Comments on EPA’s Proposal

- Some comments were supportive of EPA’s re-assessment and proposal, but many were strongly critical
- Some commenters provided suggestions for improving EPA’s MDL and ML procedures; others provided suggestions for alternative procedures
- Based on comments received, EPA revised the re-assessment and TSD

## Final Re-assessment

- On November 8, 2004 (69 FR 64704), EPA published a “Revised Assessment of Detection and Quantitation Approaches”
- The revised assessment met requirements in Clause 6.f of the Settlement Agreement
- The revised assessment was supported by a “revised assessment document” (RAD), successor to the TSD

## Withdrawal of Proposal

- Also on November 8, 2004 (69 FR 64707), EPA withdrew the proposed changes to the MDL and codification of the ML
- FR notice announced EPA plans to work with stakeholders to address concerns about use of detection and quantitation limits in EPA’s CWA programs
- The withdrawal was preceded by a September 15, 2004 (69 FR 55547) notice of EPA’s intent to perform an assessment of the detection and quantitation situation
- The FR withdrawal and September 15 notice left the status of the MDL and ML unchanged

## FACA Formation

- On December 29, 2004 (69 FR 77972), EPA announced a half-day public meeting to be held January 26, 2005 to report findings in the “Situation Assessment Report on Detection and Quantitation Approaches and Uses in [EPA’s] Clean Water Act Programs” and formation of today’s Federal Advisory Committee
- On May 24, 2005 (70 FR 29743), EPA announced today’s first meeting of the “Federal Advisory Committee to Examine Detection and Quantitation Approaches in [EPA’s] Clean Water Act Programs”

## Where we are today

- Lots of background information
- This presentation
- EPA’s FACA and detection/quantitation web sites
- Water Docket for the re-assessment and final assessment
- Includes TSD and RAD
- Notwithstanding the background information, EPA wants the FAC to operate from a clean slate to arrive at scientifically sound concepts and implementations of detection and quantitation
- No prejudices; no intransigencies; no worries

## Additional Information

- For additional information contact:
**	****	**
**	**Richard A. Reding, Chief
- 	Statistics and Analytical Support Branch
- 	Engineering and Analysis Division (4303T)
- 	Office of Science and Technology, Office of Water
- 	U.S. Environmental Protection Agency, Ariel Rios Building
- 	1200 Pennsylvania Ave, NW
- 	Washington, DC  20460
- 	Voicemail:  202-566-2237
- 	E-mail:  reding.richard@epa.gov