DEVELOPMENT OF COMPLIANCE LEVELS FROM ANALYTICAL
DETECTION AND QUANTITATION LEVELS
This issue paper provides an overview of the use of analytical detection and quantitation levels
as compliance limits and a rationale for use of the Minimum Level (ML) as the quantitation level
appropriate for such limits This paper also provides strategies for clarification of the Method
Detection Limit (MDL) and the ML to mitigate concerns by industry and others about the use of these
measurements for regulatory compliance.
BACKGROUND
The lowest level of an analyte that can be detected using an analytical method is generically
termed the "detection limit." EPA's commonly-used specific term for the detection limit has been the
MDL, which was promulgated at 40 CFR Part 136, Appendix B. Above the detection limit is the
level at which reliable quantitative measurements can be made. This level is generically termed the
"quantitation limit" or "quantitation level."
In the early 1980s, EPA's wastewater program established the ML as the quantitation level,
and in the mid-1980s, EPA's drinking water program established the practical quantitation level
(PQL) as the lowest level at which reliable measurements can be made. In the mid to late 1980s,
EPA's solid waste program adopted the PQL as the quantitation level, although the version adopted
was different from the version used in EPA's drinking water program.
In recent years, the varied concepts of detection and quantitation levels have come under
scrutiny by the regulated industry, by municipalities, and by others. Much of the concern has been
focused on the difficulties associated with implementing these diverse concepts in the analytical and
regulatory arenas; others, however, have challenged the scientific assumptions on which the concepts
are based. Comments and criticism regarding the varied approaches within EPA have reached new
levels in recent months as a result of the Agency's effort to develop a strategy regarding the
enforcement of water-quality based effluent limits (WQBELs) that are set below detection and
quantitation levels.
The purpose of this document is to provide the reader with an overview of the issues relating
to analytical detection and quantitation levels and the impact that these issues have on regulatory
compliance levels. In addition, this paper suggests a strategy for adoption of a single approach to
these issues within EPA.
COMPLIANCE LEVELS
In setting regulatory compliance levels, EPA is often faced with situations that require
monitoring near or below analytical detection or quantitation levels. In such situations, permittees
often argue that the compliance level should be set with a large safety factor to make absolutely
certain that measurements are reliable. Environmental groups frequently argue that a zero level or the
level at which a single researcher can demonstrate that the pollutant can be detected should be used as
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the compliance level EPA must weigh the advantages and disadvantages of each approach and
choose a solution that reflects both good science and good policy.
Within the Office of Water (OW) alone, EPA is responsible for setting standards and issuing
guidance concerning regulatory compliance levels associated with the requirements of the Safe
Drinking Water Act and with technology-based and water-quality based permitting under the Clean
Water Act Three recently drafted OW documents that explicitly address these standards and provide
guidance are:
• Guidance on Evaluation, Resolution, and Documentation of Analytical Problems
Associated with Compliance Monitoring (EPA 821 B-93-001, June 1993);
• The Draft Final National Guidance for the Permitting, Monitoring, and Enforcement
of Water Quality-Based Effluent Limitations Set Below Analytical Detection/
Quantitation Levels (March 22, 1994); and
• Office of Water Policy and Technical Guidance on Interpretation and Implementation
of Aquatic Life Metals Criteria (a memorandum from Martha Prothro to Regional
Water Management Division Directors and Environmental Services Division
Directors, October I, 1993)
Compliance monitoring issues similar to those addressed by OW must also be addressed by
decision makers in other EPA Program Offices. Consequently, it is appropriate to consider the
applicability of any proposed analytical measurement as a regulatory compliance level across all
Agency programs. Because measurements that are made below analytical detection and quantitation
levels are associated with increased measurement uncertainty, an understanding of these concepts is
essential to a thorough comprehension of the impact that they have when they are applied as
regulatory compliance levels. The following sections describe these concepts and their impacts.
DETECTION AND QUANTITATION LEVELS
Numerous terms have been created to describe detection and quantitation levels. These
include:
Method Detection Limit (MDL);
Method Detection Level (MDLVL);
Limit of Detection (LOD);
Reliable Detection Level (RDL);
Compliance Monitoring Detection Level (CMDL);
Limit of Quantitation (LOQ);
Practical Quantitation Level (PQL);
Reliable Quantitation Level (RQL);
Compliance Monitoring Quantitation Level (CMQL); and
Minimum Level (ML).
