Dioxin TEQ Calculators UsingDioxin TEQ Calculators Using Kaplan-Meier Technique for

H dli N d t tHandling Nondetects

Deana Crumbling, USEPA, Washington, DCRobert Tisdale Tetra Tech EM Inc Boulder CORobert Tisdale, Tetra Tech EM Inc., Boulder, CO

Introduction

• “Dioxins”: large family of closely related g y ychemicals sharing similar toxic mechanism

• Large family composed of smaller families: dioxins, furans & dioxin-like PCBs (DL-PCBs)

• Individual chemicals termed “congeners”

• 29 congeners of risk concern: 7 dioxin, 10 furan & 12 DL-PCB congeners

M t t i i 2 3 7 8 TCDD• Most toxic is 2,3,7,8-TCDD

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Dioxin TEQ

• TEQ = “toxic equivalence” = Expresses toxicity of the group in a single value

E h i d• Each congener assigned a “toxicity equivalence factor” (TEF) relative to 2,3,7,8-TCDD = 1

TEFi x Ci = TECi

Σ(TEC ) = TEQΣ(TECi) = TEQCi = Concentration for congener iTECi = Toxic Equivalent C t ti f i

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Concentration for congener i

Lack of Consistencyy• TEQ calculation straightforward if data are

unqualified and all congeners are detectedunqualified and all congeners are detected• Handling U/ND & “rejected” (R-qualified)

congeners– Common options: substitute 0, ½ RL, or RL

• Who does the TEQ calculation?– Lab might do it– Risk assessor might do it– Regulator may choose a more conservative– Regulator may choose a more conservative

substitution than an RP– Is there documentation of how it was done?

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Alternative to SubstitutionAlternative to Substitution• 2009: Dr. Dennis Helsel published article explaining

how to use the Kaplan-Meier (KM) method to deal with NDs when calculating TEQs.

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Kaplan-Meier MethodKaplan Meier Method• Substitution allows ND data with high detection limits

(th l t i t ) t t l(the least precise measurements) to strongly influence the calculated total

• KM avoids substitution• KM avoids substitution• Standard in medical and industrial statistics; slowly

gaining traction in environmental (is in ProUCL)gaining traction in environmental (is in ProUCL)• Nonparametric: data do not have to fit any specific

statistical distributions– Based on ordering of values and assigning %-iles

• At least 3 congeners must be detected

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Freely Available K-M Excel Spreadsheety p

• Downloadable from Helsel’s Practical Stats website:Downloadable from Helsel s Practical Stats website: – http://www.practicalstats.com/nada/nada/downloads.html

– Was used to build TEQ CalculatorWas used to build TEQ Calculator

Concentration # Detects # Nondetects Quantiles KMStats v 1.4 Practical Stats100 0 1 0.000 Input data to the blue cells, then sort from highest to lowest3 2 1 0 0 958 concentration Concentrations and detection limits in Col A3.2 1 0 0.958 concentration. Concentrations and detection limits in Col A.2.8 1 0 0.917 Number of detects at each concentration in Col B.2 0 8 0.000 Number of nondetects at each DL in Col C.

1.7 1 0 0.851 The example data have 1 <100, 8 <2s, 4 <1s, and 1 <0.9.1.5 1 0 0.786 Detects start at 3.2, include a detected 0.9, and go1 0 4 0.000 down to the smallest, three detected 0.5s.,

0.9 1 1 0.6880.7 2 0 0.458 ** Efron's bias correction: Always enter the smallest values (the 0.6 1 0 0.344 last row) as detects. If these data had 2 <0.5s and 1 detected0.5 3 0 0.000 0.5 as the smallest values, they should also be entered as here.

0.000

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0.000 Mean Std Error Std Dev UCL95 (t) 25th Pctl Median 75th Pctl0.000 0.949 0.165 0.807 1.231 0.000 0.700 0.9000.0000.000 Zero for a percentile is a value below the lowest in the data set.0.000 For the example data, the 25th pctl = < 0.5.

