HAZARDOUS WASTE & HAZARDOUS MATERIALSVolume 11, Number 1, 1 994Mary Ann Liebert, Inc., Publishers

OpinionDetection Limits and Variability

in Testing Methods for Environmental Pollutants:Misuse May Produce Significant Liabilities

DON G. SCROGGIN

Jenner & BlockSuite 1200

601 Thirteenth StreetWashington, DC 20005

Environmental regulatory compliance under both federal and state statutes is commonlydetermined by detecting the presence or measuring the quantity of particular pollutants presentat or near regulated facilities. Because such regulatory schemes set numerical standards fordetermining compliance, serious civil or criminal liability may arise whenever compliancestandards are set too near the detection limits of the test method used. This generic problemarises from the variability inherent in all testing methods when they are used to determine thepresence or the quantity of extremely low levels of pollutants. While this area is highly complex,the basic idea is that as the level of detection gets lower and lower, the chances of error increaseto the point that the range of error is larger than the measurement itself. Yet, surprisingly,some federal and state environmental agencies continue to propose permit limits or cleanuplevels for toxic pollutants at levels near the detection level, where total compliance may beimpossible or may require the expenditure of significant costs to remedy false indications of thepresence or excess of certain pollutants.

While these scientific principles apply generally to any situation where pollutants are

being detected near the test method's detection limits, the problems are worse where thepollutant is mixed with other media, such as contaminated water, oil or sludge. Particularlywhen the pollutants of concern are reported in the press to be suspected of causing cancer orother politically-charged health problems (such as breast cancer, sexual disfunction, learningdisabilities, or disproportionate impacts on minorities), all test data may receive close attentionfrom both regulators and environmental activist groups. For example, detection of PCBs ordioxins from or near a facility may produce both regulatory action and frightening headlinesabout health or ecological harm that may not exist. Yet reliably determining the presence or

quantity of such pollutants may be virtually impossible if the regulatory compliance limits areset near the detection limits. The potential consequences of reporting such data withoutqualification include draconian civil or even criminal environmental penalties, unnecessary butcostly remediation, and the gratuitous establishment of a basis for future toxic tort suits to bebrought against the facility by neighbors.

Variability in test measurements arise in several ways. First, because some degree ofvariability in test data is inevitably present in any chemical test, no matter how carefully

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conducted, multiple measurements of the same sample by the same laboratory will always givedifferent results, which may lead to conflicting determinations regarding how much of a pollutantis present or even whether the pollutant is present at all. It is fundamental to every analyticaltesting method that as the concentration of chemical decreases, the measured concentration willcontain more and more uncertainty, until eventually the analytical method will no longer be ableto detect or measure the substance of interest. However, such a threshold of "nondetectability"does not necessarily mean that all raw data measurements in the laboratory (such as electricalsignals from a mass spectrometer) are zero, but only that they are below the appropriatelydetermined detection limit and are, therefore, scientifically unreliable.

A second kind of variability arises when the tests are conducted at a different laboratoryor even at the same laboratory, if a different set of detection instruments or a differenttechnician is used. If final permit limitations or cleanup levels fail to account for these hiddenlimitations of the test procedures, regulated facilities may appear to be out of compliance or torequire remedial action merely as a consequence of the variability inherent in the test. Becausesuch false alarms increase the potential liability of regulated facilities and divert the resourcesof regulatory agencies away from real problems, it is in the interests of all parties to take specificsteps to assure that signals of noncompliance are real, not artifacts of the testing methods.While experienced technical experts may be well-versed in these principles, the staffs ofenvironmental agencies and environmental counsel representing affected companies may be lessaware of the critical importance of assuring that full consideration of all sources of testingvariability be incorporated into negotiated regulatory standards, permit limits, or cleanup levels.

At least two different reference "detection" levels are used by environmental agencies forregulatory purposes, and understanding the differences is critical to avoiding false indicationsof noncompliance or false detections of pollutants. The first is the Method Detection Limit(MDL), which is suitable only for detecting the presence of a pollutant at low levels, not fordetermining quantitatively how much of the pollutant is actually present. The second is thePractical Quantitation Level (PQL) or the Limitation of Quantitation (LOQ), which is theconcentration at which laboratories should be able routinely to determine quantitatively howmuch of a pollutant is present.

Several expert and authoritative scientific institutions have concluded that regulatoryactions should be based only on data at or above the limit of quantitation. For example, theAmerican Chemical Society emphasized that near the MDL (1) uncertainty in the measurednumber can be as large as the reported value itself, and (2) it is virtually impossible to confirmthe identity of the chemical substance detected. The direct conclusion of these observations isthat only the PQL is suitable for routine regulatory compliance purposes and that concentrationsat or below the MDL are indefensible for such use.