The significance and applicability of the more important and widely used of these detection and
quantitation levels are summarized in the paragraphs below.
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Method Detection Limit (MDL)
EPA's lynchpin for the lowest level at which a pollutant or contaminant can be reliably
detected is the MDL. The MDL is defined as the lowest level at which an analyte can be detected
with 99 percent confidence that the analyte concentration is greater than zero. Although EPA has not
used the MDL as a compliance level in any of its nationwide standards, it is believed that the MDL
has been incorporated as a compliance level in some permits by individual State and Regional permit
writers.
Detection of pollutants at parts-per-billion, parts-per-trillion, or lower levels in effluent or
drinking waters is not a simple process and is accompanied by a degree of uncertainty.
Consequently, nearly all definitions of detection limits, including the MDL, are based on statistical
analyses of laboratory data To determine an MDL, for example, at least seven replicate samples
with a concentration of the pollutant of interest near the estimated MDL are analyzed. The standard
deviation among the analyses is determined and multiplied by 3.14. The result of this calculation
becomes the MDL1. The factor of 3.14 is based on a t-test with six degrees of freedom and provides
a 99 percent confidence that the analyte can be detected at this concentration.
The MDL was introduced in the technical literature in 19812 and promulgated in 1984. More
than 130 EPA analytical methods for the determination of several hundred analytes incorporate the
MDL Such methods have been promulgated at 40 CFR Parts 136, 141, 143, 260 - 270, and 403 -
499.
Minimum Level (ML)
EPA uses the ML as a compliance level in its nationwide technology-based standards for
wastewater discharges. The ML is a quantitation level that corresponds to the lowest level at which
the entire analytical system gives reliable signals and an acceptable calibration point. The ML was
introduced in EPA Methods 1624 and 1625 in 1980 and was promulgated in these methods in 1984 at
40 CFR Part 136, Appendix A.
EPA's Engineering and Analysis Division (EAD) has recently clarified the procedure for
establishing the ML in order to support use of this level as a regulatory compliance level across EPA
programs. The refined procedure is now being utilized in EPA's strategy for enforcement of
WQBELs set below the analytical limit of detection, and is described in the draft WQBEL document
cited above. The clarified procedure establishes an "interim ML" as 3.18 times the MDL; the result
is exactly equal to the limit of quantitation (LOQ) established by the American Chemical Society
(ACS)3.
To ensure reliable quantitation, the analytical instrument used for compliance monitoring must
be calibrated at or below the interim ML so that the exact interim ML is included in the calibration
1 40 CFR Pan 136, Appendix B.
! Environmental Science and Technology 1981 75, p. 1427.
1 Analytical Chemistry 1980 52, p. 2242.
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range. Laboratories may find it helpful and less error prone to round the exact interim ML to a
whole number for calibration purposes.
The "final ML" for a given analytical method will be established by EPA in method validation
studies These studies will be directed at determining the level at which quantitation can be
performed reliably. The final ML will then be published in the EPA method.
Practical Quantitation Level (PQL), Reliable Detection Level (RDL), and Reliable Quantitation Level
(RQL)
The PQL has been used in drinking water and solid waste programs and defined to be the
level at which reliable measurements can be made under routine laboratory operating conditions (SO
FR 46908; 52 FR 25699). The PQL is constructed by multiplying the MDL, derived as above, by a
factor usually in the range of 5 - 10. However, PQLs with multipliers as high as 50 have been
proposed.
The PQL has been criticized because of the ambiguous nature of the multiplier and because
the resulting levels have been perceived as too high for regulatory compliance purposes. In response
to this criticism, the Drinking Water Standards Division (DWSD), the Environmental Monitoring
Systems Laboratory in Cincinnati (EMSL-Ci), and the ACS Committee on Environmental
Improvement (CEI) have introduced the concepts of the RDL and the RQL.
In the EMSL-Ci embodiment of the RDL and the RQL, the RDL is 2.623 times the MDL and
the RQL is 3.623 times the RDL. Thus, the RQL is 2.623 x 3.623 x MDL or 9.5 times the MDL.
EMSL-Ci has stated that this multiplier is necessary to allow for all sources of variability. In the
DWSD embodiment, multipliers of 2 and 2 are used, resulting in an RQL that is 4 times the MDL.
We understand that DWSD may propose one of these embodiments of the RDL/RQL for public
comment by the end of calendar year 1994.