EPA-Developed TEQ CalculatorEPA Developed TEQ Calculator

• Macro-driven Excel workbookMacro driven Excel workbook• Sheets in the workbook

– InstructionsInstructions– Written description of how NDs, EMPCs & Rs are

handled– The data entry & reporting sheet Primary worksheet– KM calculator (works “behind the scenes”; the sheet is

viewable for transparency purposes but can be hiddenviewable for transparency purposes, but can be hidden by user)

– List of congener abbreviations

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Provides a “Sensitivity Analysis”Provides a Sensitivity Analysis

• Enter the sample data once • Calculator automatically displays these TEQ values:

– TEQ using K-M method for ND congeners– TEQ substituting 0 for NDs– TEQ substituting ½ RL for NDs

TEQ substituting RL for NDs– TEQ substituting RL for NDs– TEQ substituting 0 for R-qualified congeners– TEQ substituting RL for R-qualified congenersg q g– TEQ subbing a “donor value” for R-qualified congeners

• A “donor value” is taken from related sample(s) having th tt & t tithe same congener pattern & approx concentrations

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What Can Cause a CongenerWhat Can Cause a Congener Result to be Rejected

• Ion abundance in the mass spectrometer does not meet specificationsp

• Signal-to-noise ratio too low• Relative retention time not meet specsp• Low laboratory control sample (LCS) result• Blank contaminationBlank contamination• …and others

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TEQ Calculator PurposeTEQ Calculator Purpose

• Does not make recommendations or set policy• Does not make recommendations or set policy• Allows comparisons to see whether the decision

outcome depends on how TEQ is calculatedoutcome depends on how TEQ is calculated• If R data create decision uncertainty

f– Might request reanalysis of problem sample with analytical method modifications, or

Collect new samples and use modified method– Collect new samples and use modified method

• Documentation for how TEQ values were calculated

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Calculator FeaturesCalculator Features• Default is sheet protection “on” (non-entry cells

l k d) t id tiare locked) to avoid corruption– Remove protection with provided password

C d t• Congener order sort– If congener data in different order than Calculator,

can easily reorder Calculator to matchcan easily reorder Calculator to match• Reports fraction of TEQ from D/Fs vs. DL-PCBs• J-qualifies the TEQ if >50% of TEQ fromJ qualifies the TEQ if >50% of TEQ from

qualified data• Easy to change TEF valuesEasy to change TEF values9 Aug 2012 NEMC 2012 12

Calculator Output: If no ND or RCalculator Output: If no ND or RAll calculation methods give same TEQ result

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Calculator Output: NDs PresentCalculator Output: NDs Present

Generally, the KM TEQ will fall between y, Qthe TEQs from subbing 0 & ½ DL

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When Highest TEC is NDWhen Highest TEC is NDKM algorithm requires

highest value to be a detect

2 options

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When “R” Data Is PresentWhen R Data Is Present4 optionsp

Documentation

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“ISM Basic” KM CalculatorISM Basic KM Calculator

• A simpler version of the Calculator• A simpler version of the Calculator

• Provides only the KM TEQ

• Does not handle samples with rejected data, or samples with the highest TEC from a nondetect

• Can be used to “train up” to the Advanced Calc.

• Also calculates t- and Chebyshev-UCLs forAlso calculates t and Chebyshev UCLs for triplicate ISM samples

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SummarySummary

Provides a method other than substitution for NDs• Provides a method other than substitution for NDs• Advanced KM Calculator provides a sensitivity

analysis to aid decisions with suboptimal dataanalysis to aid decisions with suboptimal data• Basic KM Calculator provides

Q f– TEQ calculations for uncomplicated data

– UCLs for ISM decision units

• Currently in peer review

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Contact InformationContact Information

Deana CrumblingOffi f S f d R di ti d T h l Office of Superfund Remediation and Technology

Innovation

Technology Innovation and Field Services Divisiongy

703-603-0643crumbling.deana@epa.gov

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