Also, the U.S. Environmental Protection Agency ("EPA') has recognized the "MDLs arenot necessarily reproducible over time in a given laboratory, even when the same analyticalprocedures, instruments, and sample matrix are used."1 EPA explains the need for the PQL asfollows:

The Agency developed the PQL concept to define a measurementconcentration that is time and laboratory independent for regulatorypurposes. The . . . MDL, although useful to individual laboratories,[does] not provide a uniform measurement concentration that could beused to set standards.2

Thus, because the MDL will vary from laboratory to laboratory, it does not provide auniform measurement standard appropriate for setting compliance limits. More important, theMDL will be significantly higher-frequently by orders of magnitude~for the same pollutant

1 50 Fed. Reg. 46906 (Nov. 13, 1985).2 See 40 C.F.R. Part 136, App. A.

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measured in media or "matrices" other than laboratory reagent water. Thus, for samplesmeasured in other matrices, such as oil, wastewater mixed with oil, sludge, or fish flesh, theMDL will be higher than published MDL values determined in reagent water.3 For example,even a small amount of oil dissolved or suspended in wastewater can have an enormous impacton the MDL and PQL for PCBs or other chemically similar pollutants.4 Aging or "weathering"of Aroclor PCBs in the environment will reduce the ability of analytical tests to detect orquantify them. Based on EPAs own data, it is not likely that even in oil-free wastewater anycompliance limit less than 5 parts per billion (5 ppb)5 would be appropriate for weatheredAroclors. And if the wastewater were contaminated by any oil, the PQL (and, therefore, theappropriate compliance limit) would be much higher than 5 ppb for weathered Aroclors.

Finally, there are legal arguments with authoritative support against using any regulatorystandards that expose a party to liability without a clear and objective standard of whatconstitutes a violation. If a violation can result from the inherent analytical variability of a testmethod, rather than from a regulated party's action or inaction, the regulated party would bedeprived of the fundamental right to clear and objective standards.

In spite of these well-established scientific, legal, and regulatory principles, permitlimitations and cleanup levels proposed by regulatory staff may fail to reflect suchconsiderations and lead to unrealistic or infeasible compliance limits. For example, numerouscurrent NPDES permits and cleanup levels for U.S. sites include limits for PCBs at or evenbelow the PQL. Compliance with such limits may be the result of random chance as much asenvironmental diligence. Further, inexperienced regulatory staffs may be simply unaware ofthese scientific principles, or they may personally disagree with established agency policystatements for other reasons. It is critical that these principles become part of the basis fornegotiating permit limits and cleanup levels at the time the compliance levels are beingestablished. Otherwise, the final compliance levels may not reflect the scientific limitations ofanalytical chemistry and the statistical variability of the test results.

There are several steps that affected facilities can take to help assure that environmentalcompliance limits include considerations of the scientific limitations of analytical chemistry andthe statistical variability of the test results. First, it is critical that the detection level and limitof quantitation be determined for each laboratory and testing method, since they will varyamong laboratories. Literature values should not be used blindly, nor should laboratory claimsfor low detection levels be taken at face value without close scrutiny. Regulatory agenciesfrequently omit such determinations from routine quality assurance/quality control ("QA/QC")requirements, so the affected facility may have to initiate, fund, and assure the credibility ofsuch additional work.

Second, when test results indicate the presence of pollutants below the quantitation level,numerical results should not be reported, because such test results are not scientifically reliable

3 Using the EPAs recommended gas Chromatographie procedure, an MDL of 0.065parts per billion (ppb) for an Aroclor 1242 standard in reagent water has been publishedby EFA, and an MDL of 0.1 to 0.5 ppb for an Aroclor 1254 standard has been publishedby the American Society for Testing Methods (ASTM). The MDL for an environmentalsample of weathered Aroclor 1254 in wastewater would be expected to be higher. EPAhas published an average PQL value for PCB congeners of 50 ppb in reagent water. 40C.F.R. 264, Appendix IX.

4 Applying multiplication factors provided by EPA to the above MDL values, onewould calculate PQLs in groundwater of 0.65 ppb for Aroclor 1242 and 1.0 to 5.0 ppb forAroclor 1254. One would calculate PQLs in oil of 6,500 ppb for Aroclor 1242 and10,000 to 50,000 ppb for Aroclor 1254 in oil.

5 One part per billion (1 ppb) is equivalent to 1 microgram per liter (1 /¿g/L) or to1,000 parts per trillion (1 ppt).

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or meaningful. Yet it is common for such raw laboratory data to be requested and submittedwithout review. Third, when pollutants are detected below the detection level, those datashould be accurately reported as "ND" or "Non-detect." This is quite simply a matter ofscientific accuracy. Finally, in situations where scientifically unreliable results are neverthelesslegally required to be reported or if the limits of the particular laboratory and test methods areunknown, the data should be accompanied by an explicit disclaimer and detailed informationexplaining why the results are not reliable. These preliminary steps may help protect affectedfacilities from self-incrimination in reporting testing data conducted at levels so low as to bescientifically unreliable or meaningless. Otherwise, such self-reported test results may becomethe uncontested basis for imposing civil or criminal penalties and asserting toxic tort damages.

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