Multiples of the Standard Deviation
All of the various detection and quantitation levels commonly used by EPA, including those
described above, are based on an estimate or a calculation of the measurement error associated with a
particular analyte, matrix, and analytical method. Calculated measurement errors are based on the
standard deviation of replicate determinations. The principle difference between each of the concepts
is the multiplier that is used on the standard deviation.
Figure 1 illustrates the detection and quantitation levels proposed and the number of standard
deviations on which these levels are based. Included in this illustration are the concepts of a
"compliance monitoring detection level" (CMDL) and "compliance monitoring quantitation level"
(CMQL), which have been proposed by the Utility Water Act Group (UWAG) and are discussed later
in this paper.
IMPACT OF QUANTITATION LEVEL ON REGULATORY COMPLIANCE LIMITS
Table 1 lists the various detection and quantitation level concepts, the number of standard
deviations on which these concepts are based, and the compliance limits that could result for two
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pollutants of environmental concern: 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin); and "oil and
grease" (O&G). The detection limit concepts are presented in Table 1 for information purposes only;
it is generally accepted that the quantitation limit should be used for regulatory compliance purposes.
Figure 2 illustrates the effect that each of the quantitation limit concepts shown in Table 1 would have
on the regulatory compliance limits for dioxin and for oil and grease.
Dioxin is regulated under several environmental programs, including the Clean Air Act, the
Safe Drinking Water Act, and the Clean Water Act. Under the Clean Water Act, dioxin is regulated
as toxic (priority) pollutant (40 CFR 401. IS) and is controlled through water quality-based standards
and through technology-based effluent guidelines Recently, for example, EPA proposed technology
based guidelines that would regulate Pulp, Paper, and Paperboard industry dioxin discharges at 10
parts-per-quad rill ion (58 FR 66078). This 10 parts-per-quadrillion compliance level corresponds to
the ML associated with the proposed analytical method. The impact of using quantitation limit
concepts other than the ML can be seen from Table 1 and Figure 2. Except for the ACS LOQ, all
other concepts result in a significantly higher compliance level.
Oil and grease (O&G) is regulated under the Clean Water Act as a conventional pollutant (40
CFR 401.16), and is controlled through the Storm Water Discharge Program, the Effluent Guidelines
Program, and the Water Quality Criteria and Standards Program. EAD is in the process of
establishing the MDL and ML for O&G. Initial results indicate that the MDL will be in the range of
3 - 5 milligrams per liter (mg/L) and the ML will be approximately 10 mg/L, as shown in Table 1
and Figure 2. EAD believes that an ML of approximately 10 mg/L is reasonable based on the
analytical technology employed. However, EAD is aware of existing permit limits for oil and grease
in the 5 - 10 mg/L range. Setting the compliance level no lower than 10 mg/L in a nationwide
standard and justifying this level with regulatory language may cause re-evaluation and possible re-
openers for these permits. EAD does not believe that an increase to 10 mg/L is excessive,
particularly if it supports a consistent regulatory strategy on the use of the ML as a compliance limit.
Higher levels based on alternative quantitation limit concepts, however, are not justified. Indeed, as
shown in Table 1 and Figure 2, some of these alternative concepts would unacceptably increase
existing regulatory compliance levels if they were to become entrenched in the regulatory process.
Of greatest concern to EAD are proposals for compliance levels that are based on the pooled
interlaboratory standard deviation and on prediction or tolerance intervals. These include the RQL
proposed by EMSL-Ci and the CMQL proposed by industry groups and associations [led primarily by
the Electric Power Research Institute (EPRI), but including UWAG, ASTM, TRW, and others].
These concepts would lead to regulatory compliance levels based on the regulated community's
perception of what the analytical technology will achieve. As is illustrated in Figure 2, such levels
will be well above existing proposed or promulgated compliance levels.
State of New York Approach
In 1988, the Division of Water of the New York Department of Environmental Conservation
published Analytical Detectability and Quantitation Guidelines for Selected Environmental
Parameters* In the New York approach, the compliance level is set at the MDL of the most
sensitive EPA analytical method, or at the water-quality based level, whichever is higher. The New
Document 0080, December 1988.
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York approach also recognizes the uncertainty introduced when the water-quality based level is above
the MDL but below the ML or PQL, but does not provide relief to the ML if the water-quality based
limit falls in this range EAD believes that this approach is open to criticism based on the uncertainty
of quantitation at the MDL and below the ML.
Soundness of the ML
EAD strongly believes that the use of the MDL-derived ML as a compliance limit represents
a scientifically sound approach that allows EPA to provide maximum protection of human health and
the environment while recognizing the uncertainty associated with analytical measurements at very
low concentrations EAD recognizes, however, that widespread consensus on this approach may not
be possible unless some concerns about the current MDL procedure are addressed and resolved.
EAD has evaluated the concerns voiced by MDL critics, and has developed a strategy for refining the
MDL procedure in order to mitigate these concerns. This strategy is described below.
STRATEGY FOR REFINEMENT AND AGENCY-WIDE ADOPTION OF THE MDL
The MDL for a variety of analytes is given in wastewater methods promulgated at 40 CFR
136, Appendix A; in wastewater methods specific to a given effluent rule promulgated at Parts 403 -
499; in drinking water methods promulgated at Parts 141 and 143; and in Office of Solid Waste
methods promulgated at Parts 260 - 270 (SW-846 by reference). Many of these methods have been
used for more than a decade for monitoring in the drinking water, wastewater, and solid waste
programs. Changing from the MDL to another concept or revising the MDL would require revision
of these methods and may require revision of the regulations that they support. If there were
consensus among the scientific, regulatory, regulated, and environmental communities for a concept
other than the MDL, the reasons for revising or replacing the MDL might be compelling. However,
the opinions concerning detection and quantitation levels are far from unanimous and are nearly as
varied as the number of people consulted on the detection/quantitation limit issue.
We have concluded that there is a subjective component to each of the detection limit concepts
presented here and elsewhere, that the MDL serves the concept of the detection limit well, that the
MDL is based on a sound statistical foundation, and that the fundamental concept of the MDL should
not be altered. The MDL concept can, however, be clarified to address the concerns of its critics.
These concerns are that:
• The existing procedure for determining the MDL may result in an overstatement of
the MDL,
• The procedure for determining the MDL is a single-laboratory procedure that does not
reflect interlaboratory variability; and
• MDLs in EPA methods are based on determinations made in reagent water that do not
reflect method performance in real-world sample matrices.
Each of these concerns is addressed in the paragraphs below.
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Iterative Determination of the MDL
The 1984 procedure for the determination of the MDL contains iterative steps to assure that
the MDL is neither overstated nor understated. Specifically, the procedure requires that the MDL
achieved be within a factor of five of the level spiked. If not, the spiking level must be adjusted and
the procedure repeated until the resulting MDL is within a factor of five of the spike level. This
factor of five wa& recently criticized by a presenter at the detection level workshop held in
conjunction with PittCon '94*. The presenter argued that the factor of five allows the MDL to be
overstated.
BAD believes that the solution to this criticism is to narrow the iteration window to a factor
of two or three, rather than five. This solution does not alter the MDL principle and does not
require fundamental changes to any existing methods or regulations.
Interlaboratory Variability
The regulated community has raised the issue that the MDL is a single-laboratory concept.
This single-laboratory limitation has been acknowledged in the rulemaking for drinking water (50 FR
46908, 52 FR 25699). As an alternative, some members of the regulated community have developed
and advanced the concepts of a compliance monitoring detection level (CMDL) and a compliance
monitoring quantitation level (CMQL).5 These levels are calculated based on the pooled
interlaboratory standard deviation and result in levels much higher than the MDL, the ML, the PQL,
and either version of the RDL and RQL.
To overcome the single laboratory limitation of the MDL, EAD's analytical methods now
contain the requirement that, prior to use of a method for data gathering or compliance monitoring
purposes, each laboratory must demonstrate that it can achieve the MDL for each analyte to be
determined using that method. EAD's methods also require use of the ML as the lowest calibration
point. Dr. Henry Kahn of the Economic and Statistical Analysis Branch within EAD points out that
the required demonstration in each laboratory makes the MDL, and thus the ML, an interlaboratory
concept.
EAD has also issued Guidance on Evaluation, Resolution, and Documentation of Analytical
Problems Associated with Compliance Monitoring.6 This guidance states that performance of an
MDL study is a means of demonstrating proficiency with an analytical method and that if the ML is
not achieved, data are considered not valid. EAD has suggested the addition of the demonstration of
the MDL as a requirement for equivalency in the performance-based methods system now under
consideration by EPA's Environmental Monitoring Management Council. EAD believes that
establishment of minimum standards is a necessary part of the regulatory process, and believes that
4 The Detection/Quantitation Workshop, March 4, 1994, held in conjunction with the Pittsburgh Conference
on Analytical Chemistry and Applied Spectroscopy, Chicago, Illinois, February 28 to March 3, 1994.
Presentation of Dr. Robert Gibbons, University of Illinois, Chicago.
5 Water Environment & Technology, 1993, 5(1), 41-44.
6 EPA 821-B-93-001, June, 1993.
7
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the ML represents the best compromise between setting a low level that is acknowledged to be
associated with high measurement error, and a high level that is not reflective of the Agency's
mission to protect human health and the environment.
The regulated community is likely to argue that a requirement for demonstration of the MDL
in each laboratory is not equal to performing an interlaboratory study to learn what the MDL should
be. However, EAD believes that the Agency must set minimum standards that are demonstrable, and
that a demonstration in each laboratory proves that the MDL can be achieved under routine
conditions.
Matrix Interferences
The regulated community has also argued that the MDLs in EPA's analytical methods are
based on the use of reagent water7, and that these MDLs cannot be achieved in a real-world sample
matrix. In response, EAD asserts that, for drinking water there is no matrix problem, and that for
wastewater, the effluent from a well-designed, well-operated Best Available Technology (BAT)
treatment system behaves nearly identically to reagent water in the analytical process. For some
indirect dischargers required to meet effluent limits equal to those for direct dischargers, EAD
acknowledges that there may be a few rare instances in which a detection level equivalent to the MDL
in reagent water cannot be achieved In instances brought to EAD's attention to date, there is no
example in which the strategies provided in the Guidance on Evaluation, Resolution, and
Documentation of Analytical Problems Associated with Compliance Monitoring have not ultimately
resolved the problem. However, EAD recognizes that there may be a few cases in which matrix
problems are intractable In these cases, EAD recommends that the discharger be allowed to use the
matrix-specific MDL procedure option in 40 CFR 136, Appendix B, and if the sample remains
intractable, EAD is willing to investigate alternative, interference-reducing options.
Advances in Analytical Technologies
EAD believes that use of the MDL-derived ML as a regulatory compliance level has the
added advantage of addressing improvements in analytical technology. Most methods used for
regulatory compliance purposes are no longer state-of-the-art by the time they are promulgated, and
EPA has not made any attempt to establish levels that will be achieved at the time of promulgation of
its regulations. An example of the lowering of detection levels by improvements in technology is
provided by comparing the MDLs in the gas chromatography/mass spectrometry (GC/MS) methods
for volatile organic pollutants promulgated in 1984 (49 FR 43234) and those proposed in 1993 (58 FR
65622). In that period, MDLs for these pollutants have been lowered by a factor of 50 - 100.
Although the projection of advances in technology is probably not a prudent regulatory development
or compliance monitoring strategy, it should be recognized that the technology advances nonetheless,
and monitoring at lower levels is possible by the time regulations take effect. Therefore, in setting
compliance levels, use of a smaller multiplier on the MDL is more reflective of the advancing
analytical technology than a larger multiplier.
7 Reagent water is water in which the analyte of interest and potentially interfering substances are not
detected
8
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ARGUMENTS FOR AGENCY-WIDE ADOPTION AND USE OF THE ML
The ML is based on the scientific concept of the LOQ developed by ACS and the
International Union of Pure and Applied Chemistry (IUPAC). EAD has relied upon these concepts
because they were developed by a committee of knowledgeable analytical and environmental
scientists. EAD believes that the concepts underlying the LOD and LOQ are equally valid concepts
today. EAD believes that ACS and IUPAC will support the LOQ, and therefore the ML, as a
reasonable estimate of the lowest level that can be quantitated reliably.
Clarification of the ML Procedure
In order to support multi-program use of the ML, the process of setting the ML has now been
refined into an exact procedure that is based on the scientific concepts of the ACS and IUPAC LOQ,
incorporates the operational procedure of the EPA MDL, and employs the pragmatic concept of
instrument calibration EAD has now tested the refined MDL in several laboratories using several
analytical methods with single and multiple analytes, and finds that the ML neither over- nor under-
states the level that can be measured reliably with an analytical method.
EAD has made the observation that increasing the multiplier by a larger factor than that
required for the ML has the practical disadvantage of shortening the dynamic range of the analytical
instrumentation. For example, the practical dynamic range over which existing GC/MS instruments
are calibrated is approximately a factor of 20. Increasing the multiplier between the MDL and the
ML to the factors stated for the PQL, RQL, or CMQL reduces this dynamic range. This decrease in
dynamic range can increase the number of dilutions required when pollutants are detected, thereby
increasing the cost of analysis. Further, the movement of the quantitation level higher into the
dynamic range renders unusable that perfectly valid portion of the dynamic range between the ML
and the alternate quantitation level. EAD acknowledges that laboratories can "desensitize" their
instruments to move the alternate, higher quantitation level closer to the low end of the dynamic
range, but argues that this action violates the reason for the higher alternate quantitation level in the
first place; i.e., to move the quantitation level higher into the dynamic range to allow a greater safety
factor for reliable quantitation. The ML obviates this problem by matching the lowest calibration
point to the level at which reliable quantitation begins.
Demonstration of the ML
A key concept behind the philosophy of the ML is that the laboratory must demonstrate that
the ML can be achieved before the analytical method can be practiced in that laboratory. EAD
believes that this demonstration is consistent with the regulatory process in which EPA must establish
minimum standards for performance, whether those standards are for the performance of a treatment
system or an analytical method. These "built-in" controls in the analytical method assure that reliable
measurements can be made and make the ML suitable for use as the compliance limit in EPA rules.
EAD also believes that demonstration of the ML is consistent with the performance-based methods
system envisioned by EPA's Environmental Monitoring Management Council, in that the ML
becomes a specification that must be met in any reference method.
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Flexibility for Permit Writers
The use of a specific MDL-denved procedure for calculating MLs also provides a mechanism
by which individual permit writers can recognize advances in analytical technology Since the ML
can be determined by a single laboratory for a given analyte in a given matrix. State and Regional
permit writers are free to require determination of matrix-specific or method-specific MDLs at any
time or point in the permitting process. Because the procedure for establishing the ML is based on
the MDL, State and Regional permit writers are allowed to re-evaluate method-specific and matrix-
specific MLs at any time, on an as-needed basis. Ultimately, this approach not only provides permit
writers with the ability to recognize advances in analytical technology, it also provides local
authorities with the flexibility to set regulatory compliance levels that are more stringent than those
promulgated at the national level, as needs dictate.
CONCLUSIONS
EAD believes that the widely used concept of the MDL should not be altered, but should be
refined to improve its efficacy. EAD further believes that the ML represents the quantitation level
most consistent with the levels set by EPA for compliance in existing regulations. EAD believes that
the ML approach should be adopted by all EPA programs.
EAD urges the Office of Research and Development, the Office of Enforcement and
Compliance Assurance, and all affected Program Offices and their supporting counsels to come to
closure on the MDL/ML issue The inconsistencies between the various detection and quantitation
limit concepts are apparent to the public and the regulated community. It is no longer satisfactory for
each Office or Division within EPA to claim that the needs of that Office or Program are sufficiently
different to warrant different approaches to detection/quantitation levels.
10
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Figure 1
Detection/Quantitation Level Concepts
EAD ACS DWSD EMSL UWAG
Organization Proposing Concept
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Table 1
Impact of Various Detection/Quantitation Limit Concepts
on Possible Regulatory Compliance Levels for
2,3,7,8-TCDD and for "Oil and Grease"
Detection/
Quantitation
Limit Concept
Proposing
Organization
Number of
Standard
Deviations
Derived Compliance Level
Dioxin*
(ppq)b
Oil & Grease
(mg/L)e
Detection Levels
MDL
LOD
RDL
RDL
CMDL
BAD
ACS
EMSL-Ci
DWSD
UWAG
3.14
3.00
8
6
22d
4.4
4.2
11
27
31
4.0 est
3.8
10
7.6
28
Quantitation Levels
ML
LOQ
RQL
PQL
CMQL
BAD
ACS
EMSL-Cl
DWSD
UWAG
10
10
30
15 - 31
45"
10e
14
42
21 - 43
63
10e
13
38
19 - 39
57
a 2,3,7, 8-Tetrachlorodibenzo-p-dioxin.
b Parts-per-quadrillion.
c Milligrams per liter.
d Back calculated from data provided by EPRI .
* Rounded per ML procedure .
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Figure 2
Effect of Quantitation Limit Concepts for
2,3,7,8-TCDD and "Oil and Grease"
100
ppq for Dioxin, mg/L for O&G
V)
0)
CD
-J
c
o
'•4-*
(tt
*-•
*4-»
c
(G
O
BAD
ACS DWSD EMSL
Organization Proposing Concept
UWAG
Dioxin J O&G